JPH11133143A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify multiple target objects having nearly equal distance and relative speed by detecting the peak frequencies of individual target objects, and detecting the existence information of individual target objects from the peak frequencies and the phase difference corresponding to them. SOLUTION: A triangular-wave modulation signal is generated by an FM modulator 10, an oscillator 12 is oscillated at the oscillation frequency corresponding to the modulation signal, and the transmission signal is transmitted from a transmission antenna 14. The reflected wave from a target object is received by reception antennas 20L, 20R, and reception signals are sent to mixers 24L, 24R. A part of the oscillation signal is mixed with the reception signals to generate beat signals by the mixers 24L, 24R, and the beat signals are sent to a fast Fourier transformer(FFT) 30. The power spectra and phase spectra of two beat signals in the frequency increase zone and frequency decrease zone of the transmission signal are obtained by the FFT 30 and are sent to a signal processing circuit 32. The existence information of individual target objects is detected from the peak frequencies and corresponding phase difference of the individual target objects by the signal processing circuit 32, and multiple target objects can be identified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radar device,
The present invention relates to a radar device that detects a target object based on signals received by a plurality of antennas.

[0002]

2. Description of the Related Art Conventionally, a radar apparatus transmits a radar beam from an antenna, receives a radar beam reflected by a target object by a plurality of antennas, and detects a distance to the target object based on a plurality of received signals. is there. For example, JP
JP-A-7-142575 discloses that a transmitting antenna for transmitting a microwave and a plurality of receiving antennas for receiving a microwave reflected by a target object are geometrically arranged, and a phase difference between received signals of the plurality of receiving antennas. A phase monopulse type radar device for measuring a distance from a target object to a target object is described.

[0003]

In a conventional phase monopulse type radar apparatus, when a plurality of target objects having substantially the same distance and relative velocity are present in different angular directions, a reception signal generated by each of the plurality of target objects is detected. There is a problem that the phase differences are combined and individual target objects cannot be identified.

The present invention has been made in view of the above points, and detects a peak frequency of each target object based on a detected frequency range of an amplitude frequency distribution and a change frequency of the phase difference. An object of the present invention is to provide a radar apparatus capable of identifying a plurality of target objects having substantially equal distances and relative velocities by detecting presence information of each target object from the detected phase difference.

[0005]

According to a first aspect of the present invention, there is provided a radar apparatus for transmitting an FM-modulated signal from a transmitting antenna and receiving a signal reflected by a target object by a plurality of receiving antennas. Power spectrum detection means for detecting the frequency distribution of the amplitude of the beat signal between the transmission signal and the reception signal; phase difference spectrum detection means for detecting the frequency distribution of the phase difference between the plurality of reception signals; and Phase difference change frequency detecting means for detecting a change frequency of the phase difference from the frequency distribution, and detecting a peak frequency of each target object based on the detected frequency range of the amplitude frequency distribution and the change frequency of the phase difference. A peak frequency detecting means for detecting presence information of each target object from the peak frequency of the target object and a phase difference corresponding thereto; And a means.

As described above, when the phase difference changes in the frequency range where the amplitude frequency distribution is detected, since the amplitude frequency distributions of a plurality of target objects are synthesized, the peak of each target object is obtained. By detecting the frequency and detecting the presence information of each target object from the corresponding phase difference, a plurality of target objects having substantially the same distance and relative speed can be identified.

According to a second aspect of the present invention, in the radar device according to the first aspect, the presence information detecting means detects a distance, a relative speed, and a direction of each target object as presence information. In this way, the distance, the relative speed, and the direction of each of the plurality of target objects can be detected.

[0008] The invention according to claim 3 is the invention according to claim 1 or 2.
In the radar device described above, when the peak frequency of the target object detected from the frequency range in which the frequency distribution of the amplitude is detected by the peak frequency detecting unit is one, the phase difference of the target object detected this time and the phase difference The apparatus includes a comparing unit that compares a phase difference between a plurality of target objects detected from a frequency range, and a presence / absence determining unit that determines the presence / absence of a plurality of target objects based on a result of the comparison.

As described above, by comparing the phase difference of the target object detected this time with the phase difference of a plurality of target objects previously detected from the frequency range, the distance and the relative speed of the plurality of target objects are determined. Even when they are the same, the presence or absence of a plurality of target objects can be determined. According to a fourth aspect of the present invention, in the radar device according to the third aspect, the presence / absence determination means is configured to determine a phase difference between the target object detected this time and the target object detected this time among a plurality of target objects previously detected from the frequency range. A substantially equal target object is regarded as the target object detected this time.

For this reason, the target object detected this time can be specified as a plurality of previously detected target objects other than the target object whose phase difference is almost equal to the target object detected this time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of a radar apparatus according to the present invention.
FIG. 2 shows a block diagram of an embodiment. In FIG. 1, an FM modulator 10 generates a triangular modulation signal and supplies it to a transmitter 12. The transmitter 12 oscillates at an oscillation frequency according to the modulation signal, and the transmission signal of the obtained millimeter wave or microwave of FM-CW (frequency modulated continuous wave) is transmitted from the transmission antenna 14. The radar device is mounted on, for example, a vehicle, and the oscillation signal is emitted, for example, toward a target object in front of the vehicle.

Receiving antennas 20L and 20R are disposed on both sides of the transmitting antenna 14 at a predetermined distance d, and reflected waves from a target object are reflected by the receiving antennas 20L and 20R.
R. Receiving antenna 20L, 20R
Each received signal is amplified by each of the amplifiers 22L and 22R and supplied to each of the mixers 24L and 24R. , Mixers 24L and 24R each include a transmitter 12
A part of the oscillation signal is supplied via the directional coupler, and a beat signal is generated by mixing the received signal and the oscillation signal. These beat signals are digitized by AD converters 26L and 26R, respectively,
It is supplied to an FT (Fast Fourier Transformer) 30.

The FFT 30 performs a fast Fourier transform on the power spectrum, which is the frequency spectrum of the amplitude of each of the two beat signals (outputs of the AD converters 26L and 26R) in the frequency increasing section of the transmission signal.
A phase spectrum which is a frequency spectrum of a phase of each of the two beat signals, a power spectrum of each of the two beat signals and a phase spectrum of each of the two beat signals in the frequency reduction section of the transmission signal are obtained and supplied to the signal processing circuit 32. .

The signal processing circuit 32 includes a vehicle speed sensor 3
4 and a steering angle signal detected by the steering angle sensor 36 are supplied. The signal processing circuit 32 is constituted by, for example, a microprocessor. FIG. 2 is a flowchart of a process executed by the signal processing circuit 32 according to the first embodiment. This process is repeatedly executed at predetermined time intervals. In FIG. 10, in step S10, the power spectrum and the frequency spectrum of the amplitude of the two beat signals in the frequency increase section of the transmission signal from the FFT 30 are calculated.
The phase spectrum of one beat signal, the power spectrum of two beat signals in the frequency reduction section of the transmission signal, and the phase spectrum of two beat signals are read.

Next, in step S20, two beat signals (AD converter 26
L, 26R output) and the phase difference spectrum of two beat signals in the frequency reduction section of the transmission signal. In the next step S30, in the power spectrum of one of the two beat signals (for example, the AD converter 26L) in each of the frequency increase section and the frequency decrease section of the transmission signal, two phase difference stable points for one peak. It is determined whether or not exists.

Here, as shown in FIG. 3, consider the case where the two target objects 40 and 41 have different directions but the same distance and the same relative speed. At this time,
Receive antenna 20L from the target object 40, 20R distance to each person receiving antenna 20R becomes longer by L _A, (the _{φ A = L A · 2π /} λ where lambda radar wavelength of the beam) the phase difference phi _A occurs . The reception antenna 20L from the target object 41, 20R distance to each person receiving antenna 20L becomes longer by L _B, a phase difference phi _B (phi
_B = L _B · 2π / λ where λ is the wavelength of the radar beam.

In such a case, the power spectrum of the beat signal in each of the frequency increasing section and the frequency decreasing section of the transmission signal is, as shown in FIG. And the phase difference of the beat signal (from the phase of the beat signal of the AD converter 26L
When the phase of the beat signal is subtracted), each of the phase differences −φ _A and φ _B has a stable point as shown in FIG.
In step S30 of FIG. 2, as described above, it is determined whether or not the two target objects 40 and 41 have the same distance but the same relative speed, although the directions are different.

If step S30 is satisfied, the step
Proceeding to step S40, target separation processing is performed. here
Is the frequency at the position where the power rises as shown in FIG.
f₁, F_Two, And the phase shown in FIG.
Frequency f₀, F_ThreeFrom the target object 4 indicated by the broken line I
Peak frequency f of the reflected power spectrum from 0
_AAnd the reflected power spectrum from the target object 41 indicated by the broken line II.
Peak frequency f _BAnd ask.

F _A = (f ₁ + f ₃ ) / 2 (1) f _B = (f ₀ + f ₂ ) / 2 (2) Further, a typical spectrum distribution of the reflection power spectrum of the single target object is given by g (f), the reflected power spectrum from the target object 40 indicated by the broken line I is P _A · g
(F−f _A ), and the reflected power spectrum from the target object 41 indicated by the broken line II is denoted by P _B · g (f−f _B ). P _A and P _B are peak values of each reflected power spectrum. The combined power spectrum indicated by the solid line III in FIG. 4A is obtained by superimposing the respective reflected power spectra, and is expressed as follows.

H (f) = P _A · g (f−f _A ) + P _B · g (f−f _B ) (3) Arbitrary frequencies α and β are selected between frequencies f _{0 to} f _3. ,
By substituting each into equation (3) and solving for P _A and P _B , the following equation is obtained.

[0021]

(Equation 1)

Thus, the target object 4 indicated by the broken line I
Peak frequency f _A as the information of the reflected power spectrum from 0, the phase difference -.phi _A, peak value P _A, the peak frequency f _B as the information of the reflected power spectrum from the target object 41 shown by the broken line II, the phase difference phi _B , it can be obtained and the peak value P _B. After execution of step S40 of FIG.
Alternatively, if step S30 is not satisfied, the process proceeds to step S50. In step S50, the pairing of the peak frequency of each target object in the frequency increase section and the frequency decrease section of the transmission signal is performed, and the distance R of each target object from each peak frequency pair is determined.
And the relative velocity V, and the direction (angle with respect to the radar beam radiation direction) θ of each target object is calculated from the phase difference corresponding to each peak frequency pair.

Here, the relative speed frequency FD and the distance frequency FR are obtained from the peak frequency F _UP in the frequency increasing section and the peak frequency F _{DO in the} frequency decreasing section, and the distance R and the relative speed V are calculated using the following equations. At the same time, the direction θ is obtained. FD = (F _DO −F _UP ) / 2 (6) FR = (F _DO + F _UP ) / 2 (7) FD = 2 · V / C · F ₀ (8) FR = 4 · F _M • dF / C · R (9)

[0024]

(Equation 2)

[0025] However, C is the speed of light, F ₀ is the center frequency of the FM-CW, F _M is the modulation frequency of the FM-CW, dF is the frequency shift width, lambda is the wavelength of the radar beam, d is the receiving antenna 2
The distance between 0L and 20R, dφ is the phase difference between the two received signals. Thereafter, in step S60, the vehicle speed sensor 34
The radius of curvature of the traveling road is obtained from the vehicle speed signal detected by the steering angle sensor 36 and the steering angle signal detected by the steering angle sensor 36. Based on the radius of curvature and the distance R and direction θ of each target object, the target A lane determination process is performed to determine whether or not the vehicle is traveling, and the processing cycle ends.

As described above, when the phase difference changes in the detected frequency range of the amplitude frequency distribution, the amplitude frequency distributions of a plurality of target objects are synthesized, so that the peak of each target object is obtained. By detecting the frequency and detecting the presence information of each target object from the corresponding phase difference, a plurality of target objects having substantially the same distance and relative speed can be identified, and the distance between each of the plurality of target objects can be determined. , Relative speed and direction can be detected.

FIG. 5 shows a flowchart of a second embodiment of the processing executed by the signal processing circuit 32. This process is repeatedly executed at predetermined time intervals. In the figure, step S11
At 0, the power spectrum of the two beat signals and the frequency spectrum of the phases of the two beat signals in the frequency increasing section of the transmission signal from the FFT 30, the power spectrum of the two beat signals and the phase of the two beat signals in the frequency decreasing section of the transmission signal Read each frequency spectrum of.

Next, in step S120, two beat signals (AD converter 2
6L, 26R output), and the phase difference spectrum of two beat signals in the frequency reduction section of the transmission signal. In the next step S130, one of the two beat signals (for example, AD) in the frequency increase section and the frequency decrease section of the transmission signal, respectively.
In the power spectrum of the converter 26L), 1
It is determined whether two phase difference stable points exist for one peak.

Here, as shown in FIG. 3, consider the case where the two target objects 40 and 41 have different directions but the same distance and the same relative speed. At this time,
Receive antenna 20L from the target object 40, 20R distance to each person receiving antenna 20R becomes longer by L _A, (the _{φ A = L A · 2π /} λ where lambda radar wavelength of the beam) the phase difference phi _A occurs . The reception antenna 20L from the target object 41, 20R distance to each person receiving antenna 20L becomes longer by L _B, a phase difference phi _B (phi
_B = L _B · 2π / λ where λ is the wavelength of the radar beam.

In such a case, the power spectrum of the beat signal in each of the frequency increasing section and the frequency decreasing section of the transmission signal is 1 as shown in FIG. 4A by combining the reflection spectra from the two target objects. And the phase difference of the beat signal (from the phase of the beat signal of the AD converter 26R, the AD converter 26L
When the phase of the beat signal is subtracted), each of the phase differences −φ _A and φ _B has a stable point as shown in FIG.
In step S130, as described above, the two target objects 4
Although 0 and 41 have different directions, it is determined whether or not the distances are the same and the relative speeds are the same.

If step S130 is satisfied, the flow advances to step S140 to perform target separation processing, and then to step S150. In step S140, FIG.
The frequencies f ₁ and f at the position where the power shown in FIG.
₂ and the peak frequency f _A of the reflected power spectrum from the target object 40 indicated by a broken line I from the frequencies f ₀ and f _{3 at} the positions where the phase starts to change as shown in FIG.
And the peak frequency f _B of the reflected power spectrum from the target object 41 is obtained by the equations (1) and (2).

Further, assuming that a typical spectrum distribution of the reflected power spectrum of the single target object is g (f),
The reflected power spectrum from the target object 40 indicated by the dashed line I is represented as P _A · g (f−f _A ), and the reflected power spectrum from the target object 41 indicated by the dashed line II is P _B · g (f
−f _B ). P _A and P _B are peak values of each reflected power spectrum. FIG. 4A shows a solid line III.
Since the combined power spectrum indicated by is obtained by superimposing the respective reflected power spectra, it is expressed by equation (3).

Any frequency α, between frequencies f _{0 to} f ₃
β is selected and substituted into equation (3) to obtain P _A , P _B
Is solved, the equations (4) and (5) are obtained. In this manner, as information on the reflected power spectrum from the target object 40 indicated by the broken line I, the peak frequency f _A and the phase difference −
phi _A, peak value P _A and the peak frequency f as the information of the reflected power spectrum from the target object 41 shown by a broken line II
_B, a phase difference phi _B, can be obtained and the peak value P _B.

On the other hand, if step S130 is not satisfied, the process proceeds to step S131, and it is determined whether or not the separation of the peak frequencies f _A and f _B of the target object has been performed in the target separation processing of step S140 in the previous processing cycle. In this case, it is rare that a plurality of target objects suddenly have the same distance and the same relative speed. Since the distance or the relative speed is slightly different before that, the previous processing cycle is determined. If target object separation has been performed in the previous processing cycle, it is determined in step S132 whether or not the phase difference and the peak value of the current processing cycle are substantially the same as the combined phase difference and the combined peak value of the previous processing cycle, respectively. Determine.

For example, the reflection power spectrum from the target object 40
Phase difference -φ_A, Peak value P_A,Eye
Information on the reflected power spectrum from the target object 41
Phase difference φ_B, Peak value P_BDisplay each vector
Is represented as shown in FIG. These two reflected power spectra
Phase difference ψ, peak value A of combined spectrum of spectrum _MP
Is represented by equations (11) and (12).

[0036]

(Equation 3)

In other words, the phase difference and peak
Peak value is the combined phase difference ψ and combined peak of the previous processing cycle.
Value A_MPTwo goals if nearly identical
Since there is an object, the process proceeds to step S133, and the previous process is performed.
Cycle phase difference-φ_A, Φ _BSeparates two target objects with
Then, the process proceeds to step S150. On the other hand, this processing cycle
Is the combined phase difference of the previous processing cycle.
ψ or synthetic peak value A_MPIf it is not almost the same as
In step S134, the phase difference and peak value of the current processing cycle
Is the phase difference of the previous processing cycle -φ_AAnd peak value P_ASo
Judge whether each is almost the same or not and satisfy this
If the target object 41 is moved to the side by the rampway on the highway, etc.
In step S135, it is determined that only the target object 40 remains.
The phase difference and peak value of the current processing cycle are
And the process proceeds to step S150.

In step S134, the current processing cycle is executed.
Phase difference or peak value is the phase difference of the previous processing cycle-
φ_AOr peak value P_AIf it is not the same as
In step S136, the phase difference and peak value of the current processing cycle are
Phase difference of previous processing cycle φ _BAnd peak value P_BEach
Judge whether it is almost the same as this, and if this is satisfied,
The target object 40 is deflected to the side by the rampway on the highway, etc.
This time in step S137 assuming that only the target object 41 remains
The phase difference and peak value of the processing cycle are
The process proceeds to step S150. In step S136
The phase difference or peak value of the current processing cycle is
Phase difference φ_BOr peak value P_BIf not almost the same as
In this case, the process proceeds to step S150.

In step S150, pairing of the peak frequency of each target object is performed in the frequency increase section and the frequency decrease section of the transmission signal, and the distance R and the relative speed V of each target object are calculated from each peak frequency pair. At the same time, the direction (angle with respect to the radar beam radiation direction) θ of each target object is calculated from the phase difference corresponding to each peak frequency pair. Here, the relative speed frequency FD and the distance frequency FR are obtained from the peak frequency F _UP in the frequency increasing section and the peak frequency F _{DO in the} frequency decreasing section, and the distance R and the relative frequency are calculated using the equations (6) to (10). The speed V is determined at the same time, and the direction θ is determined.

Thereafter, in step S160, the radius of curvature of the traveling road is obtained from the vehicle speed signal detected by the vehicle speed sensor 34 and the steering angle signal detected by the steering angle sensor 36, and the radius of curvature and the distance between each target object are determined. A lane determination process is performed based on R and the direction θ to determine whether the target object is traveling on the traveling lane of the host vehicle, and the process ends. As described above, by comparing the phase difference of the target object detected this time with the phase difference of the plurality of target objects previously detected from the frequency range, the distance and relative speed of the plurality of target objects become the same. Can determine the presence or absence of a plurality of target objects,
Further, even if a target object other than a target object having a phase difference substantially equal to that of a target object detected this time out of a plurality of target objects detected before has left, the target object detected this time can be specified.

The above-described FFT 30 and step S2
0 and S120 correspond to the power spectrum detecting means and the phase difference spectrum detecting means, and steps S30 and S13
0 corresponds to the phase difference change frequency detecting means.
0 and S140 correspond to the peak frequency detecting means, and steps S50 and S150 correspond to the presence information detecting means. Steps S131 to S137 correspond to the comparing means and the presence / absence determining means.

[0042]

As described above, the first aspect of the present invention is a radar apparatus that transmits an FM-modulated signal from a transmitting antenna and receives a signal reflected by a target object by a plurality of receiving antennas. Power spectrum detection means for detecting the frequency distribution of the amplitude of the beat signal between the transmission signal and the reception signal; phase difference spectrum detection means for detecting the frequency distribution of the phase difference between the plurality of reception signals; Phase difference change frequency detecting means for detecting the change frequency of the phase difference from the frequency distribution of the above, and detecting the peak frequency of each target object based on the detected frequency range of the amplitude frequency distribution and the change frequency of the phase difference Presence frequency detecting means for detecting presence information of each target object from the peak frequency of each target object and a phase difference corresponding thereto. And a means.

As described above, when the phase difference changes in the detected frequency range of the amplitude frequency distribution, the amplitude frequency distributions of a plurality of target objects are synthesized, and the peaks of the individual target objects are combined. By detecting the frequency and detecting the presence information of each target object from the corresponding phase difference, a plurality of target objects having substantially the same distance and relative speed can be identified.

Further, the invention described in claim 2 is the same as that in claim 1
Wherein the presence information detecting means detects the distance, relative speed and direction of each target object as presence information. In this way, the distance, the relative speed, and the direction of each of the plurality of target objects can be detected.

Further, the invention described in claim 3 is the first invention.
Or in the radar device according to 2, when the peak frequency of the target object detected from the frequency range in which the amplitude frequency distribution is detected by the peak frequency detection unit is one, the phase difference between the target object detected this time and the And a presence / absence determination means for comparing presence / absence of a plurality of target objects based on a result of the comparison with a phase difference between the plurality of target objects detected from the frequency range.

As described above, by comparing the phase difference of the target object detected this time with the phase difference of a plurality of target objects previously detected from the frequency range, the distance and the relative speed of the plurality of target objects are determined. Even when they are the same, the presence or absence of a plurality of target objects can be determined. According to a fourth aspect of the present invention, in the radar device according to the third aspect, the presence / absence determination unit determines a position of the target object detected this time among a plurality of target objects previously detected from the frequency range. A target object having substantially the same phase difference is regarded as a target object detected this time.

Therefore, the target object detected this time can be specified as a plurality of previously detected target objects other than the target object having a phase difference substantially equal to that of the target object detected this time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of a radar apparatus according to the present invention.

FIG. 2 is a flowchart of a first embodiment of a process executed by a signal processing circuit.

FIG. 3 is a diagram for explaining a case where two target objects have different directions, but have the same distance and the same relative speed.

FIG. 4 is a diagram showing a power spectrum and a phase difference spectrum of a beat signal when reflection spectra from two target objects are combined.

FIG. 5 is a flowchart of a process executed by a signal processing circuit according to a second embodiment.

FIG. 6 is a diagram showing the synthesis of two reflected power spectra.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 FM modulator 12 Transmitter 14 Transmitting antenna 20L, 20R Receiving antenna 24L, 24R Mixer 26L, 26R AD converter 30 FFT 32 Signal processing circuit 34 Vehicle speed sensor 36 Steering angle sensor

Claims (4)

[Claims] 1. A radar apparatus for transmitting an FM-modulated signal from a transmission antenna and receiving a signal reflected by a target object by a plurality of reception antennas, wherein an amplitude of a beat signal between the transmission signal and the reception signal is provided. Power spectrum detection means for detecting the frequency distribution of the phase difference spectrum detection means for detecting the frequency distribution of the phase difference between the plurality of received signals, and phase difference for detecting the change frequency of the phase difference from the frequency distribution of the phase difference Changing frequency detecting means, peak frequency detecting means for detecting a peak frequency of each target object based on the detected frequency range of the amplitude frequency distribution and the changing frequency of the phase difference, and a peak of the individual target object. A presence information detecting means for detecting presence information of each target object from the frequency and the corresponding phase difference. Apparatus. 2. The radar apparatus according to claim 1, wherein said presence information detecting means detects a distance, a relative speed, and a direction of each target object as presence information. 3. The radar device according to claim 1, wherein the peak frequency of the target object detected from the frequency range in which the amplitude frequency distribution is detected by the peak frequency detection unit is one, and the peak frequency is detected this time. Comparing means for comparing the phase difference of the target object with the phase difference of the plurality of target objects previously detected from the frequency range; and determining whether the plurality of target objects are present based on the result of the comparison. A radar apparatus comprising: a determination unit. 4. The radar apparatus according to claim 3, wherein the presence / absence determination means is a target object having a phase difference substantially equal to a target object detected this time among a plurality of target objects previously detected from the frequency range. Is regarded as a target object detected this time.