JPH11271434A - Phase monopulse radar apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phase monopulse radar apparatus which enhances the detecting reliability of the direction of a target. SOLUTION: Reflected waves from a target are received by right and left two-channel receiving antennas 16a, 16b. A signal processor 20 analyzes the frequency of received waves in respective channels, and it finds a peak frequency having the peak of an amplitude and its peak amplitude. Peaks in a plurality of channels with reference to the same target are found as a pair. A pair which is provided with a peak frequency difference at a prescribed threshold frequency difference or lower and with a peak amplitude different at a prescribed threshold amplitude difference or lower is selected. On the basis of the phase difference of the peak pair, the direction of the target is detected by a phase monopulse system. Even in a state that reflected waves of many objects are composed and received, the peak pair of the same target can be selected surely by referring to the peak amplitude difference in addition to the peak frequency difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase monopulse radar apparatus for receiving a reflected wave from a target through a plurality of channels and detecting the azimuth of the target based on the phase difference between the received waves between the channels. To improve the reliability of azimuth detection.

[0002]

2. Description of the Related Art Conventionally, various radars have been used to detect the azimuth, distance, and speed of a target. For example, a radar is also used to detect a relative bearing, a relative distance, and a relative speed with respect to a preceding vehicle on a road. One of the radars for detecting the azimuth is a phase monopulse radar. Also, as one of the radars for detecting distance and speed, F
There is an MCW (frequency modulated continuous wave) radar.

[Phase monopulse radar] In a phase monopulse radar, reflected waves from a target obtained by radiating radio waves from a transmitting antenna are received by a plurality of receiving antennas. Since the plurality of receiving antennas are spatially different in position, the phases of the reflected waves from the same target differ between the receiving antennas. The azimuth of the target can be detected by detecting this phase shift. This phase monopulse radar has an advantage that basically there is no need to mechanically move the transmitting antenna and the receiving antenna.

Referring to FIG. 1, the distance to the target is R0, the interval between the two receiving antennas is L, and the azimuth of the target is θ. The distances R1 and R2 from the antennas 1 and 2 to the target are:

R1 = R0 + (L / 2) sin θ R2 = R0− (L / 2) sin θ The phase difference Δφ between the received signals (wavelength: λ) of the two receiving antennas is

## EQU2 ## Δφ = (L / λ) · sin θ Therefore, the azimuth θ of the target is

## EQU3 ## θ = sin ^-1 {(λ / L) Δφ}. In this way, the azimuth of the target can be obtained from the phase difference of the received signal.

[FMCW radar] The FMCW radar detects the distance and velocity of a target using continuous waves. By combining the FMCW radar and the phase monopulse radar, it is possible to determine the distance, speed, and azimuth of the target.

[0006] The FMCW radar applies FW to a continuous wave transmission signal.
M modulation is performed. FIG. 2 shows the principle of relative distance and relative speed detection by the FMCW radar. For example, a transmission wave is frequency-modulated by a triangular wave. by this,
The frequency of the transmission wave repeatedly increases and decreases sequentially. When this transmission wave is radiated from the radar and reflected by the target and received, the frequencies of the transmission wave and the reception wave have a relationship as shown in FIG. However, this is a case where the relative speed of the target is zero. Then, by detecting the received wave with the reference wave (transmitted wave), a beat signal (FIG. 2 (lower)) having a frequency component of a difference between the transmitted frequency and the received frequency is obtained.

[0007] The propagation delay time τ is a time until a transmission wave is received. Assuming that the relative distance to the target is R and the speed of light is c, τ = 2R / c. Further, the repetition frequency of FM (the frequency of the triangular wave in FIG. 2) is fm, F
If the frequency shift width of M (the change width of the frequency of the reference wave) is Δf, the beat frequency fr is

## EQU4 ## fr = 4R · fm · Δf / c Therefore, from the beat signal, the beat frequency fr
Is determined, the relative distance R is determined.

FIG. 3 (upper) shows that the relative speed of the target is zero.
3 shows the relationship between the frequency of the transmission wave and the frequency of the reception wave in a case other than the above. When the target has a relative speed to the radar, the frequency of the received wave shifts up or down by the Doppler frequency fd. FIG. 3 (lower) shows a beat signal. This beat signal is obtained by adding the Doppler frequency fd to the beat frequency fr of the target having a relative speed of 0 during the up phase period in which the frequency of the transmission wave is increasing. On the other hand, in the down phase period in which the frequency of the transmission wave is decreasing, the beat signal is obtained by subtracting the Doppler frequency fd from the beat frequency fr. Therefore, the Doppler shift is determined from the frequency of the up phase period and the down phase period of the beat signal, and the relative speed of the target is determined from this.

That is, the frequency fbu, fbd of the beat signal in the up phase period and the down phase period
Is

Fbu = fr + fd fbd = fr-fd Therefore, the frequency fbu, fbd
Are obtained individually, a beat frequency fr representing a relative distance,
A Doppler frequency fd representing the relative speed is obtained.

[0010]

The phase monopulse radar described above can accurately detect the azimuth of a target in an extremely ideal environment where only a single target exists. However, in a radar use environment where reflected waves from various objects are combined and received, simply 2
It is difficult to detect the target direction with high reliability only by using the phase difference between the signals from the two receiving antennas.

Considering the case of detecting a preceding vehicle on the road, the direction of the preceding vehicle can be detected based on the phase of the reflected wave of the target preceding vehicle. At this time, it is necessary to extract or select the reflected wave of the preceding vehicle from the received wave. However, in a vehicle radar use environment, there are a plurality of preceding vehicles, and there are also objects such as trees and guardrails other than the preceding vehicles. Under the influence of the reflected waves from a large number of objects, it is difficult to accurately combine the signals from the same target to accurately detect the direction by simply applying the conventional phase monopulse method.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide highly reliable azimuth detection even in a radar use environment in which reflected waves of a plurality of targets and objects other than the targets are synthesized and received. It is an object of the present invention to provide a phase monopulse radar device which can perform the following.

It is another object of the present invention to provide a radar apparatus in which a phase monopulse radar and an FMCW radar are combined, and a radar apparatus capable of performing more reliable azimuth detection by using frequency modulation.

[0014]

(1) According to the present invention, a reflected wave from a target is received by a receiving unit of a plurality of channels.
In a phase monopulse radar device that detects the azimuth of a target based on the phase difference of a received wave between channels, an analysis unit that performs frequency analysis of the received wave of each channel to obtain a peak frequency and its peak amplitude, A peak pair detecting section for obtaining an azimuth detecting peak pair that is a set of peaks of a plurality of channels for the same target, and detecting an azimuth of the target based on a phase difference between the peaks of the azimuth detecting peak pair obtained by the peak pair detecting section. And a peak pair detecting unit, wherein the peak pair detecting unit selects a set of peaks having a peak frequency difference equal to or less than a predetermined threshold frequency difference and a peak amplitude difference equal to or less than the predetermined threshold amplitude difference as a peak pair for azimuth detection. Features.

According to the present invention, the frequency analysis of the reception wave of each reception channel, for example, the Fourier transform processing is performed.
By the frequency analysis, a peak frequency having an amplitude peak and an amplitude value of the peak are obtained. Even if the channel is different, the frequency of the peak corresponding to the same target is
Should be identical or close. Furthermore, the peak amplitude value should be the same or close even if the channel is different, if the target is the same. Therefore, a set of peaks having a peak frequency difference equal to or smaller than the predetermined threshold frequency difference and a peak amplitude difference equal to or smaller than the predetermined threshold amplitude difference is selected as the azimuth detection peak pair. This makes it possible to reliably select a set of peaks of the same target. Since the azimuth is detected based on the phase difference between the peak pairs thus selected, highly reliable azimuth detection can be performed.

Here, in a radar use environment where a plurality of targets and objects other than the target exist, such as a road,
The reflected waves from various objects are combined and received. If peak pairs are selected based only on the frequency, many peak pairs will be created due to the influence of reflected waves from various objects. The multiple peak pairs may include those that are not the same target peak pair.

On the other hand, according to the present invention, a peak pair having a small peak frequency difference and a small peak amplitude difference is selected. In other words, the azimuth is not calculated for all pairs of peaks having similar peak frequencies, but the azimuth is determined using only the pair having a small amplitude difference between the peaks. Accordingly, peaks of the same target can be further selected from peaks having similar frequencies. This makes it possible to perform highly reliable azimuth detection without being affected by a reflected wave of another object or the like.

(2) A phase monopulse radar apparatus according to a preferred aspect of the present invention includes a transmitting section for transmitting a frequency modulated wave including an ascending phase in which the frequency increases and a descending phase in which the frequency decreases, and a receiving wave based on the transmitting wave. And a beat signal generation unit that generates a beat signal by detecting the frequency of the beat signal in the analysis unit. And a pair having a smaller peak amplitude difference is set as an object of the azimuth calculation.

In this embodiment, the phase monopulse radar has F
The MCW radar is integrated, and a frequency-modulated transmission wave is transmitted. As described above, the frequency-modulated transmission wave has an up phase and a down phase, and repeatedly increases and decreases in frequency. In each of the up phase and the down phase, the azimuth detection peak pair of the above (1) is obtained from signals of a plurality of channels. Both peak pairs have a peak amplitude difference equal to or smaller than the threshold amplitude difference, and the orientation based on those peak pairs is highly reliable. However, peak pairs with smaller peak amplitude differences provide greater reliability. Therefore, the pair having the smaller peak amplitude difference is selected from the two peak pairs of the up and down, and the azimuth calculation is performed using the selected peak pair. Thereby, the detection reliability can be further improved.

(3) A phase monopulse radar apparatus according to another preferred embodiment of the present invention transmits a frequency-modulated transmission wave, and detects a reception wave based on the transmission wave to generate a beat signal. A beat signal generation unit, wherein the analysis unit performs a frequency analysis of a beat signal, and the peak pair detection unit is based on a peak pair for azimuth detection based on a reception wave of an up phase of frequency modulation and a reception wave of a down phase. The azimuth detecting unit detects each of the azimuth detecting peak pairs, and the azimuth detecting unit averages the two azimuths calculated from each of the azimuth detecting peak pairs in the up phase and the down phase based on a difference in peak amplitude difference between the two pairs. And determine the azimuth of the target.

In this embodiment, after the peak pair for azimuth detection is detected in each of the up phase and the down phase of the frequency modulation, the azimuth is calculated from the up and down peak pairs, and the average of these azimuths is calculated. Here, as described in (2), both peak pairs have a peak amplitude difference equal to or smaller than the threshold amplitude difference, and the azimuth based on these peak pairs is highly reliable. However, the orientation obtained from the peak pair having the smaller peak amplitude difference has higher reliability. Therefore, averaging is performed according to the difference in peak amplitude difference between the two pairs. A weighted averaging process in which the weight of the azimuth calculated from the peak pair having the smaller peak amplitude difference is increased is preferable. This is because the weight of the direction having higher reliability becomes larger. Thus, the detection reliability can be further improved.

(4) Another aspect of the present invention is a radar apparatus for detecting the distance, speed, and azimuth of a target by combining the FMCW method and the phase monopulse method, wherein the transmitting unit transmits a frequency-modulated transmission wave. A receiving unit that receives the reflected wave from the target on a plurality of channels, a beat signal generating unit that detects the received wave based on the transmitted wave and generates a beat signal, and performs a frequency analysis of the beat signal of each channel. , An analyzer for calculating a peak frequency and a peak amplitude thereof, a distance / speed calculator for detecting a target distance and a speed in an FMCW method based on peak frequencies of an up phase and a down phase for the same target, and a plurality of channels for the same target. Azimuth detection that detects the target azimuth by the phase monopulse method based on the phase difference between the peaks And a set of peaks belonging to each of the plurality of channels, wherein the set having a peak frequency difference of not more than a predetermined threshold frequency difference and a peak amplitude difference of not more than a predetermined threshold amplitude difference is an azimuth detecting unit. And a peak pair detection unit that determines the direction pair used for the azimuth detection.The peak pair detection unit compares the azimuth detection peak pair obtained from the up-phase received wave with the azimuth detection peak pair obtained from the down-phase received wave. Thus, a pair having a smaller peak amplitude difference is subjected to the azimuth calculation.

In this aspect, the present invention is realized in the form of a radar device in which an FMCW radar and a phase monopulse radar are integrated. A frequency-modulated transmission wave is transmitted, and a reflected wave from the target is received by a plurality of channels. A beat signal is generated by detecting the reception wave based on the transmission wave, and a frequency analysis of the beat signal is performed to obtain an amplitude peak. F based on the frequency of the peak of the up phase and the down phase for the same target.
The target distance and the speed are detected by the MCW method.
The target direction is detected by a phase monopulse method based on the phase difference between the peaks of a plurality of channels for the same target. In order to detect a set of peaks of a plurality of channels for the same target, the peak amplitude difference is referred to as described in (1) above, whereby it is possible to improve the reliability of azimuth detection. .

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] Hereinafter, a preferred embodiment of the present invention (hereinafter, referred to as an embodiment) will be described.
This will be described with reference to the drawings.

FIG. 4 shows a configuration of an FMCW / phase monopulse radar device according to an embodiment of the present invention. This radar device is for a vehicle, transmits a frequency-modulated transmission wave, and receives reflected waves from a target on left and right channels. Then, according to the principle of the phase monopulse method, the azimuth of the target is obtained from the received waves of the left and right channels. In addition, according to the principle of the FMCW method, the distance and speed of the target are obtained from the reception waves in the up phase and the down phase.

The voltage controlled oscillator (VCO) 10 functions as a frequency modulator. The VCO 10 is supplied with a triangular wave whose voltage increases and decreases with time. VCO 10 is
A high frequency frequency-modulated by the triangular wave is generated. This high frequency is distributed by the distributor 12, one of which is sent to the transmitting antenna 14. In this way, the high frequency modulated by the triangular wave is radiated to the outside as a radio wave.

The radio wave radiated from the transmitting antenna 14 is reflected by the target. In the figure, two preceding vehicles are shown as targets 1 and 2. The reflected signal is 2
It is received by two receiving antennas 16a and 16b. This 2
The two receiving antennas 16a and 16b are spatially spaced apart by a predetermined distance L. Detectors 18a and 18b are connected to the receiving antennas 16a and 16b, respectively. To the detectors 18a and 18b, a high frequency (transmission signal) frequency-modulated by a triangular wave is supplied from the distributor 12 as a reference wave. Detector 18a, 1
In 8b, the received wave and the reference wave are mixed and synchronously detected to obtain a beat signal having a frequency component of a difference between the transmission frequency and the reception frequency. In this way, the two beat signals corresponding to the left and right receiving antennas are generated by the signal processing device 20.
Supplied to

In the signal processing device 20, the frequency analyzers 22a and 22b and the peak detectors 24a and 24b
It functions as the analysis unit of the present invention. Frequency analysis unit 22a,
22b performs frequency analysis of the beat signal obtained from the received signals of the left channel and the right channel, respectively, and obtains data on the frequency components of the signal. Here, a complex FFT (Fast Fourier Transform) is performed, and a complex amplitude (voltage) for each frequency bin at an appropriate frequency interval is obtained. Hereinafter, the bin number indicates the frequency. The peak detectors 24a and 24b calculate the frequency based on the frequency analysis result.
The peak (the number of the frequency bin having the peak and its frequency b) in each of the left and right channels of the phase monopulse
in complex amplitude).

FIGS. 5A and 5B are examples of frequency analysis results of the left channel and the right channel, respectively. In the left channel, peaks UL1 and DL having a large amplitude.
1 is the peak of the up phase and the down phase of the target 1 respectively. The fact that the peak frequency of the downstream phase is higher than the upstream phase indicates that the target 1 is relatively slower (approaching) than the own vehicle. The peaks UL2 and DL2 having small amplitudes are
These are the peaks of the up phase and the down phase of the target 2, respectively. The fact that the peak frequency of the down phase is lower than the up phase indicates that the target 2 is relatively faster (away) from the own vehicle. Similarly, in the right channel, the peaks UR1 and DR1 are the peaks of the up phase and the down phase of the target 1, respectively. The peaks UR2 and DR2 are the peaks of the up phase and the down phase of the target 2, respectively.

However, in this embodiment, the radar device is mounted on a vehicle and used on a road. In such a radar use environment, there are a plurality of targets (preceding vehicles), and there are also objects such as trees and guardrails other than the targets. Reflected waves from various objects are combined and received by the radar. Therefore, actually, there are many more peaks in addition to the peaks shown in FIG. From such a large number of peaks, the left and right channel peaks of the same target are selected as follows.

Returning to FIG. 4, the azimuth detecting peak pair selecting section 26 and the amplitude difference detecting / determining section 28 function as the peak pair detecting section of the present invention. Even if the channels are different, the peak frequencies corresponding to the same target should be the same or close. Therefore, the selecting unit 26 selects the near frequency bi
The peak having n is selected from the left and right channels, and the two selected peaks are used as a peak pair. Here, a peak pair in which the difference in frequency bin between the left and right channels is equal to or smaller than a predetermined threshold frequency difference is selected.

At this stage, a fairly large number of peak pairs have been selected. As described above, there are a plurality of targets and objects such as guardrails and trees other than the targets on the road, and reflected waves of these various objects are combined and received. If peak pairs are selected based only on the frequency, many peak pairs will be created due to the influence of reflected waves from various objects. The multiple peak pairs may include those that are not the same target peak pair.

Therefore, the peak difference selected by the selection unit 26 is set as a candidate, and the amplitude difference detection / judgment unit 28 performs further narrowing down based on the amplitude value. The determination unit 28 refers to the amplitude value (peak amplitude) of both peaks of the peak pair selected by the selection unit 26, and calculates the difference between the amplitude values of both peaks (peak amplitude difference: absolute value). Even if the channels are different, the amplitudes of the peaks corresponding to the same target should be the same or close. Then, the magnitude of the peak amplitude difference is examined, and a peak pair having a small amplitude difference is selected. Here, the peak amplitude difference is compared with a predetermined threshold amplitude difference. Only a peak pair having a peak amplitude difference equal to or smaller than the threshold amplitude difference is selected as a final peak pair for azimuth detection.

In this manner, peak pairs having similar frequencies are selected as candidates, and peak pairs of the same target are further selected from these candidates by relying on the amplitude difference. Referring to FIG. 5, in the uplink phase, the left channel peak UL1 and the right channel peak UR1 are selected as the azimuth detection peak pair. Further, the peaks UL2 and UR2 also form a peak pair. Similarly, in the down phase, the peak D
L1, DR1 and peaks DL2, DR2 form a peak pair.

The azimuth calculating section 30 of the signal processing device 20 corresponds to the azimuth detecting section of the present invention, and calculates the relative azimuth of the target using the azimuth detecting peak pair selected by the judging section 28. Here, the azimuth is obtained by the phase monopulse processing.

As described with reference to FIG. 1, by comparing the phases of the signals received by the two receiving antennas 16a and 16b, the azimuth can be obtained from the phase difference. Azimuth θ
If the phase difference between two received waves is Δφ, the distance between the two receiving antennas is L, and the wavelength of the radio wave is λ,

## EQU6 ## θ = sin ^-1 {(λ / L) Δφ}. In the present embodiment, the azimuth is obtained from the phase difference between the two corresponding peaks of the beat signal.

The distance / speed detector 32 separately obtains the relative distance and the relative speed of the target using the peaks detected by the peak detectors 24a and 24b. Here, the distance and the speed are obtained by the FMCW processing. That is, as described with reference to FIGS. 2 and 3, the beat signal includes a component based on the delay of the received wave according to the distance to the target and a component based on the Doppler shift according to the speed of the target. Beat signal frequencies fbu, fbd during the up phase period and the down phase period
Is the beat frequency representing the relative distance is fr and the Doppler frequency representing the relative speed is fd,

Fbu = fr + fd fbd = fr-fd Therefore, the beat frequency fr and the Doppler frequency fd are obtained from the frequencies fbu and fbd, and the relative distance and the relative speed are obtained. In the present embodiment, the distance and the speed are obtained based on the bin numbers of the peaks corresponding to the up and down phases. This bin number corresponds to the frequency of the peak. Further, the distance and the speed can be obtained independently based on the received waves of the left and right channels, and a more accurate detection result can be obtained by using both the detected values.

Azimuth calculation unit 30 and distance / speed detection unit 3
The distance, the speed, and the azimuth obtained by 2 are used, for example, for automatic tracking control for a preceding vehicle. For the automatic tracking control, it is preferable to use a prediction filter such as a Kalman filter or an α-β filter. In the prediction filter, the smoothed position and speed are obtained using the predicted position data and the measured position data, and the smoothed data is output as target information.

The radar apparatus according to the present embodiment has been described above. As described above, in the present embodiment, the azimuth calculation is not performed on all of the peak pairs obtained in the left and right channels of the phase monopulse, but only the peak pairs in which the amplitude difference between the peaks is small (below the threshold amplitude difference). Is used to perform the azimuth calculation. As a result, a detection result can be obtained by selecting a case where there is little influence of a reflected wave from another target or a tree other than the target, such as a tree or a guardrail, so that highly reliable azimuth detection can be performed. Note that the threshold frequency difference and the threshold amplitude difference in the present embodiment are determined to appropriate values in advance. It is preferable that the threshold frequency difference is set based on the magnitude of variation in the frequency of the peak obtained from the reflected wave of the same target. Similarly, it is preferable that the threshold amplitude difference is set based on the magnitude of variation in the amplitude of the peak obtained from the reflected wave of the same target. For example, both thresholds can be set to a standard magnitude of variation, or set to a maximum value of variation. The threshold frequency difference and the threshold amplitude difference may be set based on experimental results and experience.

Second Embodiment Next, a second embodiment of the present invention will be described. The configuration of the present embodiment is the same as the configuration of the first embodiment shown in FIG. 4, and the description of the overlapping portions will be omitted as appropriate. The second embodiment differs from the first embodiment in the operation of the amplitude difference detection / determination unit 28.

In the same manner as in the first embodiment, the azimuth detecting peak pair selecting unit 26 selects a peak pair having a peak frequency difference equal to or smaller than the threshold frequency difference between channels from a number of peaks of the frequency analysis result. In addition, amplitude difference detection
In the determination unit 28, from the peak pair selected by the selection unit 26,
A peak pair having a peak amplitude difference equal to or smaller than the threshold amplitude difference is selected.

The above-mentioned selection of the peak pair is performed in each of the up phase and the down phase of the frequency modulation. A peak pair is obtained from the transmitted and received waves in the up phase, and a peak pair is obtained from the transmitted and received waves in the down phase.
As a feature of the second embodiment, the amplitude difference detection / judgment unit 28 compares the peak pair of the up phase and the peak pair of the down phase corresponding to the same target. Then, the peak pair having the smaller peak amplitude difference is designated as the final peak pair for azimuth detection. The azimuth calculation unit 30 obtains the azimuth of the target using the peak pair specified by the determination unit 28.

Referring to FIG. 5, in the up phase, the peak UL1 of the left channel and the peak UR1 of the right channel form a target 1 peak pair. In the down phase,
The peaks DL1 and DR1 form a peak pair. The peak pair (UL1, UR1) and the peak pair (DL1, DR1) are compared, and the peak pair having the smaller amplitude difference is selected as the peak pair for azimuth detection.

The radar apparatus according to the second embodiment has been described. In this embodiment, the phase monopulse radar and the FM
It is noted that the integration of the CW radar requires peak pairs for azimuth detection in each of the up phase and the down phase. Both peak pairs have a peak amplitude difference equal to or smaller than the threshold amplitude difference, and the orientation based on those peak pairs is highly reliable. However, peak pairs with smaller peak amplitude differences provide greater reliability. Therefore, the pair having the smaller peak amplitude difference is selected from the two peak pairs of the up and down, and the azimuth calculation is performed using the selected peak pair. Thereby, the detection reliability can be further improved.

[Embodiment 3] Next, referring to FIG.
A third embodiment of the present invention will be described. Embodiment 2 above
In, one of the peak pairs of the up phase and the down phase is selected, and the azimuth calculation result is obtained from the selected peak pair. On the other hand, in the third embodiment, the azimuth calculation is individually performed using both peak pairs, and thereafter, a weighted average of the azimuth output values is obtained. 6, the same components as those in the configuration of the first embodiment in FIG. 4 are denoted by the same reference numerals, and the description of these components will be omitted as appropriate.

In the signal processing device 40 of the third embodiment,
The azimuth detecting peak pair selecting unit 26 and the amplitude difference detecting / determining unit 28 select a peak pair having a peak frequency difference equal to or smaller than the threshold frequency and a peak amplitude difference equal to or smaller than the threshold amplitude difference, as in the first embodiment. The selection of the peak pair is performed in each of the upstream phase and the downstream phase of the FMCW modulation. A peak pair is obtained from the transmitted and received waves in the up phase, and a peak pair is obtained from the transmitted and received waves in the down phase.

In the second embodiment, the peak pair having a smaller amplitude difference is selected from the peak pairs for azimuth detection in the ascending and descending phases. In the third embodiment, such selection and designation are not performed. Therefore, the azimuth calculation unit 30 performs the azimuth calculation for both the up and down phases. That is, the azimuth of the target is calculated based on the phase difference of the azimuth detection peak pair obtained based on the up-phase received wave, and further, the phase difference of the azimuth detection peak pair obtained based on the down-phase received wave. Is calculated based on the target.

The azimuth averaging unit 42 and the azimuth calculating unit 30 constitute an azimuth detecting unit of the present invention. Averaging unit 42
Refers to the amplitude difference between each peak pair in the upstream and downstream phases. The azimuth calculation values obtained in each of the ascending and descending phases are averaged with weights based on the amplitude difference between the peak pairs.

The azimuth φave based on the above weighted average is
For example,

## EQU8 ## It can be obtained by φave = (Ddφu + Duφd) / (Du + Dd). Here, Du and Dd are the amplitude difference between the peak pair in the upstream phase and the amplitude difference between the peak pair in the downstream phase, respectively. φu and φd are the azimuths obtained from the peak pairs in the up phase and the azimuths obtained from the peak pairs in the down phase, respectively. The direction φave obtained by such a weighted average is output as the final target direction.

The radar apparatus according to the third embodiment has been described. Also in the third embodiment, as in the second embodiment, attention is paid to the fact that by integrating the phase monopulse radar and the FMCW radar, peak pairs for azimuth detection can be obtained in each of the up phase and the down phase. Then, an azimuth is calculated from each of the ascending and descending peak pairs, and an average of these azimuths is calculated. Here, the peak pairs of the up phase and the down phase both have a peak amplitude difference equal to or smaller than the threshold amplitude difference, and the azimuth based on these peak pairs is highly reliable. However, the orientation obtained from the peak pair having the smaller peak amplitude difference has higher reliability. Therefore, a weighted average of the azimuth is calculated according to the difference between the peak amplitude differences of the two pairs. Φave above
As shown in the calculation formula, the weight of the direction with the smaller amplitude difference, that is, the direction with higher reliability is increased. As a result, detection reliability can be improved.

As described above, in each of the upstream and downstream phases of the FMCW system, the azimuth is calculated with respect to the peak pair obtained in the left and right channels of the phase monopulse, and weighted based on the amplitude difference between the peaks to assign both positions. By averaging, the influence of reflected waves from other targets, trees other than the target, and objects such as guardrails can be reduced, and more reliable azimuth detection can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a phase monopulse radar.

FIG. 2 is a diagram illustrating the principle of an FMCW radar.

FIG. 3 is a diagram illustrating the principle of an FMCW radar.

FIG. 4 is a diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating a frequency analysis result of received signals of a left channel and a right channel of the apparatus of FIG. 4;

FIG. 6 is a diagram illustrating a configuration of a third exemplary embodiment of the present invention.

[Explanation of symbols]

10 voltage controlled oscillator (VCO), 14 transmitting antenna, 16a, 16b receiving antenna, 18a, 18b
Detector, 20, 40 Signal processing device, 22a, 22b
Frequency analyzer, 24a, 24b peak detector, 26
Azimuth detection peak pair selector, 28 amplitude difference detector / determiner, 30 azimuth calculator, 32 distance / speed detector, 42
Azimuth averaging unit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomo Harada 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. 41, Yokomichi, Toyota Central Research Institute, Inc.

Claims (2)

[Claims] 1. A phase monopulse radar device for receiving a reflected wave from a target by a plurality of channels of receiving units and detecting an azimuth of the target based on a phase difference between the received waves between the channels. An analysis unit that performs frequency analysis to obtain a peak frequency and its peak amplitude; a peak pair detection unit that obtains an azimuth detection peak pair that is a set of peaks of a plurality of channels for the same target based on the analysis result; and the peak pair detection unit An orientation detection unit that detects the orientation of the target based on the phase difference between the peaks of the orientation detection peak pair obtained by the method.The peak pair detection unit includes a peak frequency difference equal to or less than a predetermined threshold frequency difference and a predetermined threshold. Selecting a pair of peaks having a peak amplitude difference smaller than the amplitude difference as a peak pair for orientation detection. Phase mono-pulse radar apparatus. 2. The phase monopulse radar device according to claim 1, wherein the transmitting unit transmits a frequency modulation wave including an ascending phase in which the frequency increases and a descending phase in which the frequency decreases, and a reception wave is detected based on the transmission wave. A beat signal generation unit that generates a beat signal by performing a frequency analysis of the beat signal, and obtains an azimuth detection peak pair obtained from an up-phase reception wave and a down-phase reception wave. A phase monopulse radar device wherein a pair having a smaller peak amplitude difference is set as a target of the azimuth calculation by comparing the azimuth detection peak pair.