JP4643475B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar device that obtains a target shape or a center of gravity of a shape such as an aircraft, a ship, or a vehicle.

  FIG. 10 is a diagram illustrating a configuration of a conventional radar apparatus. The radar apparatus includes a signal generator 1, an exciter 2, a circulator 3, an antenna 4, a receiver 5, a signal processor 6, and a radar controller 11. The signal generator 1 generates a broadband chirp signal and sends it to the exciter 2. The exciter 2 converts the frequency of the broadband chirp signal sent from the signal generator 1 and then amplifies it, and sends it to the antenna 4 via the circulator 3 as a transmission signal.

  The antenna 4 converts the transmission signal sent from the exciter 2 through the circulator 3 into a radio wave and transmits it to the air, converts the radio wave received from the air into an electric signal, and uses the circulator 3 as a reception signal. To the receiver 5.

  The receiver 5 converts the frequency of the received signal sent from the antenna 4 via the circulator 3 and sends it to the signal processor 6. As will be described in detail later, the signal processor 6 detects a target by performing signal processing on the signal transmitted from the receiver 5. The radar controller 11 controls a processing procedure performed in the signal processor 6.

  The signal processor 6 includes a pulse compression unit 61, a DFT unit 62, a detection unit 63, and an angle measurement unit 64. The pulse compression unit 61 performs pulse compression on the signal sent from the receiver 5 and sends it to the DFT unit 62. The DFT unit 62 integrates the signal sent from the pulse compression unit 61 by discrete Fourier transform (DFT), and sends it to the detection unit 63.

  The detection unit 63 detects the target by comparing the signal sent from the DFT unit 62 with a predetermined threshold level, and sends it to the angle measurement unit 64 as a target signal. The angle measurement unit 64 performs angle measurement processing on the target signal sent from the detection unit 63 to calculate the target angle and the distance to the target.

In the conventional radar apparatus configured as described above, when recognizing the target shape, the range direction as shown in FIG. Although it can be observed with a resolution in a high range direction by using it, the cross-range direction (direction orthogonal to the range direction) has a low resolution at a normal beam width, and therefore, for example, the inverse synthetic aperture radar shown in Non-Patent Document 1 (ISAR: Inverse Synthetic Aperture Radar) or the like is used to improve the resolution in the cross range direction.
Donald R. Wehner, “High-Resolution Radar Second Edition”, Artech House (1995), pp.174-180 Supervised by Takashi Yoshida, “Revised Radar Technology”, first edition, The Institute of Electronics, Information and Communication Engineers, February 15, 2003, pp 283-285

  However, in the above-described conventional radar device, when recognizing the shape of the target, the target moves straight toward the radar device, and there is little fluctuation in the cross range direction. Synthetic aperture radar has a problem that the resolution in the cross range direction is low and the target shape cannot be recognized.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radar apparatus that can recognize a target shape without a Doppler component in the cross-range direction.

In order to solve the above-mentioned problem, the invention described in claim 1 is a receiver for receiving a reflected wave with respect to a transmission wave, and a discrete Fourier transform of a signal with a high distance resolution obtained by pulse compression of the signal from the receiver. A DFT unit that integrates the signal, a detection unit that detects a target from the signal from the DFT unit and outputs it as a target signal, and a phase or amplitude monopulse within the beam width for each range based on the target signal from the detection unit Angle measuring unit that performs angle measurement by the method multiple times , memory that stores the target position in the cross range direction determined by the angle measurement value of each range obtained by measuring the angle by the angle measuring unit, and multiple times And an addition unit for adding or logically calculating target positions of a plurality of sets stored in a memory at each number of observations to obtain a target shape.

  According to a second aspect of the present invention, in the first aspect of the invention, the DFT unit performs integration by discrete Fourier transform on each signal separated by the Doppler filter by performing Doppler decomposition processing with a longer dwell time. The detecting unit detects a target for each of the integrated signals separated from the DFT unit and outputs the target as a target signal.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a centroid operation unit that performs a centroid operation on a target shape obtained by the addition unit is provided.

  According to the present invention, it is possible to provide a radar device that can recognize the shape of a target even when the target moves straight toward the radar device, does not fluctuate in the cross range direction, and has no Doppler component.

Specifically, according to the first aspect of the present invention, the target is measured in the distance direction with high distance resolution, and the target positions of a plurality of sets obtained in each of a plurality of observation times are added. Alternatively, since a logical OR operation is performed, a shape including all angles formed by a plurality of reflection points can be recognized.

  According to the invention described in claim 2, even when there are a plurality of targets in the same range cell, in the case of a plurality of targets having different moving speeds, the targets are separated by the Doppler bank, and the invention described in claim 1 described above. Since the same processing is performed, the shape of each target can be recognized.

  Further, according to the invention described in claim 3, since the center of gravity is calculated after recognizing the target shape in the invention described in claim 1 or invention of claim 2, the characteristic of the target having a spread is calculated. The position can be extracted.

  Hereinafter, it will be described in detail with reference to the drawings of embodiments of the present invention. In the following description, the same or equivalent parts as those of the conventional radar apparatus will be described using the same reference numerals as those used in the prior art section. In the following, it is assumed that a broadband chirp signal is used as a transmission / reception signal.

  FIG. 1 is a block diagram illustrating a configuration of a radar apparatus according to Embodiment 1 of the present invention. This radar apparatus includes a signal generator 1, an exciter 2, a circulator 3, an antenna 4, a receiver 5, a signal processor 6a, and a radar controller 11a.

  The signal generator 1 generates a broadband chirp signal. The broadband chirp signal generated by the signal generator 1 is sent to the exciter 2.

  The exciter 2 converts the frequency of the broadband chirp signal sent from the signal generator 1 and further amplifies it. The signal frequency-converted and amplified by the exciter 2 is sent to the antenna 4 via the circulator 3 as a transmission signal.

  The circulator 3 switches between sending a transmission signal sent from the exciter 2 to the antenna 4 and sending a signal sent from the antenna 4 to the receiver 5.

  The antenna 4 is configured by arranging N (N is a positive integer) antenna elements at an interval d. The antenna 4 converts a transmission signal sent from the exciter 2 through the circulator 3 into a radio wave. In addition to being transmitted in the air, radio waves from the air are received and converted into electrical signals, which are sent to the receiver 5 via the circulator 3 as received signals.

  The receiver 5 converts the frequency of the received signal sent from the antenna 4 via the circulator 3. The signal whose frequency is converted by the receiver 5 is sent to the signal processor 6a. The signal processor 6a performs signal processing on the signal sent from the receiver 5, and detects the target and its shape. Details of the signal processor 6a will be described later. The radar controller 11a controls a processing procedure performed in the signal processor 6a.

  Next, details of the signal processor 6a will be described. The signal processor 6a includes a pulse compression unit 61, a DFT unit 62, a detection unit 63, an angle measurement unit 64, a memory 65, and an addition unit 66.

  The pulse compression unit 61 performs pulse compression on the signal transmitted from the receiver 5. The signal subjected to pulse compression by the pulse compression unit 61 is sent to the DFT unit 62.

  The DFT unit 62 integrates the signal sent from the pulse compression unit 61 by performing a discrete Fourier transform (DFT). A signal obtained by integration by the DFT unit 62 is sent to the detection unit 63.

  The detection unit 63 detects the target by comparing the signal sent from the DFT unit 62 with a predetermined threshold level. A target signal representing the target detected by the detection unit 63 is sent to the angle measurement unit 64. As shown in FIG. 2, this target signal is a signal observed by cutting the target in the range direction.

  As shown in FIG. 2A, when the distance resolution is low, the target shape in the range direction cannot be recognized. However, as shown in FIG. It becomes possible to recognize the shape in the range direction. In the radar apparatus according to the first embodiment, a high distance resolution as shown in FIG. In addition, in order to obtain high distance resolution, it can implement | achieve by changing the band of a chirp signal and making it a wideband chirp signal.

  The angle measurement unit 64 performs angle measurement processing on the target signal sent from the detection unit 63, that is, the signal of each range that has been cut. In the radar apparatus according to the first embodiment, it is assumed that the angle measurement unit 64 performs angle measurement using the phase monopulse angle measurement method. The phase monopulse angle measurement method is described in, for example, “Supervised by Takashi Yoshida,“ Revised Radar Technology ”, First Edition, The Institute of Electronics, Information and Communication Engineers, February 15, 2003, pp 260-264”.

ここで、
Ｘｅ（ｎ）；アンテナ素子信号（ｎ＝１〜Ｎ）
Ｎ ；アンテナ素子数
ｄ ；アンテナ素子間隔
Ｗ（ｎ） ；アンテナ素子ウェイト
λ ；波長
θ０ ；ビーム指向方向
次に、Δビームが、次式で算出される。

In the phase monopulse angle measurement method, first, the Σ beam is calculated by the following equation.

here,
Xe (n); antenna element signal (n = 1 to N)
N: number of antenna elements d; antenna element spacing W (n); antenna element weight λ; wavelength θ0; beam directing direction Next, Δ beam is calculated by the following equation.

ここで、
Ｒｅ；複素数の実数部
その後、あらかじめ用意された誤差電圧εと角度との関係を規定したモノパルス曲線を用いて、誤差電圧εから角度を読み取り、測角値φが求められる。測角部６４は、上述した方法で測角値φをレンジセル毎に算出し、クロスレンジ方向の目標位置として、メモリ６５に格納する。この測角値φの算出は、Ｍ回（Ｍは正の整数）の観測機会において実施される。 Next, the error voltage ε is calculated from the Σ beam calculated by the above equation (1) and the Δ beam calculated by the equation (2) by the following equation.

here,
Re: real part of complex number Thereafter, using a monopulse curve that defines the relationship between the error voltage ε and the angle prepared in advance, the angle is read from the error voltage ε to obtain the angle measurement value φ. The angle measurement unit 64 calculates the angle measurement value φ for each range cell by the method described above, and stores it in the memory 65 as a target position in the cross range direction. The calculation of the angle measurement value φ is performed at M observation opportunities (M is a positive integer).

  As described above, the memory 65 stores the angle measurement value φ of each range calculated by the angle measurement unit 64, that is, the target position in the cross range direction, at each of the M observation opportunities. Therefore, when the M observation opportunities are completed, the target positions of the M sets of the respective ranges are stored. The contents of the memory 65 are read by the adding unit 66.

ここで、
Ｒ；目標距離
φ；測角値［ラジアン］
以上のように構成されるレーダ装置の動作を、目標形状取得処理を中心に、図５に示すフローチャート、ならびに図３および図４に示す説明図を参照しながら説明する。この目標形状取得処理は、レーダ制御器１１の制御の下に実施される。 After the M observations are completed, the adder 66 reads M sets of target positions from the memory 65, and adds or performs an OR operation on the range-cross range axes. Thereby, a target image is obtained. The cross range Rc can be calculated by the following equation.

here,
R: Target distance φ: Angle measurement [radian]
The operation of the radar apparatus configured as described above will be described with reference to the flowchart shown in FIG. 5 and the explanatory diagrams shown in FIGS. This target shape acquisition process is performed under the control of the radar controller 11.

  First, a beam position is designated (step S1). That is, the radar controller 11 designates the beam position in one direction within the observation region defined by the azimuth direction and the elevation angle direction as shown in FIG. The beam position is sequentially changed from a predetermined position so that the entire observation area can be observed.

  Next, pulse compression is performed (step S2). That is, the signal generator 1 generates a broadband chirp signal and sends it to the exciter 2. The exciter 2 converts the frequency of the broadband chirp signal sent from the signal generator 1 and amplifies the circulator 3 after the frequency conversion and amplification. To the antenna 4.

  Thereby, a radio wave is radiated from the antenna 4 in the designated direction. The antenna 4 receives the reflected wave of the radio wave and sends it to the receiver 5 via the circulator 3. The receiver 5 converts the frequency of this signal and sends it to the pulse compression unit 61 of the signal processor 6. The pulse compression unit 61 performs pulse compression on the signal sent from the receiver 5.

  Next, range extraction is performed (step S3). That is, as shown in FIG. 3B, the pulse compression unit 61 extracts a signal in the time axis (PRI: Pulse Repetition Interval) direction corresponding to one range from the pulse-compressed signal, and outputs it to the DFT unit 62. Sent. Next, DFT processing is performed (step S4). That is, the DFT unit 62 integrates the signal of one range sent from the pulse compression unit 61 by discrete Fourier transform (DFT) and sends it to the detection unit 63 as shown in FIG.

  Next, detection is performed (step S5). That is, the detection unit 63 detects a target by comparing the signal sent from the DFT unit 62 with a predetermined threshold level, and sends it to the angle measurement unit 64 as a target signal.

  Next, angle measurement is performed (step S6). That is, the angle measurement unit 64 performs angle measurement processing on the target signal sent from the detection unit 63 according to the procedure described above. Next, storage in the memory 65 is performed (step S7). That is, the angle measurement unit 64 stores the angle measurement value obtained by the angle measurement process in the memory 65 as the target position in the cross range direction. As a result, as shown in FIG. 3D, the target position (indicated by a black circle) for one range is stored in the memory 65.

  Next, it is checked whether or not the processing for all ranges has been completed (step S8). If it is determined in step S8 that the processing for all ranges has not been completed, the process returns to step S3, and processing for the next range is performed.

  Thus, when the target positions for a plurality of ranges are obtained, the target positions vary as shown in FIG. 3D due to the difference in the target reflection points, but do not deviate from the beam width range. On the other hand, if it is determined in step S8 that the processing for all ranges has been completed, it is then checked whether or not M observations have been completed (step S9). If it is determined in step S9 that the process has not ended, the process returns to step S2 and the next observation is performed.

  If it is determined in step S9 that M observations have been completed, then addition is performed (step S10). That is, when M observations are completed, the target position of each of the M sets of ranges as shown in FIG. 4A is obtained in the memory 65. Add or OR the target positions. Thereby, as shown in FIG. 4B, the target positions of the M sets of the respective ranges are synthesized, and the target shape is obtained.

  Next, it is checked whether or not the processing for all beam positions has been completed (step S11). If it is determined in step S11 that the process has not been completed, the process returns to step S1, and processing for the next beam position is performed. On the other hand, when it is determined in step S11 that the processing for all the beam positions has been completed, the target shape acquisition processing in this radar apparatus ends.

  In the radar apparatus according to the first embodiment described above, the angle measurement unit 64 is configured to measure the angle using the phase monopulse angle measurement method, but may be configured to measure the angle using the amplitude monopulse angle measurement method. .

  In the radar apparatus according to the first embodiment described above, a method using a broadband chirp signal is employed to increase the resolution in the range direction. However, for example, a method using a step frequency can also be employed.

  As for the method using the step frequency, for example, “Donald R. Wehner,“ High-Resolution Radar Second Edition ”, Artech House (1995), pp. 200-209” and “ae Sok Son,” Range-Doppler Radar Imaging and Motion Compensation ”, Artec House (2001), pp. 13-15”.

  In the radar apparatus according to the first embodiment described above, as shown in FIG. 6A, when a plurality of targets (target 1 and target 2) exist in the same range within the same beam width, the target shape is correctly set. It cannot be recognized.

  Therefore, the radar apparatus according to the second embodiment of the present invention, after separating the target by the Doppler filter by performing the Doppler decomposition process using the difference in the moving speed of each target, as shown in FIG. The processing described in the first embodiment is performed in each filter bank.

  At this time, if the movement speeds of the targets are similar, the resolution 1 / T1 is lowered and the targets are in the same bank as shown in FIGS. 7A and 7B. Cannot be separated by Doppler filter.

  In this case, as shown in FIG. 7C and FIG. 7D, the dwell time T (PRI × number of hits), which is the time during which the target is continuously irradiated with the beam, is lengthened, and the Doppler filter resolution 1 / T2 is raised and each target is controlled to enter a different bank. The dwell time T can be increased by changing the parameters of the DFT unit 62. Accordingly, the target is separated by the Doppler filter, and thereafter, the processing described in the first embodiment is performed.

  The radar apparatus according to the third embodiment of the present invention further obtains the target center-of-gravity position from the target shape obtained by the radar apparatus according to the first or second embodiment.

  FIG. 8 is a block diagram illustrating the configuration of the radar apparatus according to the third embodiment. This radar apparatus is configured by adding a gravity center calculating unit 67 to the radar apparatus according to the first embodiment.

ここで、
Ａｘ（ｎ）；Ｘ（ｎ）の位置に射影した振幅
Ａｙ（ｎ）；Ｙ（ｎ）の位置に射影した振幅
重心位置Ｘｇは、振幅Ａｘ（ｎ）が最大となるＸ軸座標である。また、重心位置Ｙｇは、振幅Ａｙ（ｎ）が最大となるＹ軸座標である。 After the target shape is recognized by the processing of the addition unit 66, the center-of-gravity calculation unit 67 projects the amplitude onto the orthogonal axes (X axis, Y axis) as shown in FIG. = 1 to N) and Ay (m) (m = 1 to M), the center of gravity is calculated by the following equation to calculate the center of gravity positions Xg and Yg.

here,
Ax (n); Amplitude projected to the position of X (n) Ay (n); Amplitude projected to the position of Y (n) The barycentric position Xg is an X-axis coordinate at which the amplitude Ax (n) is maximum. The gravity center position Yg is a Y-axis coordinate at which the amplitude Ay (n) is maximized.

  In the third embodiment, the position of the center of gravity is obtained. However, in order to show the characteristic position in the target shape, it is also possible to obtain the other position by weighting or the like. .

  The present invention can be applied not only to the detection of a target but also to a radar apparatus that obtains the shape of the target or the center of gravity of the shape.

1 is a block diagram illustrating a configuration of a radar apparatus according to Embodiment 1 of the present invention. It is a figure for demonstrating the resolution | decomposability of the range direction of the radar apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the target shape acquisition process performed in the radar apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the addition process performed in the addition part of the radar apparatus which concerns on Example 1 of this invention. It is a flowchart for demonstrating operation | movement of the radar apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the process performed in the radar apparatus which concerns on Example 2 of this invention. It is a figure for demonstrating the process performed in the radar apparatus which concerns on Example 2 of this invention. It is a block diagram which shows the structure of the radar apparatus which concerns on Example 3 of this invention. It is a figure for demonstrating the gravity center calculation process performed in the radar apparatus which concerns on Example 3 of this invention. It is a figure for demonstrating the conventional radar apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal generator 2 Exciter 3 Circulator 4 Antenna 5 Receiver 6 Signal processor 61 Pulse compression part 62 DFT part 63 Detection part 64 Angle measurement part 65 Memory 66 Addition part 67 Center of gravity calculation part

Claims (3)

A receiver for receiving a reflected wave with respect to a transmitted wave;
A DFT unit that integrates a high-resolution signal obtained by pulse compression of the signal from the receiver by discrete Fourier transform;
A detection unit that detects a target from a signal from the DFT unit and outputs the target as a target signal;
An angle measuring unit that performs angle measurement by a phase or amplitude monopulse method multiple times within a beam width for each range based on a target signal from the detection unit, and
A memory for storing a target position in the cross range direction determined by an angle measurement value of each range obtained by measuring an angle in the angle measuring unit;
An adder that adds or logically ORs the target positions of each of a plurality of sets of ranges stored in the memory at each of the plurality of observation times, and obtains a target shape;
A radar apparatus comprising: The DFT unit performs integration by discrete Fourier transform for each signal separated by the Doppler filter by performing Doppler decomposition processing with a long dwell time.
The radar apparatus according to claim 1, wherein the detection unit detects a target for each of the integrated signals separated from the DFT unit and outputs the target as a target signal.   The radar apparatus according to claim 1, further comprising a centroid calculating unit that performs a centroid calculation on the target shape obtained by the adding unit.

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