JPH1090399A - Radar equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of cross range resolution of radar equipment by preventing the fluctuation of a reference-point frequency to partitioned frequency spectra for Doppler tracking by detecting the reference-point frequency and outputting the detected frequency as a tracking point for the calculation of a phase correcting amount. SOLUTION: A partitioned frequency analyzing circuit 15 analyzes the frequency of received signals at a certain range pin of the range-corrected received signals D at every small section in the direction of time and a data segmenting circuit 19 segments the area data of each amplitude value exceeding a set threshold 20. A front-edge frequency detecting circuit 21 detects front-edge frequency in a segmented area as a reference-point frequency f<k> and outputs the detected reference-point frequency to a smoothing circuit 17. The circuit 17 smoothes the locus of the reference-point frequency in the direction of time and a phase correcting amount calculating circuit 18 calculates the phase correcting amount ph used for phase correction from the smoothed locus. Therefore, a stable reference-point frequency f<k> can be obtained by setting the threshold to a value larger than the rising point, because the variation of the rising waveform is small even when the maximum amplitude value fluctuates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus for improving cross-range resolution by utilizing a change in a target movement and a posture angle, that is, a Doppler effect due to rotation.

[0002]

2. Description of the Related Art Conventionally, the operation principle of this type of radar device is as follows.
For example, Japanese Patent Application Laid-Open No. 63-50776 or
The details are described in JP-A-92257. FIG. 2 is a block diagram of a radar device configured according to the above-mentioned document. In the figure, 1 is a transmitter, 2 is a transmission / reception switch, 3
Is a transmitting / receiving antenna, 4 is a receiver, 5 is a range compression means,
6 is a range tracking unit, 7 is a range correction unit, 8 is a Doppler tracking unit, 9 is a phase correction unit, 10 is a cross range compression unit, 11 is a two-dimensional display buffer (hereinafter, referred to as a 2D display buffer), and 12 is a monitor. A television (hereinafter referred to as a monitor TV), D is a received signal after range correction, and ph is a phase correction amount used at the time of phase correction. FIG. 3 is a diagram showing the geometry of the radar device, and FIG. 4 is a diagram for explaining the movement of a target as viewed from the radar device. In the figure,
13 is a radar device and 14 is a target. Also, R in the figure
The ng axis represents the range direction, the X axis represents the azimuth direction, and the Y axis represents the elevation direction.

FIG. 24 is a block diagram of a conventional Doppler tracking means 80 in the radar apparatus of FIG. That is, the frequency having the maximum instantaneous amplitude is detected. In the figure, D, p
h is the same as in FIG. 2; 15 is a divisional frequency analysis circuit for performing frequency analysis of a received signal in a certain range bin after range correction in a small section in the time direction; 16 is the frequency and amplitude of the frequency and amplitude obtained by the A maximum amplitude frequency detection circuit for detecting a frequency having the maximum amplitude value as a reference point frequency with respect to the waveform, and a smoothing unit 17 for smoothing a locus in the time direction of the reference point frequency detected by the maximum amplitude frequency detection circuit 16 A circuit 18 is a phase correction amount calculation circuit that calculates a phase correction amount from a locus in the time direction of the reference point frequency smoothed by the smoothing circuit 17. FIG. 25 is a diagram illustrating a processing method of the Doppler tracking means 80, and FIG. 26 is a diagram illustrating a method of detecting the reference point frequency in the maximum amplitude frequency detection circuit 16.

Next, the operation of the above-mentioned conventional radar device will be described. Here, the target 14 (e.g., ships) is moved at a speed V _T in the X-axis direction, this time, ± theta ₀ the maximum roll angle, as shown in FIG. 4, for the period as T _0.
First, the high-frequency pulse signal generated by the transmitter 1 is emitted from the transmission / reception antenna 3 to the target 14 via the transmission / reception switch 2. The radar echo reflected from the target 14 is
The signal is again received by the transmission / reception antenna 3 as a reception signal, and is input to the receiver 4 via the transmission / reception switch 2. The received signal amplified and phase-detected by the receiver 4 is input to the range compression means 5, where a process for improving the range resolution, that is, pulse compression is performed. The range shift unit 7 corrects the distance shift of the received signal after range compression by time. At this time, the distance deviation for each time extracted from the received signal after range compression by the range tracking means 6 is used as the range correction amount. The phase correction unit 9 corrects the phase shift due to time in the received signal after the range correction. At this time, the phase shift for each time extracted from the received signal after the range correction by the Doppler tracking means 80 is used as the phase correction amount. The received signal after such phase correction is input to the cross range compression means 10, and the cross range resolution is improved by using the Doppler frequency difference.

Next, the Doppler effect due to the change in the attitude angle of the target 14, here the roll angle, and the Doppler effect due to the movement of the target 14 in the azimuth direction (X-axis direction) will be described. The target 14 has a period T as shown in FIG.
_0, it is assumed that the rolling within a range of roll angles ± theta _0. At this time, the roll angle θ _R (t) at time t
Is given by equation (1). θ _R (t) = θ _o sin (2πt / T _o ) (1) Accordingly, the Doppler frequency due to rotation at a point distant from the center of rotation by a radius r ₀ is given by equation (2) using the transmission wavelength λ. . In this type of radar device, θ _R (t) <1,
Since t <T ₀ , the Doppler frequency can be approximated by equation (3). Further, in the equation (3), r _y is r _y = r
₀ cos θ _R (t) represents the length in the Y-axis direction. That is,
You can determine the position r _y on the Y-axis by measuring the Doppler frequency.

[0006]

(Equation 1)

Now, the FFT of the cross range compression means 10
Assuming that the frequency resolution of (Fast Fourier Transform) is Δf, the cross range (Y-axis direction in this example) resolution Δr
_y can be represented by equation (4).

[0008]

(Equation 2)

Further, when the target 14 is moving at a speed V _T in the X-axis direction, the X-axis direction from the center point of the target 14 r _x
The Doppler frequency f _v (t) at a distant point is given by Expression (5) using the distance R ₀ between the radar device 13 and the center point of the target 14. _{f v (t) = (2V} T r x) / λR o (5) Accordingly, by measuring the Doppler frequency f _v (t), it is possible to obtain the position r _x on the X axis. Assuming that the frequency resolution of the FFT of the cross range compression means 10 is Δf, the cross range (X-axis direction in this example) resolution Δ
r _x can be represented by equation (6).

[0010]

(Equation 3)

[0011] As described above, the received signal having the high resolution in both the range direction and the cross range direction is:
The power is stored in the 2D display buffer 11, converted into a composite video signal whose power is proportional to the luminance, and displayed on the monitor TV 12 as a two-dimensional radar video.

Next, the operation of the Doppler tracking means 80 will be described. Among the received signals D after the range correction in which the distance shift due to time has been corrected by the range correcting means 7, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and the obtained frequency and The maximum amplitude frequency detection circuit 16 detects the frequency at which the amplitude value of the waveform of the amplitude is maximum as the reference point frequency.
After that, it is output to the smoothing circuit 17. Smoothing circuit 17
Then, the locus of the reference point frequency in the time direction is smoothed, and the phase correction amount calculating circuit 18 calculates the phase correction amount ph used at the time of phase correction from the smoothed locus.

Further, the Doppler tracking means 80 will be described with reference to FIGS. The received signal D after range correction in which the distance shift due to time has been corrected is S _{i, j} (where i
Is a range bin number, j is a pulse hit number, and i and j are natural numbers), the received signal D after range correction in a certain range bin r is represented as S _{r, j,} and a waveform as shown in FIG. can get. When frequency analysis is performed on S _{r, j} in small sections in the time direction (pulse hit direction) by the divided frequency analysis circuit 15, a waveform as shown in FIG.
The relationship between the frequency f _m and the amplitude A _m ^k (where k is a division frequency analysis number, m is a frequency bin number, and k and m are natural numbers) is represented by Expression (7). ^{_{A m k = F k (f}} m) (7) where F _k represents a function.

[0014] In the amplitude maximum frequency detecting circuit 16 for each division frequency analysis number k, and detects the frequency when the amplitude A _m ^k, as shown in FIG. 26 takes the maximum value, the reference-point frequency f it
When ^k, relationship between the time t _k and the reference-point frequency f ^k is 2
It becomes like the plot of 5 (c). When the smoothing circuit 17 performs smoothing on the plot of FIG.
Waveform shown by the solid line is obtained in (c), relationship between the time t _k and the reference-point frequency f ^'k is expressed by Equation 8. f ′ ^k = F ′ (t _k ) (8) Here, F ′ represents a function. The phase correction amount calculating circuit 18, the phase correction amount W _j used when phase correction equation (9)
And is expressed as a phase correction amount ph. Here, F ′ represents a function.

[0015]

(Equation 4)

[0016]

In the conventional radar apparatus as described above, the frequency and amplitude waveforms after the divided frequency analysis have multiple peaks, and the position of the peak at which the amplitude value is maximum fluctuates greatly with time. Often, the detected reference point frequency fluctuates, the error of the calculated phase correction amount increases,
There is a problem that the cross range resolution is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a radar apparatus which prevents fluctuation of a detected reference point frequency and thus prevents deterioration of cross-range resolution.

[0018]

According to the radar apparatus of the present invention, a received signal is range-compressed, range-corrected, phase-corrected, and cross-range-compressed for display. A reference point frequency detecting means for detecting a frequency serving as a reference point, and a Doppler tracking means for outputting the reference point frequency as a tracking point for calculating a phase correction amount.

The reference point frequency detecting means is a data extracting circuit for extracting a divided frequency spectrum having a certain amplitude or more, and a front end frequency which is a minimum frequency in the extracted data is set as a tracking point.

The reference point frequency detecting means is a data extracting circuit for extracting a divided frequency spectrum having a certain amplitude or more, and the rear end frequency which is the maximum frequency in the extracted data is set as a tracking point.

The reference point frequency detecting means is an integrating circuit which divides the frequency domain of the divided frequency spectrum into two to provide a domain center point for each frequency domain, and tracks the weighted average of the center frequencies after each integration. Points were calculated.

Further, the reference point frequency detecting means is an integrating circuit for extracting a divided frequency spectrum having a certain amplitude or more, and providing each region center point of a frequency region obtained by dividing the extracted data into two. The tracking point is calculated by a weighted average of the center frequencies.

The radar apparatus according to the present invention has a configuration in which a received signal is range-compressed, range-corrected, phase-corrected, and cross-range-compressed for display. Is provided as a Doppler tracking means for obtaining, as a tracking point, a frequency serving as a reference point for the signal after the waveform processing.

Further, the waveform processing means is a zero padding circuit for inserting 0 data in the time axis direction of the signal before the division frequency analysis, and the signal obtained by the zero padding is subjected to the division frequency analysis to obtain a tracking point. I did it.

Further, the waveform processing means is an interpolation circuit for interpolating the signal after the divided frequency analysis in the frequency axis direction, and analyzes the interpolated data to calculate a tracking point.

The waveform processing means may be a low-pass filter for extracting a low-frequency component of the signal after the division frequency analysis,
The data after passing through the low-pass filter is analyzed to calculate the tracking point.

Further, the waveform processing means is a power calculation circuit for calculating a power of the amplitude of the signal after the division frequency analysis, and analyzes the data after the power to calculate a tracking point.

The radar apparatus according to the present invention uses a different algorithm for the Doppler tracking section frequency spectrum in a configuration in which the received signal is range-compressed, range-corrected, phase-corrected, and cross-range-compressed. A plurality of reference point frequency detection circuits for detecting the frequency serving as the reference point are provided, and a tracking point is calculated from each of the detected frequencies by a predetermined calculation.

Further, in the predetermined calculation, the center frequency is calculated as the tracking point from the maximum value and the minimum value of the frequency detected based on different algorithms.

Further, in the predetermined calculation, the average frequency of the reference point frequencies detected based on different algorithms is calculated as the tracking point.

Further, a plurality of reference point frequency detection circuits of different algorithms are provided with Doppler tracking means provided with any one of the above-mentioned reference point frequency detection means, and the phase is corrected from each tracking point obtained. .

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a diagram showing one embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D and ph are as shown in FIG. Also, in the drawing, 15, 17, and 18 are the same as those in FIG. Reference numeral 19 denotes a data cutout circuit for cutting out data on the frequency and amplitude waveforms obtained by the division frequency analysis circuit 15, reference numeral 20 denotes a threshold setting circuit for setting a threshold necessary for cutting out data, and reference numeral 21 denotes a data cutout circuit. A front-end frequency detection circuit for detecting the frequency of the front edge of the extracted region as a reference point frequency. This embodiment introduces reference point frequency detection means,
Even if the maximum amplitude value of the section frequency spectrum tends to fluctuate with time, if the target spreads with a large size, the spread is stable over time, and the edge information is used as a tracking point. Therefore, edge data is extracted as a reference point frequency.

Next, the operation of the Doppler tracking means 8a configured as shown in FIG. 1 will be described with reference to FIG. 5 which describes a method of detecting the reference point frequency in the first embodiment. Among the range-corrected reception signals D in which the distance deviation due to time has been corrected by the range correction means 7, the reception signal in a certain range bin is frequency-analyzed in a small section in the time direction by the division frequency analysis circuit 15, and the data extraction circuit 19 Data is cut out in a region where each amplitude value exceeds the threshold value set by the threshold setting circuit 20. In the threshold setting circuit 20, for example, a fixed threshold for setting a fixed threshold between the main lobe level and the side lobe level or a C for setting the threshold to adaptive.
Using FAR (Constant False Alarm Rate) or the like, a threshold value is set for each waveform after each divided frequency analysis. The front end frequency detection circuit 21 detects the frequency of the front edge of the region cut out by the data cutout circuit 19 as a reference point frequency ^fk as shown in FIG. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction, and calculates the phase correction amount ph used at the time of phase correction by the phase correction amount calculating circuit 18 from the smoothed locus. By doing so, FIGS. 5A and 5B
Even if the maximum amplitude value fluctuates as shown by, there is little fluctuation in the rising waveform. Therefore, a stable frequency f ^k can be obtained by setting the threshold value to a value larger than the rising point.

FIG. 6 is a diagram showing another configuration of the first embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D and ph are as shown in FIG. 2, and 15, 17, and 18 are the same as in FIG. Reference numeral 19 denotes a data cutout circuit for cutting out data on the frequency and amplitude waveforms obtained by the division frequency analysis circuit 15, reference numeral 20 denotes a threshold setting circuit for setting a threshold necessary for cutting out data, and reference numeral 22 denotes a data cutout circuit. A rear-end frequency detection circuit that detects the frequency of the rear edge of the extracted area as a reference point frequency. This utilizes the stable value of the falling part, whereas the previous configuration uses the rising part.

The operation of the Doppler tracking means 8b configured as shown in FIG. 6 will be described with reference to FIG. Among the received signals D after range correction by the range correcting means 7, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and the data cutout circuit 1
In step 9, data is cut out for an area exceeding the threshold value. The threshold setting circuit 20 sets a threshold value for each waveform after each section frequency analysis using CFAR or the like. The rear end frequency detection circuit 22 detects the rear edge frequency of the region cut out by the data cutout circuit 19 as a reference point frequency ^fk as shown in FIG. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction, and calculates the phase correction amount ph used at the time of phase correction by the phase correction amount calculating circuit 18 from the smoothed locus. The front end frequency detection circuit and the rear end frequency detection circuit may be used in combination, and the average value of the front end and rear end frequencies may be output as the reference point frequency.

Embodiment 2 FIG. 8 is a diagram showing a configuration of a second embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D and ph are the same as those shown in FIG. In the figure, 1
5, 17 and 18 are the same elements as in FIG. 23 is a frequency setting circuit for setting a reference frequency within a frequency range allowed for the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15, and 24 is a start of a frequency range where the frequency and amplitude waveforms are allowed A first integration circuit for calculating an area by integrating from a point to a frequency set by the frequency setting circuit 23; a first area 25 for calculating a frequency when the area calculated by the first integration circuit 24 is halved Center calculation circuit, 2
Reference numeral 6 denotes a second integration circuit that integrates the frequency and amplitude waveforms from the frequency set by the frequency setting circuit 23 to the end point of the allowable frequency region to calculate the area, and 27 denotes a second integration circuit that calculates the area. A second area center calculating circuit 28 calculates a frequency when the area is reduced to half, and a second area center calculating circuit 27 calculates a frequency and amplitude waveform from the frequency calculated by the first area center calculating circuit 25. This is a weighted averaging circuit that performs weighted averaging up to the set frequency and detects a reference point frequency. In this configuration, since the frequency of the center of integration of the divided frequency spectrum is regarded as the reference point frequency, even if the peak of the amplitude value of the divided frequency spectrum is disturbed,
The fact that the integration center is stable is used.

Next, the operation of the Doppler tracking means 8c configured as shown in FIG. 8 will be described. Range correction means 7
In the received signal D after range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15. The first integrator 24 integrates the frequency and amplitude waveforms obtained by the divided frequency analyzer 15 from the start point of the allowable frequency region to the frequency set by the frequency setting circuit 23 to calculate the area. The second integration circuit 26 calculates the area by integrating the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15 from the frequency set by the frequency setting circuit 23 to the end point of the allowable frequency region. The frequency setting circuit 23 sets a reference frequency in an allowable frequency region, such as a frequency at which the amplitude value of the waveform of the frequency and the amplitude is maximized and a center frequency of the frequency region. The first area center calculation circuit 25 calculates the frequency at which the area calculated by the first integration circuit 24 becomes half,
The second area center calculation circuit 27 calculates a frequency when the area calculated by the second integration circuit 26 becomes half. In the weighted averaging circuit 28, the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15 are converted from the frequency calculated by the first area center calculation circuit 25 to the second area center calculation circuit 2.
After performing the weighted averaging up to the frequency calculated in step 7 to detect the reference point frequency f ^k , the output is output to the smoothing circuit 17. The smoothing circuit 17 smoothes the trajectory of the reference point frequency in the time direction, and calculates the phase correction amount calculating circuit 1 from the smoothed trajectory.
In step 8, a phase correction amount ph used at the time of phase correction is calculated.

Next, the operation of the Doppler tracking means 8c configured as shown in FIG. 8 will be described with reference to FIGS. FIG. 9 is a diagram for describing a method of detecting a reference point frequency according to the second embodiment. S _{i, j} (where i is a range bin number, j is a pulse hit number, i,
When j is defined as a natural number, the received signal D after range correction in a certain range bin r is represented as S _{r, j,} and FIG.
A waveform as shown in FIG. When frequency analysis of S _{r, j} is performed in a small section in the time direction (pulse hit direction) by the divided frequency analysis circuit 15, a waveform as shown in FIG. 25B is obtained, and the frequency f _m and the amplitude A _m ^k are obtained. (Where k is a division frequency analysis number, m is a frequency bin number, and k and m are natural numbers) are represented by Expression (7).

The frequency f at each section frequency analysis number k
_m and the waveform of the amplitude A _m ^k can be expressed as FIG. here,
The frequency β _k set by the frequency setting circuit 23 from the start point f _{1 of the} frequency region permitted by the first integrating circuit 24
When integrated, the area U _k is calculated by Expression (10).
The waveform is converted by the second integrating circuit 26 into the frequency setting circuit 23.
By integrating from the frequency β _k set in the above to the end point f _m of the allowable frequency region, the area V _k is calculated by the equation (11).

[0040]

(Equation 5)

The first area center calculating circuit 25 calculates the area U _k
Is calculated to satisfy Expression (12), and the frequency at that time is _defined as a _k . The second area center calculation circuit 27 calculates the frequency when the area V _k is reduced to half so as to satisfy the expression (13), and calculates the frequency at that time as b
_Let it be _k .

[0042]

(Equation 6)

The weighted averaging circuit 28 calculates the reference point frequency f ^k by using the frequency a _k and the frequency b _{k according} to equation (14).

[0044]

(Equation 7)

The relationship between time t _k and reference point frequency f ^k is shown in FIG.
It becomes like the plot of 5 (c). When the smoothing circuit 17 performs smoothing on the plot of FIG.
Waveform shown by the solid line is obtained in (c), relationship between the time t _k and the reference-point frequency f ^'k is expressed by Equation (8). The phase correction amount calculating circuit 18 calculates a phase correction amount W _j used when phase correction by equation (9) represents a phase correction amount ph.

In the detection of the reference point frequency, the S / N at the time of detection can be further improved by targeting only the frequency spectrum exceeding a preset threshold value. FIG.
FIG. 8 is a diagram showing another configuration of the Doppler tracking means according to the second embodiment of the present invention in the radar apparatus shown in FIG. 2;
In the figure, D, ph, 15, 17 and 18 are the same as the signals and elements in the other configuration diagrams. Further, in the figure, 2
3, 24, 25, 26, 27 and 28 are the same elements as in FIG. Reference numeral 19 denotes a data cutout circuit for cutting out data on the frequency and amplitude waveforms obtained by the division frequency analysis circuit 15, and reference numeral 20 denotes a threshold setting circuit for setting a threshold necessary for cutting out data.

Next, the operation of the Doppler tracking means 8d configured as shown in FIG. 10 will be described. Among the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and each amplitude value is set by the threshold setting circuit 20 by the data cutout circuit 19. Data is cut out for an area exceeding the threshold. The setting in the threshold setting circuit 20 is performed in the same manner as in the other embodiments. The first integration circuit 24 calculates the area by integrating from the start point of the cut-out frequency region to the frequency set by the frequency setting circuit 23. The second integration circuit 26 calculates the area by integrating from the frequency set above to the end point of the cut-out frequency region. The setting in the frequency setting circuit 23 is performed in the same manner as in FIG. First area center calculation circuit 25, second area center calculation circuit 27, weighted average circuit 28
Is similar to that in FIG. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction,
The phase correction amount calculation circuit 18 calculates a phase correction amount ph used at the time of phase correction from the smoothed trajectory.

Next, the operation of the Doppler tracking means 8d configured as shown in FIG. 10 will be described with reference to FIGS. FIG. 11 is a diagram for explaining another method of detecting the reference point frequency in the present embodiment. i is the range bin number, j is the pulse hit number and the received signal D after range correction
Is defined as S _{i, j} , the received signal D after range correction in a certain range bin r is represented as S _{r, j} . When frequency analysis is performed on S _{r, j} in a small section in the pulse hit direction,
The relationship between the frequency f _m and the amplitude A _m ^k is represented by Expression (7), where k is a division frequency analysis number and m is a frequency bin number.

The frequency f at each section frequency analysis number k
_m and the waveform of the amplitude A _m ^k is expressed as FIG. Here, each amplitude value is set to a threshold value set by the threshold setting circuit 20 in the data extraction circuit 19 (for example,
The frequency range [α _k , γ beyond the dotted line in FIG.
_k ] (where α _k is the start point of the frequency domain and γ _k is the end point of the frequency domain), a waveform in a hatched area is obtained. When the obtained waveform is integrated from the start point α _k of the frequency domain to the frequency β _k set by the frequency setting circuit 23 by the first integration circuit 24, the area U _k is calculated by the equation (15). The obtained waveform is converted by the second integrating circuit 26 into the frequency β set by the frequency setting circuit 23.
_k to the end point γ _{k of the} frequency domain, the area V
_k is calculated by equation (16).

[0050]

(Equation 8)

The first area center calculating circuit 25 calculates the area U _k
Is calculated to satisfy Expression (17), and the frequency at that time is _defined as a _k .

[0052]

(Equation 9)

The second area center calculating circuit 27 calculates the area V _k
Is calculated to satisfy Expression (13), and the frequency at that time is _defined as b _k . Weighted average circuit 2
8 calculates the reference point frequency f ^k by the equation (14) using the frequency a _k and the frequency b _k . Relationship between time t _k and the reference-point frequency f ^k is as the plot of FIG. 25 (c). To plot the smoothing circuit 17 FIG. 25 (c), the smoothing obtained waveform shown in solid line in FIG. 25 (c), the relationship between the time t _k and the reference-point frequency f ^'k Equation ( 8). The phase correction amount calculating circuit 18 calculates a phase correction amount W _j used when phase correction by equation (9), the phase correction amount p
Expressed as h.

Embodiment 3 FIG. FIG. 12 is a diagram showing a configuration of the Doppler tracking means according to the third embodiment of the present invention in the radar apparatus shown in FIG. In the figure, D, ph,
15, 17, and 18 are the same as those in FIG. Reference numeral 29 denotes a zeroing circuit for extending the observation time by inserting data of 0 in the time direction of the target reception signal when the division frequency analysis circuit 15 performs the division frequency analysis, and 30 is obtained by the division frequency analysis circuit 15. And a reference point frequency detection circuit for detecting a frequency serving as a reference point from the waveform of the frequency and the amplitude. In the present embodiment, a description will be given of a waveform processing means for improving the detection accuracy of the reference point frequency by processing the waveform of the signal before the divided frequency analysis or the signal after the divided frequency analysis (the divided frequency spectrum). Here, the waveform processing means extends the observation time by inserting zero data until a predetermined time in the time direction of the target reception signal. The extension result is subjected to section frequency analysis to improve the frequency resolution of the obtained frequency spectrum.

Next, the operation of the Doppler tracking means 8e configured as shown in FIG. 12 will be described with reference to FIG.
FIG. 13 is a diagram for explaining the operation of the zeroing circuit 29. Among the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15. At this time, FIG.
As described above, the observation time is extended by inserting zero data in the time direction of the target reception signal using the zeroing circuit 29. The received signal counted as 0 is divided into a divided frequency analysis circuit 1
When the frequency analysis is performed at 5, the frequency resolution is improved in accordance with the extended observation time as shown in FIG. Therefore,
The detection accuracy of the reference point in the reference point frequency detection circuit 30 at the subsequent stage is improved.

For example, assuming that the observation time of the target reception signal in the division frequency analysis circuit 15 is T, the frequency resolution Δ
f is given by equation (18). Δf = 1 / T (18) When the observation time of the reception signal to be processed by the division frequency analysis circuit 15 is extended by 0 to 2T using the zeroing circuit 29, the frequency resolution Δf ′ becomes ), The frequency resolution is doubled as compared with the equation (18). Δf ′ = 1 / (2T) (19)

The reference point frequency detection circuit 30 detects a frequency serving as a reference point from the frequency and amplitude waveforms obtained by the section frequency analysis circuit 15 as a reference point frequency f ^k , and outputs it to the smoothing circuit 17. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction, and the phase correction amount calculating circuit 18 calculates the phase correction amount ph used at the time of phase correction from the smoothed locus. In FIG. 13, 0 is added after the reception signal targeted by the section frequency analysis circuit 15.
However, it may be zero before or on both sides of the received signal.

Embodiment 4 FIG. 14 is a diagram showing the configuration of the fourth embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D, ph,
15, 17, and 18 are the same as those in FIG. Furthermore,
In the figure, reference numeral 30 is the same as that of FIG. Reference numeral 31 denotes an interpolation circuit for interpolating the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15 in the frequency direction. In the present embodiment, an interpolation circuit is used as the waveform processing means after the divided frequency analysis. By interpolating the frequency spectrum obtained by the divided frequency analysis in the frequency direction, the frequency samples when detecting the frequency serving as the reference point are equivalently made finer, and the number of samples is increased.

Next, the operation of the Doppler tracking means 8f configured as shown in FIG. 14 will be described with reference to FIG.
FIG. 15 is a diagram for explaining the operation of the interpolation circuit 31. Of the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and data is interpolated in the frequency direction by the interpolation circuit 31. In the interpolation circuit 31, for example, 2
Data interpolation is performed using linear interpolation using point data, spline interpolation using multipoint data, or the like. By this interpolation, the step width in the frequency direction becomes smaller, and the number of frequency sample points (the number of frequency bins) increases. FIG.
(A) is a waveform of the frequency and the amplitude obtained by the division frequency analysis circuit 15, and a dotted line represents a frequency sample point. When this waveform is subjected to data interpolation by the interpolation circuit 31, FIG.
, Data between frequency sample points represented by dotted lines can be interpolated. In this example, the number of frequency sample points is about twice as large as that before interpolation by data interpolation. Accordingly, the reference point frequency detection circuit 30 at the subsequent stage improves the detection accuracy of the reference point.

The reference point frequency detection circuit 30 includes an interpolation circuit 3
After detecting the reference point frequency f ^k from the frequency and amplitude waveforms interpolated in step 1, the reference point frequency f ^k is output to the smoothing circuit 17. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction, and the phase correction amount calculating circuit 18 calculates the phase correction amount ph used at the time of phase correction from the smoothed locus.

FIG. 16 is a diagram showing another configuration of the fourth embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, as a new element, 3
There is a low-pass filter that removes high-frequency components of the frequency and amplitude waveforms obtained by the second section frequency analysis circuit 15.
That is, a low-pass filter is used as the waveform processing means. According to the configuration of FIG. 16, the frequency spectrum obtained by performing the divided frequency analysis is passed through a low-pass filter to remove high-frequency components and to smooth a portion with a sharp change such as an edge. The value is multi-peaked,
It can stabilize by suppressing wobble.

Next, the operation of the Doppler tracking means 8g configured as shown in FIG. 16 will be described with reference to FIG.
FIG. 17 is a diagram illustrating the operation of the low-pass filter 32. Among the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and the high-frequency component of the waveform is removed by the low-pass filter 32. Low-pass filter 32
Then, high-frequency components are removed from the frequency and amplitude waveforms obtained by the section frequency analysis circuit 15, and the waveform of a portion where the change is sharp such as an edge is blunted. FIG. 17A shows a frequency and amplitude waveform obtained by the section frequency analysis circuit 15, which is a multimodal waveform having many edge portions. When this waveform is applied to the low-pass filter 32, a smooth single-peak waveform having a high-frequency component (edge portion) removed as shown in FIG. 17B can be obtained. Therefore, the reference point can be easily detected by the reference point frequency detection circuit 30 at the subsequent stage.

The reference point frequency detection circuit 30 detects a frequency serving as a reference point as a reference point frequency f ^k from the frequency and amplitude waveforms from which the high frequency components have been removed by the low-pass filter 32, and then sends the signal to the smoothing circuit 17. Output. Smoothing circuit 1
At 7, the locus of the reference point frequency in the time direction is smoothed, and the phase correction amount calculating circuit 18 calculates the phase correction amount ph from the smoothed locus.

FIG. 18 is a diagram showing another configuration of the fourth embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, a new element is a power calculation circuit that calculates the power of each amplitude value for the frequency and amplitude waveforms obtained by the 33 divided frequency analysis circuits 15. That is, a power calculation circuit is used as the waveform processing means.

Next, the operation of the Doppler tracking means 8h configured as shown in FIG. 18 will be described with reference to FIG.
FIG. 19 is a diagram for explaining the operation of the power calculation circuit 33. Of the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the divided frequency analysis circuit 15, and the power calculation circuit 33 calculates the power of each amplitude value. In the exponentiation calculation circuit 33,
Since the power of each amplitude value is calculated for the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15, the S /
The N ratio can be improved. FIG. 19A is a waveform of the frequency and the amplitude obtained by the divided frequency analysis circuit 15. When a power is calculated by the power calculator 33 for each amplitude value of the waveform, a waveform having an improved S / N ratio as shown in FIG. 19B can be obtained. Accordingly, the reference point frequency detection circuit 30 at the subsequent stage improves the detection accuracy of the reference point.

The reference point frequency detection circuit 30 detects the reference point frequency ^fk from the frequency and the waveform of the amplitude at which the power of each amplitude value is calculated by the power calculation circuit 33, and then detects the reference point frequency ^fk. 17 is output. The smoothing circuit 17 smoothes the locus of the reference point frequency in the time direction, and the phase correction amount calculating circuit 18 calculates the phase correction amount ph from the smoothed locus.

Embodiment 5 FIG. 20 is a diagram showing a configuration of the fifth embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D, ph,
15, 17, and 18 are the same as those in FIG. 34, a first reference point frequency detection circuit for detecting a reference point frequency from the frequency and amplitude waveforms obtained by the division frequency analysis circuit 15 using reference point frequency detection means using a first algorithm; Is a second reference point frequency detection circuit for detecting a reference point frequency from the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15 using a reference point frequency detection means using a second algorithm; This is a third reference point frequency detection circuit that detects a reference point frequency from the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15 using a reference point frequency detection unit using a third algorithm. Reference numeral 37 denotes an average value calculation circuit that calculates an average value of the reference point frequencies detected by the respective reference point frequency detection circuits.
In the present embodiment, a plurality of different algorithms, for example, a conventional reference point frequency detection method, a first embodiment of the present application, and a plurality of reference point frequency detection methods in other embodiments are used in combination, and the final value is determined by an average value thereof. The purpose of this is to obtain a basic reference point frequency.

Next, the operation of the Doppler tracking means 8i configured as shown in FIG. 20 will be described with reference to FIG.
FIG. 21 is a diagram illustrating a method of detecting a reference point frequency according to the fifth embodiment. Among the received signals D after the range correction, the received signal in a certain range bin is frequency-analyzed by the divided frequency analysis circuit 15 in a small section in the time direction. First
The reference point frequency detection circuit 34 detects a frequency serving as a reference point from the frequency and amplitude waveforms obtained by the division frequency analysis circuit 15 using the first reference point frequency detection means. The second reference point frequency detection circuit 35 uses the second reference point frequency detection means to detect a reference point frequency from the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15. Further, the third reference point frequency detection circuit 36
Frequency analysis circuit 1 using the reference point frequency detection means
A frequency serving as a reference point is detected from the frequency and amplitude waveforms obtained in step 5. The average value calculation circuit 37 calculates the average value of the reference point frequencies detected by the respective reference point frequency detection circuits as the reference point frequency f ^k for each section frequency analysis number k (each time) as shown in FIG. , To the smoothing circuit 17. As shown in FIG. 21, even if the reference point frequency detected by each reference point frequency detection circuit fluctuates greatly with time, the reference point frequency f ^k averaging them is stable. The smoothing circuit 17 smoothes the trajectory of the reference point frequency in the time direction, and thereafter, the phase correction amount calculation circuit 18 calculates the phase correction amount ph.

In the above embodiment, the case where the number of the reference point frequency detecting circuits is three has been described, but it goes without saying that the same operation as described above can be performed even when the number of the reference point frequency detecting circuits is plural.

FIG. 22 is a diagram showing another configuration of the fifth embodiment of the Doppler tracking means of the present invention in the radar apparatus shown in FIG. In the figure, D, ph, 15, 1
7, 18, 34, 35, 36 and 37 are the same as those in FIG. 38 is a maximum value calculation circuit for calculating the maximum value of the reference point frequency detected by each reference point frequency detection circuit;
Is a minimum value calculation circuit for calculating the minimum value of the reference point frequency detected by each reference point frequency detection circuit.

Next, the operation of the Doppler tracking means 8j configured as shown in FIG. 22 will be described with reference to FIG.
FIG. 23 is a diagram illustrating a method of detecting the reference point frequency by the configuration of FIG. Of the received signal D after range correction,
The received signal in a certain range bin is frequency-analyzed in a small section in the time direction by the division frequency analysis circuit 15. The first reference point frequency detection circuit 34 uses the first reference point frequency detection means to detect a frequency serving as a reference point from the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15. Also,
The second reference point frequency detection circuit 35 uses the second reference point frequency detection means to detect a reference point frequency from the frequency and amplitude waveforms obtained by the divided frequency analysis circuit 15. Further, the third reference point frequency detection circuit 36 uses the third reference point frequency detection means to
A frequency serving as a reference point is detected from the frequency and amplitude waveforms obtained in step (1). Then, the maximum value calculation circuit 38 calculates the maximum value and the minimum value calculation circuit 39 calculates the minimum value for the reference point frequency detected by each reference point frequency detection circuit. As shown in FIG. 23, the average value calculation circuit 37
After calculating the average value of the maximum and minimum values of the reference point frequency calculated by the maximum value calculation circuit 38 and the minimum value calculation circuit 39 for each time, as the reference point frequency f ^k , the calculated value is output to the smoothing circuit 17. I do. As shown in FIG. 23, even if the reference point frequency detected by each reference point frequency detection circuit fluctuates greatly with time, the reference point frequency f ^{k obtained} by averaging the maximum value and the minimum value is stable. Smoothing circuit 17
Now, smooth the trajectory of the reference point frequency in the time direction,
After that, the phase correction amount calculating circuit 18 calculates the phase correction amount ph. In the above-described embodiment, the case where the number of the reference point frequency detection circuits is three has been described.

[0072]

As described above, according to the present invention, in the Doppler tracking means, data is cut out based on the set threshold value for detecting the reference point frequency, and the data of the area cut out by the threshold value is further cut out. Since the frequency of the leading edge or trailing edge is detected as the reference point frequency, the frequency spectrum is multi-peak, and the position of the maximum amplitude value is not easily affected by the fluctuation even if it fluctuates with time. There is an effect that the reference point frequency can be detected and deterioration of the cross range resolution can be prevented.

Further, in the Doppler tracking means,
In order to detect the reference point frequency, for the frequency and amplitude waveforms after the division frequency analysis, obtain a frequency that reduces the area obtained by integrating from the start point of the frequency domain to the set frequency, and obtain the frequency domain from the set frequency. Weighted averaging up to the frequency at which the area obtained by integrating up to the end point is half, so that even if the frequency spectrum is multimodal and the position of the maximum amplitude value fluctuates with time, There is an effect that the reference point frequency can be detected stably without being affected by the influence and the degradation of the cross range resolution can be prevented.

Further, since the Doppler tracking means extends the observation time by inserting data of 0 as necessary in the time direction of the received signal when performing segmented frequency analysis for waveform processing, There is an effect that the frequency resolution after the division frequency analysis is improved, and the detection accuracy of the reference point in the reference point frequency detection circuit is improved.

Further, since the frequency and amplitude waveforms after the division frequency analysis are interpolated in the frequency direction for waveform processing in the Doppler tracking means,
The step width in the frequency direction is reduced, and there is an effect that the detection accuracy of the reference point in the reference point frequency detection circuit is improved. In addition, when a low-pass filter and a power calculation circuit are used, the same effect that the detection accuracy of the reference point is improved can be obtained.

Further, in the Doppler tracking means,
Since a plurality of reference point frequency detection means based on mutually different algorithms are used, even if the reference point frequency detected by each reference point frequency detection means fluctuates greatly with time, the frequency of the average value Absorbs the fluctuation of each reference point frequency and becomes stable. Therefore, even if the frequency spectrum is multimodal and the position of the maximum amplitude value fluctuates with time, it is hardly affected by the fluctuation, the reference point frequency can be detected stably, and the effect of preventing the degradation of the cross range resolution can be prevented. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram of Doppler tracking means according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram of a radar device.

FIG. 3 is a diagram illustrating a geometry of a radar device.

FIG. 4 is a diagram illustrating the movement of a target as viewed from a radar device.

FIG. 5 is a diagram illustrating a method of detecting a reference point frequency according to the first embodiment.

FIG. 6 is a block diagram of another Doppler tracking means according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a method of detecting another reference point frequency in the first embodiment.

FIG. 8 is a block diagram of Doppler tracking means according to Embodiment 2 of the present invention.

FIG. 9 is a diagram illustrating a method of detecting a reference point frequency according to the second embodiment.

FIG. 10 is a block diagram of another Doppler tracking means according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating a method of detecting another reference point frequency in the second embodiment.

FIG. 12 is a block diagram of Doppler tracking means according to Embodiment 3 of the present invention.

FIG. 13 is a diagram for explaining the operation of the zeroing circuit.

FIG. 14 is a block diagram of Doppler tracking means according to Embodiment 4 of the present invention.

FIG. 15 is a diagram for explaining the operation of the interpolation circuit.

FIG. 16 is a block diagram of another Doppler tracking means according to Embodiment 4 of the present invention.

FIG. 17 is a diagram for explaining the operation of the low-pass filter.

FIG. 18 is a block diagram of another Doppler tracking means according to Embodiment 4 of the present invention.

FIG. 19 is a diagram for explaining the operation of the power calculation circuit.

FIG. 20 is a block diagram of Doppler tracking means according to Embodiment 5 of the present invention.

FIG. 21 is a diagram illustrating a method of detecting a reference point frequency according to the fifth embodiment.

FIG. 22 is a block diagram of another Doppler tracking means according to the fifth embodiment of the present invention.

FIG. 23 is a diagram illustrating a method of detecting another reference point frequency in the fifth embodiment.

FIG. 24 is a block diagram of a conventional Doppler tracking means.

FIG. 25 is a diagram illustrating a processing method of Doppler tracking means.

FIG. 26 is a diagram illustrating a method of detecting the reference point frequency in the maximum amplitude frequency detection circuit.

[Explanation of symbols]

1 transmitter, 2 transmission / reception switch, 3 transmission / reception antenna,
4 receiver, 5 range compression means, 6 range tracking means, 7 range correction means, 8a, 8b, 8c, 8d, 8
e, 8f, 8g, 8h, 8i, 8j Doppler tracking means, 9 phase correction means, 10 cross range compression means,
11 2D display buffer, 12 monitor TV, 13 radar device, 14 target, 15 division frequency analysis circuit, 1
6 Maximum amplitude frequency detection circuit, 17 Smoothing circuit, 18
Phase correction amount calculation circuit, 19 data extraction circuit, 2
0 threshold setting circuit, 21 front end frequency detection circuit, 22 rear end frequency detection circuit, 23 frequency setting circuit, 24 first integration circuit, 25 first area center calculation circuit, 26 second integration circuit, 27 second Area center calculation circuit, 28 weighted averaging circuit, 290-based circuit, 30
Reference point frequency detection circuit, 31 interpolation circuit, 32 low-pass filter, 33 power calculation circuit, 34 first reference point frequency detection circuit, 35 second reference point frequency detection circuit, 36 third reference point frequency detection circuit , 37 average value calculation circuit, 38 maximum value calculation circuit, 39 minimum value calculation circuit.

Claims (14)

[Claims] 1. A radar device for performing range compression, range correction, phase correction, and cross-range compression on a received signal and displaying the received signal, wherein a reference point for detecting a frequency serving as a reference point for a divided frequency spectrum of Doppler tracking is provided. Providing frequency detection means,
A radar apparatus comprising Doppler tracking means for outputting the reference point frequency as a tracking point for calculating a phase correction amount. 2. The method according to claim 1, wherein the reference point frequency detecting means is a data extracting circuit for extracting a divided frequency spectrum having a certain amplitude or more, and a front end frequency which is a minimum frequency in the extracted data is set as a tracking point. Item 4. The radar device according to item 1. 3. The reference point frequency detecting means is a data extracting circuit for extracting a divided frequency spectrum having a certain amplitude or more, and a trailing edge frequency which is a maximum frequency in the extracted data is set as a tracking point. The radar device according to claim 1. 4. The reference point frequency detecting means is an integrating circuit that divides the frequency domain of the divided frequency spectrum into two to provide a domain center point for each frequency domain, and tracks the weighted average of the center frequencies after each integration. The radar device according to claim 1, wherein points are calculated. 5. The reference point frequency detecting means is an integrator circuit for extracting a divided frequency spectrum having a certain amplitude or more, and providing each region center point of a frequency region obtained by dividing the extracted data into two. 2. The radar apparatus according to claim 1, wherein the tracking point is calculated by a weighted average of the center frequencies of the tracking points. 6. A radar apparatus that performs range compression, range correction, phase correction, and cross range compression on a received signal and displays the signal before and after the divided frequency analysis of Doppler tracking. A radar apparatus comprising: a waveform processing means for processing a waveform of the spectrum; and a Doppler tracking means for obtaining, as a tracking point, a frequency serving as a reference point for the signal after the waveform processing. 7. The waveform processing means is a zero padding circuit for inserting 0 data in a time axis direction of the signal before the division frequency analysis,
7. The radar apparatus according to claim 6, wherein a tracking point is obtained by performing a division frequency analysis on the signal obtained by zero-padding. 8. The waveform processing means is an interpolation circuit for interpolating the signal after the divided frequency analysis in the frequency axis direction, and analyzes the data after the interpolation to calculate a tracking point. Item 7. The radar device according to item 6. 9. The waveform processing means is a low-pass filter for extracting a low-frequency component of the signal after the division frequency analysis, and analyzes the data after passing the low-pass filter to calculate a tracking point. The radar device according to claim 6, wherein: 10. The waveform processing means is a power calculation circuit for calculating a power of the amplitude of the signal after the divided frequency analysis, and analyzes the data after the power to calculate a tracking point. Item 7. The radar device according to item 6. 11. A radar apparatus that performs range compression, range correction, phase correction, and cross range compression on a received signal and displays the received signal using a different algorithm for a Doppler tracking section frequency spectrum using a different algorithm as a reference point. A plurality of reference point frequency detecting circuits for detecting a tracking point, and a tracking point is calculated by a predetermined calculation from the respective detected frequencies. 12. The radar according to claim 11, wherein the predetermined calculation calculates a center frequency as a tracking point from a maximum value and a minimum value of the reference point frequency detected based on different algorithms. apparatus. 13. The method according to claim 11, wherein the predetermined calculation calculates an average frequency of reference point frequencies detected based on different algorithms as a tracking point.
The described radar device. 14. The radar apparatus according to claim 11, wherein each of the plurality of reference point frequency detection circuits includes the Doppler tracking means according to claim 1.