JP2004257761A - Radar signal processing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar signal processing device and a radar signal processing method capable of improving the processing performance under the environment where an unnecessary wave component exists. <P>SOLUTION: Adaptive processing parts 4 are respectively mounted on each of main antennas 11-1n and auxiliary antennas 21-2m, and a clutter component is suppressed for every antenna element. Adaptive processing parts 5 are respectively mounted at the back of the adaptive processing parts 4 of the main antennas 11-1n to suppress an interference wave component from a reception signal where the clutter is suppressed. The beam formation processing is performed by a beam forming part 100 on the basis of an antenna element signal where the clutter and the interference wave component are suppressed, and an electric wave coming direction is extracted by a direction extracting part 200. Further an adaptive processing part 7 is mounted at the back of the beam forming part 100, and the unnecessary wave component is eliminated when it remains in the beam output. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radar signal processing device and a radar signal processing method for receiving a pulse-shaped radar echo, extracting a target direction such as a radio wave source, and performing processing such as beam forming.
[0002]
[Prior art]
FIG. 4 is a functional block diagram showing a configuration of a conventional radar signal processing device. In FIG. 4, an incoming pulsed radar echo is received by a plurality of antenna elements 11 to 1n and converted into antenna element signals. Each of the antenna element signals is subjected to processing such as low noise amplification, frequency conversion, and digital conversion by the reception processing unit 3 and then branched into two, and is input to the beam forming unit 100 and the direction extracting unit 200. The beam forming unit 100 forms a beam from each element signal by a digital beam forming (DBF) process or the like. The direction extracting unit 200 specifies the direction of arrival of a radio wave by a technique such as a MUSIC (Multiple Signal Classification) algorithm.
However, as is well known, various unnecessary wave components such as clutter and interfering waves are present in a radio wave reception environment, and thus the radar signal processing device cannot always exhibit the expected performance.
[0003]
FIG. 5 is a diagram schematically showing a processing result in a conventional radar signal processing device. As shown in FIG. 5A, a plurality of filter banks are formed when the received beam is Fourier-transformed, but when the Doppler frequency dispersion is large, it is difficult to sufficiently suppress the clutter component by a known method. Therefore, as shown in FIG. 5B, a clutter component larger than the true target direction may remain in the processing result. When an interfering wave arrives from the side lobe direction of the beam as shown in FIG. 5C, a large interfering wave component may be similarly detected as shown in FIG. 5B. Various techniques for solving such a problem are disclosed in the following documents, but there is a need for a signal processing apparatus capable of removing unnecessary wave components more effectively.
[0004]
Patent Literature 1 discloses an adaptive antenna device based on the Gram-Schmidt method, which can increase the processing speed and has excellent circuit expandability. Non-Patent Document 1 discloses details of an adaptive MTI (Moving Target Indication) method as one method related to unnecessary wave removal. Non-Patent Document 2 discloses p. 35-37 and P.E. 98-99, details concerning a direct solution scheme such as SMI are described. Details of the MSN (Maximum Signal Noise Ratio) system are described in 67 to 86. Either method is used to suppress clutter. Further, this document describes details regarding the MUSIC algorithm as one method of extracting the direction of arrival of a radio wave.
[0005]
[Patent Document 1]
JP-A-2-39705 [0006]
[Non-patent document 1]
Bernard L. Lewis, "ASPECTS OF RADAR SIGNAL PROCESSING," pp. 237-238
[0007]
[Non-patent document 2]
Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Science and Technology Publishing (1999)
[0008]
[Problems to be solved by the invention]
As described above, in the existing radar signal processing device, when various unnecessary wave components such as clutter and interference waves are present, it is difficult to extract the arrival direction and the target direction with high accuracy, and it is not necessarily required. The desired performance may not be achieved.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radar signal processing apparatus and a radar signal processing method that further improve processing performance in an environment where unnecessary wave components exist.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a plurality of antenna elements arranged in an array to receive radar echoes, and unnecessary wave suppressing means for suppressing unnecessary wave components included in signals received from the plurality of antenna elements. And beam forming means for forming a reception beam from the received signal in which unnecessary wave components have been suppressed by the unnecessary wave suppressing means. Further, the present invention is characterized in that it comprises arrival direction detection means for detecting an arrival direction of an arrival wave from the received signal in which unnecessary wave components have been suppressed by the unnecessary wave suppression means.
[0011]
With such a configuration, a reception beam is formed by the beam forming unit based on the antenna reception signal from which the unnecessary wave has already been removed by the unnecessary wave suppressing unit. Alternatively, the arrival direction of the arriving wave is detected by the arriving direction detection means based on the antenna reception signal from which the unnecessary wave has been already removed.
[0012]
That is, in the present invention, unnecessary components are not suppressed after the beam is formed or after the process of detecting the direction of arrival is performed, but unnecessary wave components included in the antenna element signal itself are removed prior to these processes. I try to suppress it. Therefore, it is possible to perform the beam forming process or the arrival direction detection process with higher accuracy, and it is possible to further improve the processing performance in an environment where an unnecessary wave component exists.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a functional block diagram showing an embodiment of a radar signal processing device according to the present invention. In FIG. 1, pulse radar echoes including unnecessary wave components are received by main antennas 11 to 1n and auxiliary antennas 21 to 2m, respectively, and subjected to processes such as low noise amplification and analog / digital conversion by a reception processing unit 3, and each of them is processed. It is input to the adaptive processing unit 4. The adaptive processing unit 4 suppresses a clutter component included in the received signal by performing a process between PRIs (Pulse Repetition Intervals) on a signal received from each antenna.
[0014]
The signal after the clutter suppression based on the reception signal from the auxiliary antenna 2m is branched and input to the plurality of adaptive processing units 5. Further, the signals after clutter suppression based on the received signals from the main antennas 11 to 1n are subtracted from the output of each adaptive processing unit 5 by the subtractor 6, and then input to the beam forming unit 100 and the direction extracting unit 200, respectively. A part of the output of the subtractor 6 is fed back to each adaptive processing unit 5.
[0015]
The adaptive processing unit 5 performs processing in the range direction based on the reception signal from the auxiliary antenna 2m and the feedback input from the subtractor 6 to remove the interference wave from the clutter-suppressed signals from the main antennas 11 to 1n. Suppress components.
[0016]
The beam forming unit 100 performs a beam combining process based on the received signal in which the clutter component and the interference component are suppressed, and generates a beam output signal such as a Σ beam or a Δ beam. The output is further provided to a processing system including a subtractor 8 and an adaptive processing unit 7, and an unnecessary wave component extracted by the range processing of the adaptive processing unit 7 is subtracted to generate a final beam output.
[0017]
The direction extracting unit 200 extracts the direction of arrival of an incoming wave based on an algorithm such as the MUSIC method based on the received signal in which the clutter component and the interference component are suppressed. In particular, when the incoming wave is radiated from a predetermined radio source, the direction of this radio source is extracted.
[0018]
FIG. 2 is a circuit block diagram showing a configuration of the adaptive processing units 4, 5, and 7 of FIG. Each of the adaptive processing units 4, 5, and 7 includes a tapped delay line including a plurality of delay lines 91 to 9K-1 each having a delay amount τ. The tap delay amounts τ of the adaptive processing units 5 and 7 are equal to each other and set to a length corresponding to a range cell. The tap delay amount τ in the adaptive processing unit 4 is longer than this, and is set to a length corresponding to PRI.
[0019]
In FIG. 2, the input signal Xin1 is input to the first operation cell B and is sequentially delayed by τ at each tap, and is input to the operation cell B for each tap as Xin2 to XinK. The outputs Xout1 to XoutK of each operation cell B are added and output by the adder C1, and a part thereof is fed back to each operation cell B.
[0020]
In each operation cell B, the input tap signals Xin1 to XinK are respectively multiplied by a feedback signal from the adder C1 in the multiplier B3, and then supplied to the coefficient unit B7 via the adder B4. Part of the output of the adder B4 is returned to the adder B4 via the sample delay unit B5 and the coefficient unit B6. As a result, a complex weight W is generated, and the complex weight M is multiplied by the tap signals Xin1 to XinK in each operation cell B and output as Xout1 to XoutK.
[0021]
That is, the operation cell B removes a signal component having a correlation with each of the tap signals Xin1 to XinK from the output of the adaptive processing unit. By connecting the operation cells B having such a function in an array, it is possible to adaptively suppress unnecessary wave components in the adaptive processing unit. By appropriately setting the tap delay amount τ, clutter or interference components can be adaptively removed.
[0022]
That is, in the adaptive processing unit 4, since τ is set to a length corresponding to PRI, clutter is adaptively suppressed based on the same principle as in MTI processing. Further, in adaptive processing units 5 and 7, τ is set to a length corresponding to a range cell, so that an interference wave component in one RPI is adaptively suppressed. In particular, FIG. 1 shows a configuration for implementing adaptive processing based on the MSN method by using the auxiliary antennas 2m and 21 as subarrays in the adaptive processing units 5 and 7, respectively. In addition, the range direction processing by the adaptive processing units 5 and 7 includes a Gram-Schmidt method and a direct solution method.
[0023]
FIG. 3 is a diagram schematically showing a processing result in the radar signal processing device according to the present invention. By performing the correlation processing using the received signal in each PRI by the adaptive processing unit 4, a null can be formed in the clutter direction as shown in FIG. Further, by performing the correlation processing using the received signals in the individual range cells by the adaptive processing units 5 and 7, a null can be formed in the arrival direction of the interference wave as shown in FIG. 3B.
[0024]
In the present embodiment, such processing is performed for each of the main antennas 11 to 1n and the auxiliary antennas 21 to 2m, and the clutter component and the interference wave component are converted into the reception signals from the individual antenna elements 11 to 1n and 21 to 2m. Suppress every time. Then, beam forming and arrival direction extraction processing are performed using the received signal from which unnecessary wave components have been removed. As a result, as shown in FIG. 3C, both the clutter component and the interference wave component can be suppressed to a minimum, and the accuracy of separation from the target signal can be drastically increased.
[0025]
As described above, in the present embodiment, the adaptive processing unit 4 is provided for each of the main antennas 11 to 1n and the auxiliary antennas 21 to 2m, and the clutter component is suppressed for each antenna element. An adaptive processing unit 5 is provided at a stage subsequent to the adaptive processing unit 4 of the main antennas 11 to 1n, and suppresses an interference wave component from the received signal in which clutter is suppressed. The beam forming unit 100 performs the beam forming process from the antenna element signal in which the clutter and the interference wave component are suppressed in this way, and the direction extracting unit 200 extracts the arrival direction of the radio wave. Further, an adaptive processing unit 7 is provided at a stage subsequent to the beam forming unit 100, and when an unnecessary wave component remains in the beam output, this is removed.
[0026]
With this configuration, beam forming and arrival direction extraction are performed using an antenna element signal in which unnecessary wave components are suppressed in advance, compared to a conventional method in which unnecessary wave components are removed from the result after beam formation or after the direction of arrival extraction processing. Since the processing can be performed, the accuracy of each processing can be dramatically increased. For this reason, it is possible to provide a radar signal processing device that further improves processing performance even in an environment where unnecessary wave components such as clutter and interference waves are present.
[0027]
Note that the present invention is not limited to the above embodiment. For example, if the number of auxiliary antennas is increased and the adaptive processing units 5 and 7 related to the range direction processing are connected in parallel without being limited to the display of FIG. it can.
[0028]
In FIG. 1, when the clutter frequency and the interference direction are known in advance, the unnecessary wave component may be removed by using a frequency filter and an angle filter having fixed characteristics. That is, in the present embodiment, the unnecessary wave removal based on the adaptive method capable of coping with the changing clutter frequency and the disturbance direction is performed. However, removing unnecessary wave components of the antenna element signal in advance is a main part of the concept of the present invention, so that the unnecessary wave removing method itself is not limited to the adaptive method and may be any method.
[0029]
In the present embodiment, both the beam forming process and the direction extracting process are performed, but either one of the processes may be performed. Further, in the beam forming process, the MUSIC algorithm has been described as an example, but another algorithm such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technologies) process may be used. In addition, various modifications can be made without departing from the scope of the present invention.
[0030]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a radar signal processing device and a radar signal processing method that further improve processing performance in an environment where unnecessary wave components exist.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing an embodiment of a radar signal processing device according to the present invention.
FIG. 2 is a circuit block diagram showing a configuration of adaptive processing units 4, 5, and 7 of FIG.
FIG. 3 is a diagram schematically showing a processing result in the radar signal processing device according to the present invention.
FIG. 4 is a functional block diagram showing a configuration of a conventional pulse radar signal processing device.
FIG. 5 is a diagram schematically showing a processing result in a conventional radar signal processing device.
[Explanation of symbols]
B: Operation cell, C1: Adder, B3: Multiplier, B4: Adder, B7: Coefficient unit, B5: Sample delay unit, B6: Coefficient unit, 3: Reception processing unit, 4, 5, 7 ... Adaptive processing Unit, 6 subtractor, 8 subtractor, 11 to 1n main antenna, 21 to 2m auxiliary antenna, 91 to 9K delay line, 100 beam forming unit, 200 direction extracting unit

Claims (10)

A plurality of antenna elements arranged in an array to receive radar echoes,
Unnecessary wave suppressing means for suppressing unnecessary wave components included in received signals from these plurality of antenna elements,
A radar signal processing apparatus comprising: a beam forming unit configured to form a reception beam from the reception signal in which unnecessary wave components are suppressed by the unnecessary wave suppression unit. 2. The radar signal processing apparatus according to claim 1, further comprising a residual component suppressing unit that suppresses an unnecessary wave component remaining in the reception beam formed by the beam forming unit. A plurality of antenna elements arranged in an array to receive radar echoes,
Unnecessary wave suppressing means for suppressing unnecessary wave components included in received signals from these plurality of antenna elements,
A radar signal processing device comprising: an arrival direction detection unit that detects an arrival direction of an arrival wave from the received signal in which unnecessary wave components are suppressed by the unnecessary wave suppression unit. The radar signal processing apparatus according to claim 1, wherein the unnecessary wave suppressing unit suppresses unnecessary wave components distributed in an arrangement direction of the antenna elements. The radar signal processing apparatus according to claim 1, wherein the unnecessary wave suppressing unit suppresses unnecessary wave components distributed on a frequency axis. An unnecessary wave suppressing step of suppressing unnecessary wave components included in received signals from a plurality of antenna elements arranged in an array and receiving radar echoes,
A beam forming step of forming a reception beam from the reception signal in which the unnecessary wave component has been suppressed in the unnecessary wave suppressing step. The radar signal processing method according to claim 6, further comprising a residual component suppressing step of suppressing unnecessary wave components remaining in the reception beam formed in the beam forming step. An unnecessary wave suppressing step of suppressing unnecessary wave components included in received signals from a plurality of antenna elements arranged in an array and receiving radar echoes,
An arrival direction detection step of detecting an arrival direction of an arrival wave from the received signal in which the unnecessary wave component has been suppressed in the unnecessary wave suppression step. 9. The radar signal processing method according to claim 6, wherein the unnecessary wave suppressing step is a step of suppressing unnecessary wave components distributed in an arrangement direction of the antenna elements. 9. The radar signal processing method according to claim 6, wherein the unnecessary wave suppressing step is a step of suppressing unnecessary wave components distributed on a frequency axis.

Images