JP6851957B2 - Radar system and its radar signal processing method - Google Patents

Description

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

Recently, in radar systems, a multi-static method has been developed in which multiple transmission / reception radar devices or multiple transmission devices and reception radar devices are arranged apart from each other and the target position is detected based on the observation results of each radar device. Has been done. However, in this type of radar system, if the time synchronization between the separated radar devices is insufficient or the distance accuracy is insufficient, the error of the observation position becomes large. Further, when the transmitting device is out of sight, the direct wave cannot be received, and the synchronized multi-static operation cannot be performed.

Pulse 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) CFAR (Constant False Alarm Rate), Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.87-89 (1996) BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), Nishimura, ‘Communication System Design by Digital Signal Processing, CQ Publisher, pp.222-226 (2006) Tailor Distribution, Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.134-135 (1996)

As described above, in the conventional multi-static radar system, the beat frequency cannot be observed accurately due to the influence of the time synchronization deviation between the radar devices and the deviation of the center frequency, and the target position is calculated. There was a problem that the distance accuracy was insufficient.

This embodiment has been made in view of the above problems, and can improve the observation accuracy of the beat frequency by reducing the influence of the time synchronization shift and the center frequency shift between the radar devices, and calculate the target position. It is an object of the present invention to provide a radar system capable of obtaining sufficient distance accuracy and a radar signal processing method thereof.

In order to solve the above problems, the radar system according to the present embodiment includes a transmitting device and a receiving device. The transmission device divides the transmission pulse for pulse compression into a communication period and a range period, and superimposes communication information on transmission on the pulse of the communication period and transmits the pulse. The receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, compresses the received signal with the reference signal during the range period, and obtains a reflection point having a high signal-to-noise power ratio (SN). The communication period is extracted by extracting the communication period and performing correlation processing, and the communication period is also obtained for other reflection points having a low signal-to-noise power ratio using only the range period or using the communication information. And the target distance is output by correlating the entire pulse during the range period.

The block diagram which shows the whole structure of the radar system which concerns on 1st Embodiment. The block diagram which shows the structure of the transmission device of the radar system which concerns on 1st Embodiment. The block diagram which shows the structure of the receiving device of the radar system which concerns on 1st Embodiment. The figure which shows how the transmission beam and the reception beam are formed with respect to a target in 1st Embodiment. FIG. 6 is a conceptual diagram showing a coordinate system for explaining distance observation and AZ, EL observation of target position identification by transmitting and receiving communication information in the radar system according to the first embodiment. A conceptual diagram showing a state in which a target position is identified by using a range fitting in a three-dimensional coordinate system in the radar system according to the first embodiment. The waveform diagram which shows the transmission waveform of the radar system which concerns on 1st Embodiment. The waveform diagram which shows the state of generating the communication modulation signal in the transmission pulse in the radar system which concerns on 1st Embodiment. FIG. 5 is a waveform diagram showing a state in which a communication period is extracted from a received signal and the communication signal is demodulated in the radar system according to the first embodiment. FIG. 5 is a waveform diagram showing a state in which the communication period is extracted from the correlation processing of the range period P2 column of the received signal and the communication signal is demodulated in the radar system according to the first embodiment. FIG. 5 is a waveform diagram showing a state in which the distance of the maximum bank signal is extracted from the correlation processing of the range period P2 + the communication period P3 of the received signal and the communication signal is demodulated in the radar system according to the first embodiment. The block diagram which shows the structure of the transmission device of the radar system which concerns on 2nd Embodiment. The block diagram which shows the structure of the receiving device of the radar system which concerns on 2nd Embodiment. In the radar system according to the second embodiment, the waveform diagram which shows the transmission waveform by time division synthesis of the pulse train of each of a Doppler period, a range period, and a communication period. In the radar system according to the second embodiment, a waveform diagram showing a state in which pulse trains of a Doppler period, a range period, and a communication period are time-divided and synthesized, and the pulses are modulated by a modulation signal of communication information. FIG. 5 is a waveform diagram showing a state in which a Doppler is extracted from a received signal in the radar system according to the second embodiment. FIG. 5 is a waveform diagram showing a state in which a communication period is extracted from a received signal and communication information is demodulated in the radar system according to the second embodiment. FIG. 5 is a waveform diagram showing a state in which a distance is extracted from a received signal in the radar system according to the second embodiment. The block diagram which shows the structure of the transmission device of the radar system which concerns on 3rd Embodiment. The block diagram which shows the structure of the receiving device of the radar system which concerns on 3rd Embodiment. FIG. 5 is a waveform diagram showing a state in which a transmission signal is generated by synthesizing pulse trains for each of a Doppler period, a range period, and a communication period in a radar system according to a third embodiment. In the radar system according to the third embodiment, a waveform diagram showing a state in which pulses are modulated between pulses by a modulation signal of communication information in a transmission signal obtained by synthesizing a pulse train. FIG. 5 is a waveform diagram showing a state in which pulse trains having different PRFs are separated from a received signal in the radar system according to the third embodiment. FIG. 5 is a waveform diagram showing a state in which a communication period is extracted from a received signal and communication information is demodulated in the radar system according to the third embodiment. FIG. 6 is a waveform diagram showing a state in which a Doppler is extracted from a received signal in the radar system according to the third embodiment. FIG. 6 is a waveform diagram showing a state in which a distance is extracted from a received signal in the radar system according to the third 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 11.

FIG. 1 shows the overall configuration of the radar system according to the present embodiment, FIG. 2 shows the configuration of the transmitting device, and FIG. 3 shows the configuration of the receiving device.

The radar system shown in FIG. 1 employs a multi-static system including N transmitters T1 to TN (N = 3 in FIG. 1) and a receiver R having the same configuration as each other. The transmission devices T1 to TN superimpose communication information such as a transmission position, a transmission frequency, and a transmission timing on a radar transmission wave, and transmit the communication information toward the target T. On the other hand, the receiving device R receives the radar transmission wave reflected by the target T, observes the distance, angle, and speed of the target T, extracts communication information from the received signal, and targets based on the communication information. It has a function to correct the observation result of.

As shown in FIG. 2, the transmitter Ti (i is any of 1 to N) includes a transmitter antenna device T11, a pulse modulator T12, a frequency converter T13, a modulator T14, a controller T15, and a chirp signal generator. It includes T16, an IFFT (Inverse Fast Fourier Transform) processor T17, and a communication modulation signal generator T18.

The transmitting antenna device T11 transmits a repeatedly supplied transmission signal of a specific frequency in a designated direction. On the other hand, the communication modulation signal generator T18 represents communication information including a transmission position, a transmission frequency, a transmission timing, a transmission beam directing direction, etc. in bits (0, 1) and modulates the communication information by BPSK (see Non-Patent Document 4) or the like. By doing so, a communication modulation signal is generated. This communication modulation signal is inverse Fourier transformed by the IFFT processor T17 and sent to the controller T15 together with the chirp signal generated by the chirp signal generator T16. The controller T15 divides the transmission pulse into a communication period and a range period, and transmits N hits (N> 0). In the range period, for the chirp signal and the communication modulation signal, the timing in the pulse is controlled by the intra-pulse control, the transmission pulse is generated by the modulator T14, converted into the transmission frequency by the frequency converter T13, and the pulse modulator T12. Pulse modulation is performed by a pulse gate, high output amplification is performed by the transmission antenna device T11, and transmission is performed.

As shown in FIG. 3, the receiving device R1 includes a receiving antenna device R11, a frequency converter R12, an AD (Analog-Digital) converter R13, a P2 extractor R14, a correlation processing pulse compressor R15, and an FFT (Slow-time). Processor R16, Detector R17, P3 Range Selector R18, P3 Extractor R19, Correlation Processor (Slow-time) R20, Demolator R21, P2 + P3 Selector R22, Communication Information Reference Signal Corrector R23, Correlation Processor R24 , FFT (Slow-time) processor R25, detector R26, range extractor R27, output processor R28.

That is, the signal received by the receiving antenna device R11 is frequency-converted into a baseband by the frequency converter R12 and converted into a digital signal by the AD converter R13. Then, the P2 extractor R24 extracts the modulated signal (chirp, etc.) of the pulse P2 in the range period, the correlation processor R15 performs the correlation processing (pulse compression), and the FFT processor R16 performs the pulse interval (slow-time). The FFT of the axis) is performed, and the detector R17 performs detection by CFAR (Non-Patent Document 4) or the like using a bank signal having the maximum amplitude. Here, when there are a plurality of detection points, a signal having a large SN (signal-to-noise power ratio) can be extracted. Therefore, in the P3 range selector R18, the time of the communication period P3 is based on the time axis. A range is selected, and the communication period P3 is extracted by the P3 extractor R19.

Next, the FFT processor R20 performs FFT processing on the slow-time axis to obtain a high SN, and then the demodulator R21 demodulates to obtain communication information. By demodulating the communication information, it is possible to acquire a reference signal of the transmission time, transmission frequency, transmission position, and communication period of the transmission source.

Further, in the P2 + P3 selector R22, the range period P2 and the communication period P3 are selected from the AD conversion output, the reference signal of the communication period P3 is adjusted to the range period P2 by the communication information reference signal corrector R23, and the transmission processor R24 Correlation processing of P2 + P3 is performed, FFT of the slow-time axis is performed by the FFT processor R25, the target is detected by CFAR or the like by the detector R26, the range is extracted by the range extractor R27, and the predetermined range is extracted by the output processor R28. Convert to format and output.

In the radar system according to the present embodiment, since the transmission device Ti and the reception device R are separated from each other, it is necessary to share information such as the transmission position, the transmission frequency, the transmission timing, and the transmission beam direction direction. In particular, when the transmission position moves, it is necessary to share information in real time. It is possible to secure a communication line when there is a line of sight between the transmitting device and the receiving device, but it becomes difficult to secure a communication line when there is no line of sight. As a countermeasure, communication is possible by superimposing communication information on the radar transmission wave and demodulating it as a reflected signal from the target. This is useful because it is not necessary to separately provide a communication line if communication can be performed using the direct wave of the radar even in the line-of-sight. In this embodiment, a method of superimposing communication information in a pulse and performing distance measurement will be described. As for the angle measurement processing, a general method (Non-Patent Document 2) such as monopulse processing using Σ and Δ beams can be used, so the description is omitted.

In the radar system having the above configuration, FIG. 4 shows the state of the transmission beam and the reception beam with respect to the target T of the multistatic system, and FIG. 5 is for explaining the distance observation and the AZ and EL observations of the target position identification by transmitting and receiving communication information. The coordinate system of is shown in FIG. 6, the state of performing the target position identification using the fitting by the range is shown in the three-dimensional coordinate system, the transmission waveform is shown in FIG. 7, and the communication modulation signal in the transmission pulse is generated in FIG. FIG. 9 shows how to extract the communication period from the received signal and demolish the communication signal, and FIG. 10 shows how to extract the communication period from the correlation processing of the range period P2 column of the received signal and demolish the communication signal. FIG. 10a shows a state in which the distance of the maximum bank signal is extracted from the correlation processing of the range period P2 + the communication period P3 of the received signal and the communication signal is demolished. Although the transmitted beam is represented by a pencil beam in FIG. 4, the transmitted beam may be a fan beam including omnidirectionality.

In the present embodiment, the position of the target T can be identified by observing the distance of the target T and the angles of AZ and EL with the receiving device R, as shown in FIG. Alternatively, as shown in FIG. 6, by observing a plurality of transmission-reception distances, the target position can be identified from the intersection of elliptical spheres or the like by fitting by distance. Therefore, the present embodiment provides a method for adjusting the time synchronization between the transmitting device and the receiving device with high accuracy.

In the transmission device Ti, as shown in FIG. 7, the transmission pulse is divided into a communication period P3 and a range period P2, and N hit (N> 0) transmission is performed. As the communication information, the transmission position, transmission frequency, transmission timing, transmission beam direction, etc. are represented by bits (0, 1), and as shown in FIG. 8, a signal converted by BPSK (Non-Patent Document 4) or the like is generated. Then (T18) and IFFT (T17), the communication modulation signal in the pulse is generated. For the range period, a chirp signal is generated (T16), the timing in the pulse is controlled by intra-pulse control together with the communication modulation signal (T15), and a transmission pulse including the communication period P3 and the range period P2 is generated (T14). ), Frequency conversion to the transmission frequency (T13), pulse modulation by a pulse gate (T12), high output amplification, and transmission toward the target (T11).

In the receiving device R, the signal received by the receiving antenna device R11 is frequency-converted into a baseband signal (R12) and AD-converted (R13). What is the AD-converted received signal? First, as shown in FIG. 9, the range period P2 is extracted (R14), correlation processing (pulse compression) is performed by a modulated signal (chirp or the like) (R15), and between pulses (slow-) as shown in FIG. The FFT of the time axis) is performed (R16), and the detection by CFAR (Non-Patent Document 4) or the like is performed using the bank signal having the maximum amplitude (R17). Here, when there are a plurality of detection points, a signal having a large SN (signal-to-noise power ratio) can be extracted. Therefore, the time range of the communication period P3 is selected based on the time axis (R18), and the communication period is selected. Extract P3 (R19). Next, after correlation processing is performed on the slow-time axis to obtain a high SN (R20), demodulation is performed to obtain communication information (R21).

Here, if the transmission time of the transmission source can be obtained by demodulating the communication information, the transmission and reception times can be synchronized. Moreover, if the transmission frequency is known, the local signal can be tuned and the correct Doppler can be obtained. Further, if the transmission position is known, the target position can be identified by the multi-static of FIGS. 5 and 6. Further, if the communication information can be demolished, the reference signal of the communication period can be known. Therefore, the range period P2 and the communication period P3 are selected from the received signal (R22), the reference signal of the communication period P3 is corrected, and the reference signal is corrected and shown in FIG. As described above, a reference signal including the range period P2 is generated (R23), P2 + P3 correlation processing is performed (R24), slow-time axis FFT is performed (R25), and a target is detected by CFAR or the like (R26). , Extract the range (R27) and output (R28).

The modulated signal will be formulated and described below. First, the modulated signal of the range period P2 can be expressed by the following equation, assuming that it is a chirp modulation.

In the present embodiment, the term "chirp modulation" is used, but other modulation methods such as a code modulation method may be used.

Next, considering the modulated waveform of the communication period P3, for example, in the case of BPSK (Non-Patent Document 4), the following equation is obtained.

This is used to modulate the communication period P3 within the pulse width.

Next, as shown in FIG. 8, the range period P2 is modulated by the modulation signal of the equation (1), and the communication period P3 is modulated by the modulation signal of the equation (3). Modulation of the communication period P3 may be performed by another method.

Next, a method of compressing the signal in the range period among the received signals will be formulated and described. This is a correlation process between the input signal and the pulse compression signal, and the case where this is performed in the frequency domain is formulated as follows.

First, the input signal has the following equation.

Next, the reference signal is as follows.

Multiplying by the signal of the frequency axis gives the following equation.

The pulse compression output can be calculated by inverse FFT.

From the above, as shown in FIG. 9, range extraction can be performed. If the range can be extracted, the communication period P3 can be extracted on the time axis. Therefore, the communication period P3 is demodulated next. For this purpose, FFT of the signal scom (t) of the communication period P3 is performed.

Since the communication period P3 can be extracted with high accuracy and the demodulation process can be performed only during that period, the accuracy of communication demodulation is improved. By extracting the phase information of this signal, the bits can be extracted and demodulated.

In FIG. 9, the processing for one PRI is described for the sake of simplicity, but in the case of multiple PRIs with N hits, as shown in FIG. 10, the correlation processing (R15) of the P2 column and the slow-time axis If FFT (R16) is performed and the distance is extracted (R17) from the maximum bank signal of the Doppler axis, the communication period P3 can be extracted with a high SN, and the demodulation accuracy is also improved.

Next, consider performing target range other than the target used for communication demodulation. In this case, since a small target is also included, the SN is higher when the correlation processing of the communication period P3 + the range period P2 is performed at the time of the correlation processing for the range. Therefore, the reference signals are connected.

The reference signal of the communication period P3 is the same as the Scom of the equation (3) because the demodulated signal is known. This may be connected to the reference signal Sref in the range period of Eq. (5).

Correlation processing is performed using this Scom_r.

First, the input signal has the following equation.

Next, the reference signal is as follows.

Multiplying by the signal of the frequency axis gives the following equation.

The pulse compression output can be calculated by inverse FFT.

As described above, even for reflection points with a low signal-to-noise power ratio, correlation processing is performed using the pulses of the entire communication period P3 + range period P2, and if there are multiple N-hit PRIs, slow as shown in FIG. After performing FFT (R25) on the -time axis and detecting (R26) by CFAR or the like, range extraction (R27) can be performed with a high SN. In this embodiment, the reception period of the pulse of the communication period P3 is extracted by using the correlation processing result of the pulse of the range period P2, the communication is demodulated at a high SN, and the transmission device T and the reception device R are synchronized and tuned. It is characterized in that the distance of the target T is extracted with a high SN by the correlation processing including the communication period P3.

If the target T can be detected by the correlation processing of only the range period P2 without including the communication period P3, the range by the correlation processing of only the range period P2 may be output.

From the above, as shown in FIG. 5, the AZ and EL angles seen from the receiving device can be observed from the transmission-reception distance and the angle measurement processing of the signal detected by the equation (13), so that the target position can be identified. can do.

Further, when the number of transmission devices is three as shown in FIG. 6, R1, R2, and R3 can be obtained as the respective distances from transmission 1 to reception, transmission 2 to reception, and transmission 3 to reception. Using this distance, the position (x, y, z) of the target T is calculated as shown in FIG. In this method, it is the intersection of the spherical surface of R1 and the elliptical spherical surface of R2 and R3. Among them, the intersections in the AZ angle and the three-dimensional positions in the EL angle direction observed by the receiving device R are calculated with the target existence area within a predetermined range as the center. If the solution cannot be calculated, the points in the target existence area are divided into (x, y, z) grid points, and the points (x, y, z) where the value of the following equation is minimized are calculated at each point. To do.

If the receiving device has a transmitting / receiving function, the two transmitting devices can output the midpoint of the line of intersection as the target three-dimensional observation position in the same manner.

As described above, in the radar system according to the first embodiment, the transmitting device divides the transmission pulse τ (including continuous wave) for pulse compression into the communication period P3 and the range period P2, and transmits the pulse in the communication period. The communication information is superimposed and transmitted, and the receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, and the received signal is compressed by the reference signal during the range period to obtain a high reflection point of the SN. By extracting the communication period and performing correlation processing, communication information (transmission position, transmission time, transmission frequency, transmission beam direction, etc.) is extracted, and other reflection points with a low signal-to-noise power ratio are also extracted. , Only in the range period, or by using the communication information, the target distance is output by performing the correlation processing for the entire pulse of the communication period + the range period.

According to the above configuration, the communication period P3 is extracted by the pulse of the range period P2, demodulated, and the position, transmission timing, transmission frequency, transmission beam directing direction, etc. of the transmission device are extracted from the communication information, thereby transmitting the transmission device. And the receiving device are synchronized and tuned, and the corrected reference signal is used to perform correlation processing with a long pulse train having a communication period P3 and a range period P2, so that a target distance can be output with a high SN.

(Second embodiment)
In the first embodiment, a method of dividing a pulse into a communication period and a range period has been described. However, with a short pulse such as HPRF (High Pulse Repetition Frequency), it is difficult to divide the pulse. Therefore, in the second embodiment, an example applied to the method of dividing the pulse train will be described.

The configuration of the transmitting device Ti of the radar system according to the present embodiment is shown in FIG. 12, and the configuration of the receiving device R is shown in FIG.

In the transmitter Ti shown in FIG. 12, the difference from FIG. 2 is that the reference signal generator T20 is used instead of the chirp signal generator T16, and the controller T19 that performs time division processing is used instead of the controller T15. It is in.

Further, in the receiving device R shown in FIG. 13, the difference from FIG. 3 is that the P1 selector R29 is used instead of the P2 extractor R14 and the correlation processor (pulse compression) R15, and the Doppler extractor is installed after the detector R17. R30 was added, the Doppler reference signal corrector R31 was used in place of the P3 extractor R19, and the P2 selector R32, PRI column sorter R33, and Doppler reference signal corrector R34 were used in place of the P2 + P3 selector R22. It is in.

In the transmission device Ti shown in FIG. 12, the transmission pulse train is divided into a Doppler period P1, a range period P2, and a communication period P3, as shown in FIG. The pulse trains of P1, P2, and P3 may have the same or different PRF (Pulse Repetition Frequency). In the pulse transmission modulation, as shown in FIG. 15, BPSK (Non-Patent Document 4) code-modulated with communication information is FFTed, and the pulses are modulated by the sampled modulation signal.

As shown in FIG. 16, the signal is detected at a high target of SN by the FFT of PRF1 in the Doppler period P1. If the Doppler can be extracted, the reference signal in the range period P2 is corrected, the range is compressed, and the range is extracted. If the range can be extracted, the communication period P3 can be extracted on the time axis. Therefore, as shown in FIG. 17, the communication period P3 is demodulated by the IFFT of the pulse train P3 to obtain the communication information. As communication information, the usage as a multi-static radar such as transmission position, transmission frequency, transmission timing, transmission beam directivity, etc. is the same as that of the first embodiment.

If the demodulated signal (communication information) is known, the correction signal of the communication period P3 can be known as in the first embodiment. For range extraction, the corrected reference signal and the input signal may be correlated. As the correlation processing, there is also a correlation processing method using all cells of the slow-time axis × fast-time axis, but in order to improve the SN (signal-to-noise power ratio), the correlation of the slow-time axis for each range cell Perform processing. In this case, when the PRFs of the P1 row, the P2 row, and the P3 row are the same, as shown in FIG. 18, the P2 row in the method (1), the P1 + P2 row in the method (2), or the P1 + P2 + P3 row in the method (3). There is correlation processing by. First, the general form of pulse train correlation processing will be formulated and described.

First, the input signal has the following equation.

Next, the reference signal is as follows.

Multiplying by the signal of the frequency axis gives the following equation.

Correlation processing can be calculated by inverse FFT.

As described above, the correlation processing output of the slow-time axis (cellslow number of cells) can be obtained for each range cell (cellfast number of range cells) of the fast-time axis. The total time is the number of cells of Cellfast × Cellslow, and the time of one cell is the time of the sampling time on the fast-time axis. Ranges can be extracted during this total time, as shown in FIG.

Next, each method (1) to (3) differs only in the reference signal sref0 (tslow) of the method (16).

In the case of only the P2 column of the method (1), the reference signal obtained by correcting the modulated signal in the range period by Doppler is used.

In the case of the P1 + P2 column of the method (2), the Doppler period + range period is corrected.

In the case of the P1 + P2 + P3 column of the method (3), the P1 column is added to the method (2).

The entire correlation process is performed using these reference signals. As a result, even for a reflection point having a low signal-to-noise power ratio, a small target can be detected with a high SN, and the distance and speed can be output. If there are different PRFs in the PRFs of the P1 column, the P2 column, and the P3 column, the correlation processing on the slow-time axis for each range cell is performed using the signal sequence of the same PRF including the P2 column of at least the range period. Just do it.

As described above, in the present embodiment, the reception period of the pulse of the communication period is extracted by using the correlation processing result of the pulse of the Doppler period and the range period, and the communication is demodulated with a high SN to obtain the transmitting device and the receiving device. It is characterized in that other reflection points having a low signal-to-noise power ratio are also synchronized and tuned, and the target distance is extracted with a high SN by correlation processing including a communication period, a Doppler period, and a range period.

That is, in the radar system according to the second embodiment, the transmitting device time-divides the pulse train of the radar that repeats the pulse into the communication period P3, the Doppler period P1, and the range period P2, and transmits the communication information related to the transmission to the pulse of the communication period. The receiver receives the direct wave transmitted from the transmitter or the reflected wave from the target, and transmits the received signal by using the reflection point having a high SN ratio in the FFT result of the Doppler period P1. Communication is performed by correcting the reference signal in the range period, correlating the range period P2 with the corrected reference signal to extract the range, extracting the received signal in the communication period P3, and correlating with the reference signal corrected by the Doppler. Information (transmission position, transmission time, transmission frequency, transmission beam directing direction, etc.) is extracted. For other reflection points with a low signal-to-noise power ratio, the communication period P3 corrects the reference signal using the communication information and the Doppler, and the range period P2 corrects the reference signal using the Doppler, and the communication period P3, Of the Doppler period P1 and the range period P2, the pulse train including at least the range period P2 is used for correlation processing to output the target distance.

According to the above configuration, the communication period P3 is extracted from the pulse trains of the Doppler period P1 and the range period P2, demodulated, and the position, transmission timing, and transmission frequency of the transmission device are extracted from the communication information to obtain the transmission device and reception. The target distance can be output with a high SN by synchronizing the devices in synchronization and using the corrected reference signal to perform correlation processing with a long pulse train having a communication period P3, a Doppler period P1, and a range period P2.

(Third Embodiment)
In the second embodiment, a method of dividing the pulse train into a Doppler period, a communication period, and a range period has been described. In this case, since it is time-divisioned, the pulse train becomes long and the observation time becomes long. Therefore, in the third embodiment, in order to avoid this, a method of simultaneously transmitting the P1, P2, and P3 columns as different PRFs will be described.

FIG. 19 shows the configuration of the transmitting device Ti of the radar system according to the present embodiment, and FIG. 20 shows the configuration of the receiving device R.

The transmission device Ti shown in FIG. 19 differs from FIG. 12 in that the controller T21 that performs integrated processing is used instead of the controller T19 that performs time division processing.

Further, in the receiving device R shown in FIG. 20, the difference from FIG. 13 is that the communication information reference signal corrector R23 is deleted.

In the transmission device Ti shown in FIG. 19, as shown in FIG. 21, the transmission pulse train has a communication period P3, a Doppler period P1, and a range period P2, and is synthesized so as to transmit these at the same time (T21). In the transmission modulation, as shown in FIG. 22, BPSK (Non-Patent Document 4) code-modulated with communication information is FFTed, and the pulses are modulated by the sampled modulation signal.

In the receiving device R shown in FIG. 20, as shown in FIG. 23, when the PRFs of the signal sequences P1, P2, and P3 are different, the signals can be separated by using the PRFs. When the PRF of the communication period P3 and the Doppler period P1 are the same, they may be separated into two types, P1 + P3 and P2, as shown in FIG. 24. Further, when the PRFs of the communication period P3 and the range period P2 are the same, they may be separated into two types, P1 and P2 + P3.

Using the separated signal sequences, as shown in FIG. 25, the signal is detected at a high target of SN by the FFT of PRF1 in the Doppler period P1. In the case of P1 + P3, the communication period is not added because the phases differ between the pulses due to the communication modulation signal, but if the Doppler period is lengthened, the Doppler can be extracted with a high SN. If Doppler extraction is possible, the reference signal of the range period is corrected, range compression is performed, and range extraction is performed. If range extraction is possible, the communication period P3 can be extracted on the time axis. It is demodulated by IFFT and communication information is obtained. As communication information, the usage as a multi-static radar such as transmission position, transmission frequency, transmission timing, etc. is the same as that of the first embodiment.

Next, for range extraction, the corrected reference signal and the input signal may be correlated. In this case, as in the second embodiment, the same PRF column is required in order to perform the correlation processing on the slow-time axis for each range cell. Therefore, as shown in FIG. 26, the correlation processing is performed using only the P2 column. In the case of P2 + P3 in which the communication period + range period are the same PRF, the communication period corrected by using the signal obtained by demodulating the communication information and the Doppler signal of the Doppler period also for other reflection points having a low signal-to-noise power ratio. The P2 + P3 correlation processing may be performed by combining the reference signal of P3 (first reference signal) and the reference signal of the range period P2 corrected by the Doppler signal (second reference signal) as the entire reference signal.

The generation method including the correction of these reference signals by Doppler is different from the second embodiment (FIG. 14) in which the time axis of each pulse train is the upper figure of FIG. 23 and is a time-division pulse train. Therefore, it is the same as the second embodiment except that it is necessary to set the time axis of the pulse train according to FIG. 23, and the description thereof is omitted here. The entire correlation process is performed using these reference signals. As a result, a small target can be detected with a high SN, and the distance and speed can be output.

As described above, in the present embodiment, the reception period of the pulse of the communication period is extracted by using the correlation processing result of the pulse of the Doppler period and the range period, and the communication is demodulated with a high SN to obtain the transmitting device and the receiving device. It is characterized in that other reflection points having a low signal-to-noise power ratio are also synchronized and tuned, and the target distance is extracted with a high SN by correlation processing including a communication period, a Doppler period, and a range period.

That is, in the radar system according to the present embodiment, the transmitting device sets the pulse train of the radar that repeats the pulse in three ways (P3, P1, P2) of the communication period P3, the Doppler period P1 and the range period P2, or the communication period P3 and the Doppler. Two types of PRF (P3 + P1, P2) of period P1 and range period P2, or two types of PRF (P1, P3 + P2) of Doppler period P1 and communication period P3 and range period P2, and communication information related to transmission in the pulse of communication period. Is superposed, and the pulse trains of the communication period P3, the Doppler period P1 and the range period P2 are mixed and transmitted, and the receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target and transmits the received signal. Of the FFT results of the Doppler period P1, the reference signal of the range period P2 is corrected by using the Doppler of the reflection point with high SN, the range period P2 is correlated with the corrected reference signal to extract the range, and the communication period is communicated. Communication information (transmission position, transmission time, transmission frequency, transmission beam direction, etc.) is extracted by extracting the received signal of P3 and correlating with the reference signal corrected by Doppler, and the signal-to-noise power ratio is low. The other reflection points are also subjected to correlation processing using a pulse train obtained by correcting the reference signal with a Doppler during the range period P2, and the target distance is output.

As described above, according to the present embodiment, by mixing the pulse trains of three types of PRF and transmitting them at the same time, the transmission time is shortened as compared with the case of time division, and the LPI (Low Probability of intercept) property is achieved. By extracting the communication period from the pulse trains of the Doppler period P1 and the range period P2, demodulating it, and extracting the position, transmission timing, transmission frequency, transmission beam direction, etc. of the transmission device from the communication information, the transmission device and The receiving device can be synchronized and tuned.

It should be noted that the present embodiment 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.

T1 to TN ... Transmitter, R ... Receiver, T ... Target,
T11 ... Transmit antenna device, T12 ... Pulse modulator, T13 ... Frequency converter, T14 ... Modulator, T15 ... Controller, T16 ... Chirp signal generator, T17 ... IFFT (Inverse Fast Fourier Transform) processor, T18 ... Communication Modulation signal generator, T19 ... controller, T20 ... reference signal generator, T21 ... controller,
R11 ... Receiving antenna device, R12 ... Frequency converter, R13 ... AD (Analog-Digital) converter, R14 ... P2 extractor, R15 ... Correlation processing pulse compressor, R16 ... FFT (Slow-time) processor, R17 ... Detector, R18 ... P3 range selector, R19 ... P3 extractor, R20 ... Correlation processor (Slow-time), R21 ... Demodigator, R22 ... P2 + P3 selector, R23 ... Communication information reference signal corrector, R24 ... Correlation Processor, R25 ... FFT (Slow-time) processor, R26 ... Detector, R27 ... Range extractor, R28 ... Output processor, R29 ... P1 selector, R30 ... Doppler extractor, R31 ... Doppler reference signal corrector , R32 ... P2 selector, R33 ... PRI column sorter, R34 ... Doppler reference signal corrector.

Claims (8)

A transmission device that divides a transmission pulse for pulse compression into a communication period and a range period, and superimposes communication information on transmission on the pulse of the communication period and transmits it.
The direct wave transmitted from the transmitter or the reflected wave from the target is received, the received signal is compressed by the reference signal during the range period, and the communication is performed using the reflection point having a high signal-to-noise ratio (SN). The communication information is extracted by extracting the period and performing correlation processing, and the communication period and the range period are also used for other reflection points having a low signal-to-noise power ratio using only the range period or the communication information. A radar system including a receiver that outputs a target distance by correlating the entire pulse of. A transmitter that time-divides the pulse train of the radar that repeats the pulse into a communication period, a Doppler period, and a range period, and superimposes communication information on transmission on the pulse of the communication period and transmits it.
The direct wave transmitted from the transmitter or the reflected wave from the target is received, and the received signal is used as the Doppler at the reflection point having a high signal-to-noise power ratio (SN) in the FFT result of the Doppler period. The reference signal of the range period is corrected, the range period is correlated with the corrected reference signal to extract the range, the reception period of the communication period is extracted, and the reference signal corrected by the Doppler is used for correlation processing. The communication information is extracted, and for other reflection points having a low signal-to-noise power ratio, the reference signal is corrected by using the communication information and the Doppler during the communication period, and the reference signal is corrected by using the Doppler during the range period. A radar system including a receiving device for outputting a target distance by performing correlation processing using a pulse train including at least the range period among the communication period, the Doppler period, and the range period. The pulse train of the radar that repeats the pulse is a pulse train of three pulse repetition frequencies of communication period, Doppler period and range period, or two pulse repetition frequencies of communication period, Doppler period and range period, and the communication information related to transmission is superimposed on the pulse of the communication period. Then, the transmission device that mixes and transmits the pulse trains of the communication period, the Doppler period, and the range period, and
The direct wave transmitted from the transmitter or the reflected wave from the target is received, and the received signal is used as the reference signal of the range period using the Doppler of the reflection point having a high SN ratio among the FFT results of the Doppler period. The communication information is extracted by correlating the range period with the corrected reference signal and extracting the range, extracting the received signal of the communication period and correlating with the reference signal corrected by the Doppler. A radar system including a receiving device that outputs a target distance by correcting a reference signal using the Doppler and performing correlation processing for other reflection points having a low signal-to-noise power ratio during the range period. The pulse train of the radar that repeats the pulse is made into a pulse train having two pulse repetition frequencies, that is, the Doppler period, the communication period, and the range period, and the communication information regarding transmission is superimposed on the pulse of the communication period, so that the communication period, the Doppler period, and the range are used. A transmitter that mixes and transmits pulse trains for a period, and
The direct wave transmitted from the transmitter or the reflected wave from the target is received, and the received signal is used as the Doppler at the reflection point having a high signal-to-noise power ratio (SN) in the FFT result of the Doppler period. By correcting the reference signal of the range period, correlating the range period with the corrected reference signal to extract the range, extracting the received signal of the communication period, and correlating with the reference signal corrected by the Doppler. The communication information is extracted, and for other reflection points having a low signal-to-noise power ratio, the first reference signal is corrected by using the communication information and the Doppler during the communication period, and the Doppler is used during the range period. A radar system including a receiving device that outputs a target distance by correcting a second reference signal using the reference signal and performing correlation processing using a reference signal obtained by combining the first reference signal and the second reference signal. .. The transmission device divides the transmission pulse for pulse compression into a communication period and a range period, superimposes communication information on transmission on the pulse of the communication period, and transmits the pulse.
The receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, compresses the received signal with the reference signal during the range period, and obtains a reflection point having a high signal-to-noise ratio (SN). The communication period is extracted by extracting the communication period and performing correlation processing, and the communication period is also obtained for other reflection points having a low signal-to-noise power ratio using only the range period or using the communication information. And a radar signal processing method of a radar system that outputs a target distance by correlating the entire pulse of the range period. The transmitter divides the pulse train of the radar that repeats the pulse into a communication period, a Doppler period, and a range period, superimposes the communication information on the transmission on the pulse of the communication period, and transmits the pulse.
The receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, and the received signal is the Doppler of the reflection point having a high signal-to-noise power ratio (SN) in the FFT result of the Doppler period. Is used to correct the reference signal of the range period, the range period is correlated with the corrected reference signal to extract the range, the reception period of the communication period is extracted, and the reference signal corrected by the Doppler is used for correlation processing. By doing so, the communication information is extracted, and for other reflection points having a low signal-to-noise power ratio, the reference signal is corrected by using the communication information and the Doppler during the communication period, and the Doppler is used during the range period. A radar signal processing method of a radar system that corrects a reference signal by using it, performs correlation processing by using it in a pulse train including at least the range period among the communication period, the Doppler period, and the range period, and outputs a target distance. The transmission device sets the pulse train of the radar that repeats the pulse as a pulse train of three pulse repetition frequencies of communication period, Doppler period and range period, or two pulse repetition frequencies of communication period, Doppler period and range period, and transmits to the pulse of the communication period. By superimposing the communication information, the pulse trains of the communication period, the Doppler period, and the range period are mixed and transmitted.
The receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, and the received signal is used as the Doppler at the reflection point having a high signal-to-noise power ratio (SN) in the FFT result during the Doppler period. Is used to correct the reference signal of the range period, the range period is correlated with the corrected reference signal to extract the range, the received signal of the communication period is extracted, and the reference signal corrected by the Doppler is correlated. The communication information is extracted by processing, and even for other reflection points with a low signal-to-noise power ratio, the target distance is output by correcting the reference signal using the Doppler and performing correlation processing during the range period. Radar signal processing method of the radar system. The transmission device sets the pulse train of the radar that repeats the pulse as a pulse train of two pulse repetition frequencies, the Doppler period, the communication period, and the range period, and superimposes the communication information on transmission on the pulse of the communication period, and the Doppler during the communication period. The pulse trains of the period and the range period are mixed and transmitted.
The receiving device receives the direct wave transmitted from the transmitting device or the reflected wave from the target, and the received signal is used as the Doppler at the reflection point having a high signal-to-noise power ratio (SN) in the FFT result during the Doppler period. Is used to correct the reference signal of the range period, the range period is correlated with the corrected reference signal to extract the range, the received signal of the communication period is extracted, and the reference signal corrected by the Doppler is correlated. The communication information is extracted by processing, and for other reflection points having a low signal-to-noise power ratio, the communication period is corrected by using the communication information and the Doppler to correct the first reference signal, and the range period. Is a radar system signal that outputs a target distance by correcting the second reference signal using the Doppler and performing correlation processing using a reference signal that is a combination of the first reference signal and the second reference signal. Processing method.

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