JP2022087525A - Radar system and radar signal processing method - Google Patents

Abstract

To output a target three-dimensional position or the like by suppressing a processing scale in a complicated environment of clutter and unnecessary waves even in a bistatic manner.SOLUTION: According to one embodiment, a radar system divides an observation time axis into a communication period and a pulse train period, transmits and receives transmission information during the communication period, transmits a pulse train superimposed with a first pulse train P1 for Doppler observation and a second pulse train P2 for ranging during the pulse train period, calculates an observation speed of a direct wave from a Doppler component extracted from a P1 train reception signal among the direct waves, range-compresses a P2 train reception signal by using a reference signal corrected by the observation speed of the direct wave to output a distance between the transmission and reception, calculates a target speed from the Doppler component extracted from the P1 train reception signal among reflection waves from a target, range-compresses the P2 train reception signal using the reference signal corrected by the target speed to calculate a target distance and a target angle measurement value, and calculates a target three-dimensional position from the intersection of an elliptical body that can be formed from a distance of the direct waves and the target distance and the target angle measurement value.SELECTED DRAWING: Figure 2

Description

The present embodiment relates to a radar system and a radar signal processing method.

In the radar system mounted on a high-speed projectile, HPRF (High Pulse Repetition Frequency) is used to suppress clutter. For example, a time-divided pulse train in which a CW (Continuous Wave) pulse train for Doppler extraction and an FMCW (Frequency modulated Continuous Wave) sweep (see Non-Patent Document 1) for ranging are arranged in a time-division manner is used.

However, in a bistatic or multi-static radar system that detects the target position by combining multiple transmitters, transmitter / receiver radars, and receiver radars, the time-divided pulse train increases the pulse train time. There is a problem that the search time becomes long, the processing range for calculating the speed and the distance becomes wide, and the processing scale increases. In addition, the target could not be detected in the complicated environment of clutter and unwanted waves.

FM Rangeing, Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.274-275 (1996) SS Modulation, Marubayashi,'Spectral Diffusion Communication and Its Applications', Institute of Electronics, Information and Communication Engineers, pp.1-18 (1998) Coded Radar, Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.278-280 (1996) Code code (M-sequence) generation method, M.I.Skolnik,'Introduction to radar systems', McGRAW-HILL, pp.429-430 (1980) CFAR (Constant False Alarm Rate), Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.87-89 (1996) Taylor Distribution, Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.134-135 (1996) Range compression, Ouchi,'Basics of Synthetic Aperture Radar for Remote Sensing', Tokyo Denki University Press, pp.131-149 (2003) Phase monopulse (phase comparison monopulse) method, Yoshida,'Revised radar technology', Institute of Electronics, Information and Communication Engineers, pp.262-264 (1996) Adaptive Array, SLC (Sidelobe Cancellation: Sidelobes Cancellation), Kikuma,'Adaptive Signal Processing with Array Antenna', Science and Technology Publishing, pp.17-21 (1998) LMS (Least Mean Squares), SMI (Sample Matrix Inversion), RLS (Recursive Least Squares), Kikuma,'Adaptive Signal Processing with Array Antenna', Science and Technology Publishing, pp.35-46 (1998) STAP (Space Time Adaptive Processing), Richard Klemm,'Applications of Space-Time Adaptive Processing', IEE Radar, Sonar and Navigation series14, p.359-365 (2004)

As described above, in a bistatic or multistatic radar system, when a time-division pulse train is used, the time of the pulse train becomes long, so that the search time becomes long, and processing for calculating the speed and distance is performed. There was a problem that the range became wide and the processing scale increased. In addition, the target could not be detected in the complicated environment of clutter and unwanted waves.

The subject of this embodiment is a radar system and radar capable of outputting a target three-dimensional position and the like while suppressing the processing scale in a complicated environment of clutter and unnecessary waves even in the case of bistatic type or multistatic type. The purpose is to provide a signal processing method.

In order to solve the above problems, the radar system according to the present embodiment includes an Nt (Nt ≧ 1) transmission device or a transmission / reception device and an Nr (Nr ≧ 1) reception device, and has an observation time axis. Is divided into a communication period and a pulse train period, and in the communication period, information including a transmission position, a transmission frequency, a transmission time, and a transmission beam direction is transmitted and received, and in the pulse train period, a first pulse train P1 for Doppler observation and a ranger In reception, the Doppler component is extracted from the received signal of the first pulse train P1 among the direct waves received from the transmission device, and the observation speed of the direct wave is calculated. The first process of range-compressing the received signal of the second pulse train P2 using the reference signal corrected by the observation speed of the direct wave and outputting the distance Rd between the transmitting device and the receiving device. Of the reflected waves from the target, the Doppler component is extracted from the received signal of the first pulse train P1, the target speed is calculated, and the reference signal corrected by the target speed is used to receive the second pulse train P2. The second process of range-compressing the signal by correlation processing and outputting the distance Rt to the target, and the measurement value θt (AZ, EL) of the target are calculated, and the distance Rd of the direct wave and the target are reached. A third process of calculating the three-dimensional position (x, y, z) of the target is performed from the intersection of the elliptical body that can be formed from the distance Rt and the target angle measurement value θt.

FIG. 1 is a block diagram showing a configuration of a transmission system of a bistatic radar system according to the first embodiment. FIG. 2 is a block diagram showing a configuration of a receiving system of the bistatic radar system according to the first embodiment. FIG. 3 is a flowchart showing a processing flow of the receiving system in the first embodiment. FIG. 4 is a timing diagram showing an example in which a transmission pulse train is generated using a ranged pulse train at equal intervals in the first embodiment. FIG. 5 is a timing diagram showing an example in which a transmission pulse train is generated using a randomly arranged ranging pulse train in the first embodiment. FIG. 6 is a timing diagram showing an example of observing a target Doppler frequency from a transmission / reception pulse train in the first embodiment. FIG. 7 is a timing diagram showing an example of calculating the target distance observed from the transmission / reception pulse train in the first embodiment. FIG. 8 is a timing diagram illustrating the reception positional relationship between the direct wave and the target wave within the processing distance range in the first embodiment. FIG. 9 is a conceptual diagram showing the relationship between the transmission beam and the reception beam in the first embodiment. FIG. 10 is a conceptual diagram showing the coordinate relationship between transmission, reception, and target in the first embodiment. FIG. 11 is a conceptual diagram showing a state in which an ellipsoid in which a target exists is calculated in the first embodiment, and the measured angles AZ and EL are observed to identify the three-dimensional position of the target. FIG. 12 shows how, in the first embodiment, as a method for identifying a three-dimensional position of a target, a search method is used to calculate a position where Rttgt + Rrtgt is obtained at a point on a straight line of the measured angle values AZ and EL where the target exists. It is a conceptual diagram. FIG. 13 is a block diagram showing a configuration of a receiving system of the bistatic radar system according to the second embodiment. FIG. 14 is a conceptual diagram showing a state in which a target three-dimensional position is identified and the unnecessary wave is suppressed when there is a clutter or an unnecessary wave in the second embodiment. FIG. 15 is a flowchart showing a processing flow of the receiving system in the second embodiment. FIG. 16 is a conceptual diagram showing an SLC process in which an unnecessary wave signal included in a main channel signal is suppressed by controlling an adaptive weight (complex signal) of an auxiliary channel signal in the second embodiment. FIG. 17 is a conceptual diagram showing how the clutter is suppressed before SLC in the second embodiment. FIG. 18 is a conceptual diagram showing SLC processing of the Doppler pulse train P1 in the second embodiment. FIG. 19 is a conceptual diagram showing SLC processing of the ranged pulse train P2 in the second embodiment.

Hereinafter, embodiments will be described with reference to the drawings. The multi-static type radar system is configured to detect the target position by a plurality of transmission devices, transmission / reception radar devices, and reception radar devices. From the system, the relationship between transmission and reception is extracted and bistatic. It can be easily expanded by applying the mechanism of a type radar system. Therefore, in order to describe the relationship between the transmitting device and the receiving device, a bistatic radar system will be described here.

(First Embodiment)
FIG. 1 is a block diagram showing a configuration of a transmission system of a bistatic radar system according to the first embodiment, and FIG. 2 is a block diagram showing a configuration of the reception system. FIG. 3 is a flowchart showing the processing flow of the receiving system shown in FIG. 2, and FIGS. 4 and 5 are random when the transmission pulse trains are generated using the equally spaced ranged pulse trains in the transmission system shown in FIG. 1, respectively. FIG. 6 is a timing diagram showing an example of generating a transmission pulse train using the ranged pulse trains arranged in the above, and FIG. 6 is a timing chart showing an example of observing a target Doppler frequency from the transmission / reception pulse trains.

In the transmission system shown in FIG. 1, the signal generator 11 generates a transmission type signal, the modulator 12 modulates and multiplexes the transmission information on the transmission type signal, the frequency converter 13 converts the modulated signal into a high frequency signal, and a pulse is provided. The modulator 14 pulse-modulates a high-frequency signal to generate a transmission pulse train, and the transmission antenna 15 transmits an N (N ≧ 2) hit pulse.

The transmission pulse train is composed of a communication period and a composite pulse train period.

The communication period is a period used for communication between the device of the transmission system and the device of the reception system, and multiplex modulation of transmission information such as a transmission position, a transmission time, a transmission frequency, and a transmission beam direction. There are various modulation methods, but if confidentiality is required, there is SS modulation (see Non-Patent Document 2).

The synthetic pulse train period generates a synthetic pulse train in which the Doppler pulse train P1 for Doppler extraction and the Ranged pulse train P2 for rangening are mixed. The Doppler pulse trains P1 are evenly spaced for Doppler extraction, and the ranging pulse train P2 performs code modulation between the pulses (see Non-Patent Document 3). As the code modulation method, for example, there is an M sequence (see Non-Patent Document 4). The pulse intervals of the ranged pulse train P2 may be equal intervals as shown in FIG. 4 or random intervals as shown in FIG. Here, in FIGS. 4 and 5, (a) shows a Doppler pulse train, (b) shows a ranging pulse train, (c) shows a combined pulse train of a Doppler pulse train and a ranged pulse train, and (d) shows a transmission pulse train. Random intervals improve the confidentiality of the combined pulse train. When the Doppler pulse train P1 and the ranging pulse train P2 are time-divided as in the case of FM ranging, the pulse train time becomes longer, the search time becomes longer, and the processing time range for calculating the speed and distance becomes longer. , There was a problem that the processing scale increased. On the other hand, in the mixed pulse train, the Doppler pulse train P1 and the ranging pulse train P2 are superimposed at the same time, the search time and the processing range time range are shortened, and there is an advantage that the processing scale can be reduced.

Next, the receiving system shown in FIG. 2 will be described. In the receiving system, the signal received by the receiving antenna 21 is frequency-converted by the frequency converter 22 and converted into a digital signal by the AD converter 23. Using this digital signal, information such as transmission position, transmission time, transmission frequency, and transmission beam direction is demodulated by communication demodulation. The beam controller 25 controls the receiving beam direction of the receiving antenna 21, and the frequency converter 22 performs frequency conversion according to the transmission frequency.

The received signal converted into the digital signal is branched into a direct wave detection system and a target wave detection system. In the direct wave detection system, the slow-time FFT processor 31 performs FFT processing on the slow-time axis, the Doppler extractor 32 extracts the Doppler of the direct wave, and the ranging reference signal corrector 33 performs the range reference signal. Is corrected based on the Doppler of the direct wave, the range axis correlation processing is performed by the range correlation processor 34 based on the reference signal for range, and the range of the direct wave is detected from the correlation processing result by the range detector 35. ..

On the other hand, in the target wave detection system, the slow-time FFT processor 41 performs FFT processing on the slow-time axis, the Doppler extractor 42 extracts the target Doppler, and the ranging reference signal corrector 43 performs rangeing. The reference signal is corrected based on the target Doppler, the range correlation processor 44 for range compression (see Non-Patent Document 7) performs range axis correlation processing based on the range reference signal, and the range detector 45 The range of the target wave is detected from the correlation processing result, and the target angle is measured by the angle measuring device 46. Then, the target 3D data is acquired by the 3D data calculator 51 from the direct wave detection result and the target wave detection result.

That is, in the reception system, the Doppler extraction of the direct wave and the target wave is performed using the Doppler pulse train of the received digital signal. The received pulse train is a mixed pulse train of the Doppler pulse train P1 and the ranging pulse train P2, but since the pulse intervals are different, the slow-time FFT processors 31 and 41 slow the data of the pulse intervals of the P1 row for each range cell. -Perform FFT on time axis. This situation is shown in FIG. In FIG. 6, (a) shows a mixed pulse train of the Doppler pulse train P1 and the ranging pulse train P2 transmitted within the processing distance range, (b) shows the received pulse train of the transmitted mixed pulse train, and (c) shows the Doppler pulse train P1. It shows how the target Doppler was extracted by the Doppler extractor 32 after FFT processing. The FFT process of the slow-time axis is expressed by the following equation.

このレンジセル毎のSIGp1に対して、ドップラ抽出器３２、４２では、CFAR（非特許文献５参照）処理により直接波、目標波を検出し、ドップラfd（ｍ）（ｍ＝１～M、M：目標数）を抽出する。

For SIGp1 for each range cell, the Doppler extractors 32 and 42 detect direct waves and target waves by CFAR (see Non-Patent Document 5) processing, and Doppler fd (m) (m = 1 to M, M: Target number) is extracted.

Next, in the range reference signal correctors 33 and 43, a reference reference signal for performing correlation processing using the signal of the range period is generated. As the reference reference signal, a Doppler output by the Doppler pulse train is used as shown in the following equation.

The set reference reference signal pulse train length is Mrng, and in order to set the reception distance cell length to R, the reference signal is padded with zeros as shown in the following equation. This situation is shown in FIG. In FIG. 7, (a) is a transmission pulse train P1 + P2, and (b) is a reception pulse train P1 + P2, which has a time delay due to a target distance, and a range signal length (M cell) can be obtained. (C) shows how the distance is extracted in the processing distance range (R cell) by the correlation processing of the P2 column.

この参照信号と入力信号との相関を算出するために、レンジ相関処理器３４、４４において、参照信号を次式のようにFFT処理する。

In order to calculate the correlation between the reference signal and the input signal, the range correlation processors 34 and 44 perform FFT processing on the reference signal as shown in the following equation.

一方、レンジング期間の受信信号は次式で表すことができる。

On the other hand, the received signal during the rangening period can be expressed by the following equation.

受信信号をFFTして

FFT the received signal

レンジ圧縮（非特許文献７参照）のための相関処理（３４、４４）は周波数軸の乗算を逆FFTして、次式となる。

The correlation processing (34, 44) for range compression (see Non-Patent Document 7) is obtained by inversely FFTing the multiplication of the frequency axes to obtain the following equation.

この様子を図７に示す。目標距離は、srng(t)をCFAR等によりスレショルド検出して、時間軸を距離軸に変換すれば算出することができる。速度については、CW期間のデータにより算出した結果を出力する。

This situation is shown in FIG. The target distance can be calculated by detecting the threshold of srng (t) with CFAR or the like and converting the time axis to the distance axis. For the speed, the result calculated from the data of the CW period is output.

By the above processing, the target Doppler and the distance can be calculated.

Next, the three-dimensional position identification method in the case of the bistatic system will be described with reference to FIGS. 9 to 12. FIG. 9 shows the relationship between the transmitted beam and the received beam. Since the transmission beam direction is known from the communication information, the reception beam is formed by a simultaneous multi-beam or a time-division multi-beam so as to cover the transmission beam. FIG. 10 shows the coordinate relationship between transmission, reception, and target. To identify the three-dimensional position of the target, the transmission-reception distance Rrt and the transmission-target-reception distance Rttgt + Rrtgt are calculated. As a result, as shown in FIG. 11, the ellipsoid in which the target exists can be calculated, and the three-dimensional position of the target can be identified by observing the measured angles AZ and EL from the reception.

Of this distance, the transmission-reception distance Rrt can be calculated from the transmission position and reception position of the communication information. On the other hand, the transmission-target-reception distance Rttgt + Rrtgt is calculated based on the calculation range of the direct wave of the transmission device-receiver. This is a measure for the bistatic radar system because the distance 0 is not the same when the time is different between the transmitting device and the receiving device.

Therefore, on the receiving side, it is necessary to observe both the direct wave and the distance of the reflected wave from the target. The distance can be calculated by the method of FIG. 7 after the Doppler observation of FIG. When there are a plurality of observed values, as shown in FIG. 8, the direct wave can be extracted because the amplitude is large and the distance is short. Other than that, it is regarded as a reflected wave from the target, and even if there are a plurality of targets, the target reflection distance Rttgt + Rrtgt can be calculated for each target by the equation (9).

As a method for identifying the three-dimensional position of the target, as shown in FIG. 12, since the target exists on the straight line of the measured angle values AZ and EL from the reception, the position where Rttgt + Rrtgt is obtained at the point on the straight line is searched by the search method. It should be calculated. As a reception angle measurement method, there is a phase monopulse (see Non-Patent Document 8) and the like. For phase monopulse angle measurement, in addition to the Σ beam, which is the detection beam, a ΔAZ (ΔEL) beam, which is a difference beam in which the antenna aperture is divided by the AZ axis (EL axis), is required. In the target wave extraction of the system of FIG. 1, the cell of ΔAZ (ΔEL) which is the same as the detection cell (Doppler or range cell) of at least one of the Doppler extraction 32 targeted and detected by the Σ beam or the range extraction 35 is extracted. Then, the angle measurement 36 is performed. Using this angle measurement value, a point (xs, ys, zs) on a straight line, which is the search range of FIG. 12, can be calculated. Using Rttgt + Rrtgt, the three-dimensional position (x, y, z) of the target to be minimized can be calculated by the following equation.

FIG. 3 shows the overall processing flow in the above receiving system. In FIG. 3, first, communication demodulation is performed (step S11), the directivity direction and frequency of the beam are controlled (step S12), the beam is received (step S13), and the system is branched into two systems.

On the other hand, direct wave Doppler extraction is performed (step S14), the range reference signal is corrected (step S15), and rangeing correlation processing is performed (step S16). On the other hand, the target wave is extracted by Doppler (step S17), the range reference signal is corrected (step S18), the rangeing correlation process is performed (step S19), and the angle measurement process is performed (step S20). Here, it is determined that the processing for the number of targets has been completed (step S21), and if it has not been completed, the process is changed to the next target (step S22), and the process returns to step S17. When the processing for the target number is completed, the three-dimensional position is identified by combining the direct wave ranging correlation processing result and the target angle measurement processing result (step S23), and the series of processing is completed.

The above has described the case of a bistatic radar system of a transmitting device and a receiving device. In the case of a transmitting / receiving device having a receiving function on the transmitting device side, the transmitting / receiving device can be operated as a monostatic radar. In this case, if the Doppler pulse train P1 is one type, there is a transmission blind and the target may not be observable. As a countermeasure against this, a plurality of Doppler pulse trains P1 are prepared, a range pulse train is combined, and the mixed pulse train is repeated in order. As a result, Doppler can be extracted from any of the mixed pulse trains, range can be performed, and the three-dimensional position of the target can be identified only by the transmission / reception device.

(Second embodiment)
In the first embodiment, the case where there is no unnecessary wave from the clutter or the external environment has been described. The present embodiment is characterized in that the three-dimensional position of the target is identified when there is a clutter or an unnecessary wave.

Here, since the transmission system is the same as that in FIG. 1, the description thereof will be omitted. FIG. 13 is a block diagram showing the configuration of the receiving system according to the present embodiment, and FIG. 14 is a conceptual diagram showing how the three-dimensional position of the target is identified and the unnecessary wave is suppressed when there is a clutter or an unnecessary wave. FIG. 15 is a flowchart showing a processing flow of the receiving system. In FIGS. 13 and 15, the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals, and different parts will be described here.

In FIG. 13, the difference from the first embodiment is that there is a clutter suppression treatment and an SLC treatment. In each case, the received signal of the auxiliary antenna 26 is used to suppress unnecessary waves of the main antenna (Σ, ΔAZ, ΔEL) 21. Specifically, the received signal of the auxiliary antenna 26 is frequency-converted by the frequency converter 27, converted into a digital signal by the AD converter 28, and the sidelobes of the communication signal are suppressed by the communication signal SLC 29 to the communication demodulator 24. send. Further, in the direct wave detection system, the clutter component contained in the output of the slow-time FFT processor 31 is suppressed by the clutter suppressor 36, and then the sidelobes of the direct wave are suppressed by the Doppler SLC 36a to the Doppler extractor 32. send. Further, the output of the range correlation processor 34 is sent to the range SLC 37, the sidelobes of the range correlation processing result are suppressed, and the output is sent to the range extractor 35. Similarly, in the target wave detection system, the clutter component contained in the output of the slow-time FFT processor 41 is suppressed by the clutter suppressor 47, and then the sidelobes of the target wave are suppressed by the Doppler SLC 47a to suppress the sidelobes of the target wave. Send to. Further, the output of the range correlation processor 44 is sent to the range SLC 48, the sidelobes of the range correlation processing result are suppressed, and the output is sent to the range extractor 45.

On the other hand, the received signal obtained by the auxiliary antenna 26 is input to the slow-time FFT processor 61 to perform FFT processing on the slow-time axis, the clutter component is suppressed by the clutter suppressor 62, and the reference signal corrector for ranging is used. After correcting the reference signal in 64, the correlation processing is performed by the range correlation processor 65, the signal is sent to the range SLC 37, and the SLC processing is performed together with the direct wave detection result.

The entire processing flow is shown in FIG. In this embodiment, as shown in FIG. 15, in the processing of FIG. 3, the communication signal SLC (step S24), the direct wave side Doppler SLC (step S25), the ranging SLC (step S26), and the target detection side Doppler SLC (Including clutter suppression) (step S27) and ranging SLC (including clutter suppression) (step S28) are added. Unnecessary waves can be suppressed by SLC for each of the communication modulation, the direct wave of the transmitting device to the receiving device, and the transmitting device to the target to the receiving device.

Here, the unnecessary wave suppression process of the present embodiment will be described with reference to FIGS. 16 to 19. FIG. 16 shows an SLC process for suppressing an unwanted wave signal included in a main channel signal by controlling an adaptive weight (complex signal) of an auxiliary channel signal, and FIG. 17 shows a state in which a clutter is suppressed before the SLC. FIG. 18 shows the SLC processing of the Doppler pulse train P1 and FIG. 19 shows the SLC processing of the ranged pulse train P2.

As the unwanted wave suppression process, there is generally an adaptive array (see Non-Patent Document 9). This is to suppress interference by minimizing the output power or the like by using an antenna element or a sub-array. As a method for calculating the adaptive weight, there are various methods (see Non-Patent Document 10) such as LMS (Least Mean Square), SMI (Sample Matrix Inversion), and RLS (Recursive Least-Squares). Here, for the sake of simplicity, a method using SLC (Sidelobe Canceller, see Non-Patent Document 9) as an interference suppression process by the main channel of the main beam signal and the auxiliary channel forming the auxiliary beam will be described, but another adaptive array method is applied. Needless to say, you can.

As shown in FIG. 16A, the SLC suppresses unnecessary waves by controlling the adaptive weight (complex signal) of the auxiliary channel signal from the auxiliary antenna for the unnecessary wave signal included in the main channel signal from the main antenna. It is a thing. In FIG. 15, for the sake of simplicity, the case where the auxiliary channel (auxiliary antenna) is 1 channel is assumed, but by providing a plurality of auxiliary channels in parallel, it is possible to suppress a plurality of interferences. The antenna pattern after SLC corresponds to forming a null in the jamming direction, as shown in FIG. 16 (b). In the case of a plurality of unwanted waves, as shown in FIG. 16 (c), a null can be formed in each unwanted wave direction by the plurality of auxiliary channels.

Since the clutter component is small for the communication modulation signal received from the transmitting device to the receiving device and the direct wave, unnecessary waves can be suppressed by ordinary SLC. On the other hand, the target wave of the transmitting device to the target to the receiving device has a clutter component, and it is necessary to suppress the clutter component. In this case, since the adaptive weight is affected by the strong main lobe clutter signal and does not converge to the correct weight for suppressing unwanted waves, the clutter is suppressed before SLC as shown in FIGS. 17 (a) to 17 (c). There is a need. Therefore, in the Doppler pulse train P1, as shown in FIGS. 18A to 18D, the slow-time axis is FFTed, and the range-Doppler signal is first used as the clutter suppression 26 to perform the main lobe on the Doppler axis. Suppress the clutter. In the case of an on-board radar, the main lobe clutter can be calculated if the own speed and beam directivity are known. After suppressing the clutter, the SLC process 26a is performed. As the data for calculating the adaptive weight at this time, the Doppler axis data for each range cell is used as shown by the broken line in FIG. 18 (c). As a result, the adaptive weight can be calculated, unnecessary signals can be suppressed, and Doppler extraction 22 can be performed.

For Doppler pulse P1, SLC processing for clutter suppression and unwanted wave suppression was described separately, but STAP (Space-Time Adaptive Processing, non-patent document) that simultaneously performs clutter suppression and interference suppression processing. It goes without saying that (see 11) may be applied.

Next, the SLC processing of the ranged pulse train P2 will be described with reference to FIGS. 19 (a) to 19 (d). In the Doppler pulse train, the main lobe clutter component could be suppressed because it can be converted to the Doppler axis by the slow-time axis FFT. I can't suppress it. On the other hand, when range compression is performed using the reference signal for range compression corrected by the target Doppler component, the target Doppler component and the clutter Doppler component are different, so that the clutter can be suppressed. Therefore, in FIG. 13, for the direct wave Σ and the target wave Σ, ΔAZ, and ΔEL, the extracted Doppler signal is used to correct the reference signal for ranging, range correlation processing is performed, and the clutter after range compression is performed. SLC is performed on the signal of the range axis that suppresses. This makes it possible to suppress unnecessary waves and extract a range.

Since the clutter and unnecessary waves can be suppressed by the above processing, the three-dimensional position of the target can be identified by the same method as that of the first embodiment.

In the above, the case where the Doppler pulse train and the ranging pulse train are only code modulation between pulses and there is no intra-pulse modulation has been described, but in order to improve the LPI property and to isolate the Doppler pulse train and the ranging pulse train, each Another intrapulse modulation may be applied. Needless to say, a method of isolating the Doppler pulse train and the ranging pulse train separately may be used.

In addition, the present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. Furthermore, components over different embodiments may be combined as appropriate.

11 ... signal generator, 12 ... modulator, 13 ... frequency converter, 14 ... pulse modulator, 15 ... transmit antenna,
21 ... Receive antenna, 22 ... Frequency converter, 23 ... AD converter, 24 ... Communication demodulator, 25 ... Beam controller, 26 ... Auxiliary antenna, 27 ... Frequency converter, 28 ... AD converter, 29 ... Communication signal SLC,
31 ... slow-time FFT processor, 32 ... Doppler extractor, 33 ... Rangeing reference signal corrector, 34 ... Range correlation processor, 35 ... Range detector, 36 ... Clutter suppressor, 36a ... Doppler SLC, 37 ... Range SLC,
41 ... slow-time FFT processor, 42 ... Doppler extractor, 43 ... ranging reference signal corrector, 44 ... range correlation processor, 45 ... range detector, 46 ... angle measuring processor, 47 ... clutter suppressor, 47a ... Doppler SLC, 48 ... Range SLC, 51 ... 3D data calculator,
61 ... slow-time FFT processor, 62 ... clutter suppressor, 64 ... range reference signal corrector, 65 ... range correlation processor.

Claims (3)

It is equipped with Nt (Nt ≧ 1) transmitters or transmitters and receivers and Nr (Nr ≧ 1) receivers.
The observation time axis is divided into the communication period and the pulse train period.
During the communication period, information including the transmission position, transmission frequency, transmission time, and transmission beam direction is transmitted and received.
In the pulse train period, a pulse train in which the first pulse train P1 for Doppler observation and the second pulse train P2 for rangening are superimposed is transmitted, and in reception, from the received signal of the first pulse train P1 among the direct waves received from the transmission device. The Doppler component is extracted to calculate the observation speed of the direct wave, and the reception signal of the second pulse train P2 is range-compressed using the reference signal corrected by the observation speed of the direct wave to perform the transmission device and the reception. In the first process of outputting the distance Rd between the device and the target, the Doppler component is extracted from the received signal of the first pulse train P1 of the reflected waves from the target, the target speed is calculated, and the target speed is calculated. The second process of range-compressing the received signal of the second pulse train P2 by the correlation process and outputting the distance Rt to the target using the reference signal corrected by EL) is calculated, and the three-dimensional position (x, y, z) of the target is calculated from the intersection of the elliptical body that can be formed from the distance Rd of the direct wave and the distance Rt to the target and the target angle measurement value θt. A radar system that performs the third processing. The receiving device includes a main antenna and an auxiliary antenna.
During the communication period, unnecessary waves input from the sidelobes of the main antenna are suppressed by SLC (Sidelobe Canceller) processing by the auxiliary antenna, and during the pulse train period, the received signal of the first pulse train P1 is transmitted to each range cell. FFT processing is performed to suppress the clutter component on the Doppler axis, SLC processing is performed on the Doppler axis to suppress unnecessary waves, and the received signal of the second pulse train P2 is corrected by the target Doppler component using a reference signal. The radar system according to claim 1, wherein range compression is performed by correlation processing and SLC processing is performed on the range axis to suppress unnecessary waves. Used in radar systems with Nt (Nt ≧ 1) transmitters or transmitters and receivers and Nr (Nr ≧ 1) receivers.
The observation time axis is divided into the communication period and the pulse train period.
During the communication period, information including the transmission position, transmission frequency, transmission time, and transmission beam direction is transmitted and received.
In the pulse train period, a pulse train in which the first pulse train P1 for Doppler observation and the second pulse train P2 for rangening are superimposed is transmitted, and in reception, from the received signal of the first pulse train P1 among the direct waves received from the transmission device. The Doppler component is extracted to calculate the observation speed of the direct wave, and the reception signal of the second pulse train P2 is range-compressed using the reference signal corrected by the observation speed of the direct wave to perform the transmission device and the reception. In the first process of outputting the distance Rd between the device and the target, the Doppler component is extracted from the received signal of the first pulse train P1 of the reflected waves from the target, the target speed is calculated, and the target speed is calculated. The second process of range-compressing the received signal of the second pulse train P2 by the correlation process and outputting the distance Rt to the target using the reference signal corrected by EL) is calculated, and the three-dimensional position (x, y, z) of the target is calculated from the intersection of the elliptical body that can be formed from the distance Rd of the direct wave and the distance Rt to the target and the target angle measurement value θt. A radar signal processing method for performing the third processing.

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