JP4867190B2 - Radar apparatus and angle measuring method - Google Patents

Description

  The present invention relates to a radar apparatus, and more particularly to a radar apparatus and an angle measurement method that perform digital beam forming.

  A radar device generally detects the presence of a target by observing the position, motion state, and the like by emitting a radio wave from an antenna into space and receiving a reflected signal from the target. A conventional radar apparatus employs a pencil beam pattern, a cosecant square pattern, or the like as a beam pattern, which is a gain characteristic when radio waves are transmitted and received in space, depending on the application.

Further, as a general angle measurement method in a conventional radar apparatus, for example, an amplitude comparison angle measurement method and a monopulse angle measurement method have been proposed.
FIG. 5 is a diagram illustrating the principles of the amplitude comparison angle measurement method and the monopulse angle measurement method.
In the amplitude comparison method, as shown in FIG. 5A, two adjacent pencil beams having sharp directivity are formed, and the relationship between the amplitude value ratio and angle of the two pencil beams is held in advance as a table. deep. Then, when a target is detected, a ratio of amplitude values of received signals of two pencil beams formed so as to sandwich the target is measured, and an angle measurement value is obtained from a held table. In the monopulse angle measurement method, as shown in FIG. 5 (b), two types of beam patterns, a Σ pattern and a Δ pattern, are formed, and the relationship between the ratio of the amplitude value of the Σ pattern and the Δ pattern and the angle is previously stored. Keep as. Then, when the target signal is detected, the ratio of the amplitude values of the beam patterns is measured, and the angle measurement value is obtained from the held table.

  FIG. 6 is a diagram illustrating a configuration example of a radar apparatus that employs an amplitude comparison angle measurement method. Antenna elements 1-1 to 1-L, beam controller 2, memory 3, # 1 beamformer 16, signal processor 5, TH comparator (1) 6, and # 2 beamformer 17 And a signal processor 8 and an amplitude comparison angle measurement processor 18. The beam controller 2 generates and outputs control signals to the antenna elements 1-1 to L. Each antenna element performs transmission and reception by controlling the phase and amplitude based on the control signal. The digital reception signal from each antenna element is once held in the memory. The # 1 beamformer 16 and the # 2 beamformer 17 each form an adjacent pencil beam pattern. The received signals obtained by the respective beams are subjected to signal processing such as pulse compression and integration for S / N improvement and clutter suppression in the signal processors 5 and 6, and output amplitude values to the TH comparator (1) 6. The TH comparator (1) 6 compares the amplitude value of the input received signal with a predetermined threshold value TH1, and if the amplitude value is larger than TH1, it is determined as the target signal. At this time, the amplitude comparison angle measurement processor 18 obtains the ratio between the amplitude value of the # 1 beam and the amplitude value of the # 2 beam, and obtains and outputs the angle measurement value with reference to a previously held table of amplitude ratio versus angle.

  FIG. 7 is a diagram illustrating a configuration example of a radar apparatus employing a monopulse angle measurement method. Instead of the # 1 beam former 16, the # 2 beam former 17, and the amplitude ratio angle measuring processor 18 in FIG. 6 of the amplitude ratio angle measuring method, a Σ beam former 19, Δ beam former 20, monopulse angle measuring. Other than these, the configuration and operation are the same as in FIG. 6 of the amplitude comparison angle measurement system. The Σ beam former 19 and the Δ beam former 20 form a Σ beam pattern and a Δ beam pattern, respectively. The monopulse angle processor 21 calculates the ratio between the amplitude value of the Σ beam and the amplitude value of the Δ beam, and calculates and outputs the angle value with reference to a previously stored table of amplitude ratio versus angle.

  In addition, a method for detecting a null point of a Δ pattern by a monopulse angle measurement method has been proposed (see Patent Document 1). This is a method using the fact that the beam width of the Δ pattern shows a characteristic in which the amplitude value changes sharply near the null point as compared with the beam width of the Σ pattern.

  FIG. 8 is a diagram showing the configuration of this type of radar apparatus. Two antenna elements 1-1, 1-2, a transmitter 23, a duplexer 24, mixers 25 and 26, amplitude detectors 27 and 28, TH comparators 29 and 30, a NAND gate 31 and an AND gate 32. In this radar apparatus, the pulse modulated wave signal output from the transmitter 23 is radiated from the antennas 1-1 and 1-2 via the duplex 24 and the hybrid 22. The reflected wave from the target is input to the hybrid 22 from the antennas 1-1 and 1-2, and is decomposed into a sum signal and a difference signal. The sum signal is input to the mixer 25, and the difference signal is input to the mixer 26. The sum signal and the difference signal are converted into intermediate frequency signals by the mixers 25 and 26, input to the amplitude detectors 27 and 28, respectively, and output from the amplitude detectors 27 and 28 as reception signals of the Σ beam and Δ beam, respectively. The received signal of the Σ beam and the received signal of the Δ beam are compared with the threshold values TH3 and TH4 in the TH comparator 29 and TH comparator 30, respectively, and are binarized. The output of the Δ beam is further inverted by the inverter 31, and the AND gate 32 takes the AND output of the binary output of the Σ beam.

9A and 9B are diagrams showing output waveforms of each part of the radar apparatus, where FIG. 9A shows the antenna beam pattern, FIG. 9B shows the output of the TH comparator 29, FIG. 9C shows the output of the TH comparator 30, and FIG. ) Is the output of the inverter 31, and (e) is the output of the AND gate. As can be seen from the width of the output (e) of the AND gate, the angle measurement accuracy and the like of this radar apparatus are determined by the characteristic near the null of the Δ pattern and the threshold value TH4 of the TH comparator 30.
JP-A-56-1267827

  One of the main performances of the radar apparatus is angle measurement accuracy, which is the position measurement accuracy of the number of times the target exists with respect to the radar in the azimuth direction or elevation direction. Angle measurement accuracy is an important performance in radar devices. For example, in air traffic control, the smaller the angle measurement error, the higher the safety, so that performance improvement is always required. However, if the beam width cannot be reduced in the amplitude ratio angle measurement method or the monopulse angle measurement method described above, the angle measurement accuracy cannot be improved. However, the beam width is determined by the antenna size, the number of elements, the frequency, and the like, and is limited.

  In addition, the angular resolution for recognizing each target as a separate target when two or more targets are close to each other is also an important performance, but the amplitude value of the received signal for each angle is compared with the threshold value TH. In the method of detecting a target, it is difficult to decompose a plurality of targets that are close to the beam width. For this reason, when two or more targets are close to each other, the received signals are superimposed on each other, and the angle measurement accuracy is lowered.

  Furthermore, the conventional method using the null point of the Δ pattern of the monopulse angle measurement method is not based on digital beam forming, and the width near the null point is not only widened, but also the binarized signal by the null point is compared. Output at a predetermined threshold level, and the characteristics of the center of a narrower null point cannot be used, so that the angular resolution is limited and the improvement is insufficient. Further, it is not possible to realize angle measurement with a narrower null point by simultaneously forming a plurality of received beam patterns by digital beam forming.

[Object of invention]
An object of the present invention is to provide a radar apparatus and an angle measurement method by digital beam forming having excellent angle measurement accuracy.
Another object of the present invention is to provide a radar apparatus and an angle measuring method with excellent angular resolution capable of detecting a plurality of approaching targets.
Another object of the present invention is to provide a radar apparatus and an angle measuring method for detecting a target based on the characteristics of a null point having a narrower width of an antenna beam pattern formed by digital beam forming.

  The radar apparatus according to the present invention is a radar apparatus that performs digital beam forming, and a memory for holding reception signals of a plurality of antenna elements, and an angle measuring device arranged in parallel in an angular direction from the reception signals held in the memory. A multi-angle forming beam forming unit (for example, 7 in FIG. 1) that forms a plurality of receiving beam patterns for angle measurement having a narrow null point and outputs a reception signal for each angle of the receiving beam pattern for angle measurement. ), And the smallest amplitude value is detected from the reception signals at successive angles including a large amplitude value, and the angle of the reception beam pattern for angle measurement that outputs the reception signal of the amplitude value is output as the angle measurement value. Target angle measuring means (for example, 8 to 11 in FIG. 1, 8, 15, 10, 11 in FIG. 2). An average value subtractor (for example, 9 in FIG. 1) that calculates an average value of a predetermined number of amplitude values including the received signals and subtracts the amplitude value of the received signal of interest, and for each angle after subtracting the average value A minimum value detector (for example, 10 in FIG. 1) that detects a reception signal having the minimum amplitude value among the amplitude values, or the angle measurement output means uses a predetermined threshold value from the reception signal for each angle. A target range detector (for example, 15 in FIG. 2) that identifies an angular range in which the target signal exists by comparison with a minimum value detector (for example, FIG. 2) that detects a received signal having the smallest amplitude value in the angular range. 2), and the angle measurement output means outputs the angle measurement value when the amplitude value of the output of the minimum value detector is a specific threshold value or less. For example, it is characterized by having 11) in FIGS.

  Further, a plurality of detection reception beam patterns arranged in the angular direction simultaneously and in parallel from the reception signals held in the memory are formed, and a reception signal is output at each angle corresponding to each detection beam pattern. Multi-beam forming means (for example, 4 in FIG. 1) and a received signal having a large amplitude value among the received signals output for each angle are detected as target signals, and the detection received beam pattern for detecting the target signal is detected. And target detection means (for example, 5 and 6 in FIG. 1) for determining an angle range of a plurality of angle measurement reception beam patterns formed by the angle measurement multi-beam forming means based on an angle, To do.

  Furthermore, when the angle measurement value of the target angle measurement means is output, target signal estimation means (for example, 12 and 13 in FIG. 1) for outputting an estimated target signal obtained by estimating the target signal, and the reception held in the memory A subtracter (for example, 14 in FIG. 1) that subtracts the estimated target signal from the signal and removes the detected target signal component, and the target signal estimating means detects the target signal. In this case, a beamformer (for example, 12 in FIG. 1) that forms a detection reception beam pattern at the angle, and an estimation target signal is generated as the signal component of the target signal from the amplitude value of the output of the beamformer. A target signal generator (for example, 13 in FIG. 1), and for the angle measurement by the angle measurement multi-beam forming means for the received signal held in the memory after subtracting the estimated target signal Receive video And characteristics that the formation of the beam pattern and repeating said angle measuring by the target angle measuring means.

  More specifically, the radar apparatus of the present invention is a radar apparatus that performs digital beam forming, controls the phase and amplitude for each element, performs transmission / reception, and performs A / D conversion on the received signal for digital reception. An antenna element to be output as a signal, a beam controller for generating and outputting a control signal for forming a desired beam pattern for each antenna element, a digital reception signal output from each antenna element, and a post-processing signal A multi-beam which forms a plurality of detection reception beam patterns arranged in the angle direction simultaneously and in parallel from the reception signals held in the memory, and outputs the reception signals for each angle corresponding to each beam. Signal processing such as pulse compression and integration for the S / N improvement and clutter suppression for the received signal of the former (1) and the received beam pattern for detection A signal processor that outputs an amplitude value at each angle, and a TH that detects a received signal having an amplitude value greater than TH1 by comparing the amplitude value with a threshold TH1 for the received signal after signal processing. The receiver (1) and the received signal held in the memory are densely formed with a plurality of angle measuring receive beam patterns arranged in the angle direction simultaneously in parallel, and the received signal is output for each angle corresponding to each beam. The multi-beamformer (2) and the received signal of the angle measurement receive beam pattern are subjected to signal processing such as pulse compression and integration for S / N improvement and clutter suppression, and output an amplitude value at each angle. A signal processor that calculates the average value of the amplitude value of the angle of a predetermined number of samples before and after the angle of interest for each angle, and an average value subtractor that subtracts from the amplitude value of the angle of interest, and the average value subtraction After each A minimum value detector for detecting a minimum amplitude value among the amplitude values of the degree, and the detected amplitude value is compared with a predetermined threshold TH2, and when it is smaller than TH2, it is determined as a target signal; From the TH comparator (2) that outputs the angle of the beam as an angle measurement value, the beamformer that forms the reception beam pattern for detection at the angle determined that the target exists, and the output amplitude value of the beamformer Estimated target signal generator for generating an estimated received signal as a signal component before detection and signal processing of the detected target, and target signal component detected by subtracting the estimated received signal from the received signal held in the memory And a subtractor for removing (FIG. 1).

  The angle measuring method of the present invention is the angle measuring method of a radar apparatus that performs digital beam forming, the step of holding the received signals of a plurality of antenna elements in a memory, and the angle in parallel from the received signals held in the memory. Forming a plurality of angle measurement reception beam patterns having narrow null points for angle measurement arranged in the direction, and outputting a reception signal for each angle of the angle measurement reception beam pattern; and a large amplitude value Including the step of detecting the smallest amplitude value among the received signals for each successive angle including, and outputting the angle of the received beam pattern for angle measurement that outputs the received signal of the amplitude value as the angle measurement value, The step of outputting the angle measurement value calculates an average value of a predetermined number of amplitude values including the reception signals before and after the reception signal of interest and subtracts it from the amplitude value of the reception signal of interest. And a step of detecting a reception signal having a minimum amplitude value among the amplitude values of each angle after subtracting the average value, or comparing the target signal with a predetermined threshold value from the reception signal for each angle. And a step of detecting a received signal having the smallest amplitude value in the angle range. The step of detecting the reception signal having the smallest amplitude value includes the step of outputting the angle measurement value when the amplitude value of the reception signal having the smallest amplitude value is equal to or less than a specific threshold value. .

  And forming a plurality of detection reception beam patterns arranged in the angle direction simultaneously and in parallel from the reception signals held in the memory, and outputting the reception signals for each angle corresponding to each of the detection beam patterns; , Receiving signals having a large amplitude value among the received signals output for each angle are detected as target signals, and the plurality of receiving beam patterns for angle measurement are based on the angles of the receiving beam patterns for detection that detected the target signals. A step of outputting an estimated target signal obtained by estimating a target signal when the angle measurement value is output, and subtracting the estimated target signal from the received signal held in the memory And removing the detected target signal component.

  The step of outputting the estimated target signal includes a step of forming a reception beam pattern for detection at the angle when the target signal is detected, and a signal of the target signal from the amplitude value of the output of the detection reception beam pattern. Generating an estimated target signal as a component, and repeating the angle measurement process by forming the angle-receiving beam pattern for the received signal held in the memory after subtracting the estimated target signal It is characterized by that.

  In the present invention, a plurality of receiving beam patterns for angle measurement, which are sharply changed near the null point by digital beam forming and narrowed in width, are formed simultaneously in parallel in the angular direction, so that the amplitude value decreases. It is possible to detect the target signal with high angle measurement accuracy by configuring so as to measure the angle at the point.

  In addition, the signal component before beam formation based on the detected target signal is generated by back calculation as an estimated received signal and is subtracted from the received signal stored in the memory, so that 1 of the plurality of target signals is obtained. It is possible to reliably detect each one.

  In addition, by first forming a plurality of reception beam patterns for detection and detecting the angular direction in which the target signal exists, it is configured to densely form a plurality of reception beam patterns for angle measurement in the angular direction, It is possible to perform angle measurement processing using the reception beam pattern for angle measurement only in the angle direction where the target signal exists.

Next, an embodiment of the present invention will be described in detail with reference to the drawings.
[Description of configuration]
FIG. 1 is a diagram showing the configuration of an embodiment of a radar apparatus according to the present invention. The radar apparatus shown in FIG. 1 includes antenna elements 1-1 to L, a beam controller 2, a memory 3, a multi-beamformer (1) 4, a signal processor 5, a TH comparator (1) 6, and a multi-beamformer. (2) 7, a signal processor 8, an average value subtractor 9, a minimum value detector 10, a TH comparator (2) 11, a beam former 12, an estimated target signal generator 13, and a subtractor 14.

[Description of operation]
FIG. 2 is a diagram showing the characteristics of each part of the present embodiment. An operation example of the present embodiment will be described with reference to FIGS.
The beam controller 2 generates and outputs a control signal for forming a desired beam pattern for each of the antenna elements 1-1 to L.

  Each antenna element 1-1 to L controls the phase and amplitude based on the control signal for each element, performs transmission / reception of a pulse modulated wave, A / D converts the reception signal, and outputs it to the memory 3 as a digital reception signal To do.

  The memory 3 holds the digital reception signals output from the antenna elements 1-1 to L and outputs the reception signals to the multi-beam former (1) 4 and the multi-beam former (2) 7. As will be described later, when the target signal is detected, the held reception signal is output to the subtracter 14. Further, the received signal after subtracting the estimated target signal from the output received signal is input from the subtractor 14 and held.

  As shown in FIG. 2A, the multi-beamformer (1) 4 includes a plurality of detection reception beam patterns A1 to AM that are sequentially arranged in the angular direction in parallel with each other as shown in FIG. The received signal for each angle corresponding to each detection reception beam pattern is output to the signal processor 5.

  The signal processor 5 performs signal processing such as pulse compression and integration for S / N improvement and clutter suppression for each reception signal of the detection reception beam pattern.

  The TH comparator (1) 6 compares the amplitude value of the received signal after the signal processing from the signal processor 5 with a predetermined threshold (threshold) TH1 and has an amplitude value larger than TH1. The signal is detected as a target signal, and the beam angle (value) of the reception beam pattern for detection from which the target signal is detected is output to the multi-beamformer (2) 7.

  The multi-beamformer (2) 7 is held in the memory 3 as shown in FIG. 2 (b) for an angle range with a predetermined width including the angle input from the TH comparator (1) 6. A plurality of received beam patterns for angle measurement are formed densely for each angle in the angle direction simultaneously in parallel with the received signal, and the received signal is output for each angle (for each received beam pattern for angle measurement).

  The signal processor 8 performs signal processing such as pulse compression and integration for S / N improvement and clutter suppression for each reception signal of the angle measurement reception beam pattern.

  The average value subtractor 9 calculates the average value of the amplitude values of the received signals by a predetermined number of received beam patterns for angle measurement (number of samples) including before and after the angle of interest for each angle. Subtract from the amplitude value. The average value of the amplitude value of the received signal is as shown in FIG. 2 (d), and the subtraction result from the amplitude value of the angle of interest is the null point of the received beam pattern for angle measurement as shown in FIG. 2 (e). Indicates the minimum amplitude value.

  The minimum value detector 10 detects the reception signal having the minimum amplitude value among the amplitude values at each angle after subtracting the average value, and outputs the amplitude value to the TH comparator 11.

  The TH comparator (2) 11 compares the detected amplitude value with a predetermined threshold TH2, determines that the target signal is smaller than TH2, and determines the angle of the beam (the received beam pattern for angle measurement). The angle of the null point) is output as a measured value (target angle).

  The beam former 12 has the same beam width as the detection reception beam pattern shown in FIG. 2A with respect to the beam angle (target angle) for which the target signal is determined from the reception signal held in the memory 3. A reception beam pattern for detection shown in FIG. 2 (f) whose peak coincides with the angle of the beam is formed (beam formation).

  The estimated target signal generator 13 calculates and generates an estimated received signal from the amplitude value of the output of the beam former 12 as a signal component before detection and beam processing of the detected target, and outputs it to the subtractor 14. .

Here, the beam forming equation of the beam former 12 is
A = W · X
W = [W1, W2,..., WL]: Weight given as a control signal to each antenna element X = [X1, X2,..., XL] ^T : Amplitude value of received signal of each antenna element ( ^T Represents transposition)
Then,
The calculation formula of the estimated target signal of the estimated target signal generator 13 is as follows.
X = K · A · W ^* ( ^* represents conjugate transposition)
K: coefficient for correcting the gain of signal processing

  The subtracter 14 removes the target signal component detected by subtracting the estimated received signal from the received signal held in the memory 3.

  When a plurality of target signals are included in the reception signal held in the memory 3, after the target signal component is removed, the reception signal by the reception beam pattern for angle measurement of the multi-beam former (2) 7 From, for example, a signal processor 8, an average value subtractor 9, a minimum value detector 10 and a TH comparator constituting the target angle measuring means of the present invention with respect to received signals at successive angles including the next largest amplitude value. (2) The same processing as described above is performed so that the angle (value) is output at 11. As another processing method, reception signals for each successive angle including a large amplitude value such as a predetermined value or more are sequentially selected in the angle direction and the angle (value) is output. These selection processes can be implemented by providing a selection circuit in any one of the signal processor 8, the average value subtractor 9, the minimum value detector 10, and the TH comparator (2) 11 or between the stages. Specifically, the threshold value TH2 (FIG. 2 (e)) of the TH comparator (2) 11 is sequentially increased. Similar threshold determination is performed on the average value output from the average value subtractor 9. This can be realized by performing a mutual comparison between a plurality of minimum amplitude values of the average value subtracter 9 and a plurality of average values.

  Further, in the detection of the target signal by the detection reception beam pattern, the same applies when the target signal is detected by a plurality of different detection reception beam patterns, and the signal processor 5 constituting the target detection means of the present invention, TH The comparator (1) 6 outputs angles (values) in the order of the detection received beam pattern from which the received signal with the largest amplitude is detected, or sequentially selects received signals with larger amplitude values such as a predetermined value or more in the angular direction. And output the angle. This case can also be realized, for example, by changing the threshold value TH1 of the TH comparator (1) 6.

  The above processing is repeated for each beam scan until the target is no longer detected, so that the antenna pattern (received beam for angle measurement) can be obtained by digital beam forming that allows precise control of the phase and amplitude of a large number of antenna elements. High accuracy of angle measurement using extremely narrow null points (pattern), and at the same time, even when two or more targets are close to each other, the angle measurement accuracy is not reduced sequentially, and the high angle resolution is achieved. Can be detected.

Next, the overall processing procedure of the angle measuring method of the radar apparatus described above according to the present invention will be described below.
FIG. 3 is a diagram showing a processing flow of the angle measuring method of the present invention.
First, a pulse-modulated wave is transmitted / received via a plurality of antenna elements (s1) and held in the memory 3 (s2). Next, a plurality of detection reception beam patterns arranged in the angle direction are simultaneously formed in parallel from the reception signals held in the memory, and reception signals are output for each angle corresponding to each of the detection reception beam patterns (s3). . When a received signal having a large amplitude value is detected among the received signals output for each angle (s4), an angle range based on the angle of the received beam pattern for detection detected as a target signal has an angle measurement width. A plurality of angle measuring reception beam patterns having narrow null points are formed densely (s5).

  Next, when a reception signal for each successive angle including a large amplitude value is detected from reception signals by a plurality of reception beam patterns for angle measurement (s6), a reception signal before and after that is included for a certain reception signal. Calculate the average value of the predetermined number of amplitude values, subtract from the amplitude value of the received signal of interest, detect the received signal with the smallest amplitude value among the amplitude values of each angle after subtracting the average value, and The angle of the reception beam pattern for angle measurement that outputs the reception signal of the value is output as the target angle measurement value (s7).

  When the angle measurement value is output, a detection reception beam pattern is formed at the angle at which the target signal is detected (s8), and an estimated target signal is generated by estimating the target signal based on the received signal (s9). The estimated target signal is subtracted from the held received signal (s10), and the process proceeds to step s6 for detecting the next target signal.

  Further, in the above processing operation, when a reception signal having a large amplitude value is not detected in step s6, the process proceeds to step s4 for detection of a reception signal by the detection reception beam pattern, and the reception signal having a large amplitude value is also detected in step s4. If no more is detected, the process proceeds to step s1 for transmitting and receiving a pulse-modulated wave.

  In the above embodiment, the configuration example in which the angle range where the target signal exists is specified in advance by using the multi-beamformer 4 that forms the reception beam pattern for detection has been described. However, the present invention is not limited to this configuration. However, the multi-beamformer 4, the signal processor 5, and the TH comparator 6 of FIG. 1 may be omitted. This is because the average value calculated by the average value subtracter 9 appears as a large amplitude value in the calculation result of the angle measuring reception beam pattern before and after the angle at which the target exists, as described above. This is because it can be specified in a narrower angle range. Further, the use of the above average value subtractor is not limited to this, and can be realized by using a comparator or the like in which a predetermined threshold is set, and a target angle range can be specified.

(Second Embodiment)
As the second embodiment of the present invention, the multi-beamformer (1) 4, the signal processor 5, and the TH comparator (1) 6 in the embodiment shown in FIG. A simplified configuration example in which a target range detector 15 using a comparator instead of 9 is added will be described.

  FIG. 4 is a diagram showing the configuration of the second embodiment. Since the operations of the components other than the target range detector 15 in FIG. 4 are the same as the respective configurations and operations of FIG. 1, the processing operation after the target range detector 15 will be described for the configuration and operation of the second embodiment. To do.

  The target range detector 15 compares the output of each receiving beam pattern for angle measurement with the threshold TH5 and detects the angle of the range where the target exists. Specifically, an angle range in which a plurality of amplitude values of TH5 or more (a specific threshold value or more) are continuously detected is detected, and the minimum value detector 10 detects a received signal having the minimum amplitude in the angle range. And output to the TH comparator (2) 11. The TH comparator (2) 11 compares the received signal having the minimum amplitude with the threshold TH2 and determines that the angle of the received beam pattern for angle measurement of the received signal is the target angle if it is equal to or less than TH2. Output as angular value.

  In the present embodiment, the configuration is simplified by performing detection processing using the angle-receiving beam pattern, and the target S / N to be detected is sufficiently large. However, it is effective under the condition that even a receiving beam pattern for angle measurement with a low gain can be detected.

  Also in the second embodiment, a detection reception beam pattern is formed by the beam former 12 constituting the target signal estimation means after the angle measurement value is output, and the estimated target signal generator 13 uses the amplitude value of the reception signal. An estimated target signal is generated, subtracted from the received signal held in the memory 3, the received signal after subtraction is held in the memory 3, and angle measurement processing is performed by forming a received beam pattern for angle measurement on the new received signal. The point that the operation is repeated is the same as in the above-described embodiment.

  In the flow of the angle measuring method of the second embodiment, it is obvious that steps s3 and s4 are omitted in FIG. 3, and step s7 is changed to processing by a threshold value. In this case, the processing for specifying the angle range of the angle measurement beforehand by the detection reception beam pattern is omitted.

  In the above embodiment, the comparator (2) is provided in the configuration of the target angle measurement means, the amplitude value of the received signal is compared with a predetermined threshold value, and the received signal is determined depending on the case where the amplitude value is smaller than the threshold value. Although an example in which the angle of the receiving beam pattern for angle measurement to be output is output as the angle measurement value, the angle measurement value can be directly output based on the detection result of the minimum detector 10.

It is a figure which shows the structure of embodiment of this invention. It is a figure which shows the characteristic of each part of this Embodiment. It is a figure which shows the processing flow of the angle measuring method of this invention. It is a figure which shows the structure of the 2nd Embodiment of this invention. It is a figure which shows the principle of an amplitude comparison angle measurement system and a monopulse angle measurement system. It is a figure which shows the structural example of the radar apparatus of a prior art which employ | adopted the amplitude comparison angle measuring system. It is a figure which shows the structural example of the radar apparatus of a prior art which employ | adopted the monopulse angle measuring system. It is a figure which shows the structural example of the radar apparatus of the prior art of the system which detects the null point of (DELTA) pattern. It is a figure for demonstrating operation | movement of the prior art shown in FIG.

Explanation of symbols

1-1 to L antenna element 2 beam controller 3 memory 4 multi-beamformer (1)
5 Signal processor 6 TH comparator (1)
7 Multi-beamformer (2)
8 Signal processor 9 Average value subtractor 10 Minimum value detector 11 TH comparator (2)
12 Beamformer 13 Estimated target signal generator 14 Subtractor 15 Target range detector 16 # 1 Beamformer 17 # 2 Beamformer 18 Amplitude comparison angle measurement processor 19 Σ Beamformer 20 Δ Beamformer 21 Monopulse measurement Angle processor 22 Hybrid 23 Transmitter 24 Duplexer 25, 26 Mixer 27, 28 Amplitude detector 29 TH comparator (3)
30 TH comparator (4)
31 inverter 32 and gate

Claims (14)

In radar equipment that performs digital beamforming,
A memory for holding reception signals of a plurality of antenna elements;
A plurality of angle measuring reception beam patterns having narrow angle measuring null points arranged in parallel in the angle direction from the received signals held in the memory are formed, and the angles of the angle measuring reception beam patterns Multi-beam forming means for angle measurement that outputs a received signal every time;
Target angle measurement that outputs the angle of the received beam pattern for angle measurement that detects the smallest amplitude value from the received signals at each successive angle including large amplitude values and outputs the received signal of the amplitude value as the angle measurement value Means,
Target signal estimation means for outputting an estimated target signal obtained by estimating a target signal at the time of output of the angle measurement value of the target angle measurement means;
A subtractor that removes the detected target signal component by subtracting the estimated target signal from the received signal held in the memory, and
The target signal estimating means, when a target signal is detected, a beam former that forms a reception beam pattern for detection at the angle; and
A radar apparatus comprising: an estimated target signal generator that generates an estimated target signal as a signal component of a target signal from an amplitude value of an output of the beam former.   The target angle measuring means calculates an average value of a predetermined number of amplitude values including reception signals before and after the received signal of interest, and subtracts the average value from the amplitude value of the received signal of interest, and an average value The radar apparatus according to claim 1, further comprising: a minimum value detector that detects a reception signal having a minimum amplitude value among amplitude values at respective angles after subtracting. The target angle measuring means detects a target range detector that identifies an angular range in which the target signal exists by comparing the received signal for each angle with a predetermined threshold, and a received signal having the smallest amplitude value in the angular range. The radar apparatus according to claim 1, further comprising a minimum value detector. 4. The radar apparatus according to claim 2, wherein the target angle measurement means includes a comparator that outputs the angle measurement value when an amplitude value of an output of the minimum value detector is equal to or less than a specific threshold value. . A detection multi-beam that forms a plurality of reception beam patterns for detection arranged in the angle direction simultaneously and in parallel from the reception signals held in the memory, and outputs reception signals for each angle corresponding to each of the detection beam patterns Forming means;
A reception signal having a large amplitude value among reception signals output for each angle is detected as a target signal, and the multi-beam forming unit for angle measurement forms based on the angle of the reception beam pattern for detection that has detected the target signal. The radar apparatus according to any one of claims 1 to 4, further comprising target detecting means for determining an angle range of a plurality of angle measuring reception beam patterns. The beamforming equation of the beamformer is
A = W · X
W = [W1, W2,..., WL]: Weight given as a control signal to each antenna element X = [X1, X2,..., XL] T: Amplitude value (T of received signal of each antenna element) Represents transposition)
age,
The estimated target signal generator is
X = K · A · W * (* represents conjugate transpose)
2. The radar apparatus according to claim 1, wherein the estimated target signal is calculated by a calculation formula of a coefficient for correcting a gain of signal processing.   For the received signal held in the memory after subtracting the estimated target signal, the angle measuring reception beam pattern formation by the angle measuring multi-beam forming means and the angle measurement by the target angle measuring means are repeated. The radar apparatus according to any one of claims 1 to 6. In an angle measuring method of a radar apparatus that performs digital beam forming,
Holding received signals of a plurality of antenna elements in a memory;
A plurality of angle measuring reception beam patterns having narrow angle measuring null points arranged in parallel in the angle direction from the received signals held in the memory are formed, and the angles of the angle measuring reception beam patterns Outputting a received signal every time;
A step of detecting the smallest amplitude value from reception signals for each successive angle including a large amplitude value, and outputting the angle of the reception beam pattern for angle measurement for outputting the reception signal of the amplitude value as an angle measurement value;
Outputting an estimated target signal obtained by estimating a target signal at the time of outputting the angle measurement value;
Subtracting the estimated target signal from the received signal held in the memory to remove the detected target signal component, and
Outputting the estimated target signal comprises:
When a target signal is detected, forming a reception beam pattern for detection at the angle; and
Generating an estimated target signal as a signal component of the target signal from the amplitude value of the output of the detection reception beam pattern. The step of outputting the angle measurement value includes:
Calculating an average value of a predetermined number of amplitude values including received signals before and after the received signal of interest, and subtracting from the amplitude value of the received signal of interest;
Detecting a received signal having the smallest amplitude value among the amplitude values at each angle after subtracting the average value;
The angle measuring method according to claim 8, comprising: The step of outputting the angle measurement value includes:
Identifying an angle range in which the target signal exists by comparing the received signal for each angle with a predetermined threshold;
Detecting a received signal having the smallest amplitude value in the angular range;
The angle measuring method according to claim 9, comprising: Detecting the received signal having the smallest amplitude value;
11. The angle measuring method according to claim 9, further comprising a step of outputting the angle measurement value when the amplitude value of the reception signal having the smallest amplitude value is equal to or less than a specific threshold value. Forming a plurality of detection reception beam patterns arranged in the angle direction simultaneously in parallel from the reception signals held in the memory, and outputting the reception signals for each angle corresponding to each detection beam pattern;
A reception signal having a large amplitude value among reception signals output for each angle is detected as a target signal, and the plurality of angle measurement reception beam patterns are detected based on an angle of the detection reception beam pattern from which the target signal is detected. 12. An angle measuring method according to claim 8, further comprising a step of determining an angle range. The beam forming formula of the receiving beam pattern for detection is
A = W · X
W = [W1, W2,..., WL]: Weight given as a control signal to each antenna element X = [X1, X2,..., XL] T: Amplitude value (T of received signal of each antenna element) Represents transposition)
age,
The formula to generate the estimated target signal is
X = K · A · W * (* represents conjugate transpose)
9. The angle measuring method according to claim 8, wherein K is a coefficient for correcting a gain of signal processing. 14. The angle measurement process by forming the angle measurement reception beam pattern is repeated for a reception signal held in a memory after subtracting the estimated target signal.
The angle measuring method according to claim 1.

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