JP2001116832A - Fm-cw radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous detection caused by a side lobe from being generated even when a main beam width is narrowed. SOLUTION: This FM-CW radar system for gaining a body information based on a beat signal provided by using a frequency-modulated continuous wave signal as a transmission signal to mix the transmission signal with a received signal is provided with a level distribution preparing means for preparing a level distribution classified by beat frequencies using a scanning angle as a parameter as to the beat signals, a level distribution correcting means for estimating an antenna beam pattern using a peak value of the level distribution classified by the beat frequencied as a peak value of a main lobe, and for removing a side lobe pattern thereof from the level distribution to conduct distribution correction, and a computing means for calculating the body information based on the scanning angle indicated by a level peak of the level distribution classified by the beat frequencies corrected by the level distribution correcting means and based on its beat frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM-C using a transmission signal obtained by applying frequency modulation (FM) to a continuous wave (CW).
It relates to a W radar device.

[0002]

2. Description of the Related Art An FM-CW radar apparatus is suitable for detecting an object at a relatively short distance as compared with a pulse radar.
Therefore, in recent years, research and development as means for detecting the position and relative speed of a preceding vehicle mounted on the vehicle have been promoted.

An FM-CW radar device suitable for this type of detection means is disclosed in Japanese Patent Application Laid-Open No. H11-133142.

The FM-CW radar device has an array antenna including a plurality of element antennas as a receiving antenna, and generates and scans a radar beam by a digital beam forming (DBF) technique. As described above, in this conventional apparatus, since the DBF technique is used for beam scanning, there is no need for a mechanical beam scanning mechanism, and there is an advantage that the apparatus is resistant to vibration.

[0005]

The beam width of the main lobe in the antenna beam pattern is desirably as narrow as possible in order to improve the azimuth separation accuracy, and the level of the side lobe is as low as possible to prevent erroneous detection. I want to suppress.

However, narrowing the beam width of the main lobe and lowering the level of the side lobe are generally contradictory and difficult to achieve both.

This will be described with reference to the case of the above-mentioned prior art, which is an FM-CW radar apparatus and a DBF radar apparatus.

[0008] The DBF radar device is an radar device having an array antenna composed of a plurality of element antennas as a receiving antenna, and performing generation and scanning of a radar beam by digital beam forming (DBF) technology.

In the case of a DBF radar device, the beam pattern can be changed by adjusting the amplitude distribution for each element antenna. When beam combining is performed using a uniform distribution in which the weights of the amplitudes of the element antennas are made uniform, the main lobe width can be reduced as compared with the case where other amplitude distributions are used, but the side lobe level increases. I will. That is, although the azimuth separation accuracy can be increased, erroneous detection due to side lobes is likely to occur.

On the other hand, beam combining is performed using a taper distribution or a cosine square distribution in which the amplitude of an element antenna located at the center of the array antenna is increased, and the amplitude is reduced toward element antennas located on both sides. Then, the level of the side lobe can be lowered, but the width of the main lobe becomes large. In this case, although erroneous detection due to side lobes is reduced, azimuth separation accuracy is reduced.

As described above, in the conventional apparatus, it has been difficult to achieve both suppression of erroneous detection and improvement of azimuth separation accuracy.

[0012]

SUMMARY OF THE INVENTION An FM-CW radar apparatus according to the present invention has been made in order to solve such a problem, and uses a continuous wave signal subjected to frequency modulation as a transmission signal and a reception signal. Level generating means for generating a beat frequency-specific level distribution using a scanning angle as a parameter for a beat signal in an FM-CW radar apparatus for obtaining object information based on a beat signal obtained by mixing a transmission signal with respect to the beat signal A level distribution correcting means for estimating an antenna beam pattern having a peak value of a level distribution according to beat frequency as a peak value of a main lobe and correcting a distribution by removing a side lobe pattern from the level distribution; Scan angle and beat frequency indicated by the level peak of the level distribution for each beat frequency corrected by the correction means Characterized by comprising a calculating means for calculating the object information from the.

When there are a plurality of targets having the same distance and the same speed, the beat frequency level distribution obtained by the level distribution creating means is obtained by superposing the beat frequency level distributions of the respective targets.

The shape of the level distribution for each beat frequency for each target is theoretically the same as the antenna pattern, and side lobes are formed on both sides of the main lobe. Therefore, when such a beat frequency-based level distribution is superimposed on a plurality of targets, a complex distribution shape is obtained, and a peak of a distribution due to a main lobe is extracted from the beat frequency-based level distribution obtained by the level distribution creating means. Is difficult.

For example, when there are a plurality of targets having different reflectivities, the beat frequency level distribution for a target having a low reflectivity is buried in the beat frequency level distribution for a target having a high reflectivity.
It becomes difficult to detect a target having a low reflectance.

Therefore, the level distribution correcting means performs correction for removing the side lobe pattern from the level distribution for each beat frequency. Since the influence of the side lobe is reduced in the corrected beat frequency-specific level distribution, the peak of the level distribution is mainly caused by the main lobe. Therefore, if the azimuth separation accuracy is sufficiently high, even if there are a plurality of targets having different reflectances, the peak of the level distribution based on both targets can be correctly detected.

The calculating means calculates the object information for the corrected beat frequency level distribution from the scanning angle indicated by the peak and the beat frequency of the level distribution.

As described above, in the level distribution correcting means, the one corresponding to the side lobe is removed from the level distribution for each beat frequency obtained by the level distribution creating means, so that the main beam width is narrow in order to increase the azimuth separation accuracy. Even if the antenna beam pattern is used and the side lobe level is increased, erroneous detection due to the side lobe does not occur.

That is, it is possible to achieve both high azimuth separation accuracy and suppression of erroneous detection caused by side lobes.

Preferably, the level distribution correcting means estimates an antenna beam pattern having the maximum peak value of the level distribution as the peak value of the main lobe, and removes the side lobe pattern from the level distribution.

One of the targets having the highest reflectance exists in the direction indicated by the maximum peak value of the level distribution. That is, an antenna beam pattern having the maximum peak value as the peak value of the main lobe is superimposed on the level distribution. Therefore, the antenna beam pattern is estimated,
If the side lobe pattern is removed from the level distribution, a level distribution based on another target clearly appears. Therefore, according to the corrected level distribution, it is clear that another target exists in the direction indicated by the second highest peak value.

Preferably, the level distribution correction means performs distribution correction on the level distribution corrected by itself. In particular, by estimating an antenna beam pattern in which a peak value in a direction different from the previously estimated antenna beam pattern is the peak value of the main lobe, and performing distribution correction for removing the side lobe pattern from the level distribution, a plurality of targets can be obtained. Can remove the influence of the side lobe caused by the above, so that the detection accuracy is further improved.

When the receiving antenna is an array antenna composed of a plurality of element antennas, and the formation and scanning of the antenna beam pattern are performed by digital beam forming calculation processing, the amplitude distribution for each element antenna is adjusted. The beam width of the main lobe can be reduced. When the beam width of the main lobe is reduced, the side lobe level is increased. However, since the influence of the side lobe is removed by the level distribution correcting means, no erroneous detection occurs.

[0024]

FIG. 1 is a block diagram showing a configuration of an FM-CW radar apparatus according to an embodiment of the present invention. This FM-CW radar device is also a DBF radar device that forms and scans an antenna beam by digital signal processing.

The receiving array antenna 1 has eight element antennas corresponding to each receiving channel. Each element antenna is connected to a corresponding one of the mixers 11-0 to 11-11 via an individual isolator constituting the isolator group 12.
-7.

The mixers 11-0 to 11-7 mix a part of the transmission signal with the reception signal arriving at each element antenna to obtain a beat signal. Mixer 11-0
A transmission signal component provided as a local signal to 11-7 is supplied from a voltage controlled oscillator (VCO) 14 to a branch circuit 15
And an isolator group 13.

The oscillator 14 is a varactor-controlled gun oscillator having a center frequency of f0 (for example, 60 GHz), and is controlled to f0 ± (1/2) ΔF by a control voltage output from a triangular wave generating circuit 22 for modulation. Outputs modulated wave. The FM modulation here is a triangular wave modulation in which a frequency increasing section (up section) and a frequency decreasing section (down section) are alternately continuous, and the frequency is f0−
It increases linearly from (1/2) ΔF to f0 + (1/2) ΔF, and the frequency is linear from f0 + (1/2) ΔF to f0− (1/2) ΔF in the down section within the same time as the up section. To decrease.

This FM modulated wave is supplied to the transmitting antenna 21 via the branching circuit 15 and is radiated as a transmission signal. As described above, the FM modulated wave is branched into eight channels as local signals, and each of the mixers 11-0 to 11-0 is transmitted. At 11-7, the received signals are mixed with the received signals of eight channels to generate beat signals for respective channels. The triangular wave generation circuit 2
2 periodically changes the output voltage value in a triangular waveform.

Mixer group 11, isolator group 12, 1
3, a low-noise amplifier 24, a high-speed A / D converter 25, a signal processing unit 26, and a complex FFT operation unit 27 are provided downstream of the high-frequency circuit 10 including the VCO 14 and the branch circuit 15.

The low noise amplifier (amplifier) 24 is a mixer 1
This is to amplify the 8-channel beat signals output from 1-0 to 11-7 in parallel. The amplifier 24
Has a cutoff frequency of 77 for anti-aliasing.
A low-pass filter of kHz is built in.

The high-speed A / D converter 25 is a circuit that performs A / D conversion of each of the eight-channel beat signals in parallel and simultaneously, and performs sampling at 200 kHz. At this sampling frequency, sampling is performed at 128 points in each of the up section and the down section of the triangular wave in the FM modulation. A trigger signal for starting sampling in each section is provided from the triangular wave generation circuit 22.

The signal processing unit 26 includes a high-speed A / D converter 25
, A digital beat signal for each channel is obtained, and various signal processes are performed according to the flowchart shown in FIG. 2 to perform a target (target) recognition process.

The complex FFT operation unit 27 includes a signal processing unit 26
Is a computing unit that executes the complex FFT operation in the series of processes in the processing of FIG.
The T operation is performed, and the result is returned to the signal processing unit 26.

Next, the operation procedure of the present apparatus will be described with reference to the flowchart shown in FIG.

First, in step S11, the beat signal for each channel is A / D-converted and taken into an internal memory as a digital beat signal for each channel. This A / D conversion is performed at 128 sampling points in each of the up section and the down section. Therefore, data of 128 (points) × 2 (section) × 8 (channels) = 2048 points is taken in total.

In the following step S13, FFT (Fast Fourier Transform processing) is executed for each channel based on the fetched data (digital beat signal for each channel) to obtain beat frequency information. All the beat frequency information obtained here is stored in the storage unit in the signal processing unit 26. Note that the beat frequency information for each channel includes phase information necessary for the subsequent DBF processing.

In step S15, it is determined whether or not various processes to be executed thereafter are for up section data or down section data. If the determination is affirmative, that is, if the subsequent processing is for the up-section data, the process proceeds to step S17, where the beat frequency information of the up-section stored in step S13 is read and prepared for the subsequent DBF processing. . If a negative determination is made in step S15, the process proceeds to step S19,
The beat frequency information of the down section stored in step 13 is read to prepare for the subsequent DBF processing.

In step S21, a DBF process is performed based on the beat frequency information. That is, the beat frequency information is subjected to phase rotation by digital signal processing according to the scanning angle direction for each channel, and one scanning angle is obtained by dividing -10 degrees to +10 degrees in 41 directions at intervals of 0.5 degrees. The beam is formed so that the main lobe is oriented in the direction. Then, beat signal level information using the beat frequency for each scanning angle as a variable is obtained.

In the beam formation and the acquisition of beat signal level information for each scanning angle, the beam forming is completed in the entire scanning range, that is, in all directions (41 directions) in step S23 while changing the scanning angle direction by 0.5 degrees. It is repeatedly executed until it is determined that the operation has been performed.

In the following step S25, in step S21
The same beat frequencies are grouped from each other based on the beat signal level information in all directions acquired in step (1), and a level distribution is created using the scan angle for each beat frequency as a parameter.
A plurality of beat frequencies for grouping are selected at appropriate frequency intervals according to the target to be detected.

If the target corresponding to the beat frequency is single, the level distribution for each beat frequency created here is the antenna beam pattern corresponding to the amplitude distribution determined at the time of the DBF processing in step S21. It has a shape similar to.

When there are a plurality of targets having the same beat frequency, a level distribution for each beat frequency corresponding to each target is superimposed.

FIG. 3 shows an example of an antenna beam pattern when the amplitude distribution is a uniform distribution. In this example, side lobes 31 and 32 each having three peaks are formed on both sides of the main lobe 30. Incidentally, when the amplitude distribution is changed to a taper distribution or a cosine square distribution, an antenna beam pattern as shown in FIG. 4 is obtained, the main lobe width is widened, and the side lobe level is low.

FIGS. 5 and 6 show examples of beat frequency-specific level distributions for one target when the antenna beam pattern is as shown in FIG. FIG. 5 is a beat frequency-based level distribution based on a received signal from the first target having a high reflectance in the direction of the scanning angle θ1,
FIG. 6 is a beat frequency-based level distribution based on a reception signal from a second target having a low reflectance in the direction of the scanning angle θ2.

FIG. 7 shows a beat frequency level distribution based on the received signals obtained from both the first and second targets. The beat frequency level distributions shown in FIGS. 5 and 6 are superimposed.

Assuming that the beat frequency level distribution shown in FIG. 7 is one of the beat frequency level distributions obtained in step S25, the side lobe removal correction processing performed in steps S27 to S37 will be described. Here, the value of the beat frequency in the level distribution for each beat frequency shown in FIG. 7 is “F” here.

It is preferable that the side lobe removal correction is performed a plurality of times for one beat frequency level distribution. Here, the number of executions N is 2.

In step S27, first, n = 1 is set. Here, n indicates the number of times the side lobe removal correction to be executed is the next processing, and n = 1 means the first correction processing.

In step S29, a peak having the n-th largest value is extracted from the level distribution for each beat frequency. Now, since n = 1, the first, that is, the peak of the maximum peak value is extracted. When there are a plurality of targets corresponding to the beat frequency, the direction indicated by this peak indicates one of the target directions.

Taking the level distribution of beat frequency "F" shown in FIG. 7 as an example, the peak 41 is the maximum peak, and the scanning angle θ1 indicates one azimuth of the target.

Subsequently, in step S31, step S
An antenna beam pattern in which the n-th peak value extracted in 29 is used as the main lobe peak value is estimated. Now, since n = 1, the antenna beam pattern with the maximum peak value as the main lobe peak value is estimated. FIG. 8 shows an antenna beam pattern estimated for the level distribution for each beat frequency in FIG. This antenna beam pattern has a distribution shape substantially the same as the level distribution for each beat frequency based on the first target shown in FIG.

Next, in step S33, side lobes are extracted from the antenna beam pattern estimated in step S31. FIG. 9 shows side lobes extracted from the estimated antenna beam pattern of FIG.

In step S35, a process of subtracting the side lobe extracted in step S33 from the level distribution for each beat frequency is performed, and 1 is added to n, and the result is set as a new n. Now, since n = 1, new n becomes n = n + 1 = 1 + 1 = 2. FIG. 10 shows the result of subtracting the side lobes of FIG. 9 from the level distribution for each beat frequency of FIG.

In step S37, it is determined whether or not n is greater than a preset number of correction processing times "N". Here, N = 2, and since n = 2, step S
The answer at 37 is NO, and the process returns to step S29.

In step S29, the n-th peak is extracted from the beat frequency level distribution corrected by the side lobe subtraction process in step S35. Now, since n = 2, the second peak is extracted. FIG.
Taking the level distribution for each beat frequency corrected once as shown in (1) as an example, the peak 42 is extracted.

Subsequently, in step S31, an antenna beam pattern in which the extracted peak value is used as the peak value of the main lobe is estimated as in the previous case. FIG.
7 shows an antenna beam pattern estimated for the second peak of the beat frequency-specific level distribution corrected once for zero. This antenna beam pattern corresponds to the second antenna pattern shown in FIG.
The distribution shape is almost the same as the level distribution for each beat frequency based on the target.

Then, in step S33, side lobes are extracted from the antenna beam pattern estimated in step S31. FIG. 12 shows side lobes extracted from the estimated antenna beam pattern of FIG.

In step S35, the side lobe is removed (subtracted) from the once-corrected frequency distribution for each beat frequency in FIG. 10, and n = n + 1 is executed. FIG. 13 shows the result of subtracting the side lobes of FIG. 12 from the beat frequency level distribution corrected once in FIG.

At this time, by executing n = n + 1, n = 2
Since + 1 = 3, the result in step S37 is affirmative. An affirmative determination in step S37 means that the correction process of the beat frequency-specific level distribution has been completed for the preset number N, and the process proceeds to step S39.

As a result of repeating the correction processing in steps S29 to S35 N times (here, twice), the level distribution for each beat frequency (refer to FIG. 7) for the beat frequency “F” shown as an example is shown in FIG. The level distribution for each beat frequency shown was corrected.

As is clear from the comparison between FIGS. 7 and 13, only the peaks corresponding to the two targets in the directions of θ1 and θ2 could be extracted by the correction processing.

In step S39, a peak is extracted in the beat frequency direction. That is, the beat frequency level distributions obtained for the frequencies at the predetermined intervals are arranged in the order of the beat frequency with the scanning angle being aligned, and the peak in the beat frequency direction is extracted. According to the above example, the scanning angles θ1 and θ2 have peaks at the beat frequency “F”.

In step S41, the above-described step S41 is executed.
It is determined whether a series of processes from 15 to S39 has been executed for both the up section and the down section. If the determination is negative, the process returns to step S15, and if the determination is positive, the process proceeds to step S43.

Returning from step S41 to step S15 means that a series of processes for DBF processing based on beat frequency data in the up section, correction of level distribution for each beat frequency, and extraction of peaks in the beat frequency direction are completed, and This is a case where these processes based on the beat frequency data of the section have not been executed yet.

In this case, the flow shifts to step S19 to read the beat frequency information of the down section calculated and stored in step S13, and the processing from step S21 to step S39 is executed based on the read data. Is done. Thereafter, when the process proceeds to step S41, the determination is affirmed, and the process proceeds to step S43.

In step S43, the level peak in the up section and the level peak in the down section are paired.
Pairing refers to combining level peaks estimated to be based on the same target.

The peaks in the up section and the down section based on the same target are both at the same scanning angle. Therefore, if there is a single peak in the beat frequency direction in both the up section and the down section for a certain scanning angle, the peaks may be paired. On the other hand, when there are a plurality of peaks in the beat frequency direction for a certain scan angle, pairs having similar peak levels are paired as an example of pairing. This is because the reflection level from the same target is substantially equal in both the up section and the down section.

When the pairing in step S43 is completed as described above, the process proceeds to step S45, and the distance and speed of the target are calculated by using the beat frequency of the paired level peak. This operation is FM-
This is based on the basic principle of a CW radar device.

Here, the detection principle of the FM-CW radar device will be briefly described just in case.

The center frequency of the transmission signal is f0, the frequency modulation width is ΔF, the FM modulation frequency is fm, and the beat frequency (beat frequency in a narrow sense) when the relative speed of the target is zero is fr, based on the relative speed. Assuming that the Doppler frequency is fd, the beat frequency in the up section is fb1, and the beat frequency in the down section is fb2, fb1 = fr-fd (1) fb2 = fr + fd (2) holds.

Therefore, if the beat frequencies fb1 and fb2 in the up and down sections of the modulation cycle are measured separately, fr and fd can be obtained from the following equations (3) and (4).

Fr = (fb1 + fb2) / 2 (3) fd = (fb2-fb1) / 2 (4) If fr and fd are obtained, the distance R and the velocity V of the target are calculated by the following (5) (6) ) Formula.

R = (C / (4 · ΔF · fm)) · fr (5) V = (C / (2 · f0)) · fd (6) where C is the speed of light.

In step S47, the target distance R and velocity V obtained in this manner are combined with past target information to detect the time-series movement of the target. Predict target types and future movements to perform more detailed target recognition.

It should be noted that step S25 in the present embodiment is used.
The level distribution for each beat frequency to be subjected to the sidelobe removal correction in step S39 is not limited to the level distribution for each beat frequency based on the beat frequency data obtained by beam scanning by DBF synthesis. For example, the present invention is also effective for beat frequency-based level distribution based on beat frequency data obtained by phased array type beam scanning or mechanical type beam scanning.

[0076]

As described above, according to the FM-CW radar apparatus of the present invention, the pattern estimated to be based on the side lobe of the antenna beam pattern is removed from the level distribution for each beat frequency. No erroneous detection is caused by the above.

In particular, an array antenna is used as a receiving antenna, and the formation and scanning of an antenna beam pattern are performed using a DBF.
In the case of the FM-CW radar device performed by the method described above, there is a problem that the side lobe level increases when an amplitude distribution that increases the azimuth separation accuracy is used.
According to the -CW radar apparatus, since the pattern based on the side lobe is removed from the level distribution for each beat frequency,
Even if the side lobe level increases, the probability of causing erroneous detection due to the side lobe can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an FM-CW radar device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation.

FIG. 3 shows an FM-CW radar apparatus according to the embodiment.
The figure which shows the antenna beam pattern when an amplitude distribution is made into a uniform distribution.

FIG. 4 shows an FM-CW radar apparatus according to the embodiment.
The figure which shows the antenna beam pattern when amplitude distribution is a taper distribution or a cosine square distribution.

FIG. 5 is a view showing a reflection signal pattern from a first target.

FIG. 6 is a diagram showing a reflection signal pattern from a second target.

FIG. 7 is a diagram showing a beat frequency-specific level distribution of a beat frequency “F”.

FIG. 8 is a diagram showing an antenna beam pattern estimated from the level distribution for each beat frequency in FIG. 7;

FIG. 9 is a diagram showing a side lobe pattern extracted from the antenna beam pattern of FIG. 8;

FIG. 10 is a diagram showing a corrected beat frequency-specific level distribution obtained by removing the side lobe pattern of FIG. 9 from the beat frequency-specific level distribution of FIG. 7;

11 is a diagram showing an antenna beam pattern estimated from the level distribution for each corrected beat frequency in FIG. 10;

FIG. 12 is a diagram showing a side lobe pattern extracted from the antenna beam pattern of FIG. 11;

FIG. 13 is a diagram showing the level distribution for each beat frequency in FIG. 11;
FIG. 8 is a diagram showing a level distribution for each corrected beat frequency obtained by removing the side lobe pattern of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Array antenna, 10 ... High frequency circuit, 11 ... Mixer group, 14 ... Voltage controlled oscillator, 15 ... Branch circuit, 22 ... Triangular wave generation circuit, 24 ... Low noise amplifier, 25 ... High speed A / D
Transformer, 26: signal processing unit, 27: complex FFT operation unit.

Claims (5)

[Claims] 1. An FM-CW radar device that uses a continuous wave signal subjected to frequency modulation as a transmission signal and obtains object information based on a beat signal obtained by mixing the reception signal with the transmission signal. A level distribution creating means for creating a beat frequency-specific level distribution using a scan angle as a parameter for the beat signal, and estimating an antenna beam pattern using a peak value of the beat frequency-specific level distribution as a main lobe peak value;
A level distribution correction unit for performing distribution correction by removing the side lobe pattern from the level distribution, and an object based on a scan angle and a beat frequency indicated by a level peak of a level distribution for each beat frequency corrected by the level distribution correction unit. An FM-CW radar device comprising: an arithmetic unit for calculating information. 2. The apparatus according to claim 1, wherein said level distribution correcting means estimates an antenna beam pattern having a maximum peak value of said level distribution as a peak value of a main lobe, and performs distribution correction for removing a side lobe pattern from said level distribution. The FM-CW radar device according to claim 1, wherein 3. The FM-system according to claim 1, wherein said level distribution correction means superimposes distribution correction on the level distribution corrected by itself.
CW radar device. 4. The method according to claim 1, wherein the level distribution correction unit performs distribution correction on the distribution-corrected level distribution in a superimposed manner.
The method is characterized in that the antenna beam pattern is estimated with a peak value in a direction different from the previously estimated antenna beam pattern as the peak value of the main lobe, and distribution correction is performed to remove the side lobe pattern from the level distribution. The FM-CW radar device according to claim 3. 5. The FM according to claim 1, wherein the receiving antenna is an array antenna comprising a plurality of element antennas, and the formation and scanning of the antenna beam pattern are performed by digital beam forming arithmetic processing. -CW radar equipment.