JP3656290B2

JP3656290B2 - Monopulse radar device

Info

Publication number: JP3656290B2
Application number: JP22524095A
Authority: JP
Inventors: 正伸行松; 佐々木　　邦彦; 順志宇津
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1995-09-01
Filing date: 1995-09-01
Publication date: 2005-06-08
Anticipated expiration: 2015-09-01
Also published as: JPH0968573A

Description

【０００１】
【発明の属する技術分野】
本発明は、放射パターンの一部が重なるように配設された複数のアンテナ素子を備え、各アンテナ素子を用いて所定電波を送受信させ、各アンテナ素子にて得られた受信信号に基づき、外部に存在する物標の方位等を検出する、モノパルスレーダ装置に関する。
【０００２】
【従来の技術】
従来より、自動車の衝突を未然に防ぐために運転者の視覚を補助する手段として、電波を伝送媒体とした障害物検出レーダの実現が期待されている。またこの種のレーダ装置において、前を走行する車両等，障害物の水平方向の位置を判別することは、衝突の可能性予測にきわめて重要な技術である。このため、こうした自動車用のレーダ装置としては、例えば特開昭６１−１６７８９０に開示されているようなモノパルスレーダ装置が有効であると考えられる。
【０００３】
つまり、モノパルスレーダ装置は、一般に、航空機追尾用レーダとして用いられているが、水平或は垂直方向の位置を判別するのに優れたレーダ装置であることから、自動車の走行環境のような多くの障害物が存在する状況において、きわめて有効に機能すると考えられるのである。
【０００４】
【発明が解決しようとする課題】
しかし、こうしたモノパルスレーダ装置を利用した衝突防止システムが普及し、これを搭載した車両が増加すると、各システム間の送受信電波の電波干渉は避けられないものとなり、障害物等の物標検知能力が低下することが予想される。
【０００５】
本発明は、こうした問題に鑑みなされたもので、電波を発生する他の通信装置との間で生じる電波の相互干渉を抑圧して、常に良好な物標検知能力が得られるモノパルスレーダ装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
かかる目的を達成するためになされた請求項１に記載の発明は、円偏波の電波を送受信可能であって放射パターンの一部が重なるように配設された複数のアンテナ素子と、前記各アンテナ素子が送受信する円偏波の旋回方向を切り換える偏波切換手段と、所定周期で周波数が変化する周波数変調信号を送信信号として発生する信号発生手段と、該信号発生手段からの送信信号を各アンテナ素子に入力して各アンテナ素子から電波を放射させると共に、各アンテナ素子にて受信された受信信号を各々取り出す信号入出力手段と、前記信号入出力手段を介して得られた各アンテナ素子からの受信信号を前記送信信号と混合して、各受信信号を中間周波信号に変換する周波数変換手段と、該周波数変換手段による変換後の前記各中間周波信号に基づいて外部の物標を検出する物標検出手段と、を備えたモノパルスレーダ装置において、前記周波数変換手段が、前記各アンテナ素子からの受信信号を前記送信信号を用いて各々周波数変換する複数の周波数変換部と、該複数の周波数変換部にて周波数変換された中間周波信号を順次選択して前記物標検出手段に出力する出力スイッチ手段とを備えたことを特徴とする。
【０００７】
このように構成された請求項１に記載のモノパルスレーダ装置においては、信号入出力手段が、信号発生手段から発生する送信信号（周波数変調信号）を、放射パターンの一部が重なるように配設された複数のアンテナ素子の各々に入力して、各アンテナ素子から電波を放射させると共に、各アンテナ素子にて受信された受信信号を各々取り出し、周波数変換手段が、その取り出された受信信号を送信信号と混合して中間周波信号に変換する。そして物標検出手段が、その変換後の各中間周波信号に基づいて外部の物標を検出する。この装置では、各アンテナ素子に、円偏波の電波を送受信可能な円偏波用アンテナ素子が使用され、偏波切換手段が、各アンテナ素子が送受信する円偏波の旋回方向を切り換える。
そして特に、この装置では、周波数変換手段が、複数の周波数変換部と、出力スイッチ手段とを備えている。周波数変換部は、各アンテナ素子からの受信信号を上記送信信号を用いて周波数変換し、出力スイッチ手段は、複数の周波数変換部にて周波数変換された中間周波信号を順次選択して物標検出手段に出力する。
【０００８】
つまり、モノパルスレーダ装置は、放射パターンの一部が重なるように配設された複数のアンテナ素子から電波を放射させ、その放射電波が外部の物標に当たって反射してきた反射波を各アンテナ素子にて受信することにより、各アンテナ素子にて得られた受信信号の振幅又は位相の差から物標の方位を検出するものであるが、当該装置近傍に、同一規格の他のモノパルスレーダ装置が存在したり、当該装置が送受信する電波と略同じ周波数帯の信号を送信或は受信する通信装置が存在すると、これら他の装置との間で電波干渉が発生して、その干渉波により物標の検知能力が低下してしまう。
そこで請求項１に記載のモノパルスレーダ装置では、各アンテナ素子に、円偏波の電波を送受信可能な円偏波用アンテナ素子を使用し、偏波切換手段にて各アンテナ素子が送受信する円偏波の旋回方向を切り換えることにより、干渉波による検知能力の低下を、各アンテナ素子が有する偏波識別によって防止するようにしている。
【０００９】
更に、上記構成のモノパルスレーダ装置は、従来より一般に知られているモノパルスレーダ装置に、アンテナ素子から周波数が連続的に上昇又は下降する送信信号を放射させ、アンテナ素子にて受信された受信信号と現在送信している送信信号とをミキサ回路等からなる周波数変換手段を用いて混合して、受信信号を、受信信号の周波数と送信信号の周波数との偏差に対応した周波数の中間周波信号に周波数変換することにより、その中間周波信号の周波数から、アンテナ素子から放射した送信信号が物標に当たってアンテナ素子に戻ってくるまでの時間、延いてはアンテナ素子から物標までの距離を検出するＦＭ−ＣＷレーダの技術を適用したものである。
そして、このＦＭ−ＣＷ方式のモノパルスレーダ装置を実現するに当たって、周波数変換部にて周波数変換された中間周波信号を、出力スイッチ手段により、時分割で物標検出手段に順次入力しているのである。
【００１０】
この結果、請求項１に記載のモノパルスレーダ装置によれば、例えば車両に搭載して障害物等を検出するシステムに適用したとしても、他の装置からの送信電波に影響されることなく障害物等の物標を正確に検出できるようになり、物標検知能力を高めて車両の走行安全性を向上することが可能になる。
しかも、周波数変換手段にて中間周波信号に変換された各アンテナ素子からの受信信号を受ける物標検出手段側で、これら各受信信号（中間周波信号）から物標の方位及び物標までの距離を容易に且つ正確に求めることができるため、障害物の方位及び障害物までの距離を正確に検出して、車両の障害物への衝突の危険性を車両運転者に速やかに報知し、車両走行時の安全性を向上することができる。
更に、出力スイッチ手段を備えたことにより、物標検出手段において、各アンテナ素子に対応した中間周波信号から物標の方位及び距離を正確に求めるために、入力された中間周波信号を増幅したり波形整形するための信号処理回路を、各アンテナ素子に対応して複数設ける必要がなく、装置構成を簡素化することができる。
【００１１】
なお、各アンテナ素子の円偏波の旋回方向を切り換える偏波切換手段としては、例えば、各アンテナ素子から電波を送信させて物標の検出を行う物標検出動作を１回或は複数回行う度に、円偏波の旋回方向を交互に切り換えるようにしてもよいし、また例えば、通常は任意の旋回方向の円偏波を用いて物標検出動作を行い、各アンテナ素子にて得られた受信信号が通常有り得ない信号レベルとなったときに、円偏波の旋回方向を切り換えるようにしてもよい。
【００１２】
次に、請求項２に記載の発明は、請求項１に記載の発明と同様、複数のアンテナ素子と、偏波切換手段と、信号発生手段と、信号入出力手段と、周波数変換手段と、物標検出手段とを備えたモノパルスレーダ装置である。
【００１３】
そして、請求項２に記載のモノパルスレーダ装置では、周波数変換手段が、各アンテナ素子から入力される受信信号を順次選択して取り込む入力スイッチ手段と、該入力スイッチ手段から順次入力される受信信号を上記送信信号を用いて順次周波数変換して物標検出手段に出力する一つの周波数変換部とを備えている。
【００１４】
即ち、この請求項２に記載のモノパルスレーダ装置では、信号入出力手段を介して入力される各アンテナ素子からの受信信号を、入力スイッチ手段により、時分割にて取り込み、その取り込んだ受信信号を周波数変換部にて中間周波信号に変換するのである。
【００１５】
このため、請求項２に記載のモノパルスレーダ装置によれば、請求項１に記載の装置と同様、障害物の方位及び障害物までの距離を正確に検出して、車両の障害物への衝突の危険性を車両運転者に速やかに報知し、車両走行時の安全性を向上することができるのに加え、物標検出手段に信号処理回路を複数設ける必要がなく、装置構成を簡素化できる。しかも請求項２のモノパルスレーダ装置は、周波数変換手段において受信信号を中間周波数に変換する周波数変換部についても、アンテナ素子に対応して複数設ける必要がないため、装置構成をより簡素化することができる。
【００１６】
また、周波数変換部において受信信号を中間周波信号に変換するには、信号発生手段から出力された送信信号を、各アンテナ素子に対応した信号入出力手段だけでなく、周波数変換部にも分配する必要があるが、請求項２に記載の装置では、この周波数変換部をアンテナ素子の個数に関係なく、１つにすることができるので、周波数変換部を各アンテナ素子に対応して複数設けた場合に比べて、送信信号の分配に伴う送信信号の電力低下を抑制でき、信号発生手段の出力電力を小さくすることができる。
【００１７】
次に、請求項３に記載の発明は、円偏波の電波を送受信可能であって放射パターンの一部が重なるように配設された少なくとも３個以上のアンテナ素子を備えるほか、請求項１に記載の発明と同様、偏波切換手段と、信号発生手段と、信号入出力手段と、周波数変換手段と、物標検出手段とを備えたモノパルスレーダ装置である。
【００１８】
そして、請求項３に記載のモノパルスレーダ装置では、周波数変換手段が、アンテナ素子に対応して、各アンテナ素子からの受信信号を上記送信信号を用いて各々周波数変換する３個以上の周波数変換部を備えると共に、該各周波数変換部から出力される中間周波信号の中から一対の中間周波信号を選択して物標検出手段に出力する信号選択手段を備え、該信号選択手段が選択する中間周波信号の変更により、物標検出に使用するアンテナ素子の間隔を調整可能に構成してなることを特徴とする。
【００１９】
つまり、モノパルスレーダ装置は、基本的には、２個のアンテナ素子を放射パターンの一部が重なるように各アンテナ素子を所定間隔で配置し、各アンテナ素子にて得られた受信信号の振幅又は位相の差から物標の方位を検出するものであるため、２個のアンテナ素子を備えていれば、ＦＭ−ＣＷ方式のモノパルスレーダ装置を実現できる。しかし、単に２個のアンテナ素子のみで物標の方位及び距離をしようとすると、例えば、アンテナ素子の間隔が狭いと、物標までの距離が短い場合には、各アンテナ素子の受信信号の振幅又は位相の差から物標の位置を良好に検出できるものの、物標までの距離が長い場合には、各アンテナ素子にて得られた受信信号の振幅や位相の差が極めて小さくなって、物標の位置を良好に検出できなくなるといったことがある。
【００２０】
そこで、請求項３に記載のモノパルスレーダ装置では、アンテナ素子を少なくとも３個以上設けて、周波数変換部にて中間周波信号に変換した各アンテナ素子からの受信信号の中から、信号選択手段を用いて任意の２つを選択できるように構成することにより、物標の検出に使用するアンテナ素子の間隔を調整（切換）できるようにしているのである。
【００２１】
この結果、請求項３に記載のモノパルスレーダ装置によれば、例えば当該装置から物標までの距離や、物標の検出状態等に応じて、信号選択手段が選択する中間周波信号を切り換えることにより、物標検出に用いるアンテナ素子の間隔を、物標を最も良好に検出可能な値に切り換えることができるようになり、物標（特にその方位）の検出精度をより向上して、角度測定分解能に優れたレーダ装置を実現することが可能になる。
【００２２】
次に、請求項４に記載の発明は、請求項３に記載のモノパルスレーダ装置であって、物標検出手段は、当該モノパルスレーダ装置から外部の物標までの距離を検出できるよう構成されており、更に、選択制御手段が、物標検出手段により検出された距離に基づき、該距離が長いほど、前記一対の中間周波信号に対応した一対のアンテナ素子の間隔が広くなるように信号選択手段を制御する。
【００２３】
このように構成された請求項４に記載のモノパルスレーダ装置によれば、例えば物標までの距離が所定の設定距離以上の場合はアンテナの間隔を広くし、設定距離以上でなければアンテナの間隔を狭くするというように、物標までの距離に応じて一対の中間周波信号を切り換える（換言すれば、一対のアンテナを切り換える）ことができるため、当該モノパルスレーダ装置から物標までの距離に影響されることなく、物標を正確に検出できるようになる。
【００２４】
次に、請求項５に記載の発明は、請求項１〜請求項４いずれか記載のモノパルスレーダ装置であって、物標検出手段が物標の検出を行う毎に乱数を発生する乱数発生手段と、物標検出手段が物標の検出を行う毎に乱数発生手段が発生した乱数に基づいて偏波切換手段を動作させる切換制御手段とを備えたことを特徴とする。即ち、物標検出手段が物標の検出を行う毎に、円偏波の旋回方向をランダムに切り換えるのであり、例えば、発生した乱数が偶数ならば右旋円偏波、奇数ならば左旋円偏波とするようにすることができる。
【００２５】
従って、請求項５に記載のモノパルスレーダ装置によれば、当該装置と同様のモノパルスレーダ装置等との間で電波干渉が発生しても、その干渉波による影響を受けることなく物標を検出することが可能となり、物標の検出精度を向上できる。
【００２６】
次に、請求項６に記載の発明は、請求項１〜請求項５いずれか記載のモノパルスレーダ装置において、前記各アンテナ素子は、２端子給電型の円偏波用アンテナ素子からなり、前記信号入出力手段は、前記各アンテナ素子毎に設けられ、前記送信信号を位相差９０度の送信信号に分配してアンテナ素子の２つの給電端子に出力すると共に、アンテナ素子の各給電端子から入力される一対の受信信号のうち、前記分配した送信信号とは逆方向に９０度の位相差を有する受信信号を合成して装置内に取り込む、複数の９０度ハイブリッド回路からなり、前記偏波切換手段は、前記９０度ハイブリッド回路とアンテナ素子の給電端子とを接続する一対の信号経路の一方に設けられ、位相変化量を０度及び１８０度のいずれかに切り換え可能な位相変化量可変型の移相器からなることを特徴とする。
【００２７】
即ち、９０度ハイブリッド回路は、入力端子に入力された信号を位相差９０度の信号に分配して一対の入出力端子から出力し、入出力端子に信号出力時とは逆方向の位相差（−９０度）を有する信号が入力されたときに、その信号を合成して出力端子から出力するものであるため、請求項２に記載のモノパルスレーダ装置では、各アンテナ素子に、位相差９０度の信号を受けて所定旋回方向の円偏波を送信する２端子給電型の円偏波用アンテナ素子を用い、各アンテナ素子の一対の給電端子と、９０度ハイブリッド回路の一対の入出力端子とを各々接続して、９０度ハイブリッド回路の入力端子に信号発生手段からの送信信号を入力することにより、各アンテナ素子の一対の給電端子に位相差９０度の送信信号を給電して、各アンテナ素子から所定旋回方向の円偏波の電波を放射させるのである。
【００２８】
そして、このように各アンテナ素子から所定旋回方向の円偏波の電波を放射させ、その放射電波が外部の物標に当たって反射すると、反射波の旋回方向が送信時とは逆方向になって、各アンテナ素子に入射し、各アンテナ素子の一対の給電端子には、送信時とは逆方向の位相差（−９０度）を有する信号が誘起されるため、各アンテナ素子にて物標からの反射波が受信された場合には、その受信信号が９０度ハイブリッド回路にて合成されて、その出力端子から物標検出手段に出力されることになり、各アンテナ素子の偏波識別により、物標に当たって反射してきた電波のみを受信して物標検出を行うことができる。
【００２９】
また、９０度ハイブリッド回路とアンテナ素子の給電端子とを接続する一対の信号経路の一方には、位相変化量を０度又は１８０度のいずれかに切換可能な移相器が設けられているため、この移相器の位相変化量を切り換えることにより、アンテナ素子の給電端子に入力する送信信号の位相差を９０度及び−９０度のいずれかに切り換え、アンテナ素子から放射させる電波の旋回方向を右旋回及び左旋回のいずれかに切り換えることができる。
【００３０】
従って、請求項６に記載のモノパルスレーダ装置によれば、請求項１〜請求項５いずれか記載のモノパルスレーダ装置を、比較的簡単な構成にて実現でき、また電波の旋回方向の切り換えも簡単に行うことができる。
つまり、請求項１〜請求項５いずれか記載のモノパルスレーダ装置は、例えば、各アンテナ素子を導波管円偏波アンテナとこのアンテナへの供給電力に定められた方向の磁界を与えて電波を旋回させるポラライザとから構成し、信号入出力手段をサーキュレータにより構成し、偏波切換手段をポラライザが発生する磁界の方向を切り換えて円偏波の旋回方向を切り換えるように構成しても実現できるが、この場合、フェライト回路であるサーキュレータ等を使用するので装置が大型化し、また装置構成も複雑になってしまう。
【００３１】
これに対して、請求項６に記載のモノパルスレーダ装置によれば、アンテナ素子，信号入出力手段及び偏波切換手段からなる高周波回路部を、２端子給電型円偏波用アンテナ素子，９０度ハイブリッド回路及び位相変化量可変型移相器から構成しているため、これら各部をフェライト回路を用いることなく実現でき、装置構成を簡素化して小型化を図ることができるようになるのである。
【００３２】
次に、請求項７に記載の発明は、請求項６に記載のモノパルスレーダ装置において、前記アンテナ素子，９０度ハイブリッド回路，及び移相器からなる送受信用の高周波回路部が、所定の基板上に導電パターンにて形成した平面回路からなることを特徴とする。
【００３３】
このように、請求項７に記載のモノパルスレーダ装置では、高周波回路部を、所定の基板上に導電パターン（マイクロストリップライン）からなる平面回路にて構成しているので、モノパルスレーダ装置をより小型化することができ、装置の利用範囲を拡大できる。
【００３４】
なお、高周波回路部を平面回路にて構成するには、例えば、９０度ハイブリッド回路を、ラットレース電力合成回路，ウィルキンソン電力合成回路等のマイクロストリップラインにて構成可能なハイブリッド回路にて構成するようにすればよい。
【００３５】
【発明の実施の形態】
以下に本発明が適用された実施例の車両用障害物検出装置について説明する。（第１実施例）
図１は第１実施例の車両用障害物検出装置の構成を表わすブロック図である。
【００３６】
図１に示す如く、本実施例の車両用障害物検出装置は、複数（本実施例では３個）の２端子給電型円偏波用アンテナ素子（以下単にアンテナセルという）２ａ，２ｂ，２ｃと誘電体レンズ４とからなるマルチビーム誘電体レンズアンテナ（以下単にアンテナ装置という）６、アンテナ装置６の各アンテナセル２ａ〜２ｃから所定旋回方向の円偏波の電波を放射させると共に、各アンテナセル２ａ〜２ｃからの受信信号に基づき誘電体レンズ４の前方に存在する障害物の位置を検出し、車両が障害物に衝突する虞がある場合には警報装置１２を動作させて、車両運転者にその旨を報知する電子制御装置（以下単にＥＣＵという）１０、及び、ＥＣＵ１０からの出力信号に応じて各アンテナセル２ａ〜２ｃから円偏波の電波を放射させると共に、各アンテナセル２ａ〜２ｃにて得られた受信信号を処理してＥＣＵ１０に入力する送受信回路２０、を備えている。
【００３７】
ここで、アンテナ装置６において、各アンテナセル２ａ〜２ｃは水平方向に所定間隔で配設されており、各アンテナセル２ａ〜２ｃの放射パターン（指向性）は、誘電体レンズ４によって、図２（ａ）〜（ｃ）に示す如く、水平方向に各々異なり、しかも一部が重なり合った放射パターンとなるようにされている。
【００３８】
つまり、３個のアンテナセル２ａ〜２ｃの内、中央のアンテナセル２ｂは、図２（ｂ）に示す如く、図に点線で示す誘電体レンズ４の中心軸に沿って略左右対称となる放射パターンとなり、左右のアンテナセル２ａ，２ｃは、図２（ａ），（ｃ）に示す如く、図に点線で示す誘電体レンズ４の中心軸に対して右又は左側に偏った放射パターンとなるようにされている。
【００３９】
なお、アンテナ装置６全体の放射パターン（指向性）は、これら各アンテナセル２ａ〜２ｃの放射パターンを合成した図２（ｄ）に示す放射パターンとなる。次に、送受信回路２０には、ＥＣＵ１０から出力される電圧制御された制御信号に応じて、所定周波数の送信用高周波信号（送信信号）を発生する電圧制御型の周波数可変発振器（以下単に発振器という）２２と、発振器２２からの送信信号を、各アンテナセル２ａ〜２ｃに供給するための給電用信号と各アンテナセル２ａ〜２ｃにて得られた受信信号を周波数変換するための３つのローカル信号とに４分配する第１電力分配器２４と、第１電力分配器２４にて給電用信号として分配された送信信号を、各アンテナセル２ａ〜２ｃに各々供給するための給電用信号として更に３分配する第２電力分配器２６とが備えられている。
【００４０】
そして、第２電力分配器２６にて分配された各アンテナセル２ａ〜２ｃに対する送信信号は、各アンテナセル２ａ〜２ｃに対応して設けられた９０度ハイブリッド回路２８ａ〜２８ｃの入力端子Ｂに夫々入力される。
９０度ハイブリッド回路２８ａ〜２８ｃは、入力端子Ｂに入力された送信信号を、９０度の位相差で夫々半分づつに振り分けて一対の入出力端子Ｃ，Ｄから出力し、逆に、入出力端子Ｃ，Ｄに送信信号とは逆位相（位相差−９０度）の信号を受けると、この信号を合成して出力端子Ａから出力する周知のものであり、一対の入出力端子Ｃ，Ｄの内、一方の入出力端子Ｃは、対応するアンテナセル２ａ〜２ｃの一方の給電端子Ｈに直接接続され、他方の入出力端子Ｄは、対応するアンテナセル２ａ〜２ｃの他方の給電端子Ｖに、位相変化量Φを０度又は１８０度に切換可能な位相変化量可変型移相器（以下単に移相器という）３０ａ〜３０ｃを介して接続されている。
【００４１】
従って、第２電力分配器２６から９０度ハイブリッド回路２８ａ〜２８ｃに入力された送信信号は、９０度の位相差を有する送信信号として、各アンテナセル２ａ〜２ｃの一対の給電端子に夫々供給され、各アンテナセル２ａ〜２ｃからは、夫々、所定旋回方向の円偏波の電波が放射されることになる。
【００４２】
また、各アンテナセル２ａ〜２ｃに放射電波とは逆旋回の円偏波電波が受信されると、各アンテナセル２ａ〜２ｃの給電端子に、送信時とは逆方向に９０度の位相差（−９０度）を有する受信電力が発生するため、９０度ハイブリッド回路２８ａ〜２８ｃにおいては、各アンテナセル２ａ〜２ｃにて送信電波と逆旋回の電波が受信されたとき（換言すれば送信電波が外部の物標に当たって反射してくる反射電波が受信されたとき）に、その受信信号が合成され、出力端子Ａからその合成した受信信号が出力されることになる。
【００４３】
また、９０度ハイブリッド回路２８ａ〜２８ｃの一方の入出力端子Ｄとアンテナセル２ａ〜２ｃの一方の給電端子Ｖとの間には、夫々、移相器３０ａ〜３０ｃが設けられているが、この移相器３０ａ〜３０ｃは、位相変化量Φを０度又は１８０度に切り換え可能であるため、この移相器３０ａ〜３０ｃの位相変化量Φを切り換えることにより、アンテナセル２ａ〜２ｃを介して送受信可能な円偏波の旋回方向を切り換えることができる。なお、この移相器３０ａ〜３０ｃの位相変化量Φは、ＥＣＵ１０により切り換えられる。
【００４４】
次に、９０度ハイブリッド回路２８ａ〜２８ｃの出力端子Ａは、夫々、ミキサ回路３２ａ〜３２ｃに接続されており、ミキサ回路３２ａ〜３２ｃには、第１電力分配器２４によりローカル信号として３つに分配された送信信号が夫々入力されている。つまり、本実施例では、ミキサ回路３２ａ〜３２ｃにて、９０度ハイブリッド回路２８ａ〜２８ｃの出力端子Ａから出力される受信信号と、発振器２２からの送信信号とを混合することにより、受信信号を、送信信号をローカル信号として、これら各信号の周波数の差の周波数を有する中間周波信号（ＩＦ信号）に変換するのである。
【００４５】
そして、これら各ミキサ回路３２ａ〜３２ｃからの出力信号（ＩＦ信号）は、ＩＦ回路３４ａ〜３４ｃに夫々入力され、各ＩＦ回路３４ａ〜３４ｃにおいて、増幅・波形整形された後、ＥＣＵ１０に夫々入力される。
次に、ＥＣＵ１０は、ＣＰＵ，ＲＯＭ，ＲＡＭ等を中心とする周知のマイクロコンピュータにより構成されており、障害物の検出を行う測定モードにあるときには、所定の測定周期毎に、ＦＭ−ＣＷレーダとしての送信制御を行う。即ち、発振器２２に出力する制御信号の電圧を所定の測定周期毎に、所定の下限電圧から上限電圧まで除々に変化させることにより、発振器２２から出力される送信信号の周波数を予め設定された下限周波数から上限周波数まで除々に変化させる、送信制御を実行するのである。
【００４６】
この結果、各アンテナセル２ａ〜２ｃからは、順次周波数が変化する送信信号（周波数変調信号）が、移相器３０ａ〜３０ｃの位相変化量Φ（０度又は１８０度）に対応した旋回方向の円偏波の電波として、所定の測定周期毎に繰返し放射されることになる。
【００４７】
また、ＥＣＵ１０は、この送信制御の実行中、ＩＦ回路３４ａ〜３４ｃからの出力信号（ＩＦ信号）を、図示しないＡ／Ｄ変換器を介して各々取り込み、その取り込んだ各ＩＦ信号の振幅又は位相或はその両方を比較することにより、アンテナ装置６の外部に存在する障害物の位置（方位）を検出すると共に、Ｉ／Ｆ信号を周波数分析することにより障害物までの距離及び相対速度を検出する、障害物検出処理を実行する。
【００４８】
そして、このように、送信制御の実行中に、障害物検出処理にて、障害物の方位，障害物までの距離，及び障害物との相対速度が検出されると、次に送信制御を開始するまでの間に、その検出結果から、車両が障害物に衝突する危険な状況にあるかどうかを判断し、衝突の危険性が高いと判断すると、警報装置１２を動作させて、車両運転者にその旨を報知する、衝突警報処理を実行する。
【００４９】
つまり、各アンテナセル２ａ〜２ｃから放射した電波が障害物に当たって反射すると、その電波の旋回方向は送信時とは逆旋回となり、障害物からの反射電波がアンテナセル２ａ〜２ｃにて受信された場合には、９０度ハイブリッド回路２８ａ〜２８ｃ，ミキサ回路３２ａ〜３２ｃ，及びＩＦ回路３４ａ〜３４ｃを介して、ＩＦ信号として、ＥＣＵ１０に入力されるため、ＥＣＵ１０においては、これら各部を介して各アンテナセル２ａ〜２ｃから入力される受信信号（ＩＦ信号）に基づき、障害物の有・無、並びに障害物の方位，障害物までの距離，障害物との相対速度等を検出して、車両が障害物に衝突する危険な状況にある場合には、車両運転者にその旨を報知し、車両走行時の安全性を向上するのである。
【００５０】
ところで、本実施例においては、各アンテナセル２ａ〜２ｃに円偏波用アンテナ素子を用いているため、各アンテナセル２ａ〜２ｃによる偏波識別により、自己が送信した電波が障害物に当たって反射してくる反射波のみを比較的良好に受信して障害物の検出を行うことができるようになるが、こうしたモノパルスレーダ装置を適用した車両用障害物検出装置が普及し、この装置を搭載した車両が多くなると、各車両間にて障害物検出用電波の電波干渉が発生し易くなり、この電波干渉によって、障害物の検出精度が低下するおそれがある。
【００５１】
そこで、本実施例では、ＥＣＵ１０において、図３又は図４に示す如き偏波切換処理を実行することにより、他の装置との電波干渉によって障害物の検出精度が低下するのを防止するようにされている。
即ち、図３に示す偏波切換処理では、Ｓ１００（Ｓ：ステップを表わす）にて、当該装置が障害物の検出動作を行う測定モードを終了しているか否か（測定終了？）を判断し、測定モードを終了していれば、そのまま当該処理を終了し、測定モードを終了していなければ、Ｓ１１０に移行して、上記送信制御及び障害物検出処理を実行する１測定ターンが終了するのを待つ。
【００５２】
そして、この１測定ターンが終了すると、Ｓ１２０に移行して、ＣＰＵに組込まれたランダム関数の演算回路に乱数Ｒan＃を発生させて、その値Ｒan＃を読み込み、続くＳ１３０にて、乱数Ｒan＃が偶数か否かを判断し、乱数Ｒan＃が奇数であり偶数でなければ、Ｓ１４０にて、移相器３０ａ〜３０ｃの位相変化量Φを０度に設定して、Ｓ１００に移行し、逆に乱数Ｒan＃が偶数であれば、Ｓ１５０にて、移相器３０ａ〜３０ｃの位相変化量Φを１８０度に設定して、Ｓ１００に移行する。
【００５３】
つまり、図３に示す偏波切換処理では、上述の送信制御及び障害物検出処理の実行後、次にこの制御を開始するまでの間に、乱数Ｒan＃を発生させて、その乱数Ｒan＃が偶数か奇数かによって、移相器３０ａ〜３０ｃの位相変化量Φを０度又は１８０度にランダムに切り換えるのである。
【００５４】
この結果、例えば、Ｓ１４０にて、移相器３０ａ〜３０ｃの位相変化量Φを０度に設定した場合に、他の装置からの送信電波又はその反射電波波がアンテナセル２ａ〜２ｃにて受信され、その受信信号が、９０度ハイブリッド回路２８ａ〜２８ｃ，ミキサ回路３２ａ〜３２ｃ，及びＩＦ回路３４ａ〜３４ｃを通って、ＥＣＵ１０に入力され、ＥＣＵ１０において各ＩＦ信号に基づき障害物を検出できなくなった場合であっても、その後、Ｓ１５０にて移相器３０ａ〜３０ｃの位相変化量Φが１８０度に切り換えられると、当該装置にて送受信可能な円偏波の旋回方向が右旋回から左旋回（或はその逆）に変化するため、他の装置からの電波がアンテナセル２ａ〜２ｃにて受信されても、その受信信号は、９０度ハイブリッド回路２８ａ〜２８ｃにてカットされ、ＥＣＵ１０には各アンテナセル２ａ〜２ｃから放射した電波の反射電波に対応した受信信号のＩＦ信号のみが入力されることになり、ＥＣＵ１０側では、このとき入力される各ＩＦ信号に基づき、障害物を正確に検出できるようになる。
【００５５】
一方、図４に示す偏波切換処理では、図３に示した処理と同様、Ｓ１００にて、当該装置が障害物の測定を終了するかどうかを判断し、測定を終了する場合には、そのまま当該処理を終了し、測定を継続する場合には、Ｓ１１０にて１測定ターンが終了するのを待つ。
【００５６】
そして、この１測定ターンが終了すると、Ｓ２２０に移行して、１測定ターンの間に取り込んだ各ＩＦ信号の振幅に基づき、その間に受信した受信信号の中に、予め設定された設定レベルよりも高い受信電力のピークがある受信信号が存在するかどうかを判断し、設定レベルよりも高い受信電力のピークがある受信信号が存在する場合には、その受信信号は何等かの電波干渉の影響を受けていると判断して、Ｓ２３０に移行し、移相器３０ａ〜３０ｃの位相変化量Φを、現時点の位相変化量から反転して、Ｓ１００に移行し、そうでなければ、そのままＳ１００に移行する。
【００５７】
つまり、図４に示す偏波切換処理では、上述の送信制御及び障害物検出処理の実行後、この制御を実行中に取り込んだＩＦ信号に基づき、設定レベルよりも高い受信電力のピークがある受信信号が存在したかどうかを判断することにより、今まで受信した受信信号は他の装置からの電波の影響を受けているかどうかを判定し、受信電力が異常に大きい場合には、何等かの電波干渉の影響を受けているものとして、各移相器３０ａ〜３０ｃの位相変化量Φを今までの位相変化量（０度又は１８０度）から１８０度反転させた位相変化量（１８０度又は０度）に切り換えるのである。この結果、図３に示した偏波切換処理と同様、障害物を、他の装置からの送信電波に影響されることなく、正確に検出できるようになる。
【００５８】
以上説明したように、本実施例の車両用障害物検出装置によれば、アンテナ装置６を構成するアンテナセル２ａ〜２ｃに、２端子給電型の円偏波用アンテナ素子を用いると共に、各アンテナセル２ａ〜２ｃ毎に送信信号の供給及び受信信号の取り出しを行う信号入出力回路に、９０度ハイブリッド回路２８ａ〜２８ｃを用いることにより、各アンテナセル２ａ〜２ｃから所定旋回方向の円偏波の電波を送信させ、各アンテナセル２ａ〜２ｃにて、送信時とは異なる旋回方向の電波が受信された場合にのみ、その受信信号を取り込むように構成され、しかも、その送受信時の電波の旋回方向を、移相器３０ａ〜３０ｃを用いて切り換えるようにされている。
【００５９】
従って、本実施例によれば、当該装置と同様の車両用障害物検出装置を搭載した車両や当該装置とは異なる他の通信装置との間で、電波干渉が発生しても、その干渉波による影響を受けることなく、障害物を検出することが可能になり、障害物の検出精度を向上することができる。そして、このように障害物の検出精度を向上できるため、車両の障害物への衝突の危険性を極めて正確に予測して、車両運転者に警報を与えることができ、車両の走行安全性を高めることができる。
【００６０】
また、本実施例の車両用障害物検出装置は、モノパルスレーダ装置に、ＦＭ−ＣＷレーダの技術を適用して、障害物の方位，障害物との距離，及び障害物との相対速度を検出するようにされているため、車両が障害物に衝突する危険性を正確且つ速やかに検出することができ、これによっても車両の走行安全性を高めることができる。
【００６１】
また、９０度ハイブリッド回路２８ａ〜２８ｃを、例えば、ラットレース電力合成回路，ウィルキンソン電力合成回路等にて構成すれば、９０度ハイブリッド回路２８ａ〜２８ｃを、アンテナセル２ａ〜２ｃ及び移相器３０ａ〜３０ｃと共に、所定の基板状にマイクロストリップラインにて構成して、これら各部を、所謂平面アンテナとして実現することができるため、装置の小型・軽量化を図ることもできる。
【００６２】
なお、本実施例では、９０度ハイブリッド回路２８ａ〜２８ｃの入出力端子Ｄ側に移相器３０ａ〜３０ｃを設けるものとして説明したが、この移相器３０ａ〜３０ｃは、９０度ハイブリッド回路２８ａ〜２８ｃの入出力端子Ｃ，Ｄのいずれに設けてもよい。
【００６３】
また、本実施例では、アンテナ装置６に３個のアンテナセル２ａ〜２ｃを設けた車両用障害物検出装置について説明したが、モノパルスレーダ装置では、最低２個のアンテナ素子を備えていれば、外部の物標を検出することができるため、アンテナセルを２個備えたアンテナ装置を使用してもよい。また、アンテナセルを更に増やして、隣接するアンテナセルにて得られた受信信号の振幅や位相等から各々障害物の方位や距離を各々検出し、その検出結果から、障害物の位置を特定するようにしてもよく、この場合には、障害物の位置をより高精度に検出することが可能になる。
（第２実施例）
ここで、上記実施例では、ミキサ回路３２ａ〜３２ｃにて周波数変換された各アンテナセル２ａ〜２ｃの受信信号の中間周波信号（ＩＦ信号）を、夫々、ＩＦ回路３４ａ〜３４ｃを用いて信号処理し、ＥＣＵ１０に入力するように構成したが、例えば、図５に示す第２実施例の車両用障害物検出装置のように、各ミキサ回路３２ａ〜３２ｃから出力される３種のＩＦ信号の中から一つのＩＦ信号を選択して出力する出力スイッチ回路３６を設け、この出力スイッチ回路３６が選択するＩＦ信号をＥＣＵ１０側にて高速に切り換えるように構成してもよい。つまり、３種のＩＦ信号を時分割にて高速に取り込むようにしてもよい。
【００６４】
そして、このようにすれば、ＩＦ信号を信号処理するＩＦ回路３４及びＥＣＵ１０内にてＩＦ信号をＡ／Ｄ変換するＡ／Ｄ変換器を、アンテナセルの個数に関係なく１個にすることができ、第１実施例の装置に比べて、装置構成をより簡素化して、装置の小型・軽量化を図ることができる。
（第３実施例）
また、例えば、図６に示す第３実施例の車両用障害物検出装置のように、各９０度ハイブリッド回路２８ａ〜２８ｃの出力端子Ａと、ミキサ回路３２との間に、各９０度ハイブリッド回路２８ａ〜２８ｃからの出力信号（つまり各アンテナセル２ａ〜２ｃによる受信信号）の中から、受信信号を一つ選択して取り込む入力スイッチ回路３８を設け、この入力スイッチ回路３８が選択する受信信号をＥＣＵ１０側にて高速に切り換えるように構成してもよい。つまり、９０度ハイブリッド回路２８ａ〜２８ｃを介して得られる各アンテナセル２ａ〜２ｃからの受信信号を、時分割にて高速に取り込むようにしてもよい。
そして、このようにすれば、ＩＦ回路３４及びＡ／Ｄ変換器のみならず、ミキサ回路３２をも、アンテナセルの個数に関係なく１個にすることができ、第２実施例の装置よりも更に装置構成を簡素化することができ、装置の小型・軽量化を図ることができる。また、この場合、第１電力分配器２４では、発振器２２からの送信信号を、第２電力分配器２６側とミキサ３２側とに２分配すればよく、第１電力分配器２４を通過する各送信信号の減衰量を少なくすることができる。従って、発振器２２からの送信信号の出力電力を低減することもできる。
【００６５】
なお、この場合、受信信号が選択されない（換言すればミキサ回路３２に接続されない）９０度ハイブリッド回路において、出力端子Ａに出力された受信信号が入出力端子Ｃ，Ｄ側に反射することのないように、入力スイッチ回路３８には、各９０度ハイブリッド回路２８ａ〜２８ｃの出力端子Ａを、所定の回路インピーダンスにて終端する終端抵抗Ｒａ〜Ｒｃを設け、出力端子Ａをミキサ回路３２に接続しない９０度ハイブリッド回路の出力端子Ａは、対応する終端抵抗Ｒａ〜Ｒｃにて終端できるようにする必要はある。
（第４実施例）
また次に、上記各実施例では、９０度ハイブリッド回路２８ａ〜２８ｃを介して得られた各アンテナセル２ａ〜２ｃからの受信信号を中間周波信号（ＩＦ信号）に周波数変換し、これを同時に或は時分割にてＥＣＵ１０に各々入力して、ＥＣＵ１０側で、これら３種のＩＦ信号を用いて、障害物の位置（方位，距離等）を検出するように構成したが、例えば、図７に示す第４実施例の車両用障害物検出装置のように、ミキサ回路３２ａ〜３２ｃにて中間周波信号に周波数変換された各アンテナセル２ａ〜２ｃからの受信信号（ＩＦ信号）の中から、任意の一対のＩＦ信号を選択する受信信号選択回路４０を設け、この受信信号選択回路４０にて選択された一対のＩＦ信号を、夫々、一対のＩＦ回路３４-1，３４-2を用いて信号処理し、ＥＣＵ１０に入力するように構成し、更に、ＥＣＵ１０側にて、受信信号選択回路４０が選択するＩＦ信号を変更することにより、障害物検出に使用するアンテナセルの間隔を切り換えるようにしてもよい。
【００６６】
つまり、モノパルスレーダ装置は、基本的には、一対のアンテナ素子にて得られた受信信号の振幅又は位相の差から物標の方位を検出するものであるため、２個のアンテナ素子を備えていれば、本発明のモノパルスレーダ装置を実現できるが、単に２個のアンテナ素子のみで物標の方位及び距離をしようとすると、例えば、図８（ａ）に示す如く、一対のアンテナ素子ａ，ｂの間隔Ｄ１が狭いと、物標Ｘまでの距離Ｌが短い場合には、各アンテナ素子ａ，ｂと物標Ｘとを結ぶ直線にて形成される角度θ１が比較的大きくなって、受信信号の振幅又は位相の差から物標の位置を良好に検出できるものの、物標Ｘまでの距離Ｌが長い場合には、上記角度θ１が小さくなり、各アンテナ素子ａ，ｂにて得られた受信信号の振幅や位相の差（図に示す△Ｌ１に対応する）も小さくなるため、物標Ｘの位置を良好に検出できなくなる。しかし、例えば、図８（ｂ）に示す如く、物標Ｘの検出に使用する使用するアンテナ素子を、間隔Ｄ１の狭いａ，ｂから、間隔Ｄ２の広いａ，ｃに切り換えれば、物標Ｘまでの距離Ｌが長い場合でも、各アンテナ素子ａ，ｃと物標Ｘとを結ぶ直線にて形成される角度θ２が比較的大きくなって、各アンテナ素子ａ，ｃにて得られる受信信号の振幅や位相の差（図に示す△Ｌ２に対応する）を大きくすることができ、物標の位置を良好に検出できるようになる。
【００６７】
そこで、本実施例では、受信信号選択回路４０により、ミキサ回路３２ａ〜３２ｃにて周波数変換した３種のＩＦ信号の中から任意の一対のＩＦ信号を選択して、ＥＣＵ１０に入力できるようにし、ＥＣＵ１０側にて、受信信号選択回路４０が選択するＩＦ信号，延いては障害物検出に使用するアンテナセルの間隔を切り換えることにより、ＥＣＵ１０において、障害物の位置を常に良好に検出できるようにしているのである。
【００６８】
なお、ＥＣＵ１０において、受信信号選択回路４０が選択するＩＦ信号を実際に切り換える場合には、例えば、図９に示す如き受信信号切換処理を実行するようにすればよい。
即ち、図９に示す受信信号切換処理においては、前述の図３及び図４に示した偏波切換処理と同様、Ｓ１００にて、当該装置が障害物の測定を終了するかどうかを判断し、測定を終了する場合には、そのまま当該処理を終了し、測定を継続する場合には、Ｓ１１０にて１測定ターンが終了するのを待つ。そして、この１測定ターンが終了すると、Ｓ３２０に移行して、１測定ターンの間に取り込んだＩＦ信号の周波数が非常に大きく、予め設定された設定距離以上の点に物標（障害物）が存在するか否かを判定し、障害物が設定距離以上の点に存在する場合（つまり障害物までの距離が長い場合）には、Ｓ３３０に移行して、受信信号を取り込むアンテナの間隔を広くするために、受信信号選択回路４０の一方のスイッチＳＷ１をアンテナセル２ａに対応したミキサ３２ａ側に、他方のスイッチＳＷ２をアンテナセル２ｃに対応したミキサ３２ｃ側に、夫々切り換えて、Ｓ１００に移行し、逆に、障害物が設定距離以上の点に存在しない場合（つまり障害物までの距離が短いか、障害物を検出できていない場合）には、受信信号を取り込むアンテナの間隔を狭くするために、受信信号選択回路４０の一方のスイッチＳＷ１をアンテナセル２ａに対応したミキサ３２ａ側に、他方のスイッチＳＷ２をアンテナセル２ｂに対応したミキサ３２ｂ側に、夫々切り換えて、Ｓ１００に移行する。
【００６９】
この結果、本実施例によれば、当該装置から障害物までの距離に影響されることなく、障害物の方位を常に正確に検出できるようになり、角度測定分解能に優れた障害物検出装置を実現できる。
以上、本発明を、第１〜第４実施例を挙げて具体的に説明したが、本発明は、こうした実施例に限定されるものではなく、種々の態様をとることができる。例えば、上記各実施例では、車両に搭載されて障害物の検出を行う車両用障害物検出装置について説明したが、本発明は、こうした障害物検出用のレーダ装置以外にも、例えば、車両を他の車両や目標物に追従させて自動走行させる無人搬送車誘導用のレーダ装置に適用することもできる。
【図面の簡単な説明】
【図１】第１実施例の車両用障害物検出装置の構成を表わすブロック図である。
【図２】アンテナ装置の指向特性を説明する説明図である。
【図３】ＥＣＵにおいて実行される偏波切換処理の一例を表わすフローチャートである。
【図４】同じくＥＣＵにおいて実行される偏波切換処理の他の例を表わすフローチャートである。
【図５】第２実施例の車両用障害物検出装置の構成を表わすブロック図である。
【図６】第３実施例の車両用障害物検出装置の構成を表わすブロック図である。
【図７】第４実施例の車両用障害物検出装置の構成を表わすブロック図である。
【図８】アンテナ素子の間隔と物標の検出精度との関係を説明する説明図である。
【図９】第４実施例のＥＣＵにおいて実行される受信信号切換処理を表わすフローチャートである。
【符号の説明】
２ａ〜２ｃ…アンテナセル（２端子給電型円偏波用アンテナ素子）
４…誘電体レンズ６…アンテナ装置（マルチビーム誘電体レンズアンテナ）１０…ＥＣＵ（電子制御装置）１２…警報装置２０…送受信回路
２２…発振器２４…第１電力分配器２６…第２電力分配器
２８ａ〜２８ｃ…９０度ハイブリッド回路
３０ａ〜３０ｃ…移相器（位相変化量可変型移相器）
３２，３２ａ〜３０ｃ…ミキサ回路３４，３４ａ〜３４ｃ…ＩＦ回路
３６…出力スイッチ回路３８…入力スイッチ回路
４０…受信信号選択回路[0001]
BACKGROUND OF THE INVENTION
The present invention includes a plurality of antenna elements arranged so that a part of the radiation pattern overlaps, transmits and receives a predetermined radio wave using each antenna element, and based on a received signal obtained by each antenna element, The present invention relates to a monopulse radar device that detects the azimuth and the like of a target existing in the field.
[0002]
[Prior art]
Conventionally, it has been expected to realize an obstacle detection radar using radio waves as a transmission medium as means for assisting a driver's vision in order to prevent a car collision. Further, in this type of radar apparatus, it is an extremely important technique for predicting the possibility of a collision to determine the horizontal position of an obstacle such as a vehicle traveling in front. For this reason, it is considered that a monopulse radar device as disclosed in, for example, Japanese Patent Laid-Open No. Sho 61-167890 is effective as such an automotive radar device.
[0003]
In other words, the monopulse radar device is generally used as an aircraft tracking radar, but it is an excellent radar device for discriminating the position in the horizontal or vertical direction. It can be considered to function very effectively in the presence of obstacles.
[0004]
[Problems to be solved by the invention]
However, as collision prevention systems using such monopulse radar devices become widespread and the number of vehicles equipped with them increases, radio wave interference between transmitted and received radio waves becomes unavoidable, and the ability to detect targets such as obstacles is reduced. It is expected to decline.
[0005]
The present invention has been made in view of these problems, and provides a monopulse radar device that can suppress the mutual interference of radio waves generated with other communication devices that generate radio waves and can always obtain a good target detection capability. The purpose is to do.
[0006]
[Means for Solving the Problems]
  The invention according to claim 1, which has been made to achieve the object,It can transmit and receive circularly polarized radio wavesA plurality of antenna elements arranged such that a part of the radiation pattern overlaps;Polarization switching means for switching the turning direction of circularly polarized waves transmitted and received by each antenna element, and a frequency modulation signal whose frequency changes at a predetermined cycle as a transmission signalSignal generating means for generating, and signal input / output means for inputting a transmission signal from the signal generating means to each antenna element to radiate a radio wave from each antenna element and for extracting a received signal received by each antenna element. And a received signal from each antenna element obtained via the signal input / output meansIs mixed with the transmission signal to convert each received signal into an intermediate frequency signal, and based on each intermediate frequency signal converted by the frequency converterIn a monopulse radar device comprising a target detection means for detecting an external target,The frequency conversion means sequentially selects a plurality of frequency conversion sections that respectively convert the received signals from the antenna elements using the transmission signals, and an intermediate frequency signal that has been frequency converted by the plurality of frequency conversion sections. And an output switch means for outputting to the target detecting means.
[0007]
  In the monopulse radar apparatus according to claim 1, configured as described above, the signal input / output means arranges the transmission signal (frequency modulation signal) generated from the signal generation means so that a part of the radiation pattern overlaps. Input to each of the plurality of antenna elements, radiate a radio wave from each antenna element, and take out each received signal received by each antenna element,The frequency conversion means isThe extracted received signalIs mixed with the transmission signal and converted to an intermediate frequency signal. AndTarget detection meansBased on each converted intermediate frequency signalDetect external targets. In this apparatus, a circularly polarized antenna element capable of transmitting and receiving circularly polarized radio waves is used for each antenna element, and the polarization switching means switches the direction of circularly polarized wave transmitted and received by each antenna element.
  In particular, in this apparatus, the frequency conversion means includes a plurality of frequency conversion units and output switch means. The frequency conversion unit converts the frequency of the received signal from each antenna element using the transmission signal, and the output switch means sequentially selects the intermediate frequency signals frequency-converted by the plurality of frequency conversion units to detect the target. Output to the means.
[0008]
  In other words, the monopulse radar device radiates radio waves from a plurality of antenna elements arranged so that part of the radiation pattern overlaps, and the reflected waves reflected by the radiated radio waves hitting external targets are reflected at each antenna element. By receiving, the azimuth of the target is detected from the difference in amplitude or phase of the received signal obtained by each antenna element, but there is another monopulse radar device of the same standard near the device. If there is a communication device that transmits or receives signals in the same frequency band as the radio waves transmitted and received by the device, radio interference occurs between these other devices, and the target is detected by the interference waves. The ability will be reduced.
  Therefore, in the monopulse radar device according to claim 1, a circularly polarized antenna element capable of transmitting and receiving circularly polarized radio waves is used for each antenna element, and each antenna element is transmitted and received by the polarization switching means. By switching the turning direction of the wave, a decrease in detection capability due to the interference wave is prevented by the polarization identification of each antenna element.
[0009]
  Further, the monopulse radar apparatus having the above-described configuration causes a transmission signal whose frequency continuously rises or falls from an antenna element to a conventionally known monopulse radar apparatus, and receives a reception signal received by the antenna element. The transmission signal currently being transmitted is mixed using frequency conversion means such as a mixer circuit, and the reception signal is changed to an intermediate frequency signal having a frequency corresponding to the deviation between the frequency of the reception signal and the frequency of the transmission signal. FM− that detects the time from the frequency of the intermediate frequency signal until the transmission signal radiated from the antenna element hits the target and returns to the antenna element, and thus the distance from the antenna element to the target. The CW radar technology is applied.
  In realizing this FM-CW monopulse radar apparatus, the intermediate frequency signal frequency-converted by the frequency converter is sequentially input to the target detection means in a time-division manner by the output switch means. .
[0010]
  As a result, according to the monopulse radar device of the first aspect, even if it is applied to a system that is mounted on a vehicle and detects an obstacle or the like, the obstacle is not affected by a transmission radio wave from another device. It is possible to accurately detect a target such as a vehicle, and it is possible to improve the traveling safety of the vehicle by enhancing the target detection capability.
  Moreover, on the target detection means side that receives the reception signals from the respective antenna elements converted into the intermediate frequency signals by the frequency conversion means, the direction of the target and the distance from the respective reception signals (intermediate frequency signals) to the target Can be obtained easily and accurately, the direction of the obstacle and the distance to the obstacle are accurately detected, and the vehicle driver is immediately informed of the danger of a collision with the obstacle. Safety during running can be improved.
Further, by providing the output switch means, the target detection means amplifies the inputted intermediate frequency signal in order to accurately obtain the direction and distance of the target from the intermediate frequency signal corresponding to each antenna element. It is not necessary to provide a plurality of signal processing circuits for waveform shaping corresponding to each antenna element, and the apparatus configuration can be simplified.
[0011]
As the polarization switching means for switching the turning direction of the circular polarization of each antenna element, for example, a target detection operation for detecting a target by transmitting a radio wave from each antenna element is performed once or a plurality of times. It is possible to alternately switch the direction of circular polarization rotationAnd againFor example, when a target detection operation is normally performed using circularly polarized waves in any swivel direction, and the received signal obtained by each antenna element has a signal level that is not normally possible, the swirl direction of the circularly polarized waves May be switched.
[0012]
  Next, the invention described in claim 2 is described in claim 1.Similar to the invention, the monopulse radar device includes a plurality of antenna elements, polarization switching means, signal generation means, signal input / output means, frequency conversion means, and target detection means.
[0013]
  In the monopulse radar device according to claim 2, the frequency conversion means selects the input signal that sequentially receives and receives the reception signal input from each antenna element, and the reception signal that is sequentially input from the input switch means. A frequency conversion unit that sequentially converts the frequency using the transmission signal and outputs the frequency to the target detection unit.
[0014]
  That is, in the monopulse radar device according to the second aspect, the received signal from each antenna element inputted via the signal input / output means is taken in time division by the input switch means, and the taken received signal is taken. The frequency converter converts the signal into an intermediate frequency signal.
[0015]
  Therefore, according to the monopulse radar device of the second aspect, like the device of the first aspect, the direction of the obstacle and the distance to the obstacle are accurately detected, and the vehicle collides with the obstacle. In addition to being able to promptly notify the vehicle driver of the danger of the vehicle and improving the safety during vehicle travel, it is not necessary to provide a plurality of signal processing circuits in the target detection means, and the device configuration can be simplified. . Moreover, in the monopulse radar device according to claim 2, since it is not necessary to provide a plurality of frequency conversion units for converting the received signal into the intermediate frequency in correspondence with the antenna element in the frequency conversion means, the device configuration can be further simplified. it can.
[0016]
  In addition, in order to convert the received signal into the intermediate frequency signal in the frequency conversion unit, the transmission signal output from the signal generation unit is distributed not only to the signal input / output unit corresponding to each antenna element but also to the frequency conversion unit. Although it is necessary, in the apparatus according to claim 2, since this frequency converter can be made one regardless of the number of antenna elements, a plurality of frequency converters are provided corresponding to each antenna element. Compared to the case, it is possible to suppress the power reduction of the transmission signal due to the distribution of the transmission signal, and to reduce the output power of the signal generating means.
[0017]
  Next, the invention described in claim 3 includes at least three or more antenna elements that can transmit and receive circularly polarized radio waves and are arranged so that a part of the radiation patterns overlap. As in the invention described in (1), the monopulse radar apparatus includes polarization switching means, signal generation means, signal input / output means, frequency conversion means, and target detection means.
[0018]
  Further, in the monopulse radar device according to claim 3, the frequency converting means corresponds to the antenna element, and three or more frequency converters each convert the frequency of the received signal from each antenna element using the transmission signal. And a signal selection means for selecting a pair of intermediate frequency signals from the intermediate frequency signals output from the respective frequency converters and outputting the selected signal to the target detection means, and the intermediate frequency selected by the signal selection means It is characterized in that the interval between antenna elements used for target detection can be adjusted by changing the signal.
[0019]
  That is, in the monopulse radar device, basically, two antenna elements are arranged at predetermined intervals so that a part of the radiation pattern overlaps, and the amplitude of the received signal obtained by each antenna element or Since the azimuth of the target is detected from the phase difference, an FM-CW type monopulse radar apparatus can be realized if two antenna elements are provided. However, when trying to determine the direction and distance of a target with only two antenna elements, for example, if the distance between the antenna elements is narrow and the distance to the target is short, the amplitude of the received signal of each antenna element Alternatively, the position of the target can be detected well from the phase difference, but if the distance to the target is long, the difference in amplitude and phase of the received signal obtained by each antenna element becomes extremely small, and the target In some cases, the position of the mark cannot be detected well.
[0020]
  Therefore, in the monopulse radar apparatus according to claim 3, at least three antenna elements are provided, and signal selection means is used from among the received signals from the respective antenna elements converted into intermediate frequency signals by the frequency converter. Thus, it is possible to adjust (switch) the distance between the antenna elements used to detect the target.
[0021]
  As a result, according to the monopulse radar device of the third aspect, for example, by switching the intermediate frequency signal selected by the signal selection means according to the distance from the device to the target, the detection state of the target, etc. The distance between the antenna elements used for target detection can be switched to a value that allows the target to be detected best, and the detection accuracy of the target (especially its orientation) is further improved, resulting in angle measurement resolution. It is possible to realize a radar device that is superior to the above.
[0022]
  Next, the invention according to claim 4 is the monopulse radar apparatus according to claim 3, wherein the target detection means is configured to detect a distance from the monopulse radar apparatus to an external target. Further, the selection control means is based on the distance detected by the target detection means, so that the longer the distance, the wider the distance between the pair of antenna elements corresponding to the pair of intermediate frequency signals. To control.
[0023]
  According to the monopulse radar device according to claim 4 configured in this way, for example, the distance between the antennas is widened when the distance to the target is equal to or larger than a predetermined set distance, and the distance between the antennas is not larger than the set distance. Since a pair of intermediate frequency signals can be switched according to the distance to the target (in other words, a pair of antennas can be switched), the distance from the monopulse radar device to the target is affected. This makes it possible to detect the target accurately.
[0024]
  Next, the invention according to claim 5 is the monopulse radar device according to any one of claims 1 to 4, wherein the random number generating means for generating a random number every time the target detecting means detects the target. And a switching control means for operating the polarization switching means based on the random number generated by the random number generation means each time the target detection means detects the target. That is, every time the target detection means detects a target, the direction of rotation of the circular polarization is randomly switched.For example, if the generated random number is an even number, the right-handed circularly polarized wave is generated. It can be like a wave.
[0025]
  Therefore, according to the monopulse radar device of the fifth aspect, even if radio wave interference occurs with a monopulse radar device or the like similar to the device, the target is detected without being affected by the interference wave. And the accuracy of target detection can be improved.
[0026]
  Next, the invention according to claim 6 is the monopulse radar device according to any one of claims 1 to 5, wherein each of the antenna elements is a two-terminal feed type circularly polarized antenna element, and the signal Input / output means is provided for each antenna element, distributes the transmission signal to transmission signals having a phase difference of 90 degrees, outputs the transmission signals to the two power supply terminals of the antenna element, and inputs from the power supply terminals of the antenna element. The polarization switching means comprising a plurality of 90-degree hybrid circuits that synthesize a received signal having a phase difference of 90 degrees in the opposite direction to the distributed transmission signal from a pair of received signals. Is provided in one of a pair of signal paths connecting the 90-degree hybrid circuit and the feeding terminal of the antenna element, and the phase change amount can be switched between 0 degree and 180 degrees. Characterized by comprising the quantity variable phase shifter.
[0027]
  That is, the 90-degree hybrid circuit distributes the signal input to the input terminal into signals having a phase difference of 90 degrees and outputs the signals from a pair of input / output terminals. When a signal having −90 degrees) is input, the signals are combined and output from the output terminal. Therefore, in the monopulse radar device according to claim 2, each antenna element has a phase difference of 90 degrees. Using a two-terminal feed type circularly polarized antenna element that transmits a circularly polarized wave in a predetermined turning direction, a pair of feed terminals of each antenna element, and a pair of input / output terminals of a 90-degree hybrid circuit Are connected to each other, and the transmission signal from the signal generating means is input to the input terminal of the 90-degree hybrid circuit so that the transmission signal having a phase difference of 90 degrees is fed to the pair of feeding terminals of each antenna element. Element The circularly polarized radio wave in a predetermined turning direction of letting radiation.
[0028]
  Then, when circularly polarized radio waves in a predetermined turning direction are radiated from each antenna element in this way, and the radiated radio wave hits an external target and is reflected, the turning direction of the reflected wave is opposite to that during transmission, A signal having a phase difference (−90 degrees) in the opposite direction to that at the time of transmission is induced at each antenna element and a pair of feeding terminals of each antenna element. When a reflected wave is received, the received signal is synthesized by a 90-degree hybrid circuit and output from the output terminal to the target detection means. By identifying the polarization of each antenna element, It is possible to detect a target by receiving only the radio wave reflected by the target.
[0029]
  In addition, a phase shifter capable of switching the phase change amount to either 0 degrees or 180 degrees is provided in one of the pair of signal paths connecting the 90-degree hybrid circuit and the feeding terminal of the antenna element. By switching the phase change amount of this phase shifter, the phase difference of the transmission signal input to the feeding terminal of the antenna element is switched to either 90 degrees or -90 degrees, and the turning direction of the radio wave radiated from the antenna element is changed. Switching between right turn and left turn is possible.
[0030]
  Therefore, according to the monopulse radar device according to claim 6, the monopulse radar device according to any one of claims 1 to 5 can be realized with a relatively simple configuration, and the switching of the turning direction of the radio wave is also simple. Can be done.
  In other words, the monopulse radar device according to any one of claims 1 to 5 is configured such that, for example, each antenna element is applied with a magnetic field in a direction determined by a waveguide circularly polarized antenna and power supplied to the antenna, thereby generating radio waves. It can also be realized by configuring the polarizer to rotate, configuring the signal input / output means with a circulator, and switching the polarization switching means to switch the direction of the circularly polarized wave by switching the direction of the magnetic field generated by the polarizer. In this case, since a circulator or the like which is a ferrite circuit is used, the apparatus becomes large and the apparatus configuration becomes complicated.
[0031]
  On the other hand, according to the monopulse radar apparatus of the sixth aspect, the high-frequency circuit unit including the antenna element, the signal input / output means, and the polarization switching means is replaced with a two-terminal feed type circularly polarized antenna element, 90 degrees. Since the hybrid circuit and the phase change variable phase shifter are used, these parts can be realized without using a ferrite circuit, and the apparatus configuration can be simplified and the size can be reduced.
[0032]
  Next, according to a seventh aspect of the present invention, in the monopulse radar device according to the sixth aspect, the transmission / reception high-frequency circuit unit including the antenna element, the 90-degree hybrid circuit, and the phase shifter is provided on a predetermined substrate. And a planar circuit formed of a conductive pattern.
[0033]
  Thus, in the monopulse radar device according to claim 7, since the high-frequency circuit unit is constituted by a planar circuit made of a conductive pattern (microstrip line) on a predetermined substrate, the monopulse radar device is made smaller. The range of use of the device can be expanded.
[0034]
  In order to configure the high-frequency circuit unit with a planar circuit, for example, the 90-degree hybrid circuit is configured with a hybrid circuit that can be configured with a microstrip line such as a rat race power synthesis circuit or a Wilkinson power synthesis circuit. You can do it.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
A vehicle obstacle detection device according to an embodiment to which the present invention is applied will be described below. (First embodiment)
FIG. 1 is a block diagram showing the configuration of the vehicle obstacle detection device of the first embodiment.
[0036]
As shown in FIG. 1, the vehicle obstacle detection device according to the present embodiment includes a plurality (three in the present embodiment) of two-terminal feed type circularly polarized antenna elements (hereinafter simply referred to as antenna cells) 2a, 2b, 2c. And a multi-beam dielectric lens antenna (hereinafter simply referred to as an antenna device) 6 composed of a dielectric lens 4 and circularly polarized radio waves in a predetermined turning direction from each antenna cell 2a to 2c of the antenna device 6 and each antenna. Based on the received signals from the cells 2a to 2c, the position of an obstacle existing in front of the dielectric lens 4 is detected. When there is a possibility that the vehicle may collide with the obstacle, the alarm device 12 is operated to drive the vehicle. An electronic control device (hereinafter simply referred to as an ECU) 10 for notifying the user of the fact, and circularly polarized radio waves are radiated from the antenna cells 2a to 2c in accordance with output signals from the ECU 10, Reception circuit 20 processes the received signal obtained by the antenna cell 2a~2c input to ECU 10, and a.
[0037]
Here, in the antenna device 6, the antenna cells 2 a to 2 c are arranged at predetermined intervals in the horizontal direction, and the radiation patterns (directivity) of the antenna cells 2 a to 2 c are changed by the dielectric lens 4 as shown in FIG. As shown in (a) to (c), the radiation patterns are respectively different in the horizontal direction and partially overlapped.
[0038]
That is, among the three antenna cells 2a to 2c, the central antenna cell 2b is substantially symmetrical with respect to the central axis of the dielectric lens 4 indicated by a dotted line in the drawing as shown in FIG. As shown in FIGS. 2A and 2C, the left and right antenna cells 2a and 2c have radiation patterns that are biased to the right or left with respect to the central axis of the dielectric lens 4 indicated by a dotted line in the drawing. Has been.
[0039]
Note that the radiation pattern (directivity) of the entire antenna device 6 is a radiation pattern shown in FIG. 2D, which is a combination of the radiation patterns of the antenna cells 2a to 2c. Next, in the transmission / reception circuit 20, a voltage-controlled variable frequency oscillator (hereinafter simply referred to as an oscillator) that generates a high-frequency signal for transmission (transmission signal) having a predetermined frequency in accordance with a voltage-controlled control signal output from the ECU 10. ) 22 and a power supply signal for supplying the transmission signal from the oscillator 22 to each of the antenna cells 2a to 2c and three local signals for frequency conversion of the reception signals obtained by the antenna cells 2a to 2c. The first power distributor 24 that distributes the power to the antenna cell 2 and the transmission signal distributed as the power feeding signal by the first power distributor 24 as the power feeding signal to be supplied to the antenna cells 2a to 2c, respectively. A second power distributor 26 for distributing is provided.
[0040]
And the transmission signal with respect to each antenna cell 2a-2c distributed by the 2nd power divider | distributor 26 is each input to the input terminal B of 90 degree hybrid circuit 28a-28c provided corresponding to each antenna cell 2a-2c. Entered.
The 90-degree hybrid circuits 28a to 28c distribute the transmission signal input to the input terminal B in half by a phase difference of 90 degrees and output it from the pair of input / output terminals C and D. Conversely, the input / output terminals When a signal having a phase opposite to the transmission signal (phase difference -90 degrees) is received at C and D, the signals are combined and output from the output terminal A. The pair of input / output terminals C and D One input / output terminal C is directly connected to one feeding terminal H of the corresponding antenna cell 2a to 2c, and the other input / output terminal D is connected to the other feeding terminal V of the corresponding antenna cell 2a to 2c. Are connected via phase change variable phase shifters (hereinafter simply referred to as phase shifters) 30a to 30c capable of switching the phase change amount Φ to 0 degree or 180 degrees.
[0041]
Therefore, the transmission signals input from the second power distributor 26 to the 90-degree hybrid circuits 28a to 28c are respectively supplied to the pair of power supply terminals of the antenna cells 2a to 2c as transmission signals having a phase difference of 90 degrees. Each of the antenna cells 2a to 2c radiates a circularly polarized radio wave in a predetermined turning direction.
[0042]
When each antenna cell 2a to 2c receives a circularly polarized radio wave that is reversely rotated from the radiated radio wave, a phase difference of 90 degrees in the direction opposite to that at the time of transmission is applied to the power supply terminal of each antenna cell 2a to 2c. Reception power having −90 degrees) is generated, and in the 90-degree hybrid circuits 28a to 28c, when the radio waves transmitted in the reverse direction to the transmission radio waves are received by the antenna cells 2a to 2c (in other words, the transmission radio waves are not transmitted). When a reflected radio wave reflected by an external target is received), the received signal is synthesized, and the synthesized received signal is output from the output terminal A.
[0043]
Phase shifters 30a to 30c are provided between one input / output terminal D of the 90-degree hybrid circuits 28a to 28c and one power supply terminal V of the antenna cells 2a to 2c, respectively. Since the phase shifters 30a to 30c can switch the phase change amount Φ to 0 degree or 180 degrees, the phase shifters 30a to 30c can be switched via the antenna cells 2a to 2c by switching the phase change amount Φ. The turning direction of circularly polarized waves that can be transmitted and received can be switched. The phase change amount Φ of the phase shifters 30a to 30c is switched by the ECU 10.
[0044]
Next, the output terminals A of the 90-degree hybrid circuits 28a to 28c are connected to the mixer circuits 32a to 32c, respectively. The mixer circuits 32a to 32c are divided into three as local signals by the first power distributor 24. Each distributed transmission signal is input. That is, in the present embodiment, the mixer circuit 32a to 32c mixes the reception signal output from the output terminal A of the 90-degree hybrid circuits 28a to 28c and the transmission signal from the oscillator 22, thereby converting the reception signal. The transmission signal is converted into an intermediate frequency signal (IF signal) having a frequency that is the difference between the frequencies of these signals as a local signal.
[0045]
The output signals (IF signals) from the mixer circuits 32a to 32c are input to the IF circuits 34a to 34c, respectively, amplified and shaped by the IF circuits 34a to 34c, and then input to the ECU 10, respectively. The
Next, the ECU 10 is composed of a well-known microcomputer centered on a CPU, ROM, RAM, and the like. When in the measurement mode for detecting an obstacle, the ECU 10 serves as an FM-CW radar every predetermined measurement cycle. Perform transmission control. That is, by gradually changing the voltage of the control signal output to the oscillator 22 from a predetermined lower limit voltage to an upper limit voltage every predetermined measurement period, the frequency of the transmission signal output from the oscillator 22 is set to a preset lower limit. Transmission control that gradually changes from the frequency to the upper limit frequency is executed.
[0046]
As a result, from each of the antenna cells 2a to 2c, a transmission signal (frequency modulation signal) whose frequency is changed in sequence has a turning direction corresponding to the phase change amount Φ (0 degree or 180 degrees) of the phase shifters 30a to 30c. As a circularly polarized radio wave, it is radiated repeatedly every predetermined measurement period.
[0047]
Further, during execution of this transmission control, the ECU 10 captures output signals (IF signals) from the IF circuits 34a to 34c via A / D converters (not shown), and the amplitude or phase of each captured IF signal. Or, by comparing both, the position (orientation) of the obstacle existing outside the antenna device 6 is detected, and the distance and relative velocity to the obstacle are detected by frequency analysis of the I / F signal. The obstacle detection process is executed.
[0048]
Then, when the obstacle direction, the distance to the obstacle, and the relative speed with the obstacle are detected in the obstacle detection process during the transmission control, the transmission control is started next. In the meantime, from the detection result, it is determined whether or not the vehicle is in a dangerous situation of colliding with an obstacle. If it is determined that the risk of collision is high, the alarm device 12 is operated to A collision warning process is performed to notify the fact to that effect.
[0049]
That is, when the radio wave radiated from each antenna cell 2a to 2c hits an obstacle and is reflected, the turning direction of the radio wave is reverse to that at the time of transmission, and the reflected radio wave from the obstacle is received by the antenna cells 2a to 2c. In this case, since the 90-degree hybrid circuits 28a to 28c, the mixer circuits 32a to 32c, and the IF circuits 34a to 34c are input to the ECU 10 as IF signals, the ECU 10 receives the antennas via these units. Based on the received signals (IF signals) input from the cells 2a to 2c, the vehicle detects the presence / absence of an obstacle, the direction of the obstacle, the distance to the obstacle, the relative speed with the obstacle, etc. When the vehicle is in a dangerous situation of colliding with an obstacle, the vehicle driver is notified of this fact, and safety during vehicle traveling is improved.
[0050]
By the way, in the present embodiment, since the antenna elements for circular polarization are used for the antenna cells 2a to 2c, the radio waves transmitted by the antenna cells hit the obstacle and are reflected by the polarization identification by the antenna cells 2a to 2c. Although it becomes possible to detect obstacles by receiving only the reflected waves relatively well, a vehicle obstacle detection device to which such a monopulse radar device is applied has become widespread, and a vehicle equipped with this device If the frequency increases, it becomes easy for radio interference of obstacle detection radio waves to occur between the vehicles, and the radio wave interference may reduce the accuracy of obstacle detection.
[0051]
Therefore, in this embodiment, the ECU 10 executes the polarization switching process as shown in FIG. 3 or FIG. 4 so as to prevent the obstacle detection accuracy from being lowered due to radio wave interference with other devices. Has been.
That is, in the polarization switching process shown in FIG. 3, it is determined in S100 (S: represents a step) whether or not the measurement mode in which the apparatus performs the obstacle detection operation has been completed (measurement completed?). If the measurement mode is finished, the process is finished as it is. If the measurement mode is not finished, the process proceeds to S110, and one measurement turn for executing the transmission control and the obstacle detection process is finished. Wait for.
[0052]
Then, when this one measurement turn is completed, the process proceeds to S120, where a random number Ran # is generated in the arithmetic circuit of the random function incorporated in the CPU, the value Ran # is read, and in S130, the random number Ran # If the random number Ran # is an odd number and not an even number, the phase change amount Φ of the phase shifters 30a to 30c is set to 0 degree in S140, and the process proceeds to S100, and vice versa. If the random number Ran # is even, the phase change amount Φ of the phase shifters 30a to 30c is set to 180 degrees in S150, and the process proceeds to S100.
[0053]
That is, in the polarization switching process shown in FIG. 3, a random number Ran # is generated between the execution of the transmission control and the obstacle detection process and the start of the next control, and the random number Ran # The phase change amount Φ of the phase shifters 30a to 30c is randomly switched between 0 degree and 180 degrees depending on whether the number is even or odd.
[0054]
As a result, for example, when the phase change amount Φ of the phase shifters 30a to 30c is set to 0 degrees in S140, the transmitted radio waves from the other devices or the reflected radio waves are received by the antenna cells 2a to 2c. The received signal is input to the ECU 10 through the 90-degree hybrid circuits 28a to 28c, the mixer circuits 32a to 32c, and the IF circuits 34a to 34c, and the ECU 10 can no longer detect an obstacle based on each IF signal. Even in this case, when the phase change amount Φ of the phase shifters 30a to 30c is switched to 180 degrees in S150, the turning direction of the circularly polarized wave that can be transmitted and received by the device changes from the right turn to the left turn. (Or vice versa), even if radio waves from other devices are received by the antenna cells 2a to 2c, the received signals are transmitted to the 90-degree hybrid circuits 28a to 28c. The ECU 10 receives only the IF signal of the received signal corresponding to the reflected radio wave radiated from each antenna cell 2a to 2c. The ECU 10 side receives each IF signal input at this time. Based on this, obstacles can be accurately detected.
[0055]
On the other hand, in the polarization switching process shown in FIG. 4, as in the process shown in FIG. 3, in S100, it is determined whether or not the apparatus ends the obstacle measurement. When the process is terminated and the measurement is continued, the process waits for one measurement turn to end in S110.
[0056]
Then, when this one measurement turn is completed, the process proceeds to S220, and based on the amplitude of each IF signal captured during one measurement turn, the received signal received during that time is lower than the preset set level. It is judged whether there is a received signal with a peak of high received power, and if there is a received signal with a peak of received power higher than the set level, the received signal is not affected by any radio interference. The process proceeds to S230, and the phase change amount Φ of the phase shifters 30a to 30c is inverted from the current phase change quantity, and the process proceeds to S100. Otherwise, the process proceeds to S100 as it is. To do.
[0057]
That is, in the polarization switching process shown in FIG. 4, after execution of the transmission control and obstacle detection process described above, a reception power peak higher than the set level is received based on the IF signal captured during execution of this control. By determining whether the signal exists, it is determined whether the received signal received so far is affected by radio waves from other devices. If the received power is abnormally high, The phase change amount (180 degrees or 0) obtained by inverting the phase change amount Φ of each of the phase shifters 30a to 30c by 180 degrees from the previous phase change amount (0 degree or 180 degrees) is assumed to be affected by the interference. (Degree). As a result, as in the polarization switching process shown in FIG. 3, the obstacle can be accurately detected without being affected by the transmission radio wave from another device.
[0058]
As described above, according to the vehicle obstacle detection device of the present embodiment, the antenna cells 2a to 2c constituting the antenna device 6 use the two-terminal feed type circularly polarized antenna element and each antenna. By using 90-degree hybrid circuits 28a to 28c in the signal input / output circuit for supplying the transmission signal and taking out the reception signal for each of the cells 2a to 2c, the circularly polarized waves in the predetermined turning directions can be obtained from the respective antenna cells 2a to 2c. A radio wave is transmitted, and the antenna cells 2a to 2c are configured to capture the received signal only when a radio wave in a turning direction different from that at the time of transmission is received. The direction is switched using the phase shifters 30a to 30c.
[0059]
Therefore, according to the present embodiment, even if radio wave interference occurs between a vehicle equipped with the vehicle obstacle detection device similar to the device or another communication device different from the device, the interference wave Obstacles can be detected without being affected by the above, and the obstacle detection accuracy can be improved. Since the obstacle detection accuracy can be improved in this way, the risk of collision of the vehicle with the obstacle can be predicted very accurately, and a warning can be given to the vehicle driver. Can be increased.
[0060]
In addition, the vehicle obstacle detection device of this embodiment applies FM-CW radar technology to the monopulse radar device to detect the direction of the obstacle, the distance to the obstacle, and the relative velocity with the obstacle. Therefore, the danger that the vehicle will collide with an obstacle can be detected accurately and promptly, and this can also improve the traveling safety of the vehicle.
[0061]
Further, if the 90-degree hybrid circuits 28a to 28c are configured by, for example, a rat race power synthesis circuit, a Wilkinson power synthesis circuit, or the like, the 90-degree hybrid circuits 28a to 28c are replaced with the antenna cells 2a to 2c and the phase shifters 30a to 30a. Since each part can be realized as a so-called planar antenna by being configured with a microstrip line on a predetermined substrate together with 30c, the apparatus can be reduced in size and weight.
[0062]
In the present embodiment, the phase shifters 30a to 30c are provided on the input / output terminal D side of the 90-degree hybrid circuits 28a to 28c. However, the phase shifters 30a to 30c are 90-degree hybrid circuits 28a to 28c. It may be provided at any of the input / output terminals C and D of 28c.
[0063]
Further, in this embodiment, the vehicle obstacle detection device in which the antenna device 6 is provided with the three antenna cells 2a to 2c has been described. However, if the monopulse radar device includes at least two antenna elements, Since an external target can be detected, an antenna device including two antenna cells may be used. In addition, further increase the number of antenna cells, detect the direction and distance of each obstacle from the amplitude and phase of the received signal obtained in the adjacent antenna cell, and specify the position of the obstacle from the detection result In this case, the position of the obstacle can be detected with higher accuracy.
(Second embodiment)
Here, in the above-described embodiment, the intermediate frequency signals (IF signals) of the reception signals of the antenna cells 2a to 2c subjected to frequency conversion by the mixer circuits 32a to 32c are processed using the IF circuits 34a to 34c, respectively. However, for example, as in the vehicle obstacle detection device of the second embodiment shown in FIG. 5, the three IF signals output from the mixer circuits 32a to 32c are configured. Alternatively, an output switch circuit 36 that selects and outputs one IF signal may be provided, and the IF signal selected by the output switch circuit 36 may be switched at high speed on the ECU 10 side. That is, three types of IF signals may be captured at high speed by time division.
[0064]
In this way, the IF circuit 34 for signal processing of the IF signal and the A / D converter for A / D converting the IF signal in the ECU 10 can be made one regardless of the number of antenna cells. In comparison with the apparatus of the first embodiment, the apparatus configuration can be further simplified, and the apparatus can be reduced in size and weight.
(Third embodiment)
Further, for example, each 90 degree hybrid circuit is provided between the output terminal A of each of the 90 degree hybrid circuits 28a to 28c and the mixer circuit 32 as in the vehicle obstacle detection device of the third embodiment shown in FIG. An input switch circuit 38 is provided for selecting and receiving one of the output signals from the output signals 28a to 28c (that is, the received signals by the antenna cells 2a to 2c), and the received signal selected by the input switch circuit 38 is selected. The ECU 10 may be configured to switch at high speed. That is, the reception signals from the antenna cells 2a to 2c obtained via the 90-degree hybrid circuits 28a to 28c may be captured at high speed in a time division manner.
In this way, not only the IF circuit 34 and the A / D converter but also the mixer circuit 32 can be made one regardless of the number of antenna cells, which is higher than that of the apparatus of the second embodiment. Furthermore, the apparatus configuration can be simplified and the apparatus can be reduced in size and weight. In this case, the first power distributor 24 only has to distribute the transmission signal from the oscillator 22 to the second power distributor 26 side and the mixer 32 side, and each passing through the first power distributor 24. The attenuation amount of the transmission signal can be reduced. Therefore, the output power of the transmission signal from the oscillator 22 can be reduced.
[0065]
In this case, in the 90-degree hybrid circuit in which the reception signal is not selected (in other words, not connected to the mixer circuit 32), the reception signal output to the output terminal A is not reflected to the input / output terminals C and D side. As described above, the input switch circuit 38 is provided with termination resistors Ra to Rc for terminating the output terminals A of the respective 90-degree hybrid circuits 28 a to 28 c with a predetermined circuit impedance, and the output terminal A is not connected to the mixer circuit 32. The output terminal A of the 90-degree hybrid circuit needs to be terminated by the corresponding termination resistors Ra to Rc.
(Fourth embodiment)
Next, in each of the above embodiments, the received signals from the antenna cells 2a to 2c obtained via the 90-degree hybrid circuits 28a to 28c are frequency-converted into intermediate frequency signals (IF signals), which are simultaneously or Is input to the ECU 10 in a time-sharing manner, and the ECU 10 side detects the position (direction, distance, etc.) of the obstacle using these three types of IF signals. For example, FIG. As shown in the vehicle obstacle detection device of the fourth embodiment shown, any of the received signals (IF signals) from the antenna cells 2a to 2c that have been frequency-converted to the intermediate frequency signals by the mixer circuits 32a to 32c. The reception signal selection circuit 40 for selecting a pair of IF signals is provided, and the pair of IF signals selected by the reception signal selection circuit 40 are converted into signals using the pair of IF circuits 34-1 and 34-2, respectively. Process, ECU1 Further, the interval between antenna cells used for obstacle detection may be switched by changing the IF signal selected by the reception signal selection circuit 40 on the ECU 10 side.
[0066]
In other words, the monopulse radar device basically detects the azimuth of the target from the difference in amplitude or phase of the received signals obtained by the pair of antenna elements, and therefore has two antenna elements. Then, the monopulse radar apparatus of the present invention can be realized. However, when the orientation and distance of the target are simply determined by only two antenna elements, for example, as shown in FIG. 8 (a), a pair of antenna elements a, If the distance D1 between b is narrow and the distance L to the target X is short, the angle θ1 formed by the straight line connecting the antenna elements a and b and the target X becomes relatively large, and reception is performed. Although the position of the target can be detected satisfactorily from the difference in signal amplitude or phase, when the distance L to the target X is long, the angle θ1 is reduced and obtained by the antenna elements a and b. Difference in received signal amplitude and phase (△ (Corresponding to L1) is also small, and the position of the target X cannot be detected well. However, for example, as shown in FIG. 8B, if the antenna elements used for detecting the target X are switched from a and b having a small distance D1 to a and c having a large distance D2, the target is detected. Even when the distance L to X is long, the angle θ2 formed by the straight line connecting each antenna element a, c and the target X becomes relatively large, and the received signal obtained by each antenna element a, c. Difference in amplitude and phase (corresponding to ΔL2 shown in the figure) can be increased, and the position of the target can be detected well.
[0067]
Therefore, in this embodiment, the reception signal selection circuit 40 can select an arbitrary pair of IF signals from the three types of IF signals frequency-converted by the mixer circuits 32a to 32c and input them to the ECU 10. On the ECU 10 side, by switching the IF signal selected by the reception signal selection circuit 40, and thus the interval between the antenna cells used for obstacle detection, the ECU 10 can always detect the position of the obstacle satisfactorily. It is.
[0068]
In the ECU 10, when the IF signal selected by the reception signal selection circuit 40 is actually switched, for example, a reception signal switching process as shown in FIG. 9 may be executed.
That is, in the received signal switching process shown in FIG. 9, as in the polarization switching process shown in FIGS. 3 and 4 described above, in S100, it is determined whether or not the apparatus ends the obstacle measurement, When the measurement is finished, the process is finished as it is, and when the measurement is continued, the process waits for one measurement turn to end in S110. Then, when this one measurement turn is completed, the process proceeds to S320, where the frequency of the IF signal captured during the one measurement turn is very large, and a target (obstacle) is at a point more than a preset set distance. It is determined whether or not there is an obstacle, and if the obstacle is present at a point greater than or equal to the set distance (that is, if the distance to the obstacle is long), the process proceeds to S330 and the interval between the antennas for receiving the received signals is increased. Therefore, one switch SW1 of the received signal selection circuit 40 is switched to the mixer 32a side corresponding to the antenna cell 2a, and the other switch SW2 is switched to the mixer 32c side corresponding to the antenna cell 2c, and the process proceeds to S100. On the contrary, when the obstacle does not exist at a point beyond the set distance (that is, when the distance to the obstacle is short or the obstacle is not detected), the reception signal is received. In order to reduce the interval between the two, the switch SW1 of the reception signal selection circuit 40 is switched to the mixer 32a side corresponding to the antenna cell 2a, and the other switch SW2 is switched to the mixer 32b side corresponding to the antenna cell 2b. , S100 is entered.
[0069]
As a result, according to the present embodiment, it is possible to always accurately detect the direction of the obstacle without being affected by the distance from the device to the obstacle, and the obstacle detection device having excellent angle measurement resolution can be obtained. realizable.
The present invention has been specifically described with reference to the first to fourth embodiments. However, the present invention is not limited to these embodiments, and can take various forms. For example, in each of the above-described embodiments, the vehicle obstacle detection device mounted on a vehicle and detecting an obstacle has been described. However, the present invention is not limited to such an obstacle detection radar device. The present invention can also be applied to an automatic guided vehicle radar apparatus that automatically follows another vehicle or a target.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a vehicle obstacle detection device according to a first embodiment.
FIG. 2 is an explanatory diagram for explaining directivity characteristics of an antenna device.
FIG. 3 is a flowchart showing an example of a polarization switching process executed in an ECU.
FIG. 4 is a flowchart showing another example of polarization switching processing executed in the ECU.
FIG. 5 is a block diagram showing a configuration of a vehicle obstacle detection device according to a second embodiment.
FIG. 6 is a block diagram showing a configuration of a vehicle obstacle detection device according to a third embodiment.
FIG. 7 is a block diagram showing the configuration of a vehicle obstacle detection device according to a fourth embodiment.
FIG. 8 is an explanatory diagram for explaining the relationship between antenna element spacing and target detection accuracy;
FIG. 9 is a flowchart showing a received signal switching process executed in the ECU of the fourth embodiment.
[Explanation of symbols]
2a to 2c: Antenna cell (2-terminal feed type circularly polarized antenna element)
DESCRIPTION OF SYMBOLS 4 ... Dielectric lens 6 ... Antenna apparatus (multi-beam dielectric lens antenna) 10 ... ECU (electronic control apparatus) 12 ... Alarm apparatus 20 ... Transmission / reception circuit
22 ... Oscillator 24 ... First power distributor 26 ... Second power distributor
28a-28c ... 90 degree hybrid circuit
30a-30c ... Phase shifter (variable phase change type phase shifter)
32, 32a to 30c ... mixer circuit 34, 34a to 34c ... IF circuit
36 ... Output switch circuit 38 ... Input switch circuit
40. Reception signal selection circuit

Claims

A plurality of antenna elements that are capable of transmitting and receiving circularly polarized radio waves and are arranged so that part of the radiation patterns overlap;
Polarization switching means for switching the turning direction of circularly polarized waves transmitted and received by each antenna element;
Signal generating means for generating, as a transmission signal, a frequency modulation signal whose frequency changes at a predetermined period ;
A signal input / output means for inputting a transmission signal from the signal generating means to each antenna element to radiate a radio wave from each antenna element, and for extracting a received signal received by each antenna element;
A frequency conversion means for mixing a reception signal from each antenna element obtained through the signal input / output means with the transmission signal and converting each reception signal to an intermediate frequency signal;
Target detection means for detecting an external target based on each intermediate frequency signal after conversion by the frequency conversion means ;
In a monopulse radar device comprising:
The frequency conversion means includes
A plurality of frequency converters that respectively convert the frequency of the received signal from each antenna element using the transmission signal;
An output switch means for sequentially selecting and outputting the intermediate frequency signals frequency-converted by the plurality of frequency converters to the target detection means;
A monopulse radar device comprising:

A plurality of antenna elements that are capable of transmitting and receiving circularly polarized radio waves and arranged so that a part of the radiation pattern overlaps;
  Polarization switching means for switching the turning direction of circularly polarized waves transmitted and received by each antenna element;
  Signal generating means for generating, as a transmission signal, a frequency modulation signal whose frequency changes at a predetermined period;
  A signal input / output means for inputting a transmission signal from the signal generation means to each antenna element to radiate a radio wave from each antenna element, and for extracting a reception signal received by each antenna element;
  A frequency conversion means for mixing a reception signal from each antenna element obtained through the signal input / output means with the transmission signal and converting each reception signal to an intermediate frequency signal;
  Target detection means for detecting an external target based on each of the intermediate frequency signals converted by the frequency conversion means;
  In a monopulse radar device comprising:
  The frequency conversion means includes
  Input switch means for sequentially selecting and capturing received signals input from the antenna elements;
  One frequency conversion unit that sequentially converts the received signals sequentially input from the input switch unit using the transmission signal and outputs the frequency to the target detection unit;
  A monopulse radar device comprising:

At least three antenna elements that are capable of transmitting and receiving circularly polarized radio waves and that are arranged so that part of their radiation patterns overlap;
  Polarization switching means for switching the turning direction of circularly polarized waves transmitted and received by each antenna element;
  Signal generating means for generating, as a transmission signal, a frequency modulation signal whose frequency changes at a predetermined period;
  A signal input / output means for inputting a transmission signal from the signal generation means to each antenna element to radiate a radio wave from each antenna element, and for extracting a reception signal received by each antenna element;
  A frequency conversion means for mixing a reception signal from each antenna element obtained through the signal input / output means with the transmission signal and converting each reception signal to an intermediate frequency signal;
  Target detection means for detecting an external target based on each of the intermediate frequency signals converted by the frequency conversion means;
  In a monopulse radar device comprising:
  The frequency conversion means includes
  Corresponding to the antenna elements, each of the antenna elements includes three or more frequency conversion units that respectively convert the frequency of reception signals from the antenna elements using the transmission signals,
  A signal selection unit that selects a pair of intermediate frequency signals from the intermediate frequency signals output from the frequency conversion units and outputs the selected signal to the target detection unit,
  The interval of antenna elements used for target detection can be adjusted by changing the intermediate frequency signal selected by the signal selection means.
  A monopulse radar device.

The target detection means is configured to detect a distance from the monopulse radar device to an external target,
Further, based on the distance detected by the target detection means, the signal selection means is controlled such that the longer the distance, the wider the distance between the pair of antenna elements corresponding to the pair of intermediate frequency signals. Having selection control means
The monopulse radar apparatus according to claim 3.

Random number generating means for generating a random number each time the target detecting means detects the target; and
Each time the target detection means detects the target, a switching control means for operating the polarization switching means based on the random number generated by the random number generation means,
The monopulse radar device according to any one of claims 1 to 4, further comprising:

Each antenna element comprises a two-terminal feed type circularly polarized antenna element,
  The signal input / output means is provided for each antenna element, distributes the transmission signal to transmission signals having a phase difference of 90 degrees, outputs the transmission signals to two power supply terminals of the antenna element, and from each power supply terminal of the antenna element. Among a pair of input reception signals, the reception signal having a 90-degree phase difference in the opposite direction to the distributed transmission signal is composed of a plurality of 90-degree hybrid circuits that are incorporated into the apparatus,
  The polarization switching means is provided in one of a pair of signal paths connecting the 90-degree hybrid circuit and the power supply terminal of the antenna element, and the phase change capable of switching the phase change amount between 0 degree and 180 degrees Consists of variable phase shifter
  The monopulse radar device according to any one of claims 1 to 5, wherein

7. The monopulse according to claim 6, wherein the transmission / reception high-frequency circuit unit comprising the antenna element, the 90-degree hybrid circuit, and the phase shifter comprises a planar circuit formed by a conductive pattern on a predetermined substrate. Radar device.