JP6685978B2 - Radar device and radar signal processing method thereof - Google Patents

Description

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

  The radar device uses a modulated pulse by encoding (including a random signal (noise)) as LPI (Low Probability of Intercept) technology for reducing detectability, and a range compression is performed using a reference signal for each pulse. (See Patent Document 1 and Non-Patent Document 1). However, in this method, unless the Doppler component due to the target speed is corrected, the range compression cannot be performed correctly and a compression loss occurs. Therefore, it is necessary to correct the reference signal by the speed search method, which increases the processing scale. On the other hand, a method of observing the target speed with a single pulse train without coding and using the observation result to correct the reference signal of the transmission / reception signal by the coding code is also conceivable. Because it is low, it is not worth the improvement. Further, it is necessary to increase the number of chips in order to improve the LPI property due to the encoding, but the sampling rate becomes high, so that the processing scale increases.

JP 2014-182010 JP

Coded radar, Yoshida, "Revised radar technology", IEICE, pp.278-280 (1996) Code code (M sequence) generation method, ‘M.I.Skolnik, Introduction to radar systems’, pp.429-430, McGRAW-HILL (1980) BPSK, QPSK, Nishimura, "Communication system design by digital signal processing", CQ publisher, pp.222-226 (2006) SS (Spread Spectrum) Modulation, Marubayashi, “Spread spectrum communication and its applications”, The Institute of Electronics, Information and Communication Engineers, pp.1-18 (1998) Frequency Hopping, Hagi Tani, 'Information Communication and Digital Signal Processing', Corona, pp.63-65 (1996) CFAR (Constant False Alarm Rate) processing, Yoshida, "Revised Radar Technology", IEICE, pp.87-89 (1996) Amplitude monopulse (amplitude comparison monopulse) method, Yoshida, "Revised radar technology", IEICE, pp.260-262 (1996)

  As described above, the radar device that sweeps the frequency of the transmission signal to obtain the LPI property and uses the encoding has a problem that the compression loss occurs due to the Doppler frequency component due to the target velocity during the range compression. It was In addition, when the number of coding chips is increased, the sampling rate is increased and the processing scale is increased.

  The present embodiment has been made in view of the above problems, and an object of the present invention is to provide a radar device and a radar signal processing method therefor capable of observing a target distance and speed while securing LPI property.

  In order to solve the above problems, according to the present embodiment, the observation time axis is divided into a CW period and a ranging period in a radar device that transmits and receives a pulse train that is encoded or modulated by a random signal. The CW period is divided into Lcw (Lcw ≧ 2) pieces, a transmission signal is set to a different center frequency in each divided period, and a pulse train signal modulated by a signal in which Mcw (Mcw ≧ 1) chips are repeated Mcwall times It transmits, receives the reflection from the target, performs coherent integration between pulses for each division unit, performs amplitude integration between the range and Doppler axes with the deviation of the center frequency corrected between division units, and performs Doppler from the amplitude integration result. Detect the frequency. The ranging period is divided into Lrng (Lrng ≧ 2), the transmission signal is set to a different center frequency for each divided period, and the transmission signal modulated by a signal that repeats Mr (Mr ≧ 2) chips for the Mallall times is transmitted. , A reflection from a target is received, a reference signal is corrected by the Doppler frequency detected in the CW period, the received signal is range-compressed using this reference signal, amplitude integration is performed between division units, and the amplitude integration is performed. The distance is output using the result, and the velocity is calculated from the distance and the Doppler frequency if necessary. That is, the radar device according to the present embodiment calculates the Doppler frequency by using frequency hopping (FH: Frequency Hopping) in which the frequency is changed in encoding and division in both the CW period and the ranging period, and then the reference signal is used for the Doppler frequency. By correcting the frequency and performing range compression, it is possible to perform target speed measurement and distance measurement while ensuring LPI without increasing the sampling rate more than necessary.

The block diagram showing the schematic structure of the radar device concerning a 1st embodiment. 3 is a timing chart showing the timing of a transmission pulse and a modulation code example in the first embodiment. FIG. FIG. 4 is a timing diagram showing frequency change of a transmission signal in the first embodiment. FIG. 6 is a timing chart showing the states of transmission processing, reception processing, and signal processing in the first embodiment. FIG. 3 is a conceptual diagram showing how range-Doppler data is obtained when FFT is performed on each cell between PRIs in the first embodiment. In the first embodiment, a timing diagram showing a state of changing the center frequency for each division unit within the CW period, coherent integration after correlation processing, and amplitude integration after Doppler frequency correction.

FIG. 3 is a conceptual diagram showing how the Doppler frequency is corrected when amplitude-integrating the range-Doppler signal obtained for each division unit within the CW period in the first embodiment. In the first embodiment, a timing diagram showing a state of changing the center frequency for each division unit within the ranging period and amplitude integration after correlation processing. The block diagram which shows the schematic structure of the radar apparatus which concerns on 2nd Embodiment. In the second embodiment, a conceptual diagram showing a state in which a target Doppler frequency is calculated by an amplitude monopulse using the amplitude ratio of Σ2 of the larger amplitude of two range cells adjacent to the detection range cell Σ. The block diagram which shows the schematic structure of the radar apparatus which concerns on 3rd Embodiment. In the third embodiment, a conceptual diagram showing how the target Doppler frequency is calculated by an amplitude monopulse using the amplitude ratio of Σ2 of the larger amplitude of two range cells adjacent to the detection range cell Σ. The block diagram which shows the schematic structure of the radar apparatus which concerns on 4th Embodiment. In the fourth embodiment, a timing diagram showing the timing of a transmission pulse and a modulation code example. FIG. 16 is a timing chart showing the states of transmission processing, reception processing, and signal processing in the fourth embodiment. The block diagram which shows the schematic structure of the radar apparatus which concerns on 5th Embodiment. The timing diagram which shows the timing of a transmission pulse, and a modulation code example in 5th Embodiment. The timing diagram which shows the mode of a transmission process, a reception process, and a signal process in 5th Embodiment.

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

(First Embodiment) Single pulse
A radar device according to a first embodiment will be described with reference to FIGS. 1 to 8. In the radar device according to the present embodiment, the observation period is divided into a CW period and a ranging period, the CW period and the ranging period are divided into Lcw and Lrng, respectively, and the frequency of the transmission signal is changed in each divided period. Frequency hopping (Frequency Hopping (FH), Non-Patent Document 5). Further, coding control for code modulation between or within pulses is performed. The Doppler frequency is observed during the CW period, and the target Doppler frequency is used during the ranging period to correct the reference signal for compression and perform distance measurement. The velocity is calculated from the Doppler frequency.

  FIG. 1 is a block diagram showing a schematic configuration thereof, FIG. 2 is a timing diagram showing timings of transmission pulses in the CW period and ranging period in the observation time and examples of modulation codes of the transmission pulses, and FIG. 3 is each of CW period and ranging period. 5 is a timing chart showing the frequency change of the transmission signal in FH division units in FIG. 4, FIG. 4 is a timing chart showing the state of transmission processing and reception processing for each FH division unit in the CW period and ranging period in the observation time, and FIG. FIG. 6 is a conceptual diagram showing how range-Doppler data is obtained when FFT between PRIs is performed for each range cell in FIG. 6, FIG. 6 is a diagram showing a change in center frequency for each division unit within the CW period, coherent integration after correlation processing, FIG. 7 is a timing chart showing the state of amplitude integration after Doppler frequency correction. FIG. 7 shows the range obtained for each division unit within the CW period. FIG. 8 is a conceptual diagram showing how the Doppler frequency is corrected when amplitude-integrating the Doppler signal. FIG. 8 is a timing diagram showing how the center frequency is changed for each division unit within the ranging period and how amplitude integration is performed after the correlation process. Shows.

  As shown in FIG. 1, the radar device according to the present embodiment includes an antenna 1 that forms a transmission / reception beam by a plurality of antenna elements, and a transceiver 2 that transmits a transmission signal through the antenna 1 and receives a reflection signal from a target. And a signal processor 3 for observing a target distance / velocity from a received signal obtained by the transmitter / receiver 2.

  The transceiver 2 includes a transceiver 21, a frequency converter 22, an AD (analog / digital) converter 23, a pulse modulator 24, an encoding controller 25, and a frequency controller 26. The transmission / reception unit 21 sends out a transmission pulse train toward a target through a transmission beam formed by a plurality of antenna elements of the antenna 1, synthesizes reflected signals from the target captured by each antenna element of the antenna 1 and performs reception detection. To do. The frequency conversion unit 22 converts the reception signal of the transmission / reception unit 21 into a baseband. The AD converter 23 converts the baseband received signal into a digital signal and outputs it as received data to the signal processor 3. The pulse modulator 24 modulates the transmission pulse train with the coding code generated by the coding controller 25. The frequency control unit 26 performs control for changing the transmission frequency of the transmission pulse train in units of FH division in each of the CW period and the ranging period.

  The signal processor 3 includes a CW period correlation processing unit 31, a CW period FFT processing unit 32, a CW period Doppler correction processing unit 33, a CW period amplitude integration processing unit 34, a CW period Doppler extraction unit 35, a reference signal generation unit 36, A range period correlation processing unit 37, a range period amplitude integration processing unit 38, and a range period distance extraction unit 39 are provided.

  The CW period correlation processing unit 31 performs the correlation process of the received pulse train in the FH divided periods FHD-1 to FHD-Lcw within the CW period to extract the signal of the Mcw chip. The CW period FFT processing unit 32 performs FFT between PRIs for each range cell in the PRI (range compression process) for the correlation processing result of the FH division unit in the CW period (range compression process) to obtain a target range-Doppler signal for each PRI. Ask for. The CW period Doppler correction processing unit 33 inputs the target range-Doppler signal obtained by the FFT processing, converts the target range-Doppler signal into a frequency axis according to the center frequency, zero-fills it, and returns to the time axis again Doppler correction processing During the CW period. The CW period amplitude integration processing unit 34 amplitude-integrates the target range-Doppler signal subjected to Doppler correction. The CW period Doppler extraction unit 35 extracts the target Doppler frequency from the range-Doppler signal after amplitude integration by threshold detection by CFAR or the like.

  The reference signal generation unit 36 generates, as a reference signal, a signal having a code length Mrng that is zero-filled in order to have a ranging period. The range period correlation processing unit 37 performs the correlation process between the received pulse train and the reference signal in the FH divided periods FHD-1 to FHD-Lrng within the ranging period to extract the signal of the Mrng chip. The range period amplitude integration processing unit 38 performs amplitude integration of the Mrng chip signal extracted by the correlation process within the ranging period. The range period distance extraction unit 39 performs threshold detection of the amplitude integration result by CFAR or the like, converts the detected time axis into a distance axis, and calculates the speed from the Doppler frequency as necessary.

  The processing operation of the above configuration will be described below.

  As shown in FIG. 2, the radar device according to the present embodiment divides the observation period T into a CW period and a ranging period, and divides the CW period and the ranging period into Lcw (division unit periods FHD-1 to FHD-Lcw). ), Lrng division (division unit period FHD-1 to FHD-Lrng), and as shown in FIG. 3, the transmission frequency is changed (FH) by frequency control in each division period, between pulses or within a pulse. It is characterized in that code modulation is performed by coding control. The Doppler frequency is observed during the CW period, and the target Doppler frequency is used during the ranging period to correct the reference signal for compression and perform distance measurement. The velocity is calculated from the Doppler frequency. Although FIG. 2 shows the case of single pulse transmission as an example, other transmission pulses or continuous waves may be used.

  In the case of a single pulse train, code modulation is performed in each pulse unit for each FH division unit. First, in the CW period, it is necessary to observe the Doppler frequency, and as shown in FIG. 2, the center frequency is changed, and the code of Mcw (Mcw ≧ 1) chips is used for Mcw × Mall (Mall> 1) Pulse is modulated with the same code for each Mcw chip and repeated Mcwall times. In the ranging period in the case of HPRF, Mrng pulses are code-modulated using the code of Mrng (Mrng> 1) chips.

  As a coding method, SS modulation (Non-Patent Document 4) can be considered. Specifically, for example, there is an M-sequence code (Non-Patent Document 2), and another code may be used. It is assumed that a random signal (noise) including a decimal within ± 1 is also included in this encoding. The random signal has a random phase. Using this signal code string, the signal phase is changed as shown in the following equation to generate a transmission signal. The formulation is as follows.

  The above is the case of BPSK (Binary Phase shift Keying, Non-Patent Document 3), but other phase modulation methods may be used.

  In the transmitter / receiver 2, the pulse train is pulse-modulated (24) by the code code by the encoding control (25) to generate a transmission pulse train, and the transmission pulse train is transmitted / received (21) through the antenna 1 to receive the reflected signal from the target. To do. This received signal (received pulse train) contains Doppler frequency components. The transmitter / receiver 2 frequency-converts (22) this received signal into a base band, converts it into a digital signal by AD conversion (23), and outputs it as a received pulse train to the signal processor 3. The processing contents of the signal processor 3 will be described with reference to FIG. 4 showing the above-mentioned transmission processing, reception processing, and signal processing.

  First, the received signal for each received pulse input to the signal processor 3 is given by the following equation when expressed by the Doppler frequency.

  Further, the Doppler frequency is given by the following equation according to the target distance and speed.

  This received pulse train is a pulse train in which the signal of the Mcw chip is repeated Mcwall times as described above. In order to extract the signal of this Mcw chip, the correlation process (31) is performed in the CW period. The reference signal for the correlation processing is given by the following equation.

Zero padding is performed to match the reference signal with the received signal length.

  From this, the frequency axis signal of the reference signal is given by the following equation.

On the other hand, FFT (32) the received signal

Ask for. In the correlation processing, the multiplication on the frequency axis is inversely FFT'ed to be the following expression.

The received signal after this correlation processing corresponds to the result of integration for each Mcw chip as shown in FIG. 3, and Mcwall peaks have Mcwall peaks in the PRI (Mcw times of the pulse repetition cycle of a single pulse unit) cycle. appear. As shown in FIG. 5 (a), the Mcwall signals are subjected to FFT between PRIs (slow-time axis) for each range cell (P cell) in the PRI, and as shown in FIG. 5 (b). Get range-Doppler data (range: fast-time axis, Doppler: slow-time axis).

  The above is the coherent integration processing in FH division units as shown in FIG. Next, in order to increase SN (signal to noise power ratio), the processing results between FH division units are added. Since the center frequency (carrier frequency) is changed between the FH division units, the phase relationship is different, and coherent integration cannot be performed, resulting in amplitude integration. Further, if the center frequencies are different, the Doppler frequencies are different even for the same target, so that Doppler correction is necessary before the integration, as shown in FIG. The processing for this is shown below.

  First, the output for each FH division unit can be expressed as scw (t, Ln) from the equation (9), and after converting to the frequency axis according to the center frequency, zero padding is performed again on the time axis. The return Doppler correction process is performed during the CW period (see FIG. 7).

  Doppler correction (33) can be performed on the signal scw of the FH division unit by stretching the signal on the slow-time axis according to the frequency ratio of the FH division unit. In order to correct the Doppler frequency using the signal scw, for example, the signal of the cell having the following frequency fsel is selected according to the frequency ratio based on f (1) (center frequency of Ln = 1).

  Δfsel means the multiplication of the coefficient for correcting the signal sequence stretched for each frequency f (Ln) by zero filling to the original axis and the correction coefficient for the frequency for Doppler correction.

  Note that the methods of equations (11) and (12) are examples for Doppler correction of range-Doppler data in FH division units having different center frequencies, and other methods may be used as long as they have the same purpose.

  As described above, since the range-Doppler signal corrected for each FH division unit is obtained as shown in FIG. 7, the range-Doppler signal with high SN can be obtained by performing the amplitude integration (34). With respect to the range-Doppler signal after amplitude integration, the target Doppler frequency can be extracted (35) by threshold detection by CFAR (Non-Patent Document 6) or the like.

  Next, a standard reference signal for correlation processing is generated using the signal in the ranging period (36). The target Doppler frequency output in the CW period is used as the standard reference signal.

  The set standard reference signal length is Mrng, and zero-filled is used as the reference signal before the range compression processing (correlation processing) (37) to make the code length (Mrng) into the ranging period.

  In order to calculate the correlation between this reference signal and the input signal, the reference signal is FFT processed.

On the other hand, the received signal in the ranging period can be expressed by the following equation.

The received signal is subjected to FFT processing according to the following equation.

In the range compression processing (correlation processing) (37), the multiplication on the frequency axis is inversely FFT'ed to obtain the following expression.

The signal on the time axis of each target (m = 1 to M) can be obtained from the equation (15).

  The above is the correlation detection process (37) in FH division units in the ranging period as shown in FIG. Next, in order to increase the SN (signal to noise power ratio), the amplitude integration (38) is performed on the processing result between FH minute units. In the case of the ranging period, the correlation result is obtained by using the signal obtained by correcting (36) the reference signal by Doppler, and unlike the CW period, it is not necessary to perform Doppler correction before amplitude integration, and the sum can be added as it is.

  If the signals in the FH division unit (FHD-1 to FHD-Lrng) are amplitude integrated (38), the threshold is detected by CFAR or the like, and the time axis detected in the distance extraction (39) is converted into the distance axis, the target is obtained. The distance can be calculated. The velocity can be calculated from the Doppler frequency.

  As described above, the radar device according to the present embodiment divides the observation time axis into the CW period and the ranging period when the modulated or pulse modulated by the random signal (noise) is used, and the CW period is further Lcw. The signal of the transmission pulse train is divided into pieces and the signal of the transmission pulse train is changed to a different center frequency for each divided period, and the signal of the transmission pulse train modulated by the Mcwall (Mcw ≧ 1) chip is repeated by the Mcwall signal is transmitted. The reflected signal is received, coherent integration is performed between the pulses for each division unit, and the Doppler frequency is detected from the result of amplitude integration between the range and Doppler axes in which the deviation of the center frequency is corrected between the division units. The ranging period is further divided into Lrng pieces, the transmission signal is set to a different center frequency for each divided period, and the signal of the transmission pulse train is transmitted by modulating the Mr (Mr ≥ 2) chip by repeating the Mrall signal, and the target is transmitted. It receives the reflected signal from the device, performs range compression using the reference signal corrected by the Doppler frequency, outputs the distance using the result of amplitude integration between division units, and outputs the speed from the distance and the Doppler frequency as necessary. calculate. That is, both the CW period and the ranging period are encoded and frequency hopping is used to change the frequency in units of division. After calculating the Doppler frequency, the reference signal is corrected with the Doppler frequency to perform range compression. Speed and range can be measured while maintaining LPI without raising the speed.

  In addition, in the present embodiment, a single pulse that uses coding with a chip length of 1 or modulation with a random signal is used for the transmission pulse train in the CW period and the ranging period. That is, the Doppler frequency is calculated by using both the CW period and the ranging period by using the encoded single-pulse signal, and then the reference signal is corrected with the Doppler frequency to perform range compression. It is possible to measure speed and range while ensuring LPI without raising it more than necessary.

(Second Embodiment) Amplitude monopulse (CW period)
The first embodiment has described the method of performing FH division in the CW period, performing coherent integration for each division unit, and further performing amplitude integration between division units. In this case, since the FH division is performed, the observation time of each division unit becomes short, the Doppler resolution proportional to the reciprocal of the observation time decreases, and the Doppler observation accuracy also decreases. This countermeasure will be described with reference to FIGS. 9 and 10.

  FIG. 9 is a block diagram showing the configuration of the radar device according to the second embodiment. The radar device of this embodiment has substantially the same configuration as that of the first embodiment, but differs in the processing of CW period Doppler extraction (35a). In the first embodiment, the threshold is directly detected from the signal of the amplitude integration between the FH divisions after the Doppler correction, and the Doppler frequency of the expression (12) is extracted. In the present embodiment, the Doppler frequency is calculated by an amplitude monopulse (Non-Patent Document 7) using the amplitude ratio of Σ2 of the detected Doppler cell Σ shown in FIG. 10A and the larger amplitude of two adjacent Doppler cells. .

  Regarding the Doppler frequency and the error voltage, the relationship between the two shown in FIG. 10B can be tabulated in advance. Therefore, if the error voltage ε is observed, the Doppler frequency can be calculated by referring to the table. Once the Doppler frequency is calculated, the subsequent processing is the same as in the first embodiment.

  As described above, the radar device according to the present embodiment uses the extracted Doppler cell Σ and the adjacent Doppler cell Σ2 when extracting Doppler in the CW period, and uses the error voltage, the previously calculated error voltage and Doppler correspondence table. Doppler is calculated using the table of. That is, even when the CW period is divided by frequency hopping, deterioration of Doppler accuracy can be prevented by the amplitude monopulse processing of the Doppler axis.

(Third Embodiment) Amplitude monopulse (ranging period)
The first embodiment has described the method of performing FH division in the ranging period, performing correlation processing for each division unit, and further performing amplitude integration between division units. In this case, since FH division is performed, the number of integrations for the correlation processing of each division unit becomes short, and SN becomes low, so that range observation accuracy also becomes low. This measure will be described with reference to FIGS. 11 and 12. FIG. 11 is a block diagram showing the configuration of the third radar device. The radar device of the present embodiment has almost the same configuration as that of the first embodiment, but differs in the processing of range output during the ranging period. In the first embodiment, the threshold is directly detected from the signal of the amplitude integration between the FH divisions in the ranging period to extract the range. In the present embodiment, as shown in FIG. 12A, the range is calculated by an amplitude monopulse (Non-Patent Document 7) using the amplitude ratio of Σ2 of the larger amplitude of the detection range cell Σ and two adjacent range cells. To do.

  Regarding the range and the error voltage, the relationship between the two shown in FIG. 12B can be tabulated in advance. Therefore, if the error voltage ε is observed, the range can be calculated by referring to the table.

  As described above, the radar device according to the present embodiment uses the extracted range cell Σ and the adjacent range cell Σ2 when extracting the distance in the ranging period, the error voltage, and the correspondence relationship between the error voltage and the Doppler calculated in advance. The range is calculated using the table indicating That is, even when the ranging period is divided by frequency hopping, the range accuracy can be prevented from being deteriorated by the amplitude monopulse process of the range axis.

(Fourth Embodiment) Mixed Pulse In the first embodiment, the observation time is divided into a CW period and a ranging period, a target Doppler frequency is calculated in the CW period, and the target Doppler frequency is corrected in the ranging period. The method to output the target distance by compressing the range using the reference signal was described. In addition, the case where a single pulse is used has been described as the embodiment. In this case, the ranging period also becomes a transmission signal having a relatively high repetition period (PRF), so that target non-detection may occur due to the transmission blind even at a long distance. As a countermeasure, in the present embodiment, a case where a mixed pulse of a single pulse and a long pulse is used will be described. FIG. 13 is a block diagram showing the configuration of the radar device according to the fourth embodiment. FIG. 14 shows the transmission signal, and FIG. 15 shows the outline of the reception signal and the signal processing.

  In this embodiment, the CW period is the same as that in the first embodiment. In the ranging period, a plurality of pulses having a predetermined pulse width are transmitted. If the chip length of the divided pulse in this case is Mrng, an M-sequence signal of Mrng of the entire pulse train is generated, divided by the pulse length, and sequentially modulated. Therefore, the sign of each pulse is different.

  As shown in FIG. 15, using the reference signal corrected by the Doppler frequency in the CW period, the correlation process over the entire pulse train is performed. Since this method only replaces the processing of the single pulse train of the first embodiment with a long pulse train, the same method as that of the first embodiment can be applied. As a result of the correlation process, as shown in the lower part of FIG. 15, after detecting the target by CFAR, the target distance can be output by converting the time into the distance. The speed can be calculated from the Doppler frequency as in the first embodiment.

  In this embodiment, by lengthening the PRI (pulse repetition period) in the ranging period, it is possible to suppress target non-detection due to a transmission blind in a long distance.

  As described above, the radar device according to the present embodiment uses the single pulse using the coding of the chip length 1 or the modulation by the random signal in the CW period, and the Mr (Mr ≧ 2) coding in the ranging period. Alternatively, N (N ≧ 1) pulses are transmitted and received by using a pulse modulated by a random signal, and range compression is performed by a coded signal over the entire pulse train. That is, by using the encoded single pulse in the CW period and using the encoded long pulse in the ranging period, after calculating the Doppler frequency, the reference signal is corrected with the Doppler frequency to perform range compression. Therefore, speed measurement and distance measurement can be performed while ensuring the LPI property without increasing the sampling rate more than necessary.

(Fifth Embodiment) Long Pulse In the first embodiment and the fourth embodiment, the observation period is divided into a CW period and a ranging period, the Doppler frequency is calculated in the CW period, and the target Doppler frequency is calculated in the ranging period. The method of calculating the velocity by outputting the target distance by range compression using the reference signal corrected by the frequency was described. In the description, the first embodiment described the case of a single pulse, and the second embodiment described the case of a single pulse and a long pulse. In the case of repetition by a single pulse, since there is a gap between pulses, the gap between Mcw chips becomes wide and the range of Doppler frequency due to this becomes narrow. On the other hand, in the ranging period, when the sum of the pulse widths is not sufficiently long, the code length may be short and the range side lobe may not be sufficiently reduced. As a countermeasure, in the present embodiment, a case will be described in which the CW period and the ranging period are both long pulses. FIG. 16 is a block diagram showing the configuration of the radar device according to the fifth embodiment. FIG. 17 shows a transmission signal, and FIG. 18 shows an outline of a reception signal and signal processing.

  In the present embodiment, the CW period is also a long pulse, and in order to observe the Doppler frequency, the long pulse is divided into Mcwall pieces, and each is modulated by the common spreading code of the Mcw chip. The method of extracting the signal of this Mcw chip is the same as that of the CW period of the first embodiment. That is, it is possible to generate a reference signal in a unit divided into Mcwall, obtain Mcwall peak outputs using the reference signal, and calculate the target Doppler frequency by FFT.

  In the ranging period, one long pulse is transmitted. The pulse modulation generates and modulates an M-sequence signal having a code length Mrng over the entire pulse train. As shown in FIG. 18, the received signal is subjected to correlation processing over the entire pulse train in the ranging period using the reference signal corrected by the Doppler frequency in the CW period, the target signal is extracted, the distance is output, and the speed is calculated. Outputs the result calculated from the Doppler frequency in the CW period.

  According to the present embodiment, as compared with the second embodiment, the interval of the correlation output result in the CW period becomes the code length Mcw with no gap between pulses, which is narrower than the repetition of a single pulse. Therefore, the range of the observed Doppler frequency determined by the reciprocal of the interval can be widened. Further, since the pulse in the ranging period is long, a high correlation output can be obtained, and the range side lobe can be easily lowered. On the other hand, it may be received during the pulse transmission period, and simultaneous processing of transmission and reception is required. In the case of a multi-static system in which transmission and reception are separated, this method is particularly easy to apply.

  As described above, in the radar device according to the present embodiment, in the CW period, the pulse using the coding of the chip length Mcw (Mcw ≧ 2) or the modulation by the random signal is repeated Mcwall (Mcwall ≧ 2) times Mcw × The Mcwall chip length pulse is transmitted / received, and the chip length Mr (Mr ≧ 2) pulse is transmitted / received during the ranging period, and range compression is performed by the encoded signal over the entire pulse train. That is, by using the long pulse encoded in the CW period and using the encoded pulse in the ranging period, after calculating the Doppler frequency, the reference signal is corrected with the Doppler frequency to perform range compression, so that a sampling rate is required. It is possible to perform speed measurement and distance measurement while ensuring the LPI property without increasing the above.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements within a range not departing from the gist of the present invention in an implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements of different embodiments may be combined appropriately.

  DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Transceiver, 3 ... Signal processor, 21 ... Transceiver, 22 ... Frequency converter, 23 ... AD converter, 24, 24a ... Pulse modulator, 25, 25a ... Encoding controller, 26 ... Frequency control unit, 31 ... CW period correlation processing unit, 32 ... CW period FFT processing unit, 33 ... CW period Doppler correction processing unit, 34 ... CW period amplitude integration processing unit, 35, 35a ... CW period Doppler extraction unit, 36 Reference signal generation unit, 37 range range correlation processing unit, 38 range range amplitude integration processing unit, 39, 39a range range distance extraction unit.

Claims (7)

A radar device for transmitting and receiving a pulse train that is encoded or modulated by a random signal,
The observation time axis is divided into a CW period and a ranging period,
The CW period is divided into Lcw (Lcw ≧ 2) pieces, a transmission signal is set to a different center frequency for each divided period, and a pulse train signal modulated by a signal that repeats Mcw (Mcw ≧ 1) chips Mcwall times is generated. It transmits, receives the reflection from the target, performs coherent integration between pulses for each division unit, performs amplitude integration between the range and Doppler axes with the deviation of the center frequency corrected between division units, and performs Doppler from the amplitude integration result. Frequency is detected,
The ranging period is divided into Lrng (Lrng ≧ 2), the transmission signal is set to a different center frequency for each divided period, and the transmission signal modulated by a signal in which Mr (Mr ≧ 2) chips are repeated Mall times is transmitted. , A reflection from a target is received, a reference signal is corrected by the Doppler frequency detected in the CW period, the received signal is range-compressed using the reference signal, amplitude integration is performed between division units, and the amplitude integration is performed. A radar device that outputs the distance using the results and calculates the velocity from the distance and the Doppler frequency if necessary.   During the CW period, when extracting the Doppler frequency, an error voltage is obtained using the extracted Doppler cell Σ and the adjacent Doppler cell Σ2, and the Doppler frequency is calculated based on the correspondence relationship between the previously calculated error voltage and the Doppler frequency. The radar device according to claim 1.   In the ranging period, when the Doppler frequency is extracted, the error voltage is obtained using the extracted Doppler cell Σ and the adjacent Doppler cell Σ2, and the Doppler frequency is calculated based on the correspondence relationship between the pre-calculated error voltage and the Doppler frequency. The radar device according to claim 1.   The radar device according to any one of claims 1 to 3, wherein a single pulse using coding with a chip length of 1 or modulation with a random signal is used for a transmission pulse train in the CW period and the ranging period.   During the CW period, transmission / reception is performed using a single pulse using chip length 1 encoding or modulation with a random signal, and during the ranging period, Mr (Mr ≧ 2) encoding or modulation with a random signal is used. The radar device according to any one of claims 1 to 3, wherein N (N≥1) pulses are transmitted and received, and the range compression is performed by a coded signal over the entire pulse train.   In the CW period, a pulse having a length Mcw (Mcw ≧ 2), or a pulse using modulation by a random signal is repeated Mcwall (Mcwall ≧ 2) times to transmit / receive a pulse having a length of Mcw × Mcwall, and the ranging period is used. 4. The radar device according to claim 1, wherein a pulse having a chip length Mr (Mr ≧ 2) is transmitted and received, and range compression is performed by an encoded signal over the entire pulse train. A radar device for transmitting and receiving a pulse train that is encoded or modulated by a random signal,
The observation time axis is divided into a CW period and a ranging period,
The CW period is divided into Lcw (Lcw ≧ 2) pieces, a transmission signal is set to a different center frequency for each divided period, and a pulse train signal modulated by a signal that repeats Mcw (Mcw ≧ 1) chips Mcwall times is generated. It transmits, receives the reflection from the target, performs coherent integration between pulses for each division unit, performs amplitude integration between the range and Doppler axes with the deviation of the center frequency corrected between division units, and performs Doppler from the amplitude integration result. Frequency is detected,
The ranging period is divided into Lrng (Lrng ≧ 2), the transmission signal is set to a different center frequency for each divided period, and a transmission signal modulated by a signal in which Mr (Mr ≧ 2) chips are repeated Mall times is transmitted. , A reflection from a target is received, a reference signal is corrected by the Doppler frequency detected in the CW period, the received signal is range-compressed using the reference signal, amplitude integration is performed between division units, and the amplitude integration is performed. A signal processing method for a radar device, which outputs a distance using a result and calculates a velocity from the distance and Doppler frequency as necessary.

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