Radar system and radar signal processing method

Abstract

To provide a radar system capable of suppressing an unnecessary wave and highly accurately detecting an unnecessary wave component or an observation value to a target near the unnecessary wave.SOLUTION: According to an embodiment, a radar system for receiving a single pulse transmitted from a transmission system or a reflection wave of a modulated N(N≥1) pulse signal and extracting a target signal from the received signal performs the following processing for: inputting CPI data from the received signal and extracting slow-time data per range cell; subjecting the slow-time data to FFT (Fast Fourier Transform) in a slow-time axis to detect an unnecessary wave component; observing the detected unnecessary wave component to extract a clutter width; suppressing the unnecessary wave component on the basis of extraction results of the clutter width; subjecting the signal whose unnecessary wave component was suppressed to pulse compression in a fast-time axis; detecting an observation value from the pulse-compresses signal; and determining a target from the detected observation value, performing ranging, velocimetry, and angle measuring, and outputting measurement results as target information.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present embodiment relates to a radar system and a radar signal processing method. [Background technology]

[0002] In conventional radar systems, it was necessary to suppress the effects of strong clutter when detecting small targets. Methods for suppressing clutter include the MTI (Moving Target Indicator) (see Non-Patent Document 1), but they do not provide sufficient suppression performance and have the problem of suppressing targets close to the clutter. The same problem occurs when suppressing direct waves from a transmission source in a multistatic radar or passive radar that uses a transmission source of another system instead of a transmitter. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] MTI (Moving Target Indicator), Yoshida, 'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp. 67-77 (1996) [Non-Patent Document 2] CFAR (Constant False Alarm Rate), Sekine, 'Radar Signal Processing Technology', Institute of Electronics, Information and Communication Engineers, pp.96-103 (1991) [Non-Patent Document 3] Adaptive Filter (LMS), Paulo SR Diniz. Adaptive Filtering 5th edition, Springer, pp.227-231(2020) [Non-Patent Document 4] LMS (Least Mean Squares) processing, Kikuma, 'Adaptive signal processing using array antennas', Science and Technology Publishing, pp.40-41 (1998) [Non-Patent Document 5] RLS (Recursive Least Squares) processing, Paulo SR Diniz, Adaptive Filtering 5th edition, Springer, pp328-333(2020) [Non-Patent Document 6] Lattice Filtering, Paulo SR Diniz, Adaptive Filtering 5th edition, Springer, pp.474-501(2020) [Non-Patent Document 7] STAP, Richard Klemm,'Applications of Space-Time Adaptive Processing', IEE Radar, Sonar and Navigation series14, p.720-724(2004) Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, in conventional radar systems, it is necessary to suppress the effects of clutter when detecting small targets. In multistatic radars and passive radars that use a transmission source of another system instead of a transmitter, a similar problem occurs when suppressing direct waves from the transmission source.

[0005] An object of the present embodiment is to provide a radar system and a radar signal processing method that can suppress unwanted waves (clutter, multistatic, direct waves in passive radar, etc.) and detect targets even in the vicinity of the unwanted waves with high accuracy. [Means for solving the problem]

[0006] In order to solve the above problems, according to this embodiment, a radar system that receives a reflected wave of a single pulse or a modulated N (N≧1) pulse signal transmitted from a transmission system and extracts a target signal from the received signal includes slow-time data extraction means, unwanted wave detection means, clutter width extraction means, unwanted wave suppression means, pulse compression means, observation value detection means, and measurement means. The slow-time data extraction means inputs CPI (Coherent Pulse Interval) data from the received signal and extracts slow-time data for each range cell, the unwanted wave detection means applies FFT (Fast Fourier Transform) on the slow-time data on the slow-time axis to detect unwanted wave components, the clutter width extraction means observes the detected unwanted wave components and extracts clutter width, the unwanted wave suppression means suppresses the unwanted wave components based on the extraction result of the clutter width, the pulse compression means applies pulse compression on the fast-time axis to the signal in which the unwanted wave components have been suppressed, the observation value detection means detects observation values ​​from the pulse-compressed signal, and the measurement means determines a target from the detected observation values ​​and performs distance, speed, and angle measurement, and outputs the measurement results as target information.

[0007] Here, the unwanted wave suppression means performs FFT processing on the complex signal on the slow-time axis for each cell on the fast-time axis for the received signal, extracts the main lobe of the unwanted wave from the signal width near the center speed of the unwanted wave (clutter, multistatic, direct wave in passive radar) on the Doppler axis and performs signal processing, thereby suppressing the unwanted wave component from the signal on the slow-time axis. In this way, the unwanted wave is extracted on the Doppler axis, and an adaptive filter is formed using it as a reference signal, thereby suppressing the unwanted wave signal from the received signal and extracting the target signal.

[0008] Moreover, the unwanted wave suppression means performs signal processing of the received signal by zero-filling everything except the unwanted wave main lobe on the Doppler axis and subtracting the inverse FFT signal from the original signal on the slow-time axis. That is, as an adaptive filter, the unwanted wave signals extracted for each range cell are subtracted to suppress the unwanted wave signals and extract the target signal.

[0009] Moreover, the unwanted wave suppression means performs signal processing of the received signal by padding all parts except the unwanted wave main lobe on the Doppler axis with zeros, and suppressing the unwanted waves by adaptive filter processing (LMS, RLS, lattice filter, etc.) using the inverse FFT signal as a reference signal and the original slow-time axis signal as an input. That is, the unwanted wave signal extracted for each range cell is used as a reference signal, and adaptive filter processing by LMS, RLS, lattice filter, etc. is applied to suppress the unwanted wave signal and extract the target signal.

[0010] Moreover, the unwanted wave suppression means performs adaptive filtering on the fast-time axis for signals for each bank out of M (M≧1) banks in which targets other than the L bank may exist, using L bank (L≧1) signals within the unwanted wave main lobe width on the Doppler axis as signal processing of the received signal, thereby suppressing unwanted waves input from the side lobe of the Doppler axis of the target bank. That is, in the radar system according to this embodiment, a reference signal is generated using the unwanted wave signals extracted for each range cell, and post-Doppler type adaptive filtering is performed to suppress the unwanted wave signals and extract the target signal. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of a transmission system and a reception system of a radar system according to a first embodiment. [Diagram 2] FIG. 2 is a flowchart showing a flow of processing in the reception system according to the first embodiment. [Diagram 3] FIG. 3 is a waveform diagram showing a modulated N (N≧1)-hit PRI pulse transmitted from the transmission system in the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a signal on the slow-time axis for each range cell in signal processing in the reception system of the first embodiment. [Diagram 5] FIG. 5 is a diagram showing range-Doppler characteristics of targets and clutter when the receiving system of the first embodiment is an on-board radar. [Figure 6] FIG. 6 is a diagram showing an example of processing for extracting a clutter width in signal processing in the reception system of the first embodiment. [Figure 7] FIG. 7 is a diagram showing an example of clutter suppression processing based on the clutter width in signal processing in the reception system of the first embodiment. [Figure 8] FIG. 8 is a block diagram showing the configuration of a transmission system and a reception system of a radar system according to the second embodiment. [Figure 9] FIG. 9 is a flowchart showing a flow of processing in the reception system according to the second embodiment. [Figure 10] FIG. 10 is a block diagram showing the configuration of a transmission system and a reception system of a radar system according to the third embodiment. [Figure 11] FIG. 11 is a flowchart showing a flow of processing in the reception system according to the third embodiment. [Figure 12] FIG. 12 is a block diagram showing the configuration of an adaptive filter used in the third embodiment. [Figure 13] FIG. 13 is a block diagram showing the configuration of a transmission system and a reception system of a radar system according to the fourth embodiment. [Figure 14] FIG. 14 is a flowchart showing a flow of processing in the reception system according to the fourth embodiment. [Figure 15] FIG. 15 is a block diagram showing an adaptive filter processing configuration of a reception system according to the fourth embodiment. [Figure 16] FIG. 16 is a waveform diagram showing how clutter is suppressed before and after the adaptive filter processing shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments will be described with reference to the drawings.

[0013] (First embodiment) The first embodiment will be described with reference to FIGS.

[0014] FIG. 1 is a block diagram showing the configuration of a radar system according to a first embodiment, where (a) is a block diagram showing the configuration of a transmission system, and (b) is a block diagram showing the configuration of a reception system.

[0015] In the transmission system shown in Figure 1(a), a signal generator 11 generates a transmission seed signal, a modulator 12 modulates and multiplexes transmission information onto the transmission seed signal, a frequency converter 13 converts the modulated signal into a high-frequency signal, a pulse modulator 14 pulse-modulates the high-frequency signal to generate a transmission pulse train, and a transmission antenna 15 transmits N (N≧1) hit pulses.

[0016] 1(b), a reflected wave of a pulse signal transmitted from transmitting antenna 15 is received by receiving antenna 21, the received signal is frequency-converted to baseband by frequency converter 22, and converted to a digital signal by AD converter 23 to obtain a received signal. Next, a CPI (Coherent Pulse Interval) data input unit 24 acquires CPI data from the received signal, a slow-time data extractor 25 extracts slow-time data for each range cell from the CPI data, and a slow-time axis FFT processor 26 performs an FFT (Fast Fourier Transform) on the slow-time axis to detect clutter components. Next, a clutter width extractor 27 observes the detected clutter components and extracts the clutter width. A clutter suppressor 28 suppresses the clutter components based on the clutter width extraction result. A fast-time axis compressor (PC: Pulse Compression) 29 applies pulse compression on the fast-time axis. A CFAR (Constant False Alarm Rate: see Non-Patent Document 2) 2A detects the observation values. A measuring instrument 2B identifies the target from the detected observation values ​​and measures the distance, speed and angle, and outputs the measurement results as target information.

[0017] In the above radar system, the transmission system and the reception system may be integrated, or may be installed at separate locations.

[0018] In the radar system having the above configuration, the processing operation after the reception data is acquired by the reception system will be described with reference to Fig. 2 to Fig. 7. Here, Fig. 2 is a flowchart showing the processing flow of the reception system of the first embodiment, Fig. 3 is a waveform diagram showing modulated N (N≧1) hit PRI pulses transmitted from the transmission system of the first embodiment, Fig. 4 is a diagram showing an example of a signal on the slow-time axis for each range cell in signal processing in the reception system of the first embodiment, Fig. 5 is a diagram showing the range-Doppler characteristics of targets and clutter when the reception system of the first embodiment is an on-board radar, Fig. 6 is a diagram showing an example of processing to extract clutter width in signal processing in the reception system of the first embodiment, and Fig. 7 is a diagram showing an example of clutter suppression processing based on clutter width in signal processing in the reception system of the first embodiment.

[0019] First, the signal of the N (N≧1) hit transmission pulse transmitted from the transmission system shown in FIG. 1(a) reflected by a target or the like is received by the receiving antenna 21, frequency-converted to baseband by the frequency converter 22, and converted to a digital signal by the AD converter 23, thereby obtaining the received signal. In this way, the transmission and reception data obtained by receiving the N (N≧1) hit transmission pulse is called CPI (Coherent Pulse Interval) data based on PRI (Pulse Repetition Interval) data. This CPI data is two-dimensional data on the fast-time axis for each range cell and the slow-time axis between the PRI, as shown in FIG. 4. The signal (complex signal) on the slow-time axis for each range cell shown in FIG. 4 contains target signals and clutter components depending on the range cell. The clutter components are low-frequency components near Doppler 0, especially in the case of ground clutter obtained by a ground-based radar. In an aircraft-mounted radar, clutter has a Doppler component according to the aircraft's speed and the beam formation direction, and the central speed can be determined on the radar side. On the other hand, target signals have a Doppler component according to speed unless the target is fixed, as shown in the range-Doppler characteristics in Figure 5. For simplicity, the Doppler component of clutter is assumed to be 0, and the signal processing for separating clutter and target signals will be explained with reference to the flowchart in Figure 2.

[0020] In FIG. 2, first, CPI data is input (24, step S11), the signal (complex signal) on the slow-time axis for each range cell is extracted (25, step S12), and FFT processing of the slow-time axis is performed (26, step S13). Next, the clutter width on the Doppler axis is extracted (27, step S14). In order to extract this clutter width, a noise level is extracted and an amplitude threshold is set for the noise level. The noise level may be, for example, an RMS (Root Mean Square) value in the range on the Doppler axis where no clutter or target exists. This noise level may be calculated on the Doppler axis for each range cell, or may be calculated once for the entire CPI. If the clutter width exceeding this amplitude threshold is calculated, the main lobe width of the clutter can be calculated. This process is shown in FIG. 6.

[0021] By calculating the clutter width in this way, clutter suppression processing (28, steps S15 to S17) corresponding to range cell changes can be performed to suppress clutter to the noise level as shown in Fig. 7. If the transmission waveform is chirp modulation or the like, fast-time axis pulse compression (PC) processing (29, step S18) is performed, and then targets are detected by CFAR detection processing (2A, step S19) (Non-Patent Document 2), and target information is acquired by performing distance, speed and angle measurement processing (2B, step S20).

[0022] According to this embodiment, in a radar system that receives a reflected wave of a single pulse or modulated N (N≧1) pulse signal transmitted from a transmission system and extracts a target signal from the received signal, the complex signal on the slow-time axis is subjected to FFT processing for each cell on the fast-time axis for the received signal, and the main lobe of the clutter is extracted from the signal width near the central velocity of the clutter on the Doppler axis and signal processing is performed, thereby suppressing the clutter component from the signal on the slow-time axis. In other words, by extracting clutter on the Doppler axis and forming an adaptive filter using it as a reference signal, it is possible to suppress the clutter signal from the received signal and extract the signal of a target located nearby.

[0023] In this embodiment, the PC process (29) of the fast-time axis pulse compression process is performed after the clutter suppression process (28), but it may be performed before the clutter suppression process (28).

[0024] Second embodiment A second embodiment will be described with reference to FIGS.

[0025] Fig. 8 is a block diagram showing the configuration of a radar system according to a second embodiment, where (a) is a block diagram showing the configuration of a transmission system, (b) is a block diagram showing the configuration of a reception system, and Fig. 9 is a flowchart showing the flow of processing of the reception system in the second embodiment. In Figs. 8 and 9, the same parts as in Figs. 1 and 2 are denoted by the same reference numerals.

[0026] The configuration of the transmission system shown in Fig. 8(a) is the same as that of the transmission system of the first embodiment shown in Fig. 1(a). The receiving system shown in Fig. 8(b) differs from the receiving system of the first embodiment shown in Fig. 1(b) in that the clutter suppressor 28 is composed of a zero-padding inverse FFT processor 2C, a subtractor 2D, and a slow-time axis FFT processor 2E.

[0027] Also, the processing of the reception system shown in FIG. 9 differs from the processing of the reception system of the first embodiment shown in FIG. 2 in that the clutter suppression processing (28, step S15) is composed of zero-padding inverse FFT processing (2C, step S21), subtraction processing (2D, step S22), and slow-time axis FFT processing (2E, step S23).

[0028] That is, the main lobe width can be obtained by extracting the clutter width on the Doppler axis. In this embodiment, the main lobe width is obtained from the clutter width on the Doppler axis extracted in the clutter width extraction (27, step S14), and a signal approximating the clutter component (hereinafter, clutter signal) is obtained by zero-filling the parts other than the main lobe in the zero-filling inverse FFT process (2C, step S21). Then, in the subtraction process (2D, step S22), the slow-time data extracted for each range cell from the slow-time data extractor 25 is input, and the result of the zero-filling inverse FFT process is subtracted. This process functions as an adaptive filter, and the clutter signal is subtracted from the slow-time axis signal extracted for each range cell. In this way, the slow-time axis signal from which the clutter signal has been subtracted is FFT-processed in the slow-time axis FFT process (2E, step S23), and the process proceeds to the fast-time axis pulse compression process (29, step S18).

[0029] In other words, by extracting the clutter width, the main lobe width on the Doppler axis can be known, so by filling in the parts other than the main lobe with zeros and performing inverse FFT processing, a signal that is close to the clutter signal can be generated. If the input signal is Xin and the Doppler component of the input signal is Xfft, this can be formulated as follows:

[0030]

number

[0031]

number

[0032]

number

[0033]

number

[0034] As described above, according to this embodiment, the signal processing of the received signal involves padding all but the unwanted wave main lobe on the Doppler axis with zeros, and subtracting the inverse FFT signal from the original signal on the slow-time axis, thereby subtracting the unwanted wave signals extracted for each range cell as an adaptive filter, thereby making it possible to suppress the unwanted wave signals and extract the target signal.

[0035] (Third embodiment) A third embodiment will be described with reference to FIGS.

[0036] Fig. 10 is a block diagram showing the configuration of a radar system according to a third embodiment, where (a) is a block diagram showing the configuration of a transmission system, and (b) is a block diagram showing the configuration of a reception system, and Fig. 11 is a flowchart showing the flow of processing in the reception system of the third embodiment. In Figs. 10 and 11, the same parts as in Figs. 1 and 8, and Figs. 2 and 9 are denoted by the same reference numerals. Fig. 12 is a block diagram showing the configuration of an adaptive filter used in the third embodiment.

[0037] The configuration of the transmission system shown in Fig. 10(a) is the same as that of the transmission system of the first and second embodiments shown in Fig. 1(a) and Fig. 8(a). The reception system shown in Fig. 10(b) differs from the reception systems of the first and second embodiments shown in Fig. 1(b) and Fig. 8(b) in that the clutter suppressor 28 is composed of a zero-padding inverse FFT processor 2C, an adaptive filter 2F, and a slow-time axis FFT compressor 2E. The processing of the reception system shown in Fig. 11 differs from the processing of the reception systems of the first and second embodiments shown in Fig. 2 and Fig. 9 in that the clutter suppression processing (28, step S15) is composed of a zero-padding inverse FFT processing (2C, step S21), an adaptive filter processing (2F, step S24), and a slow-time axis FFT processing (2E, step S23).

[0038] 12, input signals Xin of 1 to N cells are passed through a delay circuit (P tap) in which n delay devices 311 to 31n are connected in series, n+1 (=P) pieces of data sequentially delayed by τ time are extracted every τ time, the sum is calculated by an adder (Σ) 32, and the sum is input to a subtractor 33. Meanwhile, reference signals Xref of 1 to N cells are passed through a delay circuit (P tap) in which n delay devices 341 to 34n are connected in series, n+1 (=P) pieces of data sequentially delayed by τ time are extracted, and each of the n+1 pieces of data is input to n+1 multipliers 351 to 35 (n+1) every τ time and multiplied by the output of the subtractor 33. The multiplication results are summed up by an adder (Σ) 36, sent to the subtractor 33, and subtracted from the sum signal of the input signals to be output.

[0039] That is, when the clutter width on the Doppler axis is extracted, the clutter signal on the slow-time axis can be extracted according to equations (1) to (3) in the second embodiment, and can be used as a reference signal.

[0040]

number

[0041] By applying the adaptive filter (Non-Patent Document 3) shown in Fig. 12 using this reference signal Xref and the input signal Xin, it is possible to implement processing that can suppress clutter. Examples of adaptive filter processing include LMS (Least Mean Square) (Non-Patent Documents 3 and 4), RLS (Recursive Least Square) (Non-Patent Document 5), and Lattice Filter (Non-Patent Document 6).

[0042] For simplicity, the algorithm will be described here as LMS processing (Non-Patent Document 4). Any other processing may be used as long as it uses the signal on the slow-time axis. If the input signal is Xin and the reference signal is Xref, then the following formula can be used.

[0043]

number

[0044] In FIG. 12 and equation (6), the input signal and the reference signal are expressed such that a weight is set for the reference signal, but the input signal and the reference signal may be reversed and the weight may be set for the input signal.

[0045] As described above, by performing adaptive filtering on the input signal Xin and the reference signal Xref, a clutter-suppressed signal ε can be obtained. By performing FFT processing on this signal ε, a signal on the Doppler axis can be obtained.

[0046] The RLS method and the lattice filter method are the same in that they both use an input signal and a reference signal as input. The RLS method converges faster than the LMS method, but the processing costs are higher. The lattice filter method converges faster than the RLS method, but the processing costs are lower, and it is suitable for implementation on FPGAs (Field Programmable Gate Arrays) and GPUs (Graphics Processing Units).

[0047] (Fourth embodiment) The fourth embodiment will be described with reference to FIGS.

[0048] Fig. 13 is a block diagram showing the configuration of a radar system according to a fourth embodiment, where (a) is a block diagram showing the configuration of a transmission system and (b) is a block diagram showing the configuration of a reception system, and Fig. 14 is a flowchart showing the flow of processing by the reception system of the third embodiment. In Figs. 13 and 14, the same parts as in Figs. 1 and 2 are given the same reference numerals. Fig. 15 is a block diagram showing the adaptive filter processing configuration of the reception system of the fourth embodiment, and Fig. 16 is a waveform diagram showing how clutter is suppressed before and after the adaptive filter processing shown in Fig. 15.

[0049] The configuration of the transmission system shown in Fig. 13(a) is the same as that of the transmission system of the first to third embodiments shown in Fig. 1(a). The reception system shown in Fig. 13(b) differs from the reception system of the first embodiment shown in Fig. 1(b) in that the clutter suppressor 28 is composed of a clutter bank extractor 2G and a host Doppler type adaptive filter 2H. Also, the processing of the reception system shown in Fig. 14 differs from the processing of the reception system of the first embodiment shown in Fig. 2 in that the clutter suppression processing (28, step S15) is composed of a clutter bank extraction processing (2G, step S25) and a post-Doppler type adaptive filter processing (2H, step S26).

[0050] In the third embodiment, the signal on the slow-time axis is used when applying adaptive filtering, whereas in this embodiment, a method is adopted in which a signal on the Doppler axis is used.

[0051] First, as shown in FIG. 15, the slow-time axis signal (N cells) for each range cell extracted in the slow-time data extraction (25, step S12) is converted into n=1 to N bank signals in the slow-time axis FFT processing (26, step S13), the clutter width is extracted in the clutter width extraction processing (27, step S14) and distinguished from the side lobe portion, a main channel (CH) (m=1 to M bank) and an auxiliary channel (p=1 to P bank) are selected, and a weight (W) is applied to each signal in the auxiliary channel P bank in the adaptive filter processing (2H, step S26) to take the sum (Σ) and subtract the signal in the main channel M bank.

[0052] That is, adaptive filter processing is performed using P bank signals within the clutter main lobe width on the Doppler axis and signals for each bank out of M banks in which targets other than the P bank may exist, using signals on the fast-time axis. Here, for simplicity, the algorithm is LMS processing (Non-Patent Documents 3 and 4), but other processing may be used as long as it is post-Doppler type processing (Non-Patent Document 7) that uses the main channel and auxiliary channel of the Doppler axis.

[0053] The above adaptive filtering process can be formulated as follows:

[0054]

number

[0055] As a result of the above processing, before adaptive filter processing, clutter was received due to the Doppler axis side lobe of the main channel, as shown in Figure 16(a), but after adaptive filter processing, the Doppler axis side lobe for the clutter is reduced, as shown in Figure 16(b), making it possible to suppress the clutter.

[0056] As described above, in this embodiment, the Doppler bank corresponding to the main lobe width of the extracted clutter is selected as the auxiliary channel, so that the clutter suppression capability can be improved.

[0057] In this process, when the range in which the target exists is narrow, the number M of target banks can be limited to reduce the processing cost.

[0058] In the above embodiment, the case where clutter is suppressed as an unwanted wave has been described, but it is also possible to suppress a direct wave in a multistatic or passive radar as an unwanted wave.

[0059] In addition, the present invention is not limited to the above-mentioned embodiment as it is, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-mentioned embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0060] 11: signal generator, 12: modulator, 13: frequency converter, 14: pulse modulator, 15: transmitting antenna, 21...receiving antenna, 22...frequency converter, 23...AD converter, 24...CPI data input device, 25...slow-time data extractor, 26...slow-time axis FFT processor, 27...clutter width extractor, 28...clutter suppressor, 29...fast-time axis compressor, 2A...CFAR detector, 2B...measuring instrument (range, speed, angle), 2C...zero-filled inverse FFT processor, 2D...subtractor, 2E...slow-time axis compressor, 2F...adaptive filter, 2G...clutter bank extractor, 2H...adaptive filter (post-Doppler type), 311 to 31n...delay device, 32...summer (Σ), 33...subtractor, 341 to 34n...delay device, 351 to 35(n+1)...multiplier, 36...summer.

Claims

1. A radar system that receives a reflected wave of a single pulse or a modulated N (N≧1) pulse signal transmitted from a transmission system and extracts a target signal from the received signal, a slow-time data extraction means for inputting CPI (Coherent Pulse Interval) data from the received signal and extracting slow-time data for each range cell; an unwanted wave detection means for detecting unwanted wave components by performing FFT (Fast Fourier Transform) on the slow-time data in a slow-time axis; a clutter width extraction means for observing the detected unnecessary wave components and extracting a clutter width; an unwanted wave suppression means for suppressing unwanted wave components based on the extracted clutter width; a pulse compression means for performing pulse compression on the signal in which the unnecessary wave components have been suppressed in a fast-time axis; an observation value detection means for detecting an observation value from the pulse compressed signal; A measurement means for determining a target from the detected observation values, measuring distance, speed, and angle, and outputting the measurement results as target information; A radar system comprising:

2. The unwanted wave suppression means performs signal processing of the received signal by zero-filling all parts of the signal other than the main lobe of the unwanted wave on the Doppler axis and performing inverse FFT on the signal, and then subtracting the resultant signal from the original signal on the slow-time axis.

2. The radar system of claim 1.

3. The unwanted wave suppression means performs signal processing of the received signal by zero-filling all parts of the signal other than the main lobe of the unwanted wave on the Doppler axis, and suppressing the unwanted wave by adaptive filter processing using the inverse FFT signal as a reference signal and the original slow-time axis signal as an input.

2. The radar system of claim 1.

4. The unwanted wave suppression means performs adaptive filtering on the fast-time axis for signals of each bank among M (M ≧ 1) banks in which targets other than the L bank may exist, using L (L ≧ 1) bank signals within a main lobe width of the unwanted waves on the Doppler axis as signal processing of the received signal, thereby suppressing unwanted waves input from the side lobe of the Doppler axis of the target bank.

2. The radar system of claim 1.

5. The unnecessary wave suppression means performs FFT processing on the complex signal on the slow-time axis for each cell on the fast-time axis of the received signal, extracts the main lobe of the unnecessary wave from the signal width near the central velocity of the unnecessary wave on the Doppler axis, and performs signal processing to suppress the unnecessary wave component from the signal on the slow-time axis.

2. The radar system of claim 1.

6. 1. A radar signal processing method for a radar system that receives a reflected wave of a single pulse or a modulated N (N≧1) pulse signal transmitted from a transmission system and extracts a target signal from the received signal, Inputting CPI (Coherent Pulse Interval) data from the received signal and extracting slow-time data for each range cell; The slow-time data is subjected to a Fast Fourier Transform (FFT) on the slow-time axis to detect unnecessary wave components; Observe the detected unwanted wave components and extract the clutter width. suppressing unnecessary wave components based on the extracted clutter width; The signal in which the unnecessary wave components have been suppressed is subjected to pulse compression in the fast-time axis; Detecting an observation from the pulse-compressed signal; From the detected observation values, the target is identified, distance, speed, and angle are measured, and the measurement results are output as target information. A method for processing radar signals in a radar system.

Images