JPH1138119A - Radar equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain radar equipment which can shorten the time required for establishing tracking by improving the establishment of target detection by lowering a detection threshold when a target detection is processed by means of an N-in-M detecting circuit or a CFAR(constant false alarm rate) detecting circuit and, at the same time, can prevent the deterioration of the maximum searching distance. SOLUTION: The deterioration of the maximum searching distance of data radar equipment is suppressed by shortening the time required by the equipment for establishing tracking near the maximum searching distance by inputting the output of a distance detecting circuit 1 to a distance comparator circuit 9 and, when the distance is larger than a certain distance, outputting the output of the circuit 1 to an N-in-M detecting circuit 6 by selecting a value which is smaller than the ordinary N value of the circuit 6 as the N value of the circuit 6, and then, performing target detecting processing by lowering the N-in-M detecting threshold of the circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of a target in a radar, and more particularly to detection near a maximum detection distance.

[0002]

2. Description of the Related Art FIG.
No. 5 discloses a similar technique, FFT (Fast Fo
urier Transform) circuit and CFAR (Constant False Alar)
1 shows a configuration of a conventional radar apparatus that performs a CFAR process and has a detection circuit.

In FIG. 15, 1 is a distance detection circuit for detecting the distance of an input signal, 2 is a Doppler filter circuit for dividing the output of the distance detection circuit 1 into frequencies, and 3 is an amplitude of the output of the Doppler filter circuit 3. An amplitude calculation circuit, 4 is a memory circuit for storing the output of the amplitude calculation circuit 3, 5 is a one-dimensional CFAR detection circuit, and 6 is an N-in-M detection that generates an output when there are N out of M corresponding signals. A circuit 7 is a target tracking circuit for performing target tracking establishment processing, and 8 is an indicator for displaying a detection target.

Next, the operation will be described. In FIG. 15, a distance detection circuit 1 is a circuit that samples an input signal at a certain timing and detects the distance of the input signal, that is, how long the input signal is a reflected wave signal from a target. This output signal is input to the Doppler filter circuit 2 and is converted into frequency data for each time data.

[0005] The output of the Doppler filter circuit 2 is input to an amplitude calculation circuit 3, the amplitude of each Doppler frequency is calculated, and the result is stored in a memory circuit 4. The output of the memory circuit 4 is input to the one-dimensional CFAR detection circuit 5 for each processing unit, and the target is detected by the CFAR processing.

The function and configuration of the one-dimensional CFAR detection circuit 5 will be described with reference to FIG. The memory circuit 4 has, for example, cells corresponding to the Doppler frequency. Here, (M + 1) cells from F ₀ to F _M are the target detection ranges, and F ₋₄ to F _{M + 4.}
Up to (M + 9) cells. The number of cells outside the target detection range depends on the number of cells when averaging is performed by the averaging circuit 21 described later.

The one-dimensional CFAR detection circuit 5 performs detection processing on cells from F ₀ to F _M , which is the target detection range.
FIG. 16 shows a case where the detection process is performed on F ₀ which is the lower limit of the target detection range. In this case, the corresponding cell F ₀
Near each side _{of, F 2, F 3, F} 4 and F _-2, F _-3, averaging circuit 21 with respect to F _-4 to calculate the average value. The reason why the adjacent cells F ₁ and F ₋₁ are not included in the average calculation is that the influence of the corresponding cell on the adjacent cell is large due to the characteristics of the Doppler filter circuit 2 in a normal Doppler filter. .

In this case, the number of averaging target cells is 3
Although an example of the number is shown, another number may be used. The average value output from the two averaging circuits 21 is the “large” selection circuit 22
The larger average is selected. The output of the "large" selection circuit 22 is multiplied by a constant greater than 1 by a multiplier 23 and input to a comparison detection circuit 24 as a target detection threshold (particularly a CFAR detection threshold).

The comparison detection circuit 24 compares the amplitude value of the corresponding cell F ₀ with the CFAR detection threshold input from the multiplier 23, and when the amplitude value of F ₀ is larger than the detection threshold, it is determined that the target is detected. Judge and output the amplitude value of the detection target.

That is, the one-dimensional CFAR detection circuit 5 detects that there is a target when the amplitude value of the corresponding cell is larger than the larger value of the average value on both sides by a constant number or more. Such a detection circuit is known as the Greatest of CFAR (G
reatest OF CFAR) detection circuit. As described above, the multiplier 23 multiplies a predetermined constant value regardless of target detection information (distance, speed, amplitude).

The output of the one-dimensional CFAR detection circuit 5 is input to an N-in-M detection circuit 6. The operation of the N-in-M detection circuit will be described with reference to FIG. The period from the start of transmission until the target detection processing is performed and the target is displayed on the indicator 8 is defined as the data rate. The data rate is composed of M processing units (burst 1 to burst M), CFAR processing is performed for each burst, and the target determined as a detection target in each burst period is the N-in-M detection circuit 6. Output to

The N-in-M detection circuit 6 performs a correlation process on a distance, a speed, and an amplitude between targets for each input burst. As a result of the correlation processing, when there are N or more targets determined to be correlated in the M bursts, they are output to the target tracking circuit 7 as detection targets.

Next, the target tracking process in the target tracking circuit 7 will be described with reference to FIGS. In FIG.
(a) shows the state of the signal from the target near the maximum detection distance (Rmax) where the target first appears in the detection area of the radar, and (b) shows the signal in an enlarged manner. The signal from the vicinity of the maximum detection distance has a very small level fluctuation, and is difficult to distinguish from noise.

FIG. 19A shows a target detection state in the normal target detection processing, and the maximum detection distance (R
In the vicinity of (max), it indicates that the target detection (○) is intermittent. This is because the received power from the target is near the noise level near the maximum detection distance, and the reflection cross-sectional area of the target fluctuates.
As described above, although the target detection is unstable, it can be detected from the maximum detection distance.

FIG. 19 (b) shows a target detection state in the tracking processing, and shows a state where the target detection is unstable as in the normal processing. However, the maximum detection distance when tracking process is t ₇ when compared to the normal processing maximum detection distance t ₁ at the time, has a time delayed t _6.

This is because a process is performed to determine that the detected target is a true target. In FIG. 19B, this period is defined as the tracking establishment processing period T1.
It is called. In this case, it is determined tracking established goal in 3 data rate (t ₅ ~t _7).

Next, the operation of the tracking establishment process will be described with reference to FIG. The output of the one-dimensional CFAR detection circuit 5 is
It is output to the target tracking circuit 7 according to the detection result of the N-in-M detection circuit 6. FIG. 20 is a diagram showing details of the target tracking circuit 7.

The detection target input to the target tracking circuit 7 is
The data is input to the detection target memory circuit 31, read out for each data rate update signal, and output to the correlation circuit 32. The correlation circuit 32 performs a correlation process of a distance and a speed on the detection target of the current data rate and the detection target of the previous data rate read from the detection target memory circuit 31. As a result, if there is a correlation, a correlation signal is output to the counter circuit 33.

The counter circuit 33 counts the input correlated signal, and counts the number to a predetermined reference value.
When this value matches (in the example of FIG. 19, this value is set to 3), a tracking establishment signal is output to the AND circuit 34. A
The ND circuit 34 outputs the detection target at the data rate at which the tracking establishment signal is input to the indicator 8.

Since the target tracking circuit 8 operates as described above, the detection target is a continuous data rate of several data rates (counter circuit 23).
It operates to output the detected target to the indicator 8 only when the correlation with the target of the previous data rate is established. For this reason, in the vicinity of the maximum detection distance where the target detection situation is unstable, the target detection often becomes discontinuous, so that the target tracking is not established, and the maximum detection distance is deteriorated as compared with the case without the target tracking.

[0021]

As described above, in the conventional radar device, in a situation where the detection of the target near the maximum detection distance is discontinuous, the tracking is not established and the detection of the target is delayed. There has been a problem that the distance is shorter than that without the target tracking.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an N-in-M detection circuit or CFAR
A radar device that lowers the detection threshold at the time of performing the target detection processing by the detection circuit near the maximum detection distance, thereby improving the target detection establishment, shortening the time required for tracking establishment, and preventing the maximum detection distance from deteriorating. The purpose is to obtain.

[0023]

SUMMARY OF THE INVENTION In view of the above-mentioned object, a first invention of the present invention provides a target tracking process in a radar, in which an input signal converted to frequency and distance factor data is converted for each time data. C to determine whether or not the target is a detection target from the correlation between the value of interest and a value in the vicinity thereof
Correlation processing in distance, speed, and amplitude is performed between the FAR detection means and the targets in the plurality of outputs from the CFAR detection means, and the number of targets determined to be correlated is M among N outputs.
An N-in-M detecting means for determining that the detection target is present when there are more than N, a target tracking means for performing a correlation process on the output from the N-in-M detecting means to determine that the correlation is continued; Detecting threshold changing means for changing a target detecting threshold in one of the CFAR detecting means and the N-in-M detecting means in accordance with the state of the target, and reducing a target detecting threshold near a maximum detection distance to reduce a tracking processing time. A radar apparatus characterized by being shortened.

According to a second aspect of the present invention, the target detection threshold is used as the M / N detection threshold when the target is detected by the M / N detection means, and the detection threshold changing means detects the M / N detection threshold. 2. The radar device according to claim 1, wherein the time required for establishing tracking near the maximum detection distance is reduced by changing the distance in accordance with the target distance.

According to a third aspect of the present invention, the target detection threshold is used as the N / M detection threshold when the target is detected by the M / N detection means, and the detection threshold changing means detects the N / M detection threshold. 2. The radar apparatus according to claim 1, wherein the time required for establishing the tracking near the maximum detection distance is reduced by changing the speed according to the speed of the target.

According to a fourth aspect of the present invention, the target detection threshold is used as the N / N detection threshold when the target is detected by the N / M detection means, and the detection threshold changing means detects the N / M detection threshold. By changing according to the received power of the signal indicating the target
2. The radar device according to claim 1, wherein a time required for establishing tracking near the maximum detection distance is reduced.

According to a fifth aspect of the present invention, there is provided the radar apparatus according to any one of claims 2 to 4, wherein the N-in-M detection threshold is a value of N in N-in-M.

According to a sixth aspect of the present invention, the CFAR detecting means comprises a two-dimensional CFAR detecting circuit for performing CFAR processing in the Doppler frequency direction and the distance direction, respectively. Or the radar device described in

A seventh aspect of the present invention is characterized in that the CFAR detecting means is of the Greatest of CFAR type which multiplies a larger one of the neighboring average values on both sides of a value of interest by a constant. A radar apparatus according to any one of claims 2 to 6.

An eighth invention of the present invention is characterized in that said CFAR detecting means is of a cell averaging CFAR system which multiplies an average of neighboring average values on both sides of a value of interest by a constant. Item 7. The radar device according to any one of Items 2 to 6.

According to a ninth aspect of the present invention, the above-mentioned target detection threshold is set at the time when the CFAR detecting means detects a target.
The time required for establishing tracking near the maximum detection distance is shortened by setting an AR detection threshold, wherein the detection threshold changing means changes the CFAR detection threshold in accordance with a detected target distance. Item 1. The radar device according to item 1.

[0032] In a tenth aspect of the present invention, the target detection threshold is set at C when the CFAR detector detects a target.
The time required for establishing a tracking near the maximum detection distance is reduced by changing the CFAR detection threshold according to the speed of the detected target by the detection threshold changing means as a FAR detection threshold. Item 1. The radar device according to item 1.

According to an eleventh aspect of the present invention, the target detection threshold is set such that the CFAR detecting means detects the CF when the target is detected.
An AR detection threshold, wherein the detection threshold changing means changes the CFAR detection threshold in accordance with the received power of a signal indicating the detected target,
2. The radar device according to claim 1, wherein a time required for establishing tracking near the maximum detection distance is reduced.

According to a twelfth aspect of the present invention, the above CFAR
The detection means comprises a two-dimensional CFAR detection circuit that performs CFAR processing in the Doppler frequency direction and the distance direction, respectively, and changes the CFAR detection thresholds in the Doppler frequency direction and the distance direction. The radar device according to any one of 9 to 11, wherein

According to a thirteenth aspect of the present invention, the CFAR
10. The method according to claim 9, wherein the detecting means is of the Greatest of CFAR type which multiplies a larger one of the neighboring average values on both sides of the value of interest by a multiplier, and the multiplier is the CFAR detection threshold. 13. The radar device according to any one of the above items 12.

A fourteenth aspect of the present invention provides the above-mentioned CFAR
13. A method according to claim 9, wherein said detecting means is of a cell averaging / CFAR system which multiplies an average of neighboring average values on both sides of a value of interest by a multiplier, and the multiplier is the CFAR detection threshold. The radar device according to any one of the above.

According to the present invention, in the vicinity of the maximum detection distance where the received power is susceptible to noise and fluctuations in the radar reflection cross section, the distance comparison circuit and the N coefficient selection circuit in M or the distance comparison circuit and the CFAR coefficient selection circuit The detection threshold changing means, which is a combination of
By lowering the value of N or the CFAR coefficient at the time of medium N detection, it is possible to shorten the tracking establishment time in the tracking processing of the detection target and minimize the deterioration of the maximum detection distance.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below according to each embodiment. Embodiment 1 FIG. FIG. 1 shows a radar apparatus according to an embodiment of the present invention. In the figure, reference numerals 1 to 8 are the same as those of a conventional radar apparatus. Reference numeral 9 denotes a distance comparison circuit, and reference numeral 10 denotes an N-in-M coefficient selection circuit, which constitute detection threshold changing means.

Although the basic operation of the radar apparatus shown in FIG. 1 is the same as that of the conventional apparatus, the output of the distance detection circuit 1 is output to the Doppler filter circuit 2 and the distance comparison circuit 9 in this radar apparatus. The distance comparison circuit 9 compares whether the detected target distance R is larger or smaller than the reference value x. If the distance is equal or larger, the "large" signal is used. Output to the selection circuit 10.

Here, it is desirable that the reference value x be set to a distance at which the received power is several dB higher than the noise level. When the “large” signal is input, the N-in-M coefficient selection circuit 10 selects a value smaller than the value of N in the normal N-in-M detection circuit 6 and outputs it to the N-in-M detection circuit 6. When a “small” signal is input, the normal N value of N in M is selected and output to the N in M detection circuit 6.

Due to the above operation, the detection threshold at the time of detecting the target, that is, N in M, near the maximum detection distance.
In order to lower the value of N of N in M, which is the detection threshold,
The target detection performance is improved. Therefore, the tracking establishment time in the processing of the target tracking circuit 7 is shortened, and the deterioration of the maximum detection distance can be minimized.

This situation will be described with reference to FIG. In the figure, T2 is a tracking establishment processing period, and T3 is a CFAR coefficient.
T4 represents a period in which (the value of N of N in M) is lower than the normal value, and T4 represents a period improved in comparison with the conventional tracking processing.

In (c) of FIG. 19, the value of N of M in M in the distance section from t ₁ to t ₃ is made lower than usual, whereby
This shows a situation in which the target is detected at t ₂ , t _3, and t ₄ that has not been detected in the normal processing. This gives t ₁
Since the target is continuously detected at four data rates from t to t ₄ , tracking is established, and the detected target is displayed from t ₃ (the tracking establishment period is set to three data rates. If you have). Thus a period of t ₃ ~t ₇ compared to normal tracking processing (= T4) is improved becomes detectable by the apparatus of this embodiment.

Embodiment 2 In the above embodiment,
N of N in M, which is the target detection threshold when N in M is detected
Is changed according to the target distance, but the same effect can be obtained by changing the value according to the target speed.

Hereinafter, such an embodiment will be described. FIG. 2 shows a radar device according to another embodiment of the present invention. In FIG. 2, the output of the Doppler filter circuit 2 is input to the speed comparison circuit 11. The speed comparison circuit 11 compares whether the detected target speed v is higher or lower than the reference value y, and selects the "large" signal if the speed is equal or higher, and selects the "small" signal if the speed is smaller than the reference value y. Output to the circuit 10.

When the “small” signal is input, the N-in-M coefficient selection circuit 10 selects a value smaller than the normal N-in-M value and outputs it to the N-in-M detection circuit 6. When the “large” signal is input, the normal N value of N in M is selected and output to the N in M detection circuit 6.

In general, when the approaching target approaching speed is slow, the target is more susceptible to the ambient conditions (wind speed and wind direction) than the target approaching at a high speed, and the reflection cross-sectional area of the target tends to change. For this reason, when the target approach speed is low, the target detection near the maximum detection distance becomes discontinuous, and it is difficult to establish tracking, and the maximum detection distance may be degraded. Therefore, when the target speed v becomes equal to or less than a certain reference value y, deterioration of the maximum detection distance with respect to a target having a low approaching speed is minimized by selecting an N value of N in M smaller than usual. It becomes possible.

Embodiment 3 Further, the same effect can be obtained by changing the value of N among N in M according to the reception power of the signal indicating the target, that is, the amplitude of the signal.

Hereinafter, such an embodiment will be described. FIG. 3 shows a radar device according to another embodiment of the present invention. In FIG. 3, the output of the amplitude calculation circuit 3 is input to the amplitude comparison circuit 12. The amplitude comparison circuit 12 compares whether the amplitude (reception power) Pr of the signal indicating the detected target is larger or smaller than the reference value z. ”Signal to the N-in-M coefficient selection circuit 10.

When the "small" signal is input, the N-in-M coefficient selection circuit 10 selects a value smaller than the normal N-in-M value and outputs it to the N-in-M detection circuit 6. When the “large” signal is input, the normal N value of N in M is selected and output to the N in M detection circuit 6.

In the vicinity of the maximum detection distance, since the amplitude of the signal indicating the target is small, the signal is easily affected by noise, and the detection of the target is likely to be discontinuous. Therefore, when the amplitude Pr of the signal indicating the detection target becomes smaller than the reference value z, it is possible to minimize the deterioration of the maximum detection distance by selecting the value of N of N in M smaller than usual. it can.

Embodiment 4 FIG. In the above-described embodiment, the one-dimensional CFAR detection circuit that performs the CFAR detection processing only in the Doppler frequency direction is described. However, the two-dimensional CFAR that performs the CFAR detection processing in the distance direction in addition to the Doppler frequency direction is described. The present invention can be applied to a device provided with a detection circuit and has the same effect.

Hereinafter, such an embodiment will be described. FIG. 4 shows a radar apparatus according to another embodiment of the present invention, in which a two-dimensional CFAR detection circuit is used in the apparatus of the first embodiment in which the value of N in M changes according to the distance. In FIG. 4, the two-dimensional CFAR detection circuit 15 has C in both the Doppler frequency direction and the distance direction.
This is a circuit for performing FAR detection processing.

FIG. 5 shows the configuration of the memory circuit 4a and the two-dimensional CFAR detection circuit 15, and the operation will be described accordingly. The memory circuit 4a includes not only data cells F- ₄ to FM _{+ 4} in the Doppler frequency direction but also data cells R- _{4 in the} distance direction.
To RM _{+ 4} for storing data. The two-dimensional CFAR detection circuit 15 uses the one-dimensional C
One set of two averaging circuits 21, a "large" selection circuit 22, a multiplier 23, and a comparison detection circuit 24 of the FAR detection circuit 5 are separately provided, and an AND circuit 25 for ANDing the outputs of the two comparison detection circuits 24 is provided. .

Then, the CFAR detection processing in the Doppler velocity direction is performed at a certain distance, the CFAR detection processing in the distance direction is performed at a certain Doppler frequency, and the output result coincides with the Doppler frequency direction in the distance direction. Operates as a target.

FIGS. 6 and 7 show the two-dimensional CFAR detection circuit 15 in each of the second and third embodiments in which the value of N in M is changed according to the speed and amplitude (reception power). Is shown.

Embodiment 5 Further, in each of the above embodiments, the one-dimensional CFAR detection circuit 5 and the two-dimensional CFAR detection circuit 15 detect the presence of the target when the amplitude value of the corresponding cell is larger than the larger value of the average value on both sides by more than a constant. Test of CFAR (Greatest OF CFAR)
The case where the detection circuit is used has been described, but when the amplitude value of the corresponding cell is larger than the average value of the both-sides neighboring average value by a constant or more, the cell averaging / detection that detects the presence of the target is performed.
The present invention is also applicable to a case where a CFAR (Cell Averaging CFAR) detection circuit is used.

FIG. 8 shows, as an example, a two-dimensional CFAR detecting circuit 15a and a memory circuit 4a in the case of a two-dimensional CFAR detecting circuit 15a for cell averaging and CFAR.
And the configuration shown. In the two-dimensional CFAR detecting circuit 15a of the cell averaging / CFAR, a part of the “large” selecting circuit 22 of the two-dimensional CFAR detecting circuit 15 of the Greatest of CFAR shown in FIG.

Embodiment 6 FIG. In the above embodiments, the N detection threshold in M, that is, the value of N of N in M is changed as the target detection threshold, but the CFAR detection threshold, that is, the multiplier at the time of CFAR detection may be changed. Hereinafter, such an embodiment will be described.

FIG. 9 shows a radar apparatus according to another embodiment of the present invention. In FIG. 9, reference numerals 1 to 8 are the same as those of the conventional radar apparatus. 9 is a distance comparison circuit, and 13 is a CFAR coefficient selection circuit.

The basic operation of the radar apparatus shown in FIG. 9 is the same as that of the conventional apparatus. In this radar apparatus, the output of the distance detection circuit 1 is output to the Doppler filter circuit 2 and the distance comparison circuit 9. The distance comparison circuit 9 compares whether the detected target distance R is larger or smaller than the reference value x.
Output to the coefficient selection circuit 13. Here, it is desirable that the reference value x be set to a distance where the received power is several dB higher than the noise level.

When the “large” signal is input, the CFAR coefficient selection circuit 13 selects a value smaller than a normal CFAR coefficient and outputs it to the one-dimensional CFAR detection circuit 5. When a "small" signal is input, a normal CFAR coefficient is selected and a one-dimensional CAR coefficient is selected.
Output to the FAR detection circuit 5.

The CFAR detection process differs from the conventional device in that the value by which the output of the "large" selection circuit 22 is multiplied by the multiplier 23 in FIG. 16 is not a fixed reference value. That is, the output of the CFAR coefficient selection circuit 13 is
When the signal is input to A of the multiplier 23 of the one-dimensional CFAR detection circuit 5 shown in FIG. 16 and a "large" signal is input, the multiplier of the multiplier 23 is a multiplication smaller than a normal multiplier (CFAR coefficient).
When a "small" signal is input, the multiplier of the multiplier 23 is a normal multiplier.

Since the above operation is performed, the CFAR detection threshold C at the time of target detection is set near the maximum detection distance.
Since the multiplier at the time of FAR detection is reduced, the target detection performance is improved. Therefore, the tracking establishment time in the processing of the target tracking circuit 7 is shortened, and the deterioration of the maximum detection distance can be minimized. This is shown in FIG.
Is basically the same as that described with reference to (c) of FIG.
The occurrence of an erroneous target can be suppressed as compared with changing the value of N in the medium N.

Embodiment 7 FIG. In the above embodiment,
CFAR which is the target detection threshold when detecting CFAR
Although the multiplier at the time of detection is changed according to the target distance, the same effect can be obtained by changing the multiplier according to the target speed.

Hereinafter, such an embodiment will be described. FIG. 10 shows a radar apparatus according to another embodiment of the present invention. In FIG. 10, the output of the Doppler filter circuit 2 is input to the speed comparison circuit 11. Speed comparison circuit 1
In step 1, the detected target velocity v is compared with the reference value y to determine whether it is greater or less than the reference value y. I do.

In the CFAR coefficient selection circuit 13, when a "small" signal is input, the multiplier (CFAR) at the time of normal CFAR detection is used.
Select a multiplier with a value smaller than
Output to the detection circuit 5. When a “large” signal is input, a normal multiplier (CFAR coefficient) is selected and output to the one-dimensional CFAR detection circuit 5.

As described in the second embodiment, in general, when the approaching target approaching speed is low, the target is more easily affected by the surrounding conditions (wind speed and wind direction) than when the approaching target approaching speed is high. Is easy to change. For this reason,
When the target approach speed is low, the detection of the target near the maximum detection distance becomes discontinuous, and it is difficult to establish the tracking, and the maximum detection distance may be deteriorated. Therefore, when the target speed v becomes equal to or less than a certain reference value y, deterioration of the maximum detection distance with respect to a target having a low approach speed can be minimized by selecting a CFAR coefficient smaller than usual. Becomes

Embodiment 8 FIG. Further, the same effect can be obtained by changing the CFAR coefficient according to the reception power of the signal indicating the target, that is, the amplitude of the signal.

Hereinafter, such an embodiment will be described. FIG. 11 shows a radar device according to another embodiment of the present invention. In FIG. 11, the output of the amplitude calculation circuit 3 is
The signal is input to the amplitude comparison circuit 12. The amplitude comparison circuit 12 compares whether the amplitude (reception power) Pr of the signal indicating the detected target is larger or smaller than the reference value z. Is output to the CFAR coefficient selection circuit 13.

In the CFAR coefficient selection circuit 13, when a "small" signal is input, the multiplier (CFAR) at the time of normal CFAR detection is used.
Select a multiplier with a value smaller than
Output to the detection circuit 5. When a “large” signal is input, a normal multiplier (CFAR coefficient) is selected and output to the one-dimensional CFAR detection circuit 5.

As described in the third embodiment, near the maximum detection distance, the amplitude of the signal indicating the target is small, so that the signal is easily affected by noise, and the target detection is likely to be discontinuous. Therefore, when the amplitude Pr of the signal indicating the detection target becomes smaller than the reference value z, the CF smaller than the normal value is used.
By selecting the AR coefficient, the deterioration of the maximum detection distance can be minimized.

Embodiment 9 In the above-described embodiment, the one-dimensional CFAR detection circuit that performs the CFAR detection processing only in the Doppler frequency direction is described. However, the two-dimensional CFAR that performs the CFAR detection processing in the distance direction in addition to the Doppler frequency direction is described. The present invention can be applied to an apparatus provided with a detection process, and has the same effect.

Hereinafter, such an embodiment will be described. FIG. 12 shows a radar apparatus according to another embodiment of the present invention. In the apparatus according to the sixth embodiment in which the value of the multiplier at the time of detecting the CFAR is changed depending on the distance, the two-dimensional CFA is used.
This uses an R detection circuit. In FIG. 12, 2
The dimensional CFAR detection circuit 15 is a circuit that performs CFAR detection processing in both the Doppler frequency direction and the distance direction.

The configuration and operation of the memory circuit 4a and the two-dimensional CFAR detection circuit 15 have been described in the fourth embodiment with reference to FIG. 5, but in the case of this embodiment,
The outputs of the CFAR coefficient selection circuit 13 are A1 and A2 of the two multipliers 23 of the two-dimensional CFAR detection circuit 15 shown in FIG.
, And the multiplier of the multiplier 23 is a “large” signal,
It is changed according to the "small" signal.

FIGS. 13 and 14 show speed and amplitude.
In the apparatus according to each of the seventh and eighth embodiments, the two-dimensional CFAR detection circuit 15 is similarly used in each of the apparatuses according to the seventh and eighth embodiments in which the multiplier at the time of CFAR detection is changed by (reception power).

Embodiment 10 FIG. Embodiment 6
9, the one-dimensional CFAR detection circuit 5 and the two-dimensional CF
The AR detection circuit 15 detects the presence of a target when the amplitude value of the corresponding cell is larger than the larger value of the average value on both sides by a constant multiple or more.
Although the case of using a CFAR) detection circuit has been described, when the amplitude value of the relevant cell is larger than the average value of the average value on both sides by a constant multiple or more, it detects that there is a target.Cell averaging The present invention can be applied to a case where the circuit is used.

Cell averaging CFAR (Cell Av
eraging CFAR) detection circuit in Embodiment 5 in FIG.
2D CF of cell averaging and CFAR shown in
The description is given by taking the AR detection circuit 15a as an example. In this embodiment, in order to change the CFAR coefficient,
The outputs of the CFAR coefficient selection circuit 13 of the sixth to ninth embodiments (see FIGS. 9 to 14) are input to A1 and A2 of the two multipliers 23 of the two-dimensional CFAR detection circuit 15a shown in FIG. The multiplier of the unit 23 is changed according to the "large" signal and the "small" signal.

[0079]

As described above, according to the first aspect of the present invention, in the target tracking processing in the radar, the value of interest of the input signal converted into frequency and distance factor data for each time data is set. CFAR detecting means for determining whether or not the target is a detection target based on a correlation with a value in the vicinity thereof, and correlation processing in distance, speed, and amplitude between targets in a plurality of outputs from the CFAR detecting means. An N-in-M detecting means for determining that a target determined to be correlated is a detection target when there are N or more of the outputs in the M outputs;
A target tracking means for performing a correlation process on the output from the N-in-M detecting means to determine that the correlation is continued; and a target detecting means in one of the CFAR detecting means and the N-in-M detecting means according to the target situation. And a detection threshold changing means for changing the threshold, whereby a target detection threshold in the vicinity of the maximum detection distance is lowered to shorten the tracking processing time, and it is possible to provide a radar apparatus capable of suppressing deterioration of the maximum detection distance. Can be

In the second invention of the present invention, the target detection threshold is set as the N / M detection threshold when the target is detected by the N / M detection means, and the detection threshold changing means detects the N / M detection threshold. By changing the distance in accordance with the distance of the target, it is possible to obtain an effect such as providing a radar apparatus in which the time required for tracking establishment near the maximum detection distance is reduced.

In the third invention of the present invention, the target detection threshold is set as the N / M detection threshold when the target is detected by the M / N detection means, and the detection threshold changing means detects the M / N detection threshold. By changing the speed in accordance with the speed of the target, it is possible to obtain an effect such as providing a radar device in which the time required for tracking establishment near the maximum detection distance is reduced.

In the fourth invention of the present invention, the target detection threshold is set as the N / M detection threshold when the target is detected by the N / M detection means, and the detection threshold changing means detects the N / M detection threshold. By changing the power in accordance with the received power of the signal indicating the target, an effect such as providing a radar device in which the time required for tracking establishment near the maximum detection distance is reduced can be obtained.

According to a fifth aspect of the present invention, there is provided a radar apparatus in which the above-described N-in-M detection threshold is set to the value of N in N-in-M, and the time required for establishing tracking near the maximum detection distance is shortened by changing the threshold. The effect of being able to provide is obtained.

In the sixth aspect of the present invention, the above CFAR
Even in a radar device including a two-dimensional CFAR detection circuit in which the detection means performs the CFAR process in the Doppler frequency direction and the distance direction, the time required for establishing tracking near the maximum detection distance can be reduced.

In the seventh aspect of the present invention, the above CFAR
Even in a radar apparatus of the Greatest of CFAR system in which the detecting means multiplies a constant by the larger one of the neighboring average values on both sides of the value of interest, the time required to establish tracking near the maximum detection distance is reduced. be able to.

In the eighth aspect of the present invention, the above CFAR
Even in a radar device of the cell averaging / CFAR system in which the detection means multiplies the average of the neighboring average values on both sides of the value of interest by a constant, the time required to establish tracking near the maximum detection distance is reduced. Can be.

According to a ninth aspect of the present invention, the target detection threshold is set to a value of C when the CFAR detection means detects a target.
By setting the FAR detection threshold, the detection threshold changing means changes the CFAR detection threshold in accordance with the detected target distance, thereby shortening the time required to establish tracking near the maximum detection distance and generating an erroneous target. The effect that a radar device with less number can be provided can be obtained.

According to a tenth aspect of the present invention, the target detection threshold is a CFAR detection threshold at the time of target detection by the CFAR detection means, and the detection threshold changing means responds to a target speed at which the CFAR detection threshold is detected. By doing so, it is possible to obtain effects such as shortening the time required to establish tracking near the maximum detection distance and providing a radar apparatus with less occurrence of erroneous targets.

In the eleventh aspect of the present invention, the target detection threshold is set at a value of C when the CFAR detection means target is detected.
By setting the FAR detection threshold, the detection threshold changing means changes the CFAR detection threshold in accordance with the received power of the signal indicating the detected target, thereby reducing the time required for establishing tracking near the maximum detection distance, Advantages such as providing a radar apparatus with less occurrence of erroneous targets can be obtained.

In the twelfth aspect of the present invention, the CFA
The R detection means is composed of a two-dimensional CFAR detection circuit that performs CFAR processing in the Doppler frequency direction and the distance direction, and changes the CFAR detection thresholds in the Doppler frequency direction and the distance direction. The effects of shortening the time required for tracking establishment near the distance and providing a radar apparatus with less occurrence of erroneous targets can be obtained.

In the thirteenth aspect of the present invention, the CFA
The R detection means is of the Greatest of CFAR type which multiplies a larger one of the neighboring average values on both sides of a value of interest by a multiplier. The multiplier is used as the CFAR detection threshold, and the maximum detection is performed by changing the threshold. The effects such as the ability to provide a radar device in which the time required for establishing tracking near the distance is reduced can be obtained.

In the fourteenth aspect of the present invention, the CFA
The R detecting means is of a cell averaging CFAR system for multiplying an average of neighboring average values on both sides of a value of interest by a multiplier. The multiplier is used as the CFAR detection threshold, and by changing the threshold, the maximum detection distance The effect of being able to provide a radar device in which the time required to establish tracking in the vicinity is reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a radar device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram of a radar device according to Embodiment 2 of the present invention.

FIG. 3 is a block diagram of a radar device according to Embodiment 3 of the present invention.

FIG. 4 is a block diagram of a radar device according to Embodiment 4 of the present invention.

FIG. 5 is a diagram illustrating a memory circuit and a two-dimensional CFAR of a Greatest of CFAR system according to a fourth embodiment of the present invention;
FIG. 3 is a diagram illustrating a configuration of a detection circuit.

FIG. 6 is a block diagram showing an example of a radar device according to Embodiment 4 of the present invention.

FIG. 7 is a block diagram showing another example of a radar device according to Embodiment 4 of the present invention.

FIG. 8 shows a memory circuit and a cell-averaging-CFAR two-dimensional CFA according to a fifth embodiment of the present invention;
FIG. 3 is a diagram illustrating a configuration of an R detection circuit.

FIG. 9 is a block diagram of a radar device according to Embodiment 6 of the present invention.

FIG. 10 is a block diagram of a radar apparatus according to Embodiment 7 of the present invention.

FIG. 11 is a block diagram of a radar apparatus according to Embodiment 8 of the present invention.

FIG. 12 is a block diagram showing an example of a radar device according to Embodiment 9 of the present invention.

FIG. 13 is a block diagram showing another example of a radar device according to Embodiment 9 of the present invention.

FIG. 14 shows a cell averaging / CFAR method 2 used in the radar apparatus according to Embodiment 9 of the present invention.
FIG. 3 is a diagram illustrating a configuration of a dimensional CFAR detection circuit and a memory circuit.

FIG. 15 is a block diagram of a conventional radar device.

FIG. 16: Memory circuit and Greatest of CFA
FIG. 3 is a diagram illustrating a configuration of an R-type one-dimensional CFAR detection circuit.

FIG. 17 is a block diagram illustrating an N-in-M detection circuit.

FIG. 18 is a diagram for explaining target received power fluctuation.

FIG. 19 is a diagram for explaining the operation of tracking establishment processing.

FIG. 20 is a block diagram illustrating a configuration of a target tracking circuit.

[Explanation of symbols]

1 distance detection circuit, 2 Doppler filter circuit, 3 amplitude calculation circuit, 4, 4a memory circuit, 5 one-dimensional CFAR
Detection circuit, 6M N detection circuit, 7 Target tracking circuit, 8
Indicator, 9 distance comparison circuit, 10M N coefficient selection circuit, 11 speed comparison circuit, 12 amplitude comparison circuit, 15,
15a Two-dimensional CFAR detection circuit, 21, 26 averaging circuit.

Claims (14)

[Claims] 1. In a target tracking process in a radar,
CFAR for determining whether or not the input signal converted into data of frequency and distance factors for each time data is a detection target from a correlation between a focused value and a value in the vicinity thereof
Correlation processing in distance, speed, and amplitude is performed between the detection means and the targets in the plurality of outputs from the CFAR detection means, and there are N or more targets out of the M outputs determined to have correlation. An N-in-M detecting means that is sometimes determined to be a detection target; a target tracking means that performs a correlation process on the output from the N-in-M detecting means to determine that the correlation is continued; Detecting threshold changing means for changing the target detecting threshold in one of the CFAR detecting means and the N-in-M detecting means, wherein the target detecting threshold near the maximum detection distance is lowered to shorten the tracking processing time. Radar equipment. 2. The method according to claim 2, wherein the target detection threshold is set to N out of M.
The detection threshold changing means sets the N-in-M detection threshold at the time of target detection, and the detection threshold changing means changes the N-in-M detection threshold in accordance with the detected target distance, thereby establishing tracking near the maximum detection distance. The radar device according to claim 1, wherein a required time is shortened. 3. The method according to claim 1, wherein the target detection threshold is set to N in M.
The detection means sets an N-in-M detection threshold at the time of detecting a target, and the detection threshold changing means changes the N-in-M detection threshold in accordance with the speed of the detected target to establish tracking near the maximum detection distance. The radar device according to claim 1, wherein a required time is shortened. 4. The method according to claim 1, wherein the target detection threshold is set to N out of M
The detection threshold changing means changes the N-in-M detection threshold in accordance with the received power of a signal indicating the detected target, thereby detecting the vicinity of the maximum detection distance. 2. The radar device according to claim 1, wherein a time required for establishing tracking in the device is reduced. 5. The radar apparatus according to claim 2, wherein the N-in-M detection threshold is a value of N in N-in-M. 6. The radar apparatus according to claim 2, wherein said CFAR detection means comprises a two-dimensional CFAR detection circuit that performs CFAR processing in a Doppler frequency direction and a distance direction, respectively. 7. The CFAR detecting means according to claim 2, wherein said CFAR detecting means is of the GREATEST OF CFAR type which multiplies a larger value of a neighborhood average value on both sides of a value of interest by a constant. A radar device according to any of the above. 8. The CFAR detecting means according to claim 2, wherein the CFAR detecting means is of a cell averaging / CFAR system which multiplies a constant by an average of neighboring averages on both sides of a value of interest. A radar device according to item 1. 9. The method according to claim 6, wherein the target detection threshold is set to the CFA.
The detection threshold changing means changes the CFAR detection threshold according to the distance of the detected target as the CFAR detection threshold at the time of detecting the target of the R detection means, so that the time required to establish tracking near the maximum detection distance is obtained. The radar device according to claim 1, wherein the radar device is shortened. 10. The target detection threshold is set to the CF
The time required for tracking establishment near the maximum detection distance is obtained by setting the CFAR detection threshold at the time of target detection of the AR detection means and changing the CFAR detection threshold according to the speed of the detected target by the detection threshold changing means. The radar device according to claim 1, wherein the radar device is shortened. 11. The method according to claim 11, wherein the target detection threshold is set to the CF.
The AR detection means sets a CFAR detection threshold at the time of target detection, and the detection threshold changing means changes the CFAR detection threshold according to the received power of a signal indicating the detected target, thereby achieving tracking in the vicinity of the maximum detection distance. The radar device according to claim 1, wherein a required time is shortened. 12. The CFAR detection means comprises a two-dimensional CFAR detection circuit that performs CFAR processing in the Doppler frequency direction and the distance direction, respectively, and changes the CFAR detection thresholds in the Doppler frequency direction and the distance direction. The radar device according to any one of claims 9 to 11, wherein: 13. The CFAR detection means is of the Greatest of CFAR system in which a larger one of the average values on both sides of a value of interest is multiplied by a multiplier, and the multiplier is used as the CFAR detection threshold. 13. The radar device according to claim 9, wherein 14. The CFAR detecting means is of a cell averaging / CFAR system which multiplies an average of neighboring average values on both sides of a value of interest by a multiplier.
13. The radar device according to claim 9, wherein a FAR detection threshold is set.