JP2008309558A - Signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal processor for suppressing an unnecessary wave component by using data obtained in time-series, and accurately and sensitively observing a target at high resolution even if the signal processor is in an environment in which unnecessary waves exist. <P>SOLUTION: The signal processor comprises: antennas 11, 21 for transmitting and receiving a signal; unnecessary wave component suppressing/processing sections 12, 13, 22, 23, 30-3M-1, 31 for suppressing the unnecessary wave component contained in the received signal obtained from the antennas in time series when the signal is received at each time; and a signal processing section 33 for implementing signal processing by using the received signal obtained from the unnecessary wave component suppressing/processing sections in time series and having the suppressed unnecessary wave component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a signal processing apparatus which is applied to a radar apparatus or a receiving apparatus and performs signal processing for realizing high accuracy, high resolution and / or high sensitivity in an environment where unnecessary waves exist.

  Conventionally, a radar apparatus or a receiving apparatus is equipped with a signal processing apparatus that processes signals transmitted and received using an antenna. FIG. 7 is a diagram for explaining such a conventional signal processing apparatus. This signal processing apparatus includes a main antenna 11, a data storage unit 32, and a signal processing unit 33. The main antenna 11 includes a plurality of antenna elements, and a signal received by each antenna element is sent to the data storage unit 32 as received data.

  The data storage unit 32 stores reception data for each antenna element transmitted from the main antenna 11. The received data stored in the data storage unit 32 is read out by the signal processing unit 33. The signal processing unit 33 extracts the reception data stored in the data storage unit 32 and executes SAR (Synthetic Aperture Radar) processing, MUSIC (Multiple Signal Classification) processing, and the like.

  Here, the SAR processing is processing for imaging a target with high resolution by correlating the reference signal and the transmission / reception signal (see Non-Patent Document 1). The MUSIC process is a process for separating a target with high resolution (see Non-Patent Document 2).

  As such a signal processing device, Patent Document 1 suppresses unnecessary waves for each reception data acquired from a plurality of antenna elements, and performs adaptive processing and MUSIC processing using reception data in which the unnecessary waves are suppressed. A radar signal processing apparatus is disclosed.

The radar signal processing apparatus includes an adaptive processing unit for each main antenna and auxiliary antenna, and suppresses a clutter component for each antenna element. Further, another adaptive processing unit is provided after the adaptive processing unit of the main antenna to suppress the interference wave component from the received signal in which clutter is suppressed. The beam forming process is performed by the beam forming unit from the antenna element signal in which the clutter and the interference wave component are suppressed as described above, and the radio wave arrival direction is extracted by the direction extracting unit. Further, an adaptive processing unit is provided at the subsequent stage of the beam forming unit, and if an unnecessary wave component remains in the beam output, it is removed.
Japanese Patent Laid-Open No. 2004-257761 Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press (2003) pp. 176-178 Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Science and Technology Publishing (1999) pp. 194-199

  By the way, the radar signal processing apparatus disclosed in Patent Document 1 described above performs adaptive processing and MUSIC processing after suppressing unnecessary wave components from reception data acquired from a plurality of antenna elements. Are data acquired at the same time (data sampled at the same time), and are correlated with each other, and even when an unnecessary wave is input, it can be suppressed.

  On the other hand, in a signal processing device that performs SAR processing and MUSIC processing using received data acquired in time series (hereinafter referred to as “time series data”), that is, data sampled at different times, noise interference When unnecessary waves such as these are input, there is a problem in that unnecessary wave components cannot be suppressed because there is no correlation in time series data.

  Even when clutter or the like correlated with each other in time series data is input, if the S / C ratio (signal / clutter power ratio) of the sampled data is poor, the S obtained as a result of signal processing is obtained. The / C ratio may also deteriorate.

  The present invention has been made to solve the above-described problems, and its problem is to suppress unnecessary wave components using data acquired in time series even in an environment where unnecessary waves exist. Another object of the present invention is to provide a signal processing apparatus capable of observing a target with high accuracy, high resolution and / or high sensitivity.

  In order to solve the above-described problem, an invention according to claim 1 is directed to an antenna for transmitting and receiving signals, and an unnecessary wave component included in a reception signal acquired in time series from the antenna for each reception signal acquired at each time. And a signal processing unit that performs signal processing using a reception signal in which unnecessary wave components acquired in time series from the unnecessary wave suppression processing unit are suppressed. .

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the processing performed in the signal processing unit is SAR (Synthetic Aperture Radar) processing.

  The invention described in claim 3 is characterized in that, in the invention described in claim 1, the processing performed in the signal processing unit is MUSIC (Multiple Signal Classification) processing.

  The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the unnecessary wave suppression processing unit includes MTI (Moving Target Indication) processing, DFT (Discrete Fourier Transformation) processing, At least one of STAP (Space Time Adaptive Processing) processing, adaptive processing, or SLC (idelobe Canceller) processing is performed.

  According to the first aspect of the present invention, the unnecessary wave component included in the received signal acquired in time series from the antenna is suppressed for each received signal acquired at each time, and the unnecessary wave component is suppressed. Since signal processing is performed using a series of received signals, the influence of unnecessary waves is eliminated at the time of signal processing. As a result, the target can be observed with high accuracy, high resolution, and / or high sensitivity.

  According to the second aspect of the invention, since the SAR process is performed using the time-series received signal in which the unnecessary wave component is suppressed, the influence of the unnecessary wave is eliminated at the time of the SAR process, and the high accuracy and high The target can be observed with resolution and / or high sensitivity.

  According to the third aspect of the invention, since the MUSIC process is performed using the time-series received signal in which the unnecessary wave component is suppressed, the influence of the unnecessary wave is eliminated at the time of the MUSIC process, and the high accuracy, high The target can be observed with resolution and / or high sensitivity.

  According to the third aspect of the present invention, since unnecessary waves are suppressed by performing at least one of MTI processing, DFT processing, STAP processing, adaptive processing, or SLC processing, it is possible to suppress unnecessary waves with high accuracy. it can. As a result, the target can be observed with high accuracy, high resolution, and / or high sensitivity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The signal processing apparatus according to the first embodiment of the present invention performs SAR processing using time-series data.

  First, the principle of SAR will be described. FIG. 1 shows a model of SAR. This model shows an example of side monitoring as a general model, and shows a state in which a target is detected by performing SAR processing by transmitting and receiving microwaves with a SAR device mounted on a moving body. ing.

If the transmission / reception signal is e (t) and the reference signal for AZ compression is r (t), the signal s (t) after AZ compression processing can be calculated by the following equation (see Non-Patent Document 1).

here,
e (t); transmission / reception signal E (f); Fourier transform of e (t) r (t); reference signal R (f); Fourier transform of r (t) s (t); SAR image S (f); Fourier transform FFT [] of s (t); Fourier transform FFT ^-1 []; Inverse Fourier transform *; Complex conjugate Undesired wave components such as interference and clutter in transmission / reception signal (sample data) e (t) used for SAR processing Is included, the conventional signal processing apparatus shown in FIG. 7 may not be able to detect a desired signal. As a countermeasure, the signal processing apparatus according to the first embodiment of the present invention is configured to suppress clutter and interference by applying a frequency filter and a spatial filter at the sample data stage.

  FIG. 2 is a diagram illustrating a concept of functions realized by the signal processing device according to the first embodiment of the present invention. The beam at each sample contains unwanted waves such as interference and clutter. After the unwanted waves are suppressed using the frequency axis / angle axis filter (frequency filter / spatial filter) for the sample data, high resolution processing is performed. By performing (SAR), a sharp beam is formed.

  FIG. 3 is a block diagram illustrating the configuration of the signal processing apparatus according to the first embodiment of the present invention. The signal processing apparatus includes a main antenna 11, a first MTI processing unit 12, a first DFT processing unit 13, an auxiliary antenna 21, a second MTI processing unit 22, a second DFT processing unit 23, SLC processing units 30 to 3M-1, and a desired signal extraction. Unit 31, data storage unit 32, and signal processing unit 33.

  The main antenna 11 includes a plurality of antenna elements, and a reception signal received by each antenna element is sent to the first MTI processing unit 12 as a signal Xb.

  The first MTI processing unit 12 functions as a frequency filter (frequency axis filter), receives the signal Xb transmitted from the main antenna 11 as an input signal, and, as shown in FIG. 4A, the ground clutter included in the input signal. As shown in FIG. 4 (b), an output signal is generated by removing clutters such as sway and weather clutter on the frequency axis.

  For MTI processing, see, for example, “Yoshida et al.,“ Revised Radar Technology ”, IEICE, pp. 67-70 (1996) ". The output signal generated by the first MTI processing unit 12 is sent to the first DFT processing unit 13 as a signal Xbmti.

  The first DFT processing unit 13 functions as a frequency filter (frequency axis filter), suppresses clutter by subjecting the signal Xbmti sent from the first MTI processing unit 12 to discrete Fourier transform, and filter bank signals Xbf0 to XbfM−1. As SLC processing units 30 to 3M-1.

  The auxiliary antenna 21 includes a plurality of antenna elements, and a resin signal received by each antenna element is sent to the second MTI processing unit 22 as a signal Xa.

  The second MTI processing unit 22 functions as a frequency filter (frequency axis filter), receives the signal Xa transmitted from the auxiliary antenna 21 as an input signal, and, similar to the first MTI processing unit 12, the ground clutter included in the input signal Clutters such as weather clutter are removed on the frequency axis to generate an output signal. The output signal generated by the second MTI processing unit 22 is sent to the second DFT processing unit 23 as a signal Xamti.

  The second DFT processing unit 23 functions as a frequency filter (frequency axis filter), suppresses clutter by subjecting the signal Xamti sent from the second MTI processing unit 22 to discrete Fourier transform, and filter bank signals Xaf0 to XafM-1. As SLC processing units 30 to 3M-1.

  The SLC processing units 30 to 3M-1 function as spatial filters (angle axis filters), and are sent from the filter bank signals Xbf0 to XbfM-1 sent from the first DFT processing unit 13 and the second DFT processing unit 23. Interference is suppressed by executing SLC processing using the filter bank signals Xaf0 to XbaM-1 that come. That is, as shown in FIG. 5, the SLC processing units 30 to 3M-1 process the signal from the main antenna 11 and the signal from the auxiliary antenna 21 to reduce the antenna gain in the arrival direction of the interference wave. Suppress jamming.

  Specifically, as shown in FIG. 3, the SLC processing units 30 to 3M-1 change the weight W so that the side lobe of the main antenna 11 and the level of the auxiliary antenna 21 coincide with each other by the feedback loop of the SLC processing. Thus, a null point is formed in the main antenna pattern, and the sensitivity to the arrival direction of the interference wave is reduced to suppress the interference wave. The outputs of the SLC processing units 30 to 3M-1 are sent to the desired signal extraction unit 31. The SLC process is described in, for example, “The Institute of Electronics, Information and Communication Engineers,“ Revised Radar Technology ”, pp 295-296”.

  The desired signal extraction unit 31 extracts a bank in which a desired signal exists from the signals sent from the SLC processing units 30 to 3M-1 and sends the bank to the data storage unit 32.

  The first MTI processing unit 12, the first DFT processing unit 13, the auxiliary antenna 21, the second MTI processing unit 22, the second DFT processing unit 23, the SLC processing units 30 to 3M-1 and the desired signal extracting unit 31 described above are Corresponding to the unnecessary wave suppression processing unit, it operates for each data position, that is, for each received signal acquired in time series, every time a received signal at each time is acquired.

  The data storage unit 32 sequentially accumulates and stores the signals sent from the desired signal extraction unit 31. Therefore, time series data is stored in the data storage unit 32. The data stored in the data storage unit 32 is read by the signal processing unit 33.

  The signal processing unit 33 performs SAR processing based on clutter stored in the data storage unit 32 and time-series data in which interference is suppressed. The details of the SAR process are as described at the beginning.

  FIG. 6 is a diagram for explaining the operation of the signal processing apparatus according to the first embodiment of the present invention, and shows the relationship between transmission / reception pulses and processing when unnecessary waves are suppressed. Clutter is suppressed by MTI processing as a frequency filter for data at each sample time, for example, data pos1, and further suppression is performed by DFT processing, followed by suppression of interference by SLC processing as a spatial filter. To do. Then, the SAR process is executed using the data for each position in which unnecessary waves such as clutter and interference are suppressed by these processes.

  As described above, according to the signal processing apparatus according to the first embodiment of the present invention, since the SAR process is performed using the data after suppressing the unnecessary wave, the high-precision and high-resolution without the influence of the unnecessary wave. Output can be obtained.

  In the signal processing apparatus according to the first embodiment, after performing the MTI process, the DFT process is performed to extract the bank, and then the SLC process is performed. However, only the MTI process or the SLC process is performed. It can also be configured to perform only.

The signal processing device according to the second embodiment of the present invention is configured to perform the MUSIC processing while performing the SAR processing by the signal processing unit 33 of the signal processing device according to the first embodiment. The spectrum of MUSIC processing can be expressed by the following equation. Details of the MUSIC process are described in Non-Patent Document 2 as necessary.

here,
En; eigenvector of thermal noise of correlation matrix Rxx of sample data a; direction vector

            The above is for a linear array.

θ: Direction of incoming wave j: Imaginary unit dn: Sample position (n = 1 to N)
λ: Wavelength According to the signal processing apparatus according to the second embodiment, since the MUSIC process is performed using the data after suppressing the unnecessary wave, the influence of the unnecessary wave is eliminated at the time of the MUSIC process. , The target can be separated with high resolution.

  In addition, although the signal processing apparatus according to the first embodiment and the second embodiment described above has been described for the element space type, it can also be applied to the beam space type. The beam space type is described in “Nobuyoshi Kikuma,“ Adaptive Signal Processing by Array Antenna ”, Science and Technology Publishing (1999) pp. 33-349”.

  Further, as unnecessary wave suppression processing, adaptive processing (frequency filter, spatial filter), STAP processing, and the like can be used in addition to MTI processing, DFT processing, and SLC processing.

  The adaptive processing is described in “Nobuyoshi Kikuma,“ Adaptive signal processing by array antenna ”, Science and Technology Publication (1999) pp. 35-37, 98-99, 67-86, 17-21”. The STAP processing is described in “Richard Klemm,“ SPACE-TIME ADAPTIVE PROCESSING ”, IEE RADAR, SONAR, NAVIGATION AND AVIONICS 9, pp. 110-118 (1998)”.

  In the first and second embodiments described above, the case where clutter and interference included in the sample data are suppressed has been described. However, the present invention can be configured to suppress only clutter or only interference.

  Even in a complex environment where clutter and interference exist, each sample data is suppressed only by interference by SLC processing, and clutter is suppressed by high resolution processing by SAR processing or MUSIC processing. It can also be configured.

  In addition, the signal processing devices according to the first and second embodiments described above can be applied even when the position of the ground radar is fixed at one place or when the position is moved by rotation or the like.

  Furthermore, the signal processing apparatus according to the first and second embodiments described above can be applied not only to a radar apparatus but also to a receiving apparatus that can receive a desired signal.

  The present invention is applicable to a radar device or a receiving device that performs SAR processing or MUSIC processing using time-series data.

It is a figure which shows the model for demonstrating the principle of SAR performed with the signal processing apparatus which concerns on Example 1 of this invention. It is a figure which shows the concept of the function implement | achieved by the signal processing apparatus which concerns on Example 1 of this invention. It is a block diagram which shows the structure of the signal processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating suppression of the clutter performed by the signal processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating suppression of the interference performed with the signal processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating operation | movement of the signal processing apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the conventional signal processing apparatus.

Explanation of symbols

11 Main antenna 12 First MTI processing unit 13 First DFT processing unit 21 Auxiliary antenna 22 Second MTI processing unit 23 Second DFT processing unit 30 SLC processing unit 31 Desired signal extraction unit 32 Data storage unit 33 Signal processing unit

Claims (4)

An antenna for transmitting and receiving signals;
An unnecessary wave suppression processing unit that suppresses an unnecessary wave component included in a reception signal acquired in time series from the antenna for each reception signal acquired at each time;
A signal processing unit that performs signal processing using a reception signal in which unnecessary wave components acquired in time series from the unnecessary wave suppression processing unit are suppressed;
A signal processing apparatus comprising:   The signal processing apparatus according to claim 1, wherein the processing performed by the signal processing unit is SAR (Synthetic Aperture Radar) processing.   The signal processing apparatus according to claim 1, wherein the processing performed by the signal processing unit is MUSIC (Multiple Signal Classification) processing.   The unnecessary wave suppression processing unit performs at least one of MTI (Moving Target Indication) processing, DFT (Discrete Fourier Transformation) processing, STAP (Space Time Adaptive Processing) processing, adaptive processing, or SLC (idelobe Canceller) processing. The signal processing device according to claim 1, wherein the signal processing device is a signal processing device.

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