JP5871559B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus that calculates a relative speed and a relative distance to a plurality of targets existing in space.

  In a conventional radar apparatus having a distance ambiguity within a PRI (Pulse Repetition Interval) which is a pulse repetition period, as shown in FIG. Pulse Doppler processing using a transmission signal of a constant frequency to calculate (speed), and a transmission signal subjected to frequency modulation over a plurality of PRIs to calculate a beat frequency including target distance information and speed information And FM (Frequency Modulation) using a ranging method.

When calculating the relative speed and relative distance with a plurality of targets existing in space, Non-Patent Document 1 shown below performs processing with FM ranging of two different frequency modulation bandwidths over a plurality of PRIs. The combination of the target candidate detected by the pulse Doppler processing and the target candidate detected by the processing by FM ranging of two different frequency modulation bandwidths is solved using the Doppler frequency and the beat frequency.
In this way, by solving the target candidate combination using the Doppler frequency that is the processing result of the pulse Doppler processing and the two beat frequencies that are the processing results of FM ranging with two different frequency modulation bandwidths, Even when a plurality of targets are present in the space, it is possible to calculate the relative speed and relative distance to each target.

Guy Morris, “AIRBORNE PULSED DOPPLER RADAR second edition,” Artech House, pp. 95-98, 1996.

Since the conventional radar apparatus is configured as described above, the relative speed and relative distance to each target can be calculated even when a plurality of targets are present in space. However, in addition to the pulse Doppler processing, it is necessary to perform processing with FM ranging with two different frequency modulation bandwidths, and thus 1 CPI must be divided into three. As a result, since the observation time in each process is shortened, there is a problem that the target detection performance deteriorates.
In order to increase the distance resolution in FM ranging, it is necessary to increase the frequency modulation bandwidth. However, since the distance that can be calculated without ambiguity is shortened in proportion to the resolution, there is a limit to increasing the resolution. There was also a problem.

  The present invention has been made to solve the above-described problems, and provides a radar apparatus capable of improving the detection performance of a plurality of targets existing in space and improving the ranging performance. With the goal.

The radar apparatus according to the present invention pulse-modulates a carrier signal having a constant frequency during the first processing period, and pulse-modulates the carrier signal that is frequency-modulated over a plurality of pulse repetition periods during the second processing period. Then, the transmission means that radiates the carrier signal after pulse modulation to the space as a transmission signal, and when the transmission signal radiated from the transmission means to the space is reflected back to the target, the transmission signal is received as the reception signal. The received signal is converted into a received video signal using a carrier signal having a constant frequency during the first processing period, and the received signal is converted into a received video signal during the second processing period. A receiving means for converting to a received beat signal, and a received video signal converted by the receiving means is converted to a frequency domain signal, and a received video signal in the frequency domain is output. In addition, a frequency domain conversion unit that generates a distance-beat frequency map indicating a distance and a beat frequency within a pulse repetition period by converting the received beat signal converted by the reception unit into a frequency domain signal, and a frequency domain conversion A target candidate is detected from a frequency-domain received video signal output from the means, and a target candidate is detected from a distance-beat frequency map generated by the frequency domain conversion unit; Among the combinations of target candidates detected from the received video signal of the region and target candidates detected from the distance-beat frequency map, correct based on the Doppler frequency, beat frequency, and distance within the pulse repetition period of each target candidate a combination selecting means for selecting a combination, the combination selecting means Using the distance of the Doppler frequency and the pulse repetition period of each target candidates according to a more selected combination, and a relative speed and a relative distance calculation means for calculating the relative velocity and relative distance of each target candidate, combination selection means Calculates the difference in beat frequency or Doppler frequency of each target candidate using the Doppler frequency, beat frequency, and distance within the pulse repetition period of each target candidate, and calculates the difference in Doppler frequency or Doppler frequency of each target candidate. The combination with the smallest difference is selected as the correct combination.

According to the present invention, a carrier signal having a constant frequency is pulse-modulated during the first processing period, and a carrier signal that is frequency-modulated over a plurality of pulse repetition periods is pulse-modulated during the second processing period, Transmitting means that radiates the carrier signal after pulse modulation to the space as a transmission signal, and when the transmission signal radiated from the transmission means to the space is reflected back to the target, the transmission signal is received as a reception signal, The received signal is converted into a received video signal using a carrier signal having a constant frequency during one processing period, and the received signal is received by using a carrier signal that is frequency-modulated during the second processing period. Receiving means for converting into a signal, and converting the received video signal converted by the receiving means into a signal in the frequency domain and outputting a received video signal in the frequency domain By converting the received beat signal converted by the receiving means into a frequency domain signal, a frequency domain converting means for generating a distance-beat frequency map indicating the distance and beat frequency within the pulse repetition period, and the frequency domain converting means A target candidate is detected from the output frequency domain received video signal, and a target candidate is detected from the distance-beat frequency map generated by the frequency domain conversion unit. Among the combinations of target candidates detected from the received video signal and target candidates detected from the distance-beat frequency map, a correct combination is selected based on the Doppler frequency, beat frequency, and distance within the pulse repetition period of each target candidate. a combination selection means for selecting, selects the combination selecting means Using the distance of the Doppler frequency and the pulse repetition period of each target candidates according to a combination which comprises a relative speed and a relative distance calculation means for calculating the relative velocity and relative distance of each target candidate, the combination selecting means, Using each target candidate's Doppler frequency, beat frequency, and distance within the pulse repetition period, calculate the difference in beat frequency or Doppler frequency of each target candidate, and calculate the difference in beat frequency or Doppler frequency of each target candidate. Since it is configured to select the combination that minimizes the correct combination, it is possible to improve the detection performance of a plurality of targets existing in the space and to improve the ranging performance. .

It is a block diagram which shows the radar apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the pulse Doppler process and RGH process in 1CPI. It is explanatory drawing which shows the transmission RF signal at the time of a pulse Doppler process, and a reception RF signal. It is explanatory drawing which shows the relationship between the transmission RF signal with which frequency modulation and intra-pulse code modulation were performed by 1 CPI, and a reception RF signal. It is explanatory drawing which shows the distance by FM ranging, the signal after a correlation process, and the ranging result in PRI. It is explanatory drawing which shows 4 bit Barker code. It is explanatory drawing which shows the distance-beat frequency map in PRI. It is explanatory drawing which shows the improvement of the detection performance of the radar apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows that only the beat frequency is obtained by FM ranging of the conventional radar apparatus. Distance in PRI - is an explanatory diagram showing the detection processing of the target candidate by CFAR processing for the beat frequency map _{R FM R PC (k h,} l). CFAR threshold CFAR_th _(k h, l) is an explanatory diagram showing processing in the case where the cell exceeds are set. It is explanatory drawing which shows the Doppler frequency and beat frequency of target (1) (2). It is explanatory drawing which shows the combination of several target candidates by the conventional radar apparatus. It is explanatory drawing which shows the combination process of the target candidate by the combination selection part 13. FIG. It is explanatory drawing which shows the relationship between the target relative distance R and the PRI inner distance turn-around number NR _{, rtn} . It is explanatory drawing which shows the specific example of the selection result of the combination by the combination selection part 13. FIG. It is a block diagram which shows the radar apparatus by Embodiment 2 of this invention. It is explanatory drawing which shows the specific example of the selection result of the combination by the combination selection part 20. FIG. It is a block diagram which shows the radar apparatus by Embodiment 3 of this invention. It is explanatory drawing which shows the processing content of the combination selection part 30 when the number of the target candidates detected by the pulse Doppler process differs from the number of the target candidates detected by the RGH process. It is explanatory drawing which shows the process by FM ranging of two frequency modulation bandwidths different from the pulse Doppler process in the conventional radar apparatus.

Embodiment 1 FIG.
1 is a block diagram showing a radar apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a signal transmission processor 1 is a processing unit that outputs a transmission RF signal to a transmission / reception switch 6, and includes a local oscillator 2, a pulse modulator 3, an intra-pulse modulation signal generator 4, and a transmitter 5. Yes.
The local oscillator 2 generates a first local oscillation signal L _0P (t), which is a carrier signal having a constant frequency, during the first processing period, which is a processing period of pulse Doppler processing, and generates a first local oscillation signal L A process of outputting _0P (t) to the pulse modulator 3 and the receiver 8 is performed.
Further, the local oscillator 2 is a carrier that is frequency-modulated over a plurality of pulse repetition intervals (PRI) during a second processing period, which is a processing period of RGH (Range Gate High Pulse Frequency Frequency) processing. It generates a second local oscillation signal L ₀ is the signal _(t), and carries out a process of outputting a second local oscillation signal L _{0 (t)} to the pulse modulator 3 and the receiver 8.

When the pulse modulator 3 receives the first local oscillation signal L _0P (t) from the local oscillator 2, the pulse modulator 3 pulse-modulates the first local oscillation signal L _0P (t), and the pulsed modulated local oscillation signal L ′. _0P (t) is output to the transmitter 5 receives from local oscillator 2 second local oscillation signal _L 0 (t), and a second local oscillation signal _L 0 (t) is pulse modulation, pulse modulation Processing for outputting the subsequent local oscillation signal L ′ ₀ (t) to the transmitter 5 is performed.
The intra-pulse modulation signal generator 4 generates the intra-pulse modulation signal φ (t) (for example, the 4-bit Barker code shown in FIG. 6) and outputs the intra-pulse modulation signal φ (t) to the transmitter 5 To do.
The intra-pulse modulation signal φ (t) is not limited to the 4-bit Barker code shown in FIG. 6, and other bit Barker codes may be used, or other code modulation signals and frequency modulation signals may be used.

The transmitter 5 outputs the pulse-modulated local oscillation signal L ′ _0P (t) output from the pulse modulator 3 to the transmission / reception switch 6 as the first transmission RF signal in the processing period of the pulse Doppler processing, and RGH In the processing period of the processing, the local oscillation signal L ′ ₀ (t) after the pulse modulation output from the pulse modulator 3 using the intra-pulse modulation signal φ (t) output from the intra-pulse modulation signal generator 4. Is subjected to intra-pulse modulation, and the local oscillation signal after intra-pulse modulation is output to the transmission / reception switch 6 as the second transmission RF signal.

The transmission / reception switch 6 outputs the transmission RF signal output from the signal transmission processor 1 to the antenna 7, thereby radiating the transmission RF signal to the space, while the transmission RF signal radiated to the space is the target (space). When the antenna 7 receives a transmission RF signal that is a target reflected RF signal by being reflected back by a plurality of existing targets), the transmission RF signal is output to the receiver 8 as a reception RF signal. Implement the process.
The signal transmission processor 1, the transmission / reception switch 6 and the antenna 7 constitute transmission means.

In the processing period of the pulse Doppler processing, the receiver 8 uses the first local oscillation signal L _0P (t) output from the local oscillator 2 to receive the received RF signal output from the transmission / reception switch 6 as the received video signal S. _In the processing period of the RGH process, the reception RF signal output from the transmission / reception switch 6 is received using the second local oscillation signal L ₀ (t) output from the local oscillator 2. A process of converting to a beat signal S (n, m) is performed.
The transmission / reception switch 6, the antenna 7 and the receiver 8 constitute reception means.

The signal processor 9 includes a correlation processing unit 10, a frequency domain conversion processing unit 11, a target candidate detection unit 12, a combination selection unit 13, and a target relative speed / relative distance calculation unit 14. The correlation processing unit 10, frequency domain Each of the conversion processing unit 11, the target candidate detection unit 12, the combination selection unit 13, and the target relative speed / relative distance calculation unit 14 is dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or a one-chip microcomputer) However, the signal processor 9 may be composed of a computer having a CPU, a RAM, a ROM, and an interface circuit.
When the signal processor 9 is composed of a computer, the processing contents of the correlation processing unit 10, the frequency domain conversion processing unit 11, the target candidate detection unit 12, the combination selection unit 13, and the target relative speed / relative distance calculation unit 14 are described. The stored program may be stored in the ROM of the computer, and the CPU of the computer may execute the program stored in the ROM.

The correlation processing unit 10 performs a correlation process between the received beat signal S (n, m) converted by the receiver 8 and the reference signal Ex (m _τ ) corresponding to the intra-pulse modulation component of the second transmission RF signal. Then, a process of outputting the pulse compression signal R _{V · Ex} (n, l), which is a result of the correlation processing, to the frequency domain transform processing unit 11 is performed. The correlation processing unit 10 constitutes a correlation unit.
The frequency domain conversion processing unit 11 converts the received video signal S _V (n) converted by the receiver 8 into a frequency domain signal, and the received video signal F ″ _V (k _V ) in the frequency domain is a target candidate detection unit. 12, and the pulse compression signal R _{V · Ex} (n, l) output from the correlation processing unit 10 is converted into a frequency domain signal, thereby indicating the distance r _pri and the beat frequency fb in the PRI. distance inner -. beat frequency map _{R FM R PC (k h,} l) carrying out the process of generating the frequency domain transform processor 11 constitutes a frequency domain transform means.

The target candidate detection unit 12 detects a target candidate from the received video signal F ″ _V (k _V ) in the frequency domain output from the frequency domain conversion processing unit 11, and at the same time within the PRI generated by the frequency domain conversion processing unit 11. A target candidate is detected from the distance-beat frequency map R _FM R _PC (k _h , l), and the target candidate detection unit 12 constitutes a target candidate detection unit.
The combination selection unit 13 selects each of the combinations of the target candidates detected from the frequency domain received video signal F ″ _V (k _V ) by the target candidate detection unit 12 and the target candidates detected from the distance-beat frequency map. A process of selecting a correct combination based on the target candidate Doppler frequency fd, beat frequency fb, and PRI internal distance r _pri is performed.The combination selection unit 13 constitutes a combination selection unit.

The target relative speed / relative distance calculation unit 14 calculates the relative speed v and the relative distance R of each target candidate using the Doppler frequency fd and the PRI inner distance r _pri of each target candidate related to the combination selected by the combination selection unit 13. Perform the calculation process. The target relative speed / relative distance calculation unit 14 constitutes a relative speed / relative distance calculation means.
The display 15 displays the relative speed v and the relative distance R of each target candidate calculated by the target relative speed / relative distance calculation unit 14 as target information on the screen.

Next, the operation will be described.
In the first embodiment, as shown in FIG. 2, two processes of a pulse Doppler process and an RGH process are performed in 1 CPI.
FIG. 2 shows an example in which 1 CPI is equally divided and observation of pulse Doppler processing and RGH processing are performed.
In Non-Patent Document 1, as described above, in order to perform three processes with 1 CPI, 1 CPI is divided into three equal parts, and the observation time of each process becomes one third of 1 CPI (see FIG. 21). In the first embodiment, the observation time for each process is one half of 1 CPI.
For this reason, in this Embodiment 1, the observation time of one process becomes longer than the conventional radar apparatus, and detection performance improves.

First, processing contents until generation of a received video signal F ″ _V (k _V ) in pulse Doppler processing will be described.
FIG. 3 is an explanatory diagram showing a transmission RF signal and a reception RF signal during pulse Doppler processing.
In FIG. 3, f ₀ represents a transmission frequency, T _pri represents a pulse repetition period PRI, T ₀ represents an observation time of a received video signal, and T ₁ represents a transmission pulse width.

First, the local oscillator 2 of the signal transmission processor 1 receives the first local oscillation signal L at the transmission frequency f ₀ , which is a carrier signal having a constant frequency, during the observation time T ₀ of the received video signal that is the processing period of the pulse Doppler processing. _0P (t) is generated, and the first local oscillation signal L _0P (t) is output to the pulse modulator 3 and the receiver 8.
Pulse modulator 3 receives the local oscillator 2 first local oscillation signal L _{0P (t),} the first local oscillation signal L _{0P (t)} is a pulse modulation, the local oscillation signal L after the pulse modulation ' _0P (t) is output to the transmitter 5.
In the pulse Doppler processing for generating the received video signal F ″ _V (k _V ), the intra-pulse modulation signal generator 4 does not operate because it is not necessary to perform intra-pulse modulation on the transmission RF signal.

Transmitter 5 'receives the _{0P (t),} the local oscillation signal L after the pulse-modulated' local oscillation signal L after the pulse modulation from the pulse modulator 3 duplexer _0P a _(t) as the first transmit RF signal To the device 6.
When the transmission / reception switch 6 receives the first transmission RF signal from the signal transmission processor 1, the transmission / reception switch 6 outputs the first transmission RF signal to the antenna 7, thereby radiating the first transmission RF signal to space.
At this time, when a plurality of targets are present in the space, the first transmission RF signal radiated into the space is reflected by the plurality of targets, and the first transmission RF signal is reflected on the antenna 7 as the target reflected RF signal. Come back.
When the antenna 7 receives the reflected RF signal, the transmission / reception switch 6 outputs the reflected RF signal to the receiver 8 as the first received RF signal Rx _{tgt, P} (n, t).

When receiving the first reception RF signal Rx _{tgt, P} (n, t) from the transmission / reception switch 6, the receiver 8 uses the first local oscillation signal L _0P (t) output from the local oscillator 2. The first received RF signal Rx _{tgt, P} (n, t) is converted into a received video signal S _V (n).
That is, the receiver 8 uses the first local oscillation signal L _0P (t) output from the local oscillator 2 to down-convert the first received RF signal Rx _{tgt, P} (n, t) and By performing amplification and phase detection on the received RF signal Rx _{tgt, P} (n, t) after conversion, the received video signal S _V (n) represented by the following equation (1) (at time t = 0) A received video signal from a target having a relative distance R ₀ and a relative speed v is obtained, and the received video signal S _V (n) is output to the frequency domain conversion processing unit 11 of the signal processor 9.

式（１）において、Ａ_Ｖは受信ビデオ信号の振幅、ｎはパルス番号、Ｎはパルス数、ｃは光速を表している。

In the formula (1), A _V is the received video signal amplitude, n represents pulse number, N is the number of pulses, c is represents speed of light.

式（２）において、ｋ_ＶはＦＦＴ後のサンプリング番号を表している。 When the frequency domain transform processing unit 11 of the signal processor 9 receives the received video signal S _V (n) from the receiver 8, as shown in the following equation (2), the received video signal S _V (n) is converted to the received video signal S _V (n). H _V point fast Fourier transform (FFT: fast Fourier transform) doing, it converts the received video signal _S V (n) into a frequency domain signal, the received video signal _F "V in the frequency domain _{(k V)} It outputs to the target candidate detection part 12.

In the formula (2), _{k V} represents the sampling number after FFT.

なお、周波数領域変換処理部１１は、Ｈ_Ｖ＞Ｎの場合、受信ビデオ信号Ｓ_Ｖ（ｎ）に０の埋め込みを行う。パルス数Ｎより大きいＦＦＴ点数Ｈ_Ｖで、受信ビデオ信号Ｓ_Ｖ（ｎ）をＦＦＴすることで、より高精度に目標のドップラ周波数ｆｄ、即ち、相対速度ｖを算出することが可能になる。 Here, the Doppler frequency fd and the relative speed v have the relationship shown in the following formula (3).

The frequency domain transform processing unit 11 embeds 0 in the received video signal S _V (n) when H _V > N. In the pulse number N is greater than FFT points _{H V,} the incoming video signal _S V (n) By an FFT and the target with higher precision Doppler frequency fd, that is, it is possible to calculate the relative velocity v.

Next, the contents of processing until the reception beat signal S (n, m) is obtained in the RGH processing will be described.
FIG. 4 is an explanatory diagram showing a relationship between a transmission RF signal and a reception RF signal subjected to frequency modulation and intra-pulse code modulation with 1 CPI.
In FIG. 4, f ₀ is the transmission start frequency, _TL is the frequency sweep time of the transmission RF signal, B _L is the bandwidth of the transmission RF signal, T ₀ is the observation time of the received beat signal, and B ₀ is the time interval of T ₀ . , T _p is the transmission pulse width, φ ₀ is the initial phase of the transmission RF signal and the local oscillation signal, and c is the speed of light.
FIG. 4 shows an example in which the frequency modulation within the frequency sweep time _TL of the transmission RF signal is up-chirp modulation.

In the RGH processing, when the signal transmission processor 1 outputs a transmission RF signal, the distance ambiguity of the PRI internal distance r _pri is eliminated, and the distance resolution calculated by the beat frequency fb (distance by FM ranging) is used. Parameters for enabling transmission of a transmission RF signal that increases the distance resolution in the PRI are set.
FIG. 5 is an explanatory view showing the distance by FM ranging, the signal after correlation processing, and the distance measurement result in PRI.
First, a parameter setting method related to a transmission RF signal at the time of RGH processing will be described with reference to FIG.

In order to eliminate the distance ambiguity of the PRI inner distance r _pri and to make the distance resolution in the PRI (distance resolution after correlation processing) higher than the distance distance resolution by FM ranging, the following equation (4) For calculating distance distance resolution ΔR ′ _FM , sampling interval ΔR _FM , distance resolution ΔR ′ _PC after correlation processing, and 1PRI folding distance R _pri , satisfying the expressions (5) and (6) The parameters (the reception beat signal observation time T ₀ , the transmission RF signal bandwidth B ₀ , the pulse repetition period T _pri and the sampling frequency F _samp at the time interval of T ₀ ) are set.

The distance resolution ΔR ′ _FM of distance by FM ranging is calculated by the following formula (7), and the sampling interval ΔR _FM of distance by FM ranging is calculated by the following formula (8).
Further, the distance resolution ΔR ′ _PC after the correlation processing is calculated by the following equation (9), and the folding distance R _{pri of} 1PRI is calculated by the following equation (10).
In Expression (8), H represents the number of FFT points for FM ranging.

The signal transmission processor 1 operates based on the parameters set as described above, and outputs a transmission RF signal to the transmission / reception switch 6.
That is, the local oscillator 2 of the signal transmission processor 1 generates the second local oscillation signal L ₀ (t) with the frequency sweep time T _L and the bandwidth B _L , and the second local oscillation signal L ₀ (t ) To the pulse modulator 3 and the receiver 8.
When the pulse modulator 3 receives the second local oscillation signal L ₀ (t) from the local oscillator 2, the pulse modulator 3 performs pulse modulation on the second local oscillation signal L ₀ (t), and the pulsed modulated local oscillation signal L ′. ₀ (t) is output to the transmitter 5.

For example, the intra-pulse modulation signal generator 4 generates a 4-bit Barker code shown in FIG. 6 as an intra-pulse modulation signal φ (t), and outputs the intra-pulse modulation signal φ (t) to the transmitter 5.
Here, an example in which the intra-pulse modulation signal φ (t) is a 4-bit Barker code is shown. However, the intra-pulse modulation signal φ (t) is not limited to the 4-bit Barker code, and other bit Barker codes may be used. Alternatively, other code modulation signals and frequency modulation signals may be used.

When receiving the local oscillation signal L ′ ₀ (t) after pulse modulation from the pulse modulator 3, the transmitter 5 uses the intra-pulse modulation signal φ (t) output from the intra-pulse modulation signal generator 4, The pulse-modulated local oscillation signal L ′ ₀ (t) is modulated in the pulse, and the pulse-modulated local oscillation signal is output to the transmission / reception switch 6 as a second transmission RF signal.
When the transmission / reception switch 6 receives the second transmission RF signal from the signal transmission processor 1, the transmission / reception switch 6 outputs the second transmission RF signal to the antenna 7, thereby radiating the second transmission RF signal to space.
At this time, when a plurality of targets are present in the space, the second transmission RF signal radiated into the space is reflected by the plurality of targets, and the second transmission RF signal is reflected on the antenna 7 as a target reflected RF signal. Come back.
When the antenna 7 receives the reflected RF signal, the transmission / reception switch 6 outputs the reflected RF signal to the receiver 8 as the second received RF signal Rx _{tgt, P} (n, t).

When receiving the second reception RF signal Rx _{tgt, P} (n, t) from the transmission / reception switch 6, the receiver 8 uses the second local oscillation signal L ₀ (t) output from the local oscillator 2. The second received RF signal Rx _{tgt, P} (n, t) is converted into a received beat signal S (n, m).
That is, the receiver 8 uses the second local oscillation signal L ₀ (t) output from the local oscillator 2 to down-convert the second received RF signal Rx _{tgt, P} (n, t) and By performing amplification and phase detection on the received RF signal Rx _{tgt, P} (n, t) after conversion, a received beat signal S (n, m) represented by the following equation (11) is obtained, and The received beat signal S (n, m) is output to the correlation processing unit 10 of the signal processor 9.

式（１１）において、＊は複素共役、Ａ_Ｓは受信ビート信号の振幅、ｍは１ＰＲＩ内のサンプリング番号，Ｍは１ＰＲＩ内のサンプリング点数、Δｔは１ＰＲＩ内のサンプリング時間を表している。

In the formula (11), * the complex conjugate, _{A S} is the received beat signal amplitude, m is the sampling number in 1PRI, M is the number of sampling points in 1PRI, Delta] t represents the sampling time in 1PRI.

Next, processing contents of the correlation processing unit 10 and the frequency domain transform processing unit 11 for the received beat signal S (n, m) will be described.
When receiving the received beat signal S (n, m) from the receiver 8, the correlation processing unit 10 receives the received beat signal S (n, m) and the same A / P as the intra-pulse modulation component of the second transmission RF signal. Correlation processing with the D-converted reference signal Ex (m _τ ) is performed, and the pulse compression signal R _{V · Ex} (n, l) that is the result of the correlation processing is output to the frequency domain conversion processing unit 11.
Hereinafter, the processing content of the correlation process part 10 is demonstrated concretely. Here, an example in which the correlation processing unit 10 performs correlation processing in the frequency domain will be described.

The reference signal Ex (m _τ ) after A / D conversion which is the same as the intra-pulse modulation component of the second transmission RF signal is expressed by the following equation (12).
In the formula (12), m _tau sampling number, M _tau is a sampling number of 1PRI, represented by the following formula (13).
F _samp is the sampling frequency, and floor (X) is the maximum integer that does not exceed the variable X.

When receiving the received beat signal S (n, m) from the receiver 8, the correlation processing unit 10 converts the received beat signal S (n, m) to a fast Fourier transform (FFT) as shown in the following equation (14). : Fast Fourier Transform) to convert the received beat signal S (n, m) into a frequency domain signal.
Moreover, the correlation processing unit 10, as shown in the following equation (15), the reference signal Ex the (m _tau) by FFT, converts the reference signal Ex the (m _tau) into a frequency domain signal.
Then, the correlation processing unit 10 multiplies F _V (n, k _r ), which is a frequency domain signal, and F _Ex (k _r ) as shown in the following equation (16).

ただし、＊は複素共役、ｌはＰＲＩ内サンプリング番号、Ｌ’は相関処理のＦＦＴ点数を表している。
なお、相関処理部１０は、Ｌ’＞Ｍの場合、受信ビート信号Ｓ（ｎ，ｍ）に０を代入し、Ｌ’＞Ｍ_τの場合、参照信号Ｅｘ（ｍ_τ）に０を代入する。

Here, * represents a complex conjugate, l represents a sampling number in PRI, and L ′ represents an FFT score for correlation processing.
The correlation processing unit 10 substitutes 0 for the received beat signal S (n, m) when L ′> M, and substitutes 0 for the reference signal Ex (m _τ ) when L ′> M _τ. .

Further, when the correlation processing unit 10 samples the signal after the correlation processing with higher accuracy than the sampling interval of the received beat signal S (n, m), the correlation processing unit 10 sets 0 according to the following equation (17).
L in the equation (17) is an inverse fast Fourier transform (IFFT) point of correlation processing, and is represented by the following equation (18).
However, q is an integer greater than or equal to 0. When q = 0, the sampling interval is the same as the sampling interval of the received beat signal S (n, m).

Finally, as shown in the following equation (19), the correlation processing unit 10 multiplies a result F _{V · Ex} (n) of F _V (n, k _r ) and F _Ex (k _r ), which are frequency domain signals. , K _r ) is subjected to inverse fast Fourier transform (IFFT), and the IFFT result is output to the frequency domain transform processing unit 11 as a correlation processing result.
The correlation processing result is the pulse compression signal R _{V · Ex} (n, l), and the relative distance R _PC (l) in PRI corresponding to the sampling number l of the pulse compression signal R _{V · Ex} (n, l). Is represented by the following formula (20).

なお、周波数領域変換処理部１１は、Ｈ＞Ｎの場合、パルス圧縮信号Ｒ_Ｖ・Ｅｘ（ｎ，ｌ）に０の埋め込みを行う。パルス数Ｎより大きいＦＦＴ点数Ｈで、パルス圧縮信号Ｒ_Ｖ・Ｅｘ（ｎ，ｌ）をＦＦＴすることで、より高精度に目標のビート周波数ｆｂを算出することが可能になる。 When the frequency domain transform processing unit 11 receives the pulse compression signal R _{V · Ex} (n, l) from the correlation processing unit 10, as shown in the following equation (21), the pulse compression signal R _{V · Ex} (n , L) is FFTed at the point H in the PRI direction, and a distance-beat frequency map R _FM R _PC (k _h , l in the PRI indicating the distance r _pri in the PRI and the beat frequency fb as shown in FIG. ) And the distance-beat frequency map R _FM R _PC (k _h , l) is output to the target candidate detection unit 12.

The frequency domain conversion processing unit 11 embeds 0 in the pulse compression signal R _{V · Ex} (n, l) when H> N. The target beat frequency fb can be calculated with higher accuracy by performing FFT on the pulse compression signal R _{V · Ex} (n, l) with an FFT point number H greater than the pulse number N.

Here, the relative distance R, the relative speed v, and the beat frequency fb have the relationship shown in the following formula (22), and the relative distance R and the return distance R _{pri in} PRI have the relationship shown in the following formula (23). is there. k _h represents a sampling number after IFFT.
As shown in Expression (22), the beat frequency fb includes distance information and speed information, and in order to obtain the target candidate distance and speed correctly, it is necessary to correctly combine the Doppler frequency fd and the beat frequency fb. is there.

  As in the case of the conventional radar apparatus shown in FIG. 21, in order to perform an FM ranging method using frequency modulation different from pulse Doppler processing with 1 CPI, as compared with the case where 1 CPI is divided into three equal parts, this Embodiment 1 In order to perform pulse Doppler processing and RGH processing with 1 CPI, when 1 CPI is divided into two equal parts, as shown in FIG. 8, the power of the target signal after correlation processing and FFT between PRIs is improved, and detection performance is improved. .

In FM ranging of a conventional radar apparatus, as shown in FIG. 9, when FFT is performed between pulses after passing through a narrowband filter without sampling the received beat signal in the PRI, only the beat frequency fb is obtained. Is obtained.
The distance-beat frequency map R _FM R _PC (k _h , l) in the PRI shown in FIG. 7 is compared with the beat frequency fb in FIG. 9 in addition to the information on the beat frequency fb, the distance r in the PRI It can be seen that _pri information is obtained.

When the frequency domain transform processing unit 11 generates the received video signal F ″ _V (k _V ) in the frequency domain in the above pulse Doppler processing, the target candidate detecting unit 12 applies the received video signal F ″ _V (k _V ) to the received video signal F ″ _V (k _V ). A plurality of target candidates are detected by performing CFAR (Constant False Alarm Rate) processing, and the Doppler frequencies fd of the plurality of target candidates are output to the combination selection unit 13.
Further, the target candidate detection unit 12 generates a distance-beat frequency map R _FM R _PC (k _h , l) in the PRI in the RGH process, and the distance-beat frequency map is generated. A plurality of target candidates are detected by performing CFAR processing on R _FM R _PC (k _h , l), and the beat frequencies fb of the plurality of target candidates and the distance r _pri in the PRI are output to the combination selection unit 13.
The target candidate detection process by the target candidate detection unit 12 will be specifically described below.

Figure 10 is a distance in the PRI - is an explanatory diagram showing the detection processing of the target candidate by CFAR processing for the beat frequency map _{R FM R PC (k h,} l).
When the target candidate detection unit 12 receives the distance-beat frequency map R _FM R _PC (k _h , l) in the PRI from the frequency domain conversion processing unit 11, the target candidate detection unit 12 performs the CFAR processing represented by the following equation (24). To detect target candidates.

ただし、目標候補検出部１２は、図１１に示すように、ＣＦＡＲ閾値であるＣＦＡＲ＿ｔｈ（ｋ_ｈ，ｌ）を越えるセルが集合している場合、その集合の中で、振幅が最も大きいセルを目標候補として検出する。 In Expression (24), R _FM R _{PC, CFAR} (k _h , l) represents a target candidate detection result by the CFAR process, and “0” is set to the target candidate.
abs (x) represents the absolute value of the variable x, and CFAR_th (k _h , l), which is the CFAR threshold value of the CFAR process, is calculated by the following equation (25).
CFAR_cor represents a CFAR coefficient, Samp_cell represents a sample cell, and ave (Z (p)) represents an average value of the array Z (p).

However, the target candidate detection unit 12, as shown in FIG. 11, if a CFAR threshold CFAR_th _(k h, l) is the cell exceed are set, in the set, the target amplitude has the largest cell Detect as a candidate.

Here, the target candidate detection unit 12, the distance in the PRI - beat frequency map _{R FM R PC (k h,} l) showed that to detect a target candidate by performing the CFAR processing for the pulse Doppler processing "the same concept applies to the V _{(k V),} the received video signal F" of the processing the received video signal F in the frequency domain the result to detect the target candidate by performing the CFAR processing for V _{(k V)} Can do.

In the combination selection unit 13, the target candidate detection unit 12 detects a target candidate from the received video signal F ″ _V (k _V ) in the frequency domain, and the distance-beat frequency map R _FM R _PC (k _h , l) in the PRI. When target candidates are detected from the above, processing for combining these target candidates is performed, and processing for selecting a correct combination from a plurality of combinations is performed.
Hereinafter, the processing content of the combination selection unit 13 will be described in detail, but before that, a combination of target candidates by a conventional radar apparatus will be described.

In the conventional radar apparatus, a case where target candidates are combined at the Doppler frequency that is the processing result of the pulse Doppler processing and the beat frequency that is the processing result of the FM ranging of one frequency modulation bandwidth will be described.
FIG. 12 shows the case of target (1) with relative distance R ₁ and relative speed v ₁ , target (2) with relative distance R ₂ and relative speed v ₂ , and Doppler frequency fd of targets (1) and (2). , Beat frequency fb.
In this case, as shown in FIG. 13, there are two combinations of the Doppler frequency fd and the beat frequency fb, and the speed and distance can be calculated from the relationship of the above equations (3) and (22).
However, the conventional radar apparatus cannot uniquely determine which one of the two combinations, combination A and combination B, is correct.
Therefore, in the conventional radar apparatus, as shown in FIG. 21, it is necessary to use the Doppler frequency fd that is the processing result of the pulse Doppler processing and the beat frequency fb that is the processing result of the FM ranging of the two frequency modulation bandwidths. is there. As a result, there is a problem that the observation time of each process is shortened and the detection performance deteriorates.

式（２６）において、Ｎ_{Ｒ，ｒｔｎ}はＰＲＩ内距離折返し数である（図１５を参照）。図１５は目標相対距離ＲとＰＲＩ内距離折返し数Ｎ_{Ｒ，ｒｔｎ}の関係を示す説明図である。 FIG. 14 is an explanatory diagram showing target candidate combination processing by the combination selection unit 13.
The combination selection unit 13 uses the Doppler frequency fd that is the processing result of the pulse Doppler processing, the beat frequency fb that is the processing result of the RGH processing using one frequency modulation bandwidth, and the distance r _pri in the PRI. The target candidate combination process is performed.
Here, there is a relationship represented by the following equation (26) among the relative velocity v corresponding to the Doppler frequency fd, the beat frequency fb, and the distance r _pri in the PRI.

In Expression (26), NR _{, rtn} is the distance folding number within PRI (see FIG. 15). FIG. 15 is an explanatory diagram showing the relationship between the target relative distance R and the PRI inner-distance turn-back number N _{R, rtn} .

式（２７）（２８）において、ｉ_ＰＤはパルスドップラ処理の目標候補番号、ｉ_ＲＧＨはＲＧＨ処理の目標候補番号、ｆｄ_ｉＰＤはパルスドップラ処理の目標候補番号ｉ_ＰＤのドップラ周波数、ｆｂ_ｉＲＧＨはＲＧＨ処理の目標候補番号ｉ_ＲＧＨのビート周波数、ｎ_{Ｒ，ｒｔｎ}はＰＲＩ内距離折返し数の候補、ｎ_{Ｒ，ｒｔｎ，ｍａｘ}はＰＲＩ内距離の最大折返し数、ｒ_{ｐｒｉ，ｉＲＧＨ}はＲＧＨ処理の目標候補番号ｉ_ＲＧＨのＰＲＩ内距離、｜Ｘ｜は変数Ｘの絶対値である。 When the combination selection unit 13 performs the combination processing of a plurality of target candidates, the PRI in which the differences D _{iPD, iRGH, nR, rtn of the} beat frequency fb indicated by the following equation (27) are minimized from among the plurality of combinations. A combination for calculating the inner distance folding number N _{R, rtn} is selected (see formula (28)).
The candidate for the PRI internal distance wrap number satisfying the equation (28) becomes the target PRI internal distance wrap number, and the PRI internal distance ambiguity is solved.

In the formula _{(27) (28), i} PD is the target candidate number of pulse Doppler _{processing, i RGH} goals candidate number of RGH _{processing, fd iPD} the Doppler frequency of the target candidate number _{i PD} pulse Doppler _{processing, fb iRGH} the RGH Process target candidate number i _RGH beat frequency, n _{R, rtn} is a candidate for the number of return distances within PRI, n _{R, rtn, max} is the maximum number of return values for a distance within PRI, r _{pri, iRGH} is a target candidate number for RGH process i _RGH distance in PRI, | X | is the absolute value of variable X.

この組み合わせにより、式（２７）の算出結果は、図１６のようになる。 As shown in FIG. 14, when the number of targets is two, two combinations are conceivable, the combination A is represented by the following formula (29), and the combination B is represented by the following formula (30). .

With this combination, the calculation result of Expression (27) becomes as shown in FIG.

In this case, _min of the target candidate (1,1) belonging to combination _{A (D 1,1, nR, rtn} ) is, min of the target candidate that belongs to the combination B (1, 2) _{(D 1, 2 , NR, rtn} ) and min (D _{2, 2, nR, rtn} ) of the target candidate (2, 2) belonging to the combination A is the target candidate (2, 1) belonging to the combination B because of _{min (D 2,1, nR, rtn} ) smaller than, the combination selecting unit 13 as a correct combination, to select the combination a.
Thereby, the combination selection unit 13 calculates the Doppler frequency fd of the target candidates (1, 1) and (2, 2) belonging to the combination A, the distance r _{pri in the} PRI, and the number of in-PRI distance _folds N _{R and rtn} . Output to the target relative speed / relative distance calculation unit 14.

Here, although the combination selection part 13 showed what selects the combination with which the difference _{DiPD, iRGH, nrtn of the} beat frequency fb which Formula (27) shows from the some combination becomes the minimum, Doppler frequency fd And a combination that minimizes the difference in the Doppler frequency fd may be selected.

表示器１５は、目標相対速度・相対距離算出部１４が各目標候補の相対速度ｖ及び相対距離Ｒを算出すると、目標情報として、各目標候補の相対速度ｖ及び相対距離Ｒを画面上に表示する。 When the target relative speed / relative distance calculation unit 14 receives the Doppler frequency fd of each target candidate belonging to the correct combination, the distance r _{pri in the} PRI, and the number of in-PRI distance turns N _{R, rtn} from the combination selection unit 13, These are substituted into the following equations (31) and (32) to calculate the relative speed v and the relative distance R of each target candidate.

When the target relative speed / relative distance calculation unit 14 calculates the relative speed v and relative distance R of each target candidate, the display unit 15 displays the relative speed v and relative distance R of each target candidate on the screen as target information. To do.

As is apparent from the above, according to the first embodiment, during the processing period of the pulse Doppler processing, the first local oscillation signal L _0P (t) having the transmission frequency f ₀ that is a carrier signal having a constant frequency is pulsed. During the processing period of RGH processing, the second local oscillation signal L ₀ (t), which is a carrier signal that is frequency-modulated over a plurality of PRIs, is pulse-modulated, and the carrier signal after pulse modulation is transmitted The signal transmission processor 1 that radiates to the space as an RF signal, and when the transmission RF signal radiated to the space is reflected back to the target, the transmission RF signal is received as a reception RF signal, and processing of pulse Doppler processing in the period, using a first local oscillation signal L _{0P (t),} converts the received RF signal to the incoming video signal S _{V (n),} the processing period of RGH process, the second local oscillator No. L ₀ using a _(t), the received beat signal of the received RF signal S (n, m) and a receiver 8 for converting the converted received video signal S _{V (n)} the frequency regions by the receiver 8 And the received video signal F ″ _V (k _V ) in the frequency domain is output, and the received beat signal S (n, m) converted by the receiver 8 is converted into a frequency domain signal. in the distance in the PRI indicating the distance _{r pri} and the beat frequency fb in the PRI - beat frequency map _{R FM R PC (k h,} l) and frequency domain conversion processing unit 11 for generating, from the frequency domain transform processor 11 The target candidate is detected from the output frequency domain received video signal F ″ _V (k _V ), and the distance-beat frequency map R _FM R _PC in the PRI generated by the frequency domain conversion processing unit 11 is detected. A target candidate detection unit 12 that detects a target candidate from (k _h , l), and a target candidate detected from the received video signal F ″ _V (k _V ) in the frequency domain by the target candidate detection unit 12 and a distance in the PRI− beat frequency map _{R FM R PC (k h,} l) from the combinations of the detected target candidates, the Doppler frequency fd of each target candidate, the correct combination based on the distance _{r pri} in the beat frequency fb and PRI A combination selection unit 13 for selection, and the target relative speed / relative distance calculation unit 14 uses the Doppler frequency fd of each target candidate related to the combination selected by the combination selection unit 13 and the distance r _pri in the PRI, Since the relative velocity v and the relative distance R of each target candidate are calculated, the detection performance of a plurality of targets existing in the space can be improved. It is an effect which can increase the ranging performance.

That is, according to the first embodiment, the Doppler frequency fd that is the processing result of the pulse Doppler processing, the beat frequency fb that is the processing result of the RGH processing using one frequency modulation bandwidth, and the PRI internal distance r _pri are used. Since it is possible to determine a combination of a plurality of target candidates, it is possible to lengthen the observation time of each process. As a result, the target candidate detection performance is improved, and the relative speed v and the relative distance R of the plurality of target candidates can be calculated with high accuracy.
Further, by solving the PRI internal distance ambiguity and using the high resolution PRI internal distance, it becomes possible to calculate the high resolution distance.

In the first embodiment, the frequency domain transform processing unit 11 performs FFT on the received video signal S _V (n) converted by the receiver 8 to convert the received video signal S _V (n) into the frequency domain. In addition, the pulse compression signal R _{V · Ex} (n, l) output from the correlation processing unit 10 is subjected to FFT to convert the pulse compression signal R _{V · Ex} (n, l) in the frequency domain. Although what was converted into a signal is shown, before the received video signal S _V (n) or the pulse compression signal R _{V · Ex} (n, l) is FFTed, the received video signal S _V (n) or the pulse compression A window function process may be performed on the signal R _{V · Ex} (n, l) to reduce the influence of clutter.
Specifically, before the frequency domain transform processing unit 11 performs FFT on the received video signal S _V (n) and the pulse compression signal R _{V · Ex} (n, l), for example, a received video with a Hamming window in the PRI direction. A side lobe in the beat frequency direction of the clutter may be suppressed by multiplying the signal S _V (n) and the pulse compression signal R _{V · Ex} (n, l).
Thereby, it becomes possible to improve the detection performance of the target candidate without being buried in the clutter side lobe.

Further, the frequency domain conversion processing unit 11 may perform filter processing on the received video signal S _V (n) and the pulse compression signal R _{V · Ex} (n, l) to reduce the influence of clutter. Good.
Specifically, the frequency domain transform processing unit 11 performs a filter (FIR (Finite Impulse Response) filter or IIR (Infinite Impulse Response) filter that suppresses the main beam clutter in the PRI direction based on the relationship between the radar and the main beam clutter. ) Filter) may be used to perform a filtering process on the received video signal S _V (n) and the pulse compression signal R _{V · Ex} (n, l).

In the first embodiment, the correlation processing unit 10 performs the correlation process between the received beat signal S (n, m) and the reference signal Ex (m _τ ), but the reference signal Ex (m _τ ) May be implemented to reduce the effect of clutter.
Specifically, before the correlation processing unit 10 performs the correlation process between the received beat signal S (n, m) and the reference signal Ex (m _τ ), for example, a Hamming window is set in the PRI inner distance direction as the reference signal Ex. By multiplying (m _τ ), side lobes in the PRI distance direction may be suppressed.
Thereby, it becomes possible to improve the detection performance of the target candidate without being buried in the clutter side lobe.

Embodiment 2. FIG.
FIG. 17 is a block diagram showing a radar apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
Similar to the combination selection unit 13 in FIG. 1, the combination selection unit 20 detects the target candidate detected from the frequency domain received video signal F ″ _V (k _V ) by the target candidate detection unit 12 and the distance-beat frequency in the PRI. Processing for selecting a correct combination based on the Doppler frequency fd, beat frequency fb, and PRI inner distance r _pri of each target candidate from the combinations with the target candidates detected from the map R _FM R _PC (k _h , l) However, unlike the combination selection unit 13 in FIG. 1, the combination that minimizes the sum of the differences of the beat frequencies fb or the sum of the differences of the Doppler frequencies fd is selected as the correct combination. The combination selecting unit 20 constitutes a combination selecting unit.

Next, the operation will be described.
However, since the combination selection unit 20 is the same as that of the first embodiment except that the combination selection unit 20 is mounted on the signal processor 9 instead of the combination selection unit 13, only the processing content of the combination selection unit 20 will be described. .

FIG. 18 is an explanatory diagram illustrating a specific example of a combination selection result by the combination selection unit 20.
If the beat frequency difference _{DiPD, iRGH, nR, rtn} represented by the equation (27) can always be accurately calculated, the correct combination can be selected. However, due to the influence of noise, observation error, etc., the equation (27 The beat frequency difference _{DiPD, iRGH, nR, rtn} indicated by () may not be calculated accurately.

Originally, even when calculated as follows:
Combination A Combination B
min (D _{1,1, nR, rtn} ) <min (D _{1,2, nR, rtn} )
min ( _{D2,2, nR, rtn} ) <min ( _{D2,1, nR, rtn} )
It may be calculated as follows due to the influence of noise, observation error, etc. (see FIG. 18).
Combination A Combination B
min (D _{1,1, nR, rtn} ) <min (D _{1,2, nR, rtn} )
min ( _{D2,2, nR, rtn} )> min ( _{D2,1, nR, rtn} )

そして、組み合わせ選択部２０は、上記の総和が最小となる組み合わせが、正しい組み合わせであるとして選択する。 When calculated in this way, since the directions of the equal signs of the two comparison results are different, neither the combination A nor the combination B can be selected.
Therefore, in the combination selection unit 20 of the second embodiment, in order to reduce the influence of the temporary error so that the correct combination can be selected, as shown in the following expression (33), the expression (28) The sum of the combination candidates of the calculation results is calculated.

Then, the combination selection unit 20 selects the combination that minimizes the above sum as the correct combination.

In the example of FIG. 18, the min (D _{1,1, nR, rtn} ) of the target candidate (1,1) belonging to the combination A and the min (D _{2,2, nR, rtn} ) of the target candidate (2,2). ) Is the min (D _{1,2, nR, rtn} ) of the target candidate (1,2) belonging to the combination B and min (D _{2,1, nR, rtn} ) of the target candidate (2,1). Therefore, the combination A is selected as the correct combination.
Thus, the combination selection unit 20 calculates the Doppler frequency fd of the target candidates (1, 1) and (2, 2) belonging to the combination A, the distance r _{pri in the} PRI, and the number of in-PRI distance _folds N _{R and rtn} . Output to the target relative speed / relative distance calculation unit 14.

  In this example, the combination selection unit 20 selects the combination that minimizes the sum of the differences in the beat frequency fb from among a plurality of combinations, but calculates the sum of the differences in the Doppler frequency fd, You may make it select the combination from which the sum total of the difference of the Doppler frequency fd becomes the minimum.

  As apparent from the above, according to the second embodiment, the combination selection unit 20 selects the combination that minimizes the sum of the differences of the beat frequencies fb or the difference of the Doppler frequencies fd as the correct combination. Thus, the influence of noise environment and observation error is reduced, and the relative speed and relative distance of a plurality of targets can be calculated with high accuracy.

Embodiment 3 FIG.
19 is a block diagram showing a radar apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG.
Similar to the combination selection unit 13 in FIG. 1, the combination selection unit 30 detects the target candidate detected from the frequency domain received video signal F ″ _V (k _V ) by the target candidate detection unit 12 and the distance-beat frequency in the PRI. Processing for selecting a correct combination based on the Doppler frequency fd, beat frequency fb, and PRI inner distance r _pri of each target candidate from the combinations with the target candidates detected from the map R _FM R _PC (k _h , l) However, unlike the combination selection unit 13 of FIG. 1, the number of target candidates detected from the received video signal F ″ _V (k _V ) in the frequency domain by the target candidate detection unit 12 and the distance - If the beat frequency map _{R FM R PC (k h,} l) and the number of detected target candidates from different, by setting the number of both target candidate into the same number Et all to determine the combination of the target candidate, from the combinations of all of the target candidate, and to select the correct combination. The combination selection unit 30 constitutes a combination selection unit.

Next, the operation will be described.
However, since the combination selection unit 30 is the same as that of the first embodiment except that the combination selection unit 30 is mounted on the signal processor 9 instead of the combination selection unit 13, only the processing content of the combination selection unit 30 will be described. .

FIG. 20 is an explanatory diagram showing the processing contents of the combination selection unit 30 when the number of target candidates detected by the pulse Doppler processing is different from the number of target candidates detected by the RGH processing.
FIG. 20 shows an example in which the number of target candidates detected by the pulse Doppler process is two and the number of target candidates detected by the RGH process is three.
When the number of target candidates detected by the pulse Doppler process is different from the number of target candidates detected by the RGH process, the combination selection unit 30 sets the number of both target candidates to the same number.
In the example of FIG. 20, the number of target candidates detected by pulse Doppler processing is one less than the number of target candidates detected by RGH processing. All combinations are determined on the assumption that the Doppler frequency fd of any one of the target candidates is equal to the target candidate (1) detected by the pulse Doppler processing.
Further, as shown in the following equation (35), it is assumed that the Doppler frequency fd of any target candidate detected by the RGH process is equivalent to the target candidate (2) detected by the pulse Doppler process. Determine all combinations.

When all the combinations are determined, the combination selection unit 30 selects the correct combination from a plurality of combinations by calculating Expression (27) and Expression (28), as in the combination selection unit 13 of FIG. To do.
Alternatively, as in the combination selection unit 20 in FIG. 17, the correct combination is selected from a plurality of combinations by calculating the expression (33).

In this example, the number of target candidates detected by the pulse Doppler process is one less than the number of target candidates detected by the RGH process. However, the present invention is not limited to this example. For example, the target candidate is detected by the RGH process. When the number of target candidates that are detected is one less than the number of target candidates detected by the pulse Doppler processing, the beat frequency fb and PRI internal distance r _{pri of} any target candidate detected by the pulse Doppler processing is RGH All combinations are determined on the assumption that the target candidate (1) detected in the processing is equivalent.
Further, assuming that the beat frequency fb and the PRI internal distance r _{pri of} any target candidate detected by the pulse Doppler processing are equivalent to the target candidate (2) detected by the RGH processing, all combinations are set. decide.

As apparent from the above, according to the third embodiment, the combination selection unit 30 determines the number of target candidates detected from the received video signal F ″ _V (k _V ) in the frequency domain by the target candidate detection unit 12. , the distance in the PRI - beat frequency map _{R FM R PC (k h,} l) if the the number of detected target candidates from different combinations of target candidates after setting the number of both target candidate into the same number Since the number of target candidates detected by the pulse Doppler process is different from the number of target candidates detected by the RGH process, the target relative speed and the relative distance can be calculated. There is an effect.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 signal transmission processor (transmission means), 2 local oscillator, 3 pulse modulator, 4 intra-pulse modulation signal generator, 5 transmitter, 6 transmission / reception switch (transmission means, reception means), 7 antenna (transmission means, reception) Means), 8 receiver (reception means), 9 signal processor, 10 correlation processing section (correlation means), 11 frequency domain conversion processing section (frequency domain conversion means), 12 target candidate detection section (target candidate detection means), 13, 20, 30 Combination selection unit (combination selection unit), 14 Target relative speed / relative distance calculation unit (relative speed / relative distance calculation unit), 15 Display.

Claims (11)

A carrier signal having a constant frequency is pulse-modulated during the first processing period, a carrier signal that is frequency-modulated over a plurality of pulse repetition periods is pulse-modulated during the second processing period, and the carrier signal after pulse modulation is used. And transmitting means that radiates to the space as a transmission signal, and when the transmission signal radiated from the transmission means to the space is reflected back to the target, the transmission signal is received as a reception signal, and during the first processing period Then, the received signal is converted into a received video signal using the carrier signal having the constant frequency, and the received signal is converted into a received beat signal using the frequency-modulated carrier signal during the second processing period. And receiving means for converting the received video signal converted by the receiving means into a frequency domain signal and outputting a frequency domain received video signal, A frequency domain converting unit that generates a distance-beat frequency map indicating a distance and a beat frequency within a pulse repetition period by converting the received beat signal converted by the receiving unit into a frequency domain signal; and the frequency domain converting unit A target candidate detecting means for detecting a target candidate from a frequency-domain received video signal output from the means and detecting a target candidate from a distance-beat frequency map generated by the frequency domain converting means; and the target candidate detecting means From the combinations of the target candidates detected from the received video signal in the frequency domain and the target candidates detected from the distance-beat frequency map, the Doppler frequency, beat frequency, and pulse repetition period of each target candidate are set. Combination selection means for selecting the correct combination based on the above combination Using the distance in the Doppler frequency and the pulse repetition period of each target candidates according to a combination selected by the selection means so, a relative velocity and a relative distance calculation means for calculating the relative velocity and relative distance of each target candidate,
The combination selection means calculates the difference between the beat frequencies of the target candidates or the difference of the Doppler frequencies using the Doppler frequency, beat frequency, and distance within the pulse repetition period of each target candidate, and calculates the beat frequency of each target candidate. A radar apparatus, wherein a combination that minimizes a difference or a difference in Doppler frequency is selected as a correct combination. A carrier signal having a constant frequency is pulse-modulated during the first processing period, a carrier signal that is frequency-modulated over a plurality of pulse repetition periods is pulse-modulated during the second processing period, and the carrier signal after pulse modulation is used. And transmitting means that radiates to the space as a transmission signal, and when the transmission signal radiated from the transmission means to the space is reflected back to the target, the transmission signal is received as a reception signal, and during the first processing period Then, the received signal is converted into a received video signal using the carrier signal having the constant frequency, and the received signal is converted into a received beat signal using the frequency-modulated carrier signal during the second processing period. And receiving means for converting the received video signal converted by the receiving means into a frequency domain signal and outputting a frequency domain received video signal, A frequency domain converting unit that generates a distance-beat frequency map indicating a distance and a beat frequency within a pulse repetition period by converting the received beat signal converted by the receiving unit into a frequency domain signal; and the frequency domain converting unit A target candidate detecting means for detecting a target candidate from a frequency-domain received video signal output from the means and detecting a target candidate from a distance-beat frequency map generated by the frequency domain converting means; and the target candidate detecting means From the combinations of the target candidates detected from the received video signal in the frequency domain and the target candidates detected from the distance-beat frequency map, the Doppler frequency, beat frequency, and pulse repetition period of each target candidate are set. Combination selection means for selecting the correct combination based on the above combination Using the distance in the Doppler frequency and the pulse repetition period of each target candidates according to a combination selected by the selection means so, a relative velocity and a relative distance calculation means for calculating the relative velocity and relative distance of each target candidate,
The combination selection means calculates the difference between the beat frequencies of the target candidates or the difference of the Doppler frequencies using the Doppler frequency, beat frequency, and distance within the pulse repetition period of each target candidate, and calculates the beat frequency of each target candidate. A radar apparatus, wherein a combination that minimizes a sum of differences or a sum of differences of Doppler frequencies is selected as a correct combination. The transmission means pulses the carrier signal so that the distance ambiguity of the distance within the pulse repetition period is eliminated and the distance resolution within the pulse repetition period is higher than the distance resolution of the distance calculated from the beat frequency. As parameters for modulation, the observation time of the received beat signal, the bandwidth of the transmission signal at the time interval of the observation time, the pulse repetition period, and the sampling frequency are set, and the carrier signal is determined according to the parameters. 3. The radar apparatus according to claim 1, wherein pulse modulation is performed. When the number of target candidates detected from the received video signal in the frequency domain by the target candidate detection means is different from the number of target candidates detected from the distance-beat frequency map,
If the number of target candidates detected from the frequency domain received video signal by the target candidate detection means is smaller than the number of target candidates detected from the distance-beat frequency map, the target candidate detection means detects from the frequency domain received video signal. The target candidate detected from the received video signal in the frequency domain and the distance-beat frequency map are detected by associating any one of the target candidates with a plurality of target candidates detected from the distance-beat frequency map. Decide the combination with the goal candidate,
If the number of target candidates detected from the distance-beat frequency map is less than the number of target candidates detected from the received video signal in the frequency domain, any target candidate detected from the distance-beat frequency map Is associated with a plurality of target candidates detected from the received video signal in the frequency domain, thereby combining a target candidate detected from the received video signal in the frequency domain and a target candidate detected from the distance-beat frequency map. Decide
The radar apparatus according to any one of claims 1 to 3, wherein a correct combination is selected from all the determined combinations of target candidates.   The frequency domain transforming means performs a filtering process on the received video signal or received beat signal converted by the receiving means to reduce the influence of clutter. The radar device according to any one of the above.   5. The frequency domain transforming unit according to claim 1, wherein the frequency domain transforming unit performs window function processing on the received video signal or received beat signal converted by the receiving unit to reduce the influence of clutter. The radar device according to any one of the above.   The frequency domain transforming means transforms the received video signal into a frequency domain signal with a number of points larger than the number of pulses of the received video signal transformed by the receiving means. The radar apparatus according to any one of 6.   The frequency domain transforming means transforms the received beat signal into a frequency domain signal at a point larger than the number of pulses related to the received beat signal converted by the receiving means. The radar device according to claim 1. When the transmission means modulates the carrier signal after pulse modulation in the pulse, and radiates the carrier signal after the pulse modulation as a transmission signal to the space,
9. Correlation means for performing correlation processing between the reception beat signal converted by the reception means and a reference signal corresponding to an intra-pulse modulation component of the transmission signal is provided. The radar device according to any one of the above.   10. The radar apparatus according to claim 9, wherein the correlation means performs window function processing during correlation to reduce the influence of clutter.   The correlation means converts the reception beat signal and the reference signal converted by the reception means into a frequency domain signal, performs correlation processing between the frequency domain reception beat signal and the frequency domain reference signal, and performs correlation. 10. The radar apparatus according to claim 9, wherein the correlation processing result is converted into a time domain signal with a number of points larger than the number of processed signals sampled.

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