JP6852007B2 - Radar system and its radar signal processing method - Google Patents

Description

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

In the conventional radar system, as an LPI (Low Probability of Intercept) radar that reduces the detectability, there are radars using coding (Patent Document 1 and Non-Patent Document 1). This is the one in which the inside of a pulse is SS-modulated (Non-Patent Document 2), or the one in which each pulse is encoded and range-compressed using a reference signal. In recent years, the performance of the radar wave receiving device has also been widened, and it is expected that sufficient LPI characteristics may not be ensured only by SS modulation, and a method for further ensuring LPI characteristics is desired.

Japanese Unexamined Patent Publication No. 2014-182010

Coded Radar, Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.278-280 (1996) SS Modulation, Marubayashi,'Spectral Diffusion Communication and Its Applications', Institute of Electronics, Information and Communication Engineers, pp.1-18 (1998) Code code (M-sequence) generation method, M.I.Skolnik, ‘Introduction to radar systems’, McGRAW-HILL, pp.429-430 (1980) BPSK, QPSK, Nishimura,'Communication System Design by Digital Signal Processing', CQ Publisher, pp.222-226 (2006) CFAR processing, Yoshida,'Revised radar technology', Institute of Electronics, Information and Communication Engineers, pp.87-89 (1996) MIMO processing, JIAN LI, PETER STOICA, ‘MIMO RADAR SIGNAL PROCESSING’, WILEY, pp.163-170, pp.1-5 (2009)

As described above, in the conventional radar system, the LPI property is enhanced by SS modulation within or between pulses, but sufficient LPI property can be obtained only by SS modulation within or between pulses. In some cases, it could not be secured.

The present embodiment has been made in view of the above problems, and an object of the present invention is to provide a radar system capable of observing a target speed and distance while ensuring sufficient LPI characteristics, and a radar signal processing method thereof.

In order to solve the above problems, the radar system according to the present embodiment uses a modulated pulse by a coded or random signal, and a pulse train in which the pulse width, pulse interval, and pulse amplitude for range extraction are changed for each pulse. And the transmission system that transmits the radar signal generated by mixing the pulse sequence for Doppler extraction with a constant pulse interval and thinned out at a predetermined thinning rate ρ (ρ ≧ 0) from the transmitting antenna, and the receiving antenna. For the reflected signal of the radar signal, the Doppler is extracted with the pulse train for Doppler extraction, and the range is extracted by correlation processing using the reference signal for range extraction corrected by the extracted Doppler, and the speed and range are extracted. It is equipped with a receiving system that outputs. That is, by extracting Doppler from the thinned-out pulse train for Doppler extraction and changing the pulse width, pulse interval, pulse amplitude, etc., LPI property can be ensured, and distance measurement and speed measurement can be performed.

The block diagram which shows the schematic structure of the transmission system of the radar system which concerns on 1st Embodiment. The block diagram which shows the schematic structure of the receiving system of the radar system which concerns on 1st Embodiment. FIG. 6 is a conceptual diagram showing how a transmitting fan beam and a receiving multi-beam are formed in the first embodiment. In the first embodiment, a timing diagram showing how to generate a mixed pulse train of a transmission system. In the first embodiment, a timing diagram showing a state in which a Doppler signal is extracted from a received signal with respect to a transmitted signal by a mixed pulse train. In the first embodiment, a timing diagram showing a state in which a pulse train is extracted from a received signal and processing of a slow-time axis for each range cell is performed. In the first embodiment, a timing diagram showing a state in which a target range is extracted by correlation processing using a Doppler correction reference signal. In the first embodiment, a timing diagram showing a state in which a target range is extracted by sliding the time axis in cell units and convolving and integrating the time axis. The block diagram which shows the schematic structure of the transmission system of the radar system which concerns on 2nd Embodiment. The block diagram which shows the schematic structure of the receiving system of the radar system which concerns on 2nd Embodiment. In the second embodiment, a conceptual diagram showing a transmission aperture division for angle deception. In the second embodiment, the block diagram which shows the processing system which converts a high rate signal into a low rate signal. In the second embodiment, a timing diagram showing how a mixed pulse train is generated in a transmission system. The figure which shows the mode of converting a received signal from a high rate signal to a low rate signal in the 2nd Embodiment. In the second embodiment, the figure which shows the state of correlating each of the high rate received signal with the in-pulse code string for Doppler extraction and the in-pulse code string for range extraction. In the second embodiment, it is a figure which shows the state of correlating each of the high-rate received signal with the in-pulse code string for sub-array of M system. The figure which shows the state of performing Doppler extraction using the composite output of the sub-array division signal generated from the high-rate transmission / reception signal in the 2nd Embodiment. The figure which shows the mode of performing the range extraction using the composite output of the sub-array division signal generated from the high-rate transmission / reception signal in the 2nd Embodiment.

Hereinafter, embodiments will be described with reference to the drawings. In the description of each embodiment, the same parts are designated by the same reference numerals, and duplicate description will be omitted.

(First Embodiment)
The radar system according to the first embodiment will be described with reference to FIGS. 1 to 8.

1 to 8 show a configuration and a processing example of the radar system according to the first embodiment, FIG. 1 is a block diagram showing a schematic configuration of a transmission system, and FIG. 2 is a block diagram showing a schematic configuration of a reception system. , FIG. 3 is a conceptual diagram showing how a transmitting fan beam and a receiving multi-beam are formed, FIG. 4 is a timing diagram showing how a mixed pulse train is generated in a transmitting system, and FIG. A timing diagram showing how the signal is extracted, FIG. 6 is a timing diagram showing how the slow-time axis is processed for each range cell by extracting a pulse train from the received signal, and FIG. 7 is a target by correlation processing using a Doppler correction reference signal. FIG. 8 is a timing diagram showing how the range of the above is extracted, and FIG. 8 is a timing diagram showing how the target range is extracted by sliding the time axis in cell units and convolving and integrating.

First, in the transmission system shown in FIG. 1, the reference signal for transmission generated by the reference signal generator 11 is sent to the modulator 13 together with the random code generated by the code generator 12, and the control from the pulse controller 14 is performed. A random pulse train is generated by performing coding modulation on the reference signal according to the pulse, converted into a radio frequency (RF) signal by the frequency converter 15, power is amplified by the high output amplifier 16, and transmitted from the transmitting antenna 17.

Next, in the receiving system shown in FIG. 2, the reflected signal from the target is captured by the receiving antenna 21, the noise is reduced and amplified by the low noise amplifier 22, and then the frequency is converted to the baseband by the frequency converter 23. It is converted into a digital signal by the AD converter 24. After that, the Doppler pulse train extractor 25 extracts the Doppler pulse train from the received signal, the FFT (Fast Fourier Transform) processor 26 converts it into a signal in the frequency domain, and the Doppler extractor 27 extracts the Doppler from the target. Extract the frequency signal. Subsequently, the range extraction reference signal corrector 28 generates a range extraction reference signal, and corrects the reference signal using the already extracted Doppler frequency signal. On the other hand, the range pulse train extractor 29 extracts the range pulse train, the corrected reference signal is used to correlate with the range pulse train with the correlation processor 2A, and the range extractor 2B determines the target range from the correlation result. Extract, calculate the target speed with the output processor 2C, and output the range / speed information.

In the above configuration, the processing operation will be described below. In the radar system according to the present embodiment, as shown in FIG. 3, the transmission beam covers the observation range, and the reception beam is assumed to be a multi-beam formed simultaneously by time division or DBF (Digital Beam Forming). Consider the case where time integration is possible. However, it does not necessarily mean that long-term integration is necessary.

The transmission pulse is a mixed pulse train generated as shown in FIG. 4 (c) by synthesizing the pulse train for Doppler extraction shown in FIG. 4 (a) and the pulse train for range extraction shown in FIG. 4 (b). The pulse train for Doppler extraction breaks the periodicity and secures the LPI property by thinning out the pulse trains at equal intervals on the time axis. The range extraction pulse train changes at least one of pulse width, pulse interval, and amplitude for each pulse. In FIG. 4, for the sake of clarity, it is assumed that the pulse amplitude is constant. By synthesizing (mixing) this pulse train for Doppler extraction and the pulse train for range extraction, the pulse specifications (pulse width, pulse interval, pulse amplitude) of the ESM (Electronic Support Measure) device used for the receiving device of the other party. ) Shall perform deception processing that makes radar identification difficult. The horizontal axis of FIG. 4 is the time on the fast-time axis.

A method of generating a transmission signal in the transmission system shown in FIG. 1 will be described. The reference signal generation (11) for obtaining a high frequency signal (RF signal) is modulated by the modulator (13) with the modulation signal that generates the intra-pulse and inter-pulse code by the code generation (12), and the high frequency (RF) The signal is frequency-converted (15), high-output amplified (16), high-output amplified according to the pulse width generated by the modulator (13), and transmitted from the transmitting antenna (17). At this time, the code sequence, the pulse width, the pulse interval, and the pulse amplitude are changed for each pulse by the pulse control (14).

The pulse train Sig1 for Doppler extraction is a pulse in which the same code is repeated between pulses, but the signal is randomly thinned out in order to make it difficult to detect the repetition period.

The pulse train Sig2 for range extraction is modulated by a random code (M-sequence, etc., Non-Patent Documents 3 and 4) within and between pulses. This signal sequence is used to generate transmission waveforms with different pulse widths and pulse intervals. The state of this mixed waveform is shown in FIG.

By synthesizing this, the mixed pulse train of the following equation can be generated.

Next, the reception process will be described in the reception system shown in FIG. The signal received by the receiving antenna 21 is low-noise amplified (22), frequency-converted (23), and AD-converted (24) to become a digital signal. The received signal obtained in this way has the following equation.

In this embodiment, since a relatively long observation time is assumed, Doppler correction is required when correlating the pulse train for range extraction. First, a pulse train for Doppler extraction with a known pulse interval is extracted (25) from the received pulse train.

This situation is shown in FIG. 5A shows a transmission pulse train, FIG. 5B shows a reception pulse train, FIG. 5C shows a pulse train for Doppler extraction, and FIG. 5D shows a Doppler extraction result.

Here, the Doppler pulse train extraction (25) is a process of dividing the Doppler pulse train into PRI (Pulse Repetetion Interval), and includes a range extraction pulse train. Since this range extraction pulse can be suppressed by the slow-time axis FFT shown below, the pulse sequence for range extraction is removed in FIG. 5 for the sake of simplicity. On the other hand, there is also a method of discriminating between pulses for Doppler extraction and range extraction using intra-pulse modulation, which will be described in the second embodiment.

Using the pulse train for Doppler extraction, FFT (26) on the slow-time axis is performed for each cell on the fast-time axis in order to perform Doppler extraction.

This situation is shown in FIG. FIG. 6A shows a received pulse train, and FIG. 6B shows a slow-time axis. Using this Sr1out (ωs, tf), Doppler fd (ωs = 2πfd) can be extracted (27) by detecting with CFAR (Non-Patent Document 6) or the like on the range-Doppler axis, and the velocity can be determined by the following equation. Can be converted.

Next, a method of performing distance measurement using a pulse train for range extraction will be described. Since the sign of this signal sequence is different for each pulse, as shown in FIG. 7, the signal sequence is subjected to the correlation processing (2A) with the reference signal. In FIG. 7, (a) shows a transmission pulse train, (b) shows a reception pulse train, and (c) shows a range extraction result.

First, the received signal Sr (tf) is FFTed on the fast-time axis. In this case, it does not depend on the pulse number pn.

The reference signal is zero-padded to make the signal lengths uniform, including correction (28) by the Doppler extracted by the Doppler extraction pulse train.

Next, this is FFT.

From the equations (8) and (10), the correlation output Sr2 is obtained by the following equation.

As a result, since the correlation output can be obtained on the range (fast-time) axis, the target can be detected by CFAR processing or the like, and the target distance (range) can be extracted (2B) (see FIG. 7). As a result, the target Doppler and the distance can be output (2C).

The case where the correlation processing of the input signal and the reference signal is performed including the pulse amplitude of 0 has been described above. This processing has an advantage that the processing scale is small, but if the portion where the pulse amplitude is 0 is also included, the correlation processing including noise is performed, so that the SN (signal-to-noise power ratio) is lowered. As a countermeasure for this, as shown in FIG. 8, a method of extracting range (time) axis cells in which the transmission pulse amplitude is other than 0 and performing correlation processing can be considered. In FIG. 8, (a) is a transmission pulse train, (b) is a reception pulse train, (c) is a reception signal extraction result, (d) is a result of extracting only the reception signal time, and (e) is a range extraction result. .. Here, since there is no periodicity in the portion where the transmission pulse amplitude is other than 0, it is necessary to perform convolution integration with the range cell shifted, which increases the processing scale but can improve the SN. The processing in this case is embodied below.

First, the input signal is Sr (tf), and the received signal cell sequence having the start time t is extracted according to the signal sequence having the transmission amplitude other than 0.

The reference signal is padded with zeros in order to make the signal lengths uniform, including the correction (28) by the Doppler extracted by the Doppler extraction pulse train.

Convolution integration is performed using (12) and (13).

As a result, each correlation output Sr (t) corresponding to the time axis (range axis) can be obtained, so that the target distance can be output using CFAR or the like.

In the Doppler extraction, when there is acceleration, the pulse train is divided into time series at the time of FFT of the slow-time axis in FIGS. 5 and 6, and FFT is performed in each division unit to perform the time series Doppler. You may extract fd (t). By applying the time-series Doppler fd (t) to the reference signal correction of Eq. (9), the present embodiment can be applied even when the relative target of the radar and the target has acceleration.

As described above, according to the radar system according to the first embodiment, the pulse width, pulse interval, and pulse amplitude for range extraction are set for each pulse by using a modulated pulse by coding or a random signal (noise). The changed pulse train and the pulse interval for Doppler extraction are constant, and the pulse trains thinned out at a predetermined thinning rate ρ (ρ ≧ 0) are overlapped (mixed) and transmitted from the transmitting antenna to the signal received by the receiving antenna. On the other hand, the Doppler is extracted with the pulse train for Doppler extraction, the target range is extracted by correlation processing using the reference signal for range extraction corrected by the extracted Doppler, and the speed and range are output. That is, by extracting the Doppler from the thinned-out pulse train for Doppler extraction and changing the pulse width, pulse interval, pulse amplitude, etc., distance measurement and speed measurement can be performed while ensuring LPI property.

(Second embodiment) Angle deception
In the first embodiment, a method of deceiving an ESM device used as a receiving device on the other side by changing the pulse width, pulse interval, and pulse amplitude for each pulse has been described. In the second embodiment, a method of deceiving the angle measurement of the ESM device for each pulse will be described with reference to FIGS. 9 to 18. 9 to 18 show a configuration and a processing example of the radar system according to the second embodiment, FIG. 9 is a block diagram showing a schematic configuration of a transmission system, and FIG. 10 is a block diagram showing a schematic configuration of a reception system. , FIG. 11 is a conceptual diagram showing transmission aperture division for angle deception, FIG. 12 is a block diagram showing a processing system for converting a high rate signal into a low rate signal, and FIG. 13 shows a state in which a mixed pulse train is generated in the transmission system. The timing diagram shown, FIG. 14 is a diagram showing how a received signal is converted from a high-rate signal to a low-rate signal, and FIG. 15 is an in-pulse code sequence for Doppler extraction and an in-pulse code sequence for range extraction from the high-rate received signal, respectively. A diagram showing how the correlation processing is performed, FIG. 16 is a diagram showing how the high-rate reception signal is correlated with the intra-pulse code sequence for the sub-array of the M system, and FIG. 17 is a diagram showing the sub-array division signal generated from the high-rate transmission / reception signal. FIG. 18 is a diagram showing a state in which Doppler extraction is performed using the combined output, and FIG. 18 is a diagram showing a state in which range extraction is performed using the combined output of the sub-array division signal generated from the high-rate transmission / reception signal.

First, in order to carry out angle deception, the transmission system is divided into M systems (121 to 171, ..., 12M to 17M) as shown in FIG. 9, and the transmission aperture is divided into M as shown in FIG. , The modulated signal is changed at each aperture. As a result, when observing the radar wave, the ESM device on the other side has a plurality of signal sources within the received beam width, and the measured angle value can be deceived by vector synthesis having different amplitudes and phases. ..

Next, the reception of the transmission division signal will be described with reference to FIGS. 10 to 18. In addition, in FIG. 17 and FIG. 18, for the sake of simplicity, it is assumed that the transmission aperture division is two systems (L and R, M = 2).

First, each transmission signal of the division unit is shown in the Doppler extraction pulse train of FIG. 13 (a), the range extraction pulse train of FIG. 13 (b), and the mixed pulse train of FIG. 13 (c) so that they can be separated by the reception process. As described above, a pulse having an arbitrary width is sampled at a high rate, and code modulation or the like is performed in units of a predetermined sample having the same width to secure isolation in the transmission aperture division unit. As a result, MIMO processing (Non-Patent Document 6), which is a DBF for transmission and reception, is performed. In the case of the transmission opening divided into two, it corresponds to the transmission / reception DBF of the M × N channel of transmission M = 2ch and reception N = 1ch. Further, different code sequences, pulse widths, and pulse intervals are used between pulses. In addition, the amplitude can be changed for each pulse as needed.

In the receiving system, as shown in FIG. 10, the received signal captured by the receiving antenna 21 is amplified by the low noise amplifier 22, converted into a baseband by the frequency converter 23, and converted into a digital signal by the AD converter 24. Will be converted. Since this signal is a high rate sampling signal, it is converted into a low sampling rate signal by the rate converter 2D. After that, it is distributed to the pulse train extractor 251 to 25M for Doppler and the pulse train extractor 291 to 29M for the range.

Next, the pulse train for Doppler of the M system extracted by the pulse train extractor for Doppler 251 to 25M is converted into a signal in the frequency domain by the FFT processor 261 to 26M, and the phase is corrected and synthesized by the synthesizer 2E after correction. , The Doppler frequency signal is extracted by the Doppler extractor 27. Subsequently, the range extraction reference signal corrector 28 generates a range extraction reference signal, and corrects the reference signal using the already extracted Doppler frequency signal. On the other hand, the range pulse train extracted by the range pulse train extractor 291 to 29M of the M system is extracted, and the corrected reference signal is used to correlate with the range pulse train with the correlation processor 2A1 to 2AM, and after correction. After the phase is corrected and synthesized by the synthesizer 2F, the target range is extracted from the correlation synthesis result by the range extractor 2B, the target speed is calculated by the output processor 2C, and the range / speed information is output.

Here, as shown in FIG. 12, the rate converter 2D includes a time axis dividing unit 2D1, a fast-time FFT processing unit 2D2, a frequency dividing unit 2D3, a multiplication unit 2D4, a fast-time Fourier processing unit 2D5, and a phase correction. It is composed of a unit 2D6, a correlation result addition unit 2D7, a reference signal generation unit 2D8, a reference signal fast-time FFT processing unit 2D9, and a frequency division unit 2DA.

In the rate converter 2D having the above configuration, first, when the code modulation signal shown in FIG. 14A is input, as shown in FIG. 14B, the signal is output for each predetermined time width Tdiv on the fast-time axis. The time axis is divided (2D1), and the fast-time axis signal in each Tdiv is FFT (2D2).

In the case of a pulse for Doppler extraction, Tdiv = PRI because the pulse interval PRI (Pulse Repetition Interval) before thinning is determined. This is divided (2D3) into the frequency band of the M system as shown in FIG. 14 (c).

Next, a reference signal is generated (2D8) in order to correlate the reference signal for each frequency division.

This is FFT (2D9).

This is frequency divided (2DA).

Using this, the correlation processing for each frequency division is multiplied (2D4) to obtain an Fourier (2D5), and the following equation is obtained.

The correlation processing result for each frequency division is phase-corrected (2D6) and added (2D7) as shown in FIG. 14 (d).

The corrected phase is a term for correcting the phase due to the center frequency difference for adding the signals for each frequency division band, and can be expressed by the following equation.

The signal of the formula (22) is a low-rate signal as compared with the input signal of the high-rate formula (15).

This method of converting a high-rate signal into a low-rate signal can be applied to both dopp extraction and range extraction signals because the fast-time axis signal can be divided into predetermined Tdivs and applied. In particular, it can be applied to a case where the pulse interval is random, such as for range extraction.

For example, FIG. 15 shows an application example in which the modulation code is changed between the Doppler extraction and the range extraction when the transmission subarray division number M is 1. In FIG. 15, (a) is a received pulse train, (b) is a received pulse train divided by Tdiv and aligned on the time axis (slow-time), and (c) is in-pulse coding for Doppler extraction converted to a low rate. Correlation processing result in the column, (d) shows the correlation processing result in the in-pulse code string for range extraction converted to a low rate.

Here, a method of converting a high-rate signal into a low-rate signal is applied to each of the fast-time axes divided by the Tdiv.

Further, FIG. 16 shows an application example in which the modulation code is changed for each transmission subarray. In FIG. 16, (a) is a received pulse train, (b) is a received pulse train divided by Tdiv and aligned on the time axis (slow-time), and (c) is an in-pulse code string for subarray 1 converted to a low rate. As a result of the correlation processing in (d), the correlation processing result in the in-pulse code string for the sub-array M converted to a low rate is shown. This can also be applied to the case where the modulation code is changed for each of the Doppler extraction, the range extraction, and the transmission subarray. In this case, different modulation codes of M (number of transmission subarrays) × 2 (for Doppler extraction and range extraction) are required.

FIG. 17 shows a process of converting an input high-rate signal into a low-rate signal and extracting a Doppler using this method. FIG. 17 shows a case where the transmission sub-array is divided into two, L and R, for the sake of simplicity, but of course, any M sub-array may be used. In FIG. 17, (a) and (b) are transmission signals L and R, (c) are reception pulse trains L and R, (d) are Doppler extraction pulse trains L and R, and (e) are FFT pulse trains L and R. (F) shows the extraction result of the pulse train for Doppler extraction.

In the above configuration, for the transmission signals L and R, the slow-time axis FFT (261 to 26M) corresponding to the time axis of the entire PRI interval is performed for each of the divided L and R as in the first embodiment. , CFAR, etc., based on the signal obtained by synthesizing (2E) the L and R signals by correcting the phase by MIMO processing (see Non-Patent Document 6) so that the phases of each subarray are aligned according to the position of the aperture division and the observation direction. Doppler is extracted (27). Next, FIG. 18 shows how the high-rate signal of the input is converted into the low-rate signal and the range is extracted. In FIG. 18, (a) and (b) are transmission signals L and R, (c) are reception pulse trains L and R, (d) are correlation processing results L and R, and (e) is a range from the synthesis of subarray division signals. It shows how to extract (distance).

Next, the rate converter 2D converts the signal into a low-rate signal. At this time, as shown in FIGS. 15 and 16, the Tdiv signal is divided by a predetermined time width Tdiv and converted into a low rate signal, but in the case of range extraction, after the conversion to a low rate, the divided Tdiv signal is uniaxially arranged. Sort again in chronological order. Using this signal, the signal extracted by the range pulse train extraction (291 to 29M) is subjected to correlation processing (low rate) on the fast-time axis (low rate) by the reference signal corrected by the reference signal Doppler correction (28). 2A1 to 2AM), after phase correction according to the position and observation direction of the aperture division, synthesis (2F) is performed, range extraction (2B) is performed by CFAR or the like, and Doppler and range are output (2C).

In this method, since the aperture is divided into M for the transmission code code and the reception is MIMO processing in which the signal using all openings is used to synthesize the M-divided signal, SN deterioration due to the division and synthesis does not occur. In the range extraction, not only the range extraction pulse train but also the Doppler extraction pulse train may be included.

As described above, according to the radar system according to the second embodiment, when a modulated pulse by coding or a random signal (noise) is used in the transmission system, the pulse width, pulse interval, and pulse for range extraction are used. A mixed pulse train in which the pulse train in which the amplitude is changed for each pulse and the pulse train in which the pulse interval for Doppler extraction is constant and thinned out at a predetermined thinning ratio ρ (ρ ≧ 0) is overlapped is generated, and the opening of the transmitting antenna is opened. Intra-pulse modulation for Doppler extraction and range extraction is performed by using M-type signals obtained by dividing M (M ≧ 1) and changing the intra-pulse modulation of the pulse train in the division unit of the transmission aperture. The changed signal is used and transmitted from the transmitting antenna.

On the other hand, in the receiving system, after the signal received at the full aperture of the antenna is demodulated in-pulse modulation and converted into a low-rate signal, the pulse train is separated for the M type transmission signal, and the transmission aperture is divided. Doppler extraction is performed by correcting and adding according to the phase of the phase center of the unit. Next, using the reference signal for range extraction corrected by the extracted Doppler, the result of correlation processing for the M type transmission signal is corrected and added according to the phase of the phase center of the transmission aperture division unit. Extract the range and output the speed and range. That is, the Doppler is extracted by the thinned-out pulse train for Doppler extraction, the transmission aperture is divided, and the code sequence is changed in each division unit to ensure the LPI property for the angle measurement performance of the other receiver and to measure the distance. And speed measurement is possible.

Further, in the above system, the high-rate sampling signal is divided into Tdivs having a predetermined time width, and the result Sig_fft of the fast-time frequency axis FFTed in each Tdiv and the signal of the time axis corresponding to the modulated signal in the pulse are displayed. Using the FFT fast-time axis frequency axis result Ref_fft, Sig_fft and Ref_fft are each divided into Ndivs of the same frequency band, and correlation processing is performed for each division to correspond to the central frequency of each divided frequency band. After the phase correction is performed, the results of each correlation processing are combined to obtain a low-rate sampling signal, and the Doppler and range are extracted. That is, by dividing the transmission aperture and converting a high-rate signal such as in-pulse modulation in which the code sequence is changed for each division into a low-rate signal, the processing scale can be reduced, and distance measurement and speed measurement can be performed.

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 ... Reference signal generator, 12 ... Code generator, 13 ... Modulator, 14 ... Pulse controller, 15 ... Frequency transform, 16 ... High power amplifier, 17 ... Transmit antenna, 21 ... Receive antenna, 22 ... Low noise Amplifier, 23 ... frequency converter, 24 ... AD converter, 25, 251 to 25 M ... pulse train extractor for Doppler, 26, 261 to 26 M ... FFT processor, 27 ... Doppler extractor, 28 ... reference signal correction for range extraction Instrument, 29,291-29M ... Range pulse train extractor, 2A, 2A1-2AM ... Correlation processor, 2B ... Range extractor, 2C ... Output processor, 2D ... Rate converter, 2D1 ... Time axis divider, 2D2 ... fast-time FFT processing unit, 2D3 ... frequency division unit, 2D4 ... multiplication unit, 2D5 ... fast-time Fourier processing unit, 2D6 ... phase correction unit, 2D7 ... correlation result addition unit, 2D8 ... reference signal generation unit, 2D9 ... Reference signal fast-time FFT processing unit, 2DA ... frequency division unit, 2E ... corrected synthesizer, 2F ... corrected synthesizer.

Claims (5)

In radar systems using coded or random signal modulated pulses
A pulse train in which the pulse width, pulse interval, and pulse amplitude for range extraction are changed for each pulse and a pulse train in which the pulse interval for Doppler extraction is constant and thinned at a predetermined thinning rate ρ (ρ ≧ 0) are mixed. And the transmission system that transmits the radar signal generated by
For the reflected signal of the radar signal received by the receiving antenna, the Doppler is extracted with the pulse train for Doppler extraction, and the range is extracted by correlation processing using the reference signal for range extraction corrected by the extracted Doppler. , A radar system equipped with a receiving system that outputs speed and range. In radar systems using coded or random signal modulated pulses
A pulse train in which the pulse width, pulse interval, and pulse amplitude for range extraction are changed for each pulse and a pulse train in which the pulse interval for Doppler extraction is constant and thinned at a predetermined thinning rate ρ (ρ ≧ 0) are mixed. To generate a mixed pulse train, divide the transmission antenna aperture into M (M ≧ 1), and use M-type signals in which the intra-pulse modulation of the pulse train is changed in the division unit of the transmission aperture, and further if necessary. , A transmission system that transmits radar signals with different in-pulse modulation for Doppler extraction and range extraction from a transmission antenna,
The reflected signal of the radar signal received at the full aperture of the receiving antenna is demodulated by intra-pulse modulation and converted into a low-rate signal, and then the pulse train is separated for the M type transmission signal to divide the transmission aperture. The Doppler was extracted by correcting and adding according to the phase of the phase center of the unit, and then the reference signal for range extraction corrected by the extracted Doppler was used to perform correlation processing on the M type transmission signal. A radar system including a receiving system that outputs a speed and a range by correcting the result according to the phase of the phase center of the transmission aperture division unit, adding the result, and extracting the range. The receiving system divides the high-rate sampling signal into a predetermined time width, and the first result of the fast-time frequency axis obtained by FFT for each time width and the time axis corresponding to the modulated signal in the pulse. Using the second result of the frequency axis of the fast-time axis in which the signal is FFT, the first result and the second result are each divided into N same frequency bands, and each division correlates. The radar system according to claim 2, wherein the radar system is processed, after phase correction corresponding to the central frequency of each divided frequency band, each correlation processing result is synthesized, a low-rate sampling signal is obtained, and a Doppler and a range are extracted. In a radar signal processing method of a radar system using a modulated pulse with a coded or random signal.
A pulse train in which the pulse width, pulse interval, and pulse amplitude for range extraction are changed for each pulse and a pulse train in which the pulse interval for Doppler extraction is constant and thinned at a predetermined thinning rate ρ (ρ ≧ 0) are mixed. The radar signal generated by the above is transmitted from the transmitting antenna,
For the reflected signal of the radar signal received by the receiving antenna, the Doppler is extracted with the pulse train for Doppler extraction, and the range is extracted by correlation processing using the reference signal for range extraction corrected by the extracted Doppler. , Radar signal processing method of radar system that outputs speed and range. In a radar signal processing method of a radar system using a modulated pulse with a coded or random signal.
A pulse train in which the pulse width, pulse interval, and pulse amplitude for range extraction are changed for each pulse and a pulse train in which the pulse interval for Doppler extraction is constant and thinned at a predetermined thinning rate ρ (ρ ≧ 0) are mixed. To generate a mixed pulse train, divide the transmission antenna aperture by M (M ≧ 1), and use M-type signals in which the intra-pulse modulation of the pulse train is changed in the division unit of the transmission aperture, and further if necessary. , Transmit radar signals with different in-pulse modulation for Doppler extraction and range extraction from the transmitting antenna,
After the reflected signal of the radar signal received at the full aperture of the receiving antenna is demodulated by intra-pulse modulation and converted into a low-rate signal, the pulse train is separated for the M type transmission signal, and the transmission aperture is divided. The Doppler was extracted by correcting and adding according to the phase of the phase center of the unit, and then the reference signal for range extraction corrected by the extracted Doppler was used to perform correlation processing on the M type transmission signal. A radar signal processing method of a radar system that outputs the speed and range by correcting the result according to the phase of the phase center of the transmission aperture division unit, adding it, and extracting the range.

Images