JPH05327400A - Passing band variable circuit - Google Patents
Passing band variable circuitInfo
- Publication number
- JPH05327400A JPH05327400A JP16040692A JP16040692A JPH05327400A JP H05327400 A JPH05327400 A JP H05327400A JP 16040692 A JP16040692 A JP 16040692A JP 16040692 A JP16040692 A JP 16040692A JP H05327400 A JPH05327400 A JP H05327400A
- Authority
- JP
- Japan
- Prior art keywords
- filter
- frequency
- filters
- variable
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Filters And Equalizers (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、例えば、通信機におけ
る中間周波段の混信除去に適用する通過帯域可変回路に
関し、特に中心周波数の高、低の隣接妨害信号を除去す
る通過帯域可変回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pass band variable circuit applied to, for example, interference removal in an intermediate frequency stage in a communication device, and more particularly to a pass band variable circuit for removing adjacent interference signals having high and low center frequencies. ..
【０００２】[0002]
【従来の技術】従来から、通信機における中間周波段は
混信除去を目的として種々の回路が用いられている。例
えば、図５に示すように、中心周波数ｆo のフィルタ２
１と、これより高い中心周波数ｆ2 のトラップ２２とを
接続し、入力信号から中心周波数ｆo に隣接する高い周
波数ｆ2 の妨害信号を除去する回路がある。この回路で
は、フィルタ２１とこれより高い中心周波数のトラップ
２２を使用していることから、図６に示すように、フィ
ルタ２１の周波数特性の曲線（ａ）と、トラップ２２の
周波数特性の曲線（ｂ）とが加わった特性となり、中心
周波数のｆo に隣接する一方の高い周波数ｆ2 の妨害信
号は除去できるが、低い周波数ｆ1 の妨害信号を除去で
きなかった。この場合、さらに低い周波数ｆ1 の妨害信
号を除去するように、中心周波数ｆ1 のトラップを使用
すればよいが、トラップの使用個数を増やすので、フィ
ルタ損失が増加するとともにコストが上昇し、実用的で
ない。2. Description of the Related Art Conventionally, various circuits have been used in an intermediate frequency stage in a communication device for the purpose of removing interference. For example, as shown in FIG. 5, a filter 2 having a center frequency fo
There is a circuit that connects 1 and a trap 22 having a higher center frequency f 2 to remove an interference signal having a higher frequency f 2 adjacent to the center frequency fo from the input signal. In this circuit, since the filter 21 and the trap 22 having a center frequency higher than this are used, as shown in FIG. 6, the curve (a) of the frequency characteristic of the filter 21 and the curve (a) of the frequency characteristic of the trap 22 ( b) is added, and the interference signal of one high frequency f 2 adjacent to the center frequency fo can be removed, but the interference signal of low frequency f 1 cannot be removed. In this case, a trap with a center frequency f 1 may be used so as to remove an interfering signal with a lower frequency f 1. However, since the number of traps used is increased, the filter loss is increased and the cost is increased. Not relevant.
【０００３】そこで、中心周波数ｆo の低い周波数の隣
接妨害信号を除去する回路として、図７に示すように、
ミキサー２３と、ミキサ−２３に局部信号発振器２４と
中心周波数ｆi のフィルタ２５とを接続し、この回路に
入力した周波数ｆo をミキサ−２３に入力するととも
に、局部信号発振器２４により±Δｆの周波数の信号を
発生させ、この信号もミキサ−２３に入力し、ｆo ±Δ
ｆのＲＦ信号としてフィルタ２５に通し、この中心周波
数ｆo の範囲外の周波数の信号を除去し、その後再び周
波数変換して中心周波数ｆo に戻すようにした回路が知
られている。この１段構成にした回路においては、図８
に示すように、、中心周波数ｆo に対して低い周波数ｂ
の隣接信号は除去できる。Therefore, as a circuit for removing an adjacent interfering signal having a low center frequency fo, as shown in FIG.
A mixer 23 and a mixer 23 are connected to a local signal oscillator 24 and a filter 25 having a center frequency fi, and the frequency fo input to this circuit is input to the mixer 23, and the local signal oscillator 24 changes the frequency of ± Δf. A signal is generated and this signal is also input to the mixer-23, fo ± Δ
A circuit is known in which an RF signal of f is passed through a filter 25 to remove a signal having a frequency outside the range of the center frequency fo, and then the frequency is converted again to return to the center frequency fo. In the circuit having this one-stage configuration, as shown in FIG.
As shown in, the low frequency b with respect to the center frequency fo
Adjacent signals of can be removed.
【０００４】[0004]
【発明が解決しようとする課題】上記の局部信号発振器
を１個用い、ミキサー回路を通してフィルタを通す回路
においては、低い周波数又は高い周波数の何れか一方の
隣接信号が除去できるだけである。両方の隣接信号を除
去するためには、ミキサー回路を２個以上使用しなけれ
ばならず、損失が増すとともに、価格が高くなる等の問
題点があった。In a circuit using one of the above local signal oscillators and passing a filter through a mixer circuit, it is only possible to remove adjacent signals of either low frequency or high frequency. In order to remove both adjacent signals, it is necessary to use two or more mixer circuits, which causes problems such as an increase in loss and an increase in price.
【０００５】本発明は上記従来技術の有する実情に鑑み
てなされたもので、簡易な回路で、混信除去能力にすぐ
れた中間周波段を構成することがきる通過帯域可変回路
を提供することを目的としている。The present invention has been made in view of the actual situation of the above-mentioned prior art, and it is an object of the present invention to provide a passband variable circuit capable of constructing an intermediate frequency stage having a simple circuit and excellent in interference removal capability. I am trying.
【０００６】[0006]
【課題を解決するための手段】本発明に係る通過帯域可
変回路は、所定の周波数の信号を通過させるフィルタを
直列に接続し、各フィルタ間に可変容量を接続し、該可
変容量の負荷容量を変化させて通過帯域幅を変化させる
ことを特徴とする。A passband variable circuit according to the present invention comprises a filter for passing a signal of a predetermined frequency connected in series, a variable capacitor connected between the filters, and a load capacitance of the variable capacitor. Is changed to change the pass band width.
【０００７】[0007]
【作用】上記のように、通過させる信号の周波数のフィ
ルタを直列に接続し、各フィルタ間に可変容量又はバリ
キャプを接続し、フィルタと可変容量又はバリキャプで
直列共振回路を構成し、可変容量又はバリキャプの負荷
容量を変化させて、所定の信号の高、低の周波数の隣接
妨害信号を除去する。なお、上記フィルタはそれぞれ異
なる周波数特性とし、上記信号の周波数のフィルタ及び
この周波数よりそれぞれ高、低の周波数とし、信号の周
波数のフィルタを挟んで接続してもよい。As described above, the filters for the frequencies of the signals to be passed are connected in series, the variable capacitors or varicaps are connected between the filters, and the filters and the variable capacitors or varicaps constitute a series resonance circuit. The load capacitance of the varicap is changed to remove adjacent interference signals of high and low frequencies of a given signal. The filters may have different frequency characteristics, and may have filters of the frequency of the signal and higher and lower frequencies than the frequency, and may be connected with the filter of the frequency of the signal sandwiched therebetween.
【０００８】[0008]
【実施例】以下、本発明の一実施例を図面に基づいて説
明する。図１は、本発明による通過帯域可変回路の一実
施例を説明するための回路図である。本発明による通過
帯域可変回路は、通過させる信号の中心周波数ｆｏのフ
ィルタ１と、このフィルタ１の中心周波数ｆｏより高い
周波数のフィルタ２をフィルタ１の入側に接続し、中心
周波数ｆｏより低い周波数のフィルタ３を、フィルタ１
を挟んで直列に出側に接続し、フィルタ１，２間に可変
容量４を接続し、さらにフィルタ１，3 間に可変容量５
を接続して構成している。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram for explaining one embodiment of a pass band variable circuit according to the present invention. The passband variable circuit according to the present invention connects a filter 1 having a center frequency fo of a signal to be passed and a filter 2 having a frequency higher than the center frequency fo of the filter 1 to the input side of the filter 1 and lowering the frequency lower than the center frequency fo. Filter 3 and Filter 1
The filter is connected in series with the filter in between, the variable capacitor 4 is connected between the filters 1 and 2, and the variable capacitor 5 is connected between the filters 1 and 3.
Are connected and configured.
【０００９】上記フィルタ１，２，３を、圧電体セラミ
ックスを分極してなる圧電基板の主面に電極を設けて形
成した圧電素子から構成する。このフィルタの等価回路
図は図２に示すようになる。本実施例のフィルタ１，
２，３の個々の周波数特性は図３でそれぞれ曲線
（ａ），（ｂ），（ｃ）で示されるが、フィルタ２と可
変コンデンサ４、フィルタ１と可変コンデンサ５、及び
フィルタ３で形成したバンドパスフィルタの周波数特性
は、図４にＢＷで示す曲線になる。ここで可変コンデン
サの負荷容量を変えることにより、通過帯域の幅を変え
て狭くすることができる。通過帯域の周波数特性は、さ
らに可変容量を変えてフィルタの通過帯域幅を狭くする
ことができ、所定の周波数の高低ｆH ，ｆL の両隣接妨
害信号を除去し、混信を防止する。Each of the filters 1, 2 and 3 is composed of a piezoelectric element formed by providing electrodes on the main surface of a piezoelectric substrate formed by polarizing piezoelectric ceramics. The equivalent circuit diagram of this filter is shown in FIG. Filter 1 of the present embodiment
The individual frequency characteristics of Nos. 2 and 3 are shown by curves (a), (b), and (c) in FIG. 3, respectively, and are formed by the filter 2 and the variable capacitor 4, the filter 1 and the variable capacitor 5, and the filter 3. The frequency characteristic of the bandpass filter is a curve indicated by BW in FIG. By changing the load capacitance of the variable capacitor, the width of the pass band can be changed and narrowed. With regard to the frequency characteristics of the pass band, the variable capacitance can be further changed to narrow the pass band width of the filter, and high-low f H and f L adjacent interference signals of a predetermined frequency are removed to prevent interference.
【００１０】なお、上記実施例において、圧電共振子か
らなるフィルタで、中心周波数がそれぞれ異なる例で説
明したが、ＬＣフィルタ等、各フィルタを異なる特性の
ものとしてもよいし、全てのフィルタを同じ中心周波数
にしてもよい。In the above-mentioned embodiment, the filters having the piezoelectric resonators have different center frequencies. However, the filters may have different characteristics, such as LC filters, or all the filters have the same characteristics. It may be the center frequency.
【００１１】[0011]
【発明の効果】以上のように本発明によれば、フィルタ
を接続し、各フィルタ間に可変容量を接続して通過帯域
可変回路を構成したので、簡易な小型な回路に形成する
ことができる。そして、各可変容量を変えることによっ
て通信機等の所定の周波数の中間周波段の信号の中心周
波数から外れる周波数の幅を調節し、隣接妨害信号を除
去する。通過帯域幅を変更できるので、中心周波数の高
低の隣接妨害信号を容易に除去でき、通信機等の中間周
波段の混信をなくすことができる。As described above, according to the present invention, since the filters are connected and the variable capacitors are connected between the filters to configure the pass band variable circuit, it is possible to form a simple and small circuit. .. Then, by changing each variable capacitance, the width of the frequency deviating from the center frequency of the signal of the intermediate frequency stage of a predetermined frequency of the communication device or the like is adjusted, and the adjacent interfering signal is removed. Since the pass band width can be changed, adjacent interference signals having high and low center frequencies can be easily removed, and interference in the intermediate frequency stage of a communication device or the like can be eliminated.
【図１】本発明の一実施例による通過帯域可変回路を説
明するための回路図である。FIG. 1 is a circuit diagram for explaining a pass band variable circuit according to an embodiment of the present invention.
【図２】上記実施例の等価回路図である。FIG. 2 is an equivalent circuit diagram of the above embodiment.
【図３】上記実施例の各フィルタの周波数特性を示すグ
ラフである。FIG. 3 is a graph showing frequency characteristics of each filter of the above-mentioned embodiment.
【図４】上記実施例の周波数特性を示すグラフである。FIG. 4 is a graph showing frequency characteristics of the above-mentioned embodiment.
【図５】従来例の中間周波段の混信除去回路を示す回路
図である。FIG. 5 is a circuit diagram showing a conventional interference cancellation circuit of an intermediate frequency stage.
【図６】上記従来例の周波数特性を示すグラフである。FIG. 6 is a graph showing the frequency characteristic of the conventional example.
【図７】他の従来例の通過帯域可変回路を示す回路図で
ある。FIG. 7 is a circuit diagram showing another conventional pass band variable circuit.
【図８】他の従来例の周波数特性を示すグラフである。FIG. 8 is a graph showing frequency characteristics of another conventional example.
１，２，３ フィルタ ４，５ 可変容量 1,2,3 filter 4,5 variable capacitance
Claims (1)
タを直列に接続し、各フィルタ間に可変容量を接続し、
該可変容量の負荷容量を変化させて通過帯域幅を変化さ
せることを特徴とする通過帯域可変回路。1. A filter for passing a signal of a predetermined frequency is connected in series, and a variable capacitor is connected between each filter,
A pass band variable circuit characterized in that a pass band width is changed by changing a load capacitance of the variable capacitor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16040692A JPH05327400A (en) | 1992-05-25 | 1992-05-25 | Passing band variable circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16040692A JPH05327400A (en) | 1992-05-25 | 1992-05-25 | Passing band variable circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05327400A true JPH05327400A (en) | 1993-12-10 |
Family
ID=15714252
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16040692A Pending JPH05327400A (en) | 1992-05-25 | 1992-05-25 | Passing band variable circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05327400A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016076093A1 (en) * | 2014-11-11 | 2016-05-19 | 株式会社村田製作所 | Filter circuit, rf front end circuit, and communication device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6226902B2 (en) * | 1982-09-20 | 1987-06-11 | Hiraoka Shokusen | |
| JPS63228813A (en) * | 1987-03-18 | 1988-09-22 | Fujitsu Ltd | Timing extracting filter |
| JPH02140007A (en) * | 1988-11-18 | 1990-05-29 | Murata Mfg Co Ltd | Low pass filter |
| JPH0232224B2 (en) * | 1987-11-19 | 1990-07-19 | Nippon Hekizai Kogyo Kk | KABEZAIYOZORYUKOTSUZAI |
-
1992
- 1992-05-25 JP JP16040692A patent/JPH05327400A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6226902B2 (en) * | 1982-09-20 | 1987-06-11 | Hiraoka Shokusen | |
| JPS63228813A (en) * | 1987-03-18 | 1988-09-22 | Fujitsu Ltd | Timing extracting filter |
| JPH0232224B2 (en) * | 1987-11-19 | 1990-07-19 | Nippon Hekizai Kogyo Kk | KABEZAIYOZORYUKOTSUZAI |
| JPH02140007A (en) * | 1988-11-18 | 1990-05-29 | Murata Mfg Co Ltd | Low pass filter |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016076093A1 (en) * | 2014-11-11 | 2016-05-19 | 株式会社村田製作所 | Filter circuit, rf front end circuit, and communication device |
| JPWO2016076093A1 (en) * | 2014-11-11 | 2017-07-06 | 株式会社村田製作所 | Filter circuit, RF front-end circuit, and communication device |
| US10340874B2 (en) | 2014-11-11 | 2019-07-02 | Murata Manufacturing Co., Ltd. | Filter circuit, RF front end circuit, and communication apparatus |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5543764A (en) | Filter having an electromagnetically tunable transmission zero | |
| US6879224B2 (en) | Integrated filter and impedance matching network | |
| JP2505135B2 (en) | LC filter | |
| JPH0216802A (en) | Band elimination filter | |
| JPH07147503A (en) | Dielectric filter | |
| US4013982A (en) | Piezoelectric crystal unit | |
| WO2007018436A2 (en) | Radio frequency filter | |
| US5376908A (en) | Interdigital strip line filter having a plurality of different width resonant electrodes | |
| US5157362A (en) | Narrow band notch filter with extended passband | |
| JPH05327400A (en) | Passing band variable circuit | |
| CA1112726A (en) | Multiple pole bandpass filter having monolithic crystal elements | |
| JP2002319836A (en) | Ladder type filter | |
| US5369382A (en) | Two-pole monolithic crystal filter including shunt resonator stages | |
| JPS62263701A (en) | Dc cut-off circuit | |
| US5075651A (en) | VHF wide-bandwidth low impedance monolithic crystal filter having bridged electrodes | |
| US3716808A (en) | Bandpass filter including monolithic crystal elements with resonating portions selected for symmetrical response | |
| US3704433A (en) | Band-elimination filter | |
| JPS62110301A (en) | Tuning type band-pass filter | |
| JPH0754892B2 (en) | Filter circuit | |
| JPS62140501A (en) | Mic filter | |
| US3858127A (en) | Stable and compact low frequency filter | |
| JPH0112401Y2 (en) | ||
| US3947784A (en) | Dual-coupled monolithic crystal element for modifying response of filter | |
| JPH082001B2 (en) | Band pass filter | |
| CA1065420A (en) | Multiple electrode crystal frequency discriminator circuit |