JP2002071793A - Radar equipment - Google Patents

Abstract

(57) [Problem] To provide an on-vehicle radar device capable of separating the positions of a moving other vehicle or a plurality of stationary objects and their relative velocities with respect to the own vehicle and detecting them with high accuracy. SOLUTION: As in a two-frequency CW system, two frequencies f are used.
A portion that alternately modulates 1 and f2 and a portion that modulates the frequency near f0 are used together. The two-frequency CW method and the monopulse method detect the position of the moving object and the relative speed with respect to the stationary object. In the frequency modulation area near f0, the relative speed between the stationary object and the radar-equipped vehicle is calculated from the relative speed obtained by the two-frequency CW method. And the azimuth angle. The position of another moving vehicle, the positions of a plurality of stationary objects, which have been difficult in the past, and their relative speeds to the own vehicle can be separately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle radar apparatus for detecting a reflector with high accuracy using continuous radio waves, and more particularly to a position of a stationary object such as a running obstacle or another vehicle and the like. The present invention relates to a radar device which detects their relative speed with respect to the radar with high accuracy.

[0002]

2. Description of the Related Art Radar systems using radio waves are known in order to prevent collision of automobiles and to ensure safe traveling.
The method and principle of radar collision prevention are described in detail in, for example, "Development Trend of Automotive Millimeter-Wave Radar" in IEICE Journal (October 1996, Vol. 79 No. 10).

[0003] Radar systems are roughly classified into pulse systems,
There are an FMCW (Frequency Modulated Continuous Wave) system, a two-frequency CW system, and a spread spectrum system, and three systems except for the pulse system use temporally continuous signals.

The FMCW system and the dual frequency CW system related to the present invention are described in "Introduction" by Merrill I. Skolnik.
This is described in detail in sections 3.3 and 3.5 of TO RADAR SYSTEMS. The monopulse method for obtaining the angle in the horizontal direction is described in section 5.4 of the same book.

In these radar devices, the relative speed between the other vehicle and the own vehicle is measured together with the position of the moving other vehicle or the stationary object.

In the FMCW radar, several tens to several hundreds μs
In a short time, the frequency is changed linearly by several tens to several hundred MHz in proportion to the passage of time, and the frequency difference between the reflected wave with a time delay and the transmitted wave is proportional to the distance to the object Use

[0007] In this distance measurement, a perfect proportional relationship is determined between frequency modulation and time. If the proportional relationship is broken, an error in distance measurement occurs. In order to improve the distance measurement accuracy, it is necessary to obtain a portion where the frequency difference between the transmitted wave and the reflected wave is small. However, there is a limit to the frequency analysis accuracy, and therefore, the distance resolution is poor.

In the detection of the azimuth angle in the FMCW method, for example, the radio wave beam is narrowed down, the direction of the radio wave beam is changed by changing the direction of the antenna, and it is determined that the target is located in the direction in which the reflected wave is obtained. The method is general.

In this case, the antenna becomes large or complicated in order to narrow the beam. That is, when an array antenna is used, a large number of antennas are required, and the device is further increased in size and complicated. In the mechanical scanning type, since there is a movable part that moves the antenna at high speed, the reliability deteriorates after long-term use.

In the two-frequency CW method, a Doppler signal of a reflected wave obtained at two frequencies is detected, a distance is obtained from a phase difference of the Doppler signal at each frequency, and an azimuth angle is obtained from an amplitude ratio. The phase difference and the amplitude are calculated for each frequency from the result of the frequency analysis.

[0011] A plurality of stationary objects ahead have substantially the same Doppler frequency corresponding to the speed of the radar-equipped vehicle. To obtain a frequency analysis result, the frequency components of the reflected waves from the plurality of stationary objects are reduced to one. Often included in peaks. Therefore, it is theoretically difficult to separate a plurality of stationary objects from a set of phase difference and amplitude obtained from the peak.

[0012]

The FMCW radar has poor range resolution. To detect the azimuth angle, for example, if you use an array antenna to narrow the radio beam,
The antenna shape becomes larger. To narrow the radio beam,
When a mechanical scanning type antenna that changes the direction of the antenna is used, the reliability of the movable unit is reduced during long-term use.

In the two-frequency CW radar, the Doppler frequencies of the reflected waves from a plurality of stationary objects enter one frequency peak which is substantially the same, and it is difficult to separate their positions.

As described above, each radar system has its own problem. In particular, when there are a plurality of stationary objects, they cannot be detected separately from each other, so that the danger determination may be insufficient.

An object of the present invention is to provide a radar apparatus capable of detecting the positions of a stationary object and a moving other vehicle and their relative speed with respect to the own vehicle with high accuracy.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention radiates radio waves from a radar device mounted on a vehicle and processes reflected waves to determine the position of another vehicle or a stationary object with respect to the vehicle. In a radar device that detects relative speed, an oscillator having frequency control means that alternately switches between two oscillation frequencies and frequency-modulates during the switching, a transmission antenna that radiates radio waves from the oscillator to a detection target, A plurality of receiving antennas for detecting a reflected wave from the detection target, a plurality of mixers for mixing the oscillating signal and each of the received signals, and a calculating means for calculating the sum and difference of the frequency-modulated mixed signals, Analysis means for determining the frequency distribution and phase distribution of each mixed signal; and a peak for determining the frequency at which the amplitude peaks and the phase thereof from the results of determining the frequency distribution and phase distribution. And the distance calculation means for calculating the distance to the target from the phase difference at the two switched frequencies among the peaks of the mixed signal alternately switched at the two frequencies, and alternately switched at the two frequencies. An azimuth angle determining means for obtaining an azimuth angle from a peak amplitude ratio of a plurality of mixed signals at at least one frequency of the mixed signal; and a candidate for obtaining a stationary object candidate peak among the mixed signal peaks alternately switched at the two frequencies. Determining means, selecting means for selecting a peak corresponding to a stationary object from a peak of a sum or difference signal of the mixed signals whose frequency has been temporally changed, and a stationary object candidate peak, and frequency-modulated mixing with the stationary object candidate peak Distance calculation means for calculating the distance to the detection target from the frequency difference between the sum or difference signal and the peak corresponding to the stationary object, and frequency-modulated and mixed Or an azimuth angle calculating means for obtaining an azimuth angle from a peak amplitude ratio between a plurality of signals at a stationary object peak of a difference signal to an object to be detected, and a sign of an amplitude ratio of a stationary object peak of a sum or difference signal mixed by frequency modulation. Means for obtaining the sign of the azimuth angle from
We propose a radar device that detects the positions and relative velocities of moving and stationary objects.

In order to achieve the above object, the present invention radiates radio waves from a radar device mounted on the own vehicle and processes reflected waves to determine the position and relative speed of another vehicle or a stationary object with respect to the own vehicle. In a radar device for detection, an oscillator equipped with frequency control means for alternately switching at two oscillation frequencies and frequency-modulating during the switching, a transmitting antenna for radiating radio waves from the oscillator to a detection target, and a detection target A plurality of receiving antennas for detecting reflected waves of the respective antennas, computing means for computing a sum and a difference between the received signals of the respective receiving antennas, a plurality of mixers for mixing the oscillation signal and the respective received signals, and frequency modulation Calculation means for calculating the sum and difference of the mixed signals, analysis means for determining the frequency distribution and the phase distribution of each mixed signal, and the results of determining the respective frequency distributions and the phase distributions A peak position determining means for determining a frequency at which a width becomes a peak and a phase thereof, and a distance for calculating a distance to a target from a phase difference at two switched frequencies among peaks of a mixed signal alternately switched at two frequencies. Calculating means, azimuth angle determining means for obtaining an azimuth angle from a peak amplitude ratio of a plurality of mixed signals at at least one of the mixed signals alternately switched at two frequencies, and a mixed signal alternately switched at two frequencies Candidate determining means for obtaining a candidate peak of a stationary object among the peaks of the above, and a selection of selecting a peak corresponding to the stationary object from the peak of the sum or difference signal of the mixed signal whose frequency has been temporally changed and the peak of the stationary object candidate Means and a distance from the frequency difference between the stationary object candidate peak and the peak corresponding to the stationary object of the sum or difference signal of the frequency-modulated mixed signal to the object to be detected A distance calculating means for calculating, and an azimuth angle calculating means for obtaining an azimuth angle from a peak amplitude ratio between a plurality of signals at a stationary object peak of a sum or difference signal mixed by frequency modulation to an object to be detected; Means for obtaining the sign of the azimuth angle from the sign of the amplitude ratio of the stationary object peak of the sum or difference signal, and proposes a radar device for detecting the positions and relative velocities of the moving object and the stationary object.

It is possible to provide a calculation means for calculating the average value by calculating the distance to the detection target and the azimuth angle by a combination of a plurality of detection signals.

It is also possible to provide a setting means for presetting the relationship between time and frequency in the frequency modulation of the oscillator in accordance with the distance to the object to be detected and the own vehicle speed.
The function of the frequency control means of the oscillator may be executed by a computer. The function of the calculating means for obtaining the sum and difference of the mixed signals can also be executed by the computer.

There is provided arithmetic means for averaging or comparing the position of the moving object obtained by alternately switching the oscillation frequency between the two frequencies or the positions of the moving object and the stationary object obtained by frequency modulation to increase the reliability of the measurement. You may.

It is also possible to provide a tracking means for tracking the position of a stationary object obtained by frequency-modulating in the positive or negative direction over time over a plurality of measurement times.

In any radar apparatus, if an A / D converter for simultaneously performing analog-to-digital conversion of a reflected signal obtained by the left and right antennas or a sum and difference signal of the reflected signals obtained by the left and right antennas is provided, Sampling can be accelerated.

In the radar device of the present invention, modulation of the transmission radio wave and detection sampling timing are devised. That is, a part that modulates two frequencies alternately as in the two-frequency CW method and a part that modulates the modulation frequency over time are used together. The reflected signal is sampled in each of a part that modulates alternately and a part that changes the frequency with time. Both reflected signals of a part that modulates two frequencies alternately and a part that modulates the modulation frequency over time are detected by two receiving antennas arranged on the left and right, and frequency-converted to an intermediate frequency.

In the two-frequency CW system, the position of a moving object is detected by using the mono-pulse system together. That is, the Doppler waveform of the object is detected from the intermediate frequency signals of the reflected waves at the two frequencies. These are subjected to frequency analysis, and the Doppler frequency is obtained as the peak. The distance to the target and the azimuth angle are calculated from the phase and amplitude of the Doppler peak frequency.

At this time, the present invention is different from the prior art in that
The purpose is to accurately obtain the Doppler frequency of the radar-equipped vehicle, in other words, the Doppler frequency of the relative speed with respect to a stationary object, from the Doppler peaks obtained by the two frequency modulations.

The Doppler frequency of the stationary object is used in the next portion that modulates the frequency in time, and is used to separate and detect a plurality of stationary objects.

In the portion where the frequency is changed with time, the distance from the peak to the stationary object and the azimuth angle calculated from the frequency analysis result and the like are calculated using the Doppler frequency of the stationary object obtained by the two-frequency CW method.

More specifically, the sum and difference of the signals of the left and right antennas are first calculated from the intermediate frequency signal of the reflected wave of the portion whose frequency changes temporally, and this is subjected to frequency analysis. For stationary objects, the sum signal forms a peak at the frequency obtained by subtracting the frequency dependent on the distance to the stationary object from the Doppler frequency, and the difference signal adds the Doppler frequency to the frequency dependent on the distance to the stationary object. A peak is formed. That is, there is a peak of a stationary object at a frequency position symmetric about the Doppler frequency. Even if there are a plurality of stationary objects, if the distances are different, the peak frequencies are different, so that they can be separated.

The frequency obtained by subtracting the frequency dependent on the distance to the stationary object from the Doppler frequency has information on the distance to the stationary object. Since the Doppler frequency of a stationary object is known in the two-frequency CW method, the distance to the stationary object can be calculated from the known Doppler frequency.

Further, the peak amplitude of the sum signal peak and the difference signal peak depends on the azimuth angle due to a slight difference in the path difference depending on the position in the azimuth direction. In the present invention,
The azimuth angle is calculated from the difference in the amplitude. As a result, the positions of a plurality of stationary objects can be detected separately, and the two-frequency C
Together with the W method, the positions of a moving object and a stationary object can be detected.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a radar apparatus according to the present invention will be described with reference to FIGS.

[0032]

FIG. 1 is a block diagram showing a basic configuration of a radar apparatus according to a first embodiment of the present invention. The radar device 100 obtains the position of the detection target 1 such as a moving vehicle or a stationary object and the relative speed with respect to the radar device 100, that is, the own vehicle.

FIG. 2 is a diagram showing an example of a state in which the radar device 100 is installed in front of a vehicle. Radar device 100
Is fixed at a position where transmission and reception radio waves are not obstructed.

FIG. 3 shows a radar device 100 mounted on a vehicle.
It is a figure which shows an example of the external appearance of. The transmitting antenna 102 and the two left and right receiving antennas 103 and 104 are antennas such as a horn antenna, a parabolic antenna, and a patch planar antenna. These antennas are arranged horizontally horizontally and transmit and receive radio waves forward. A processing circuit is mounted behind the antenna, and power is supplied from a battery of an automobile or the like.

In FIG. 1, an oscillator 101 whose modulation frequency can be controlled by a voltage is provided on the transmission side of the radar device 100, and a signal is radiated from a transmission antenna 102. The reflected waves from the detection target 1 are detected by the two receiving antennas 103 and 104 arranged on the left and right.

The mixers 105 and 106 mix a part of the oscillating signal from the oscillator 101 and the signals received from the receiving antennas 103 and 104, respectively. That is, mixer 1
Numerals 05 and 106 multiply the reflected wave and the transmission wave, convert the reflected wave to a lower intermediate frequency, and output it. This intermediate frequency signal includes information on the reflected wave. A / D converter 107 with amplifier,
108 converts the analog signals of the intermediate frequency from the left and right antennas into digital signals,
Transfer to The signal processor 110 executes processing of the detected radar signal.

The arbitrary waveform generator 111 controls the oscillation frequency of the oscillator 101, for example, as shown in FIG. The arbitrary waveform generator 111 includes A / D converters 107 and 1
The control of the conversion timing of 08 and the timing of data acquisition of the waveform memory are determined. Signal processor 110
When the waveform memory 109 stores the waveform data, the data is fetched and an obstacle is detected.

The processing result is displayed on the display 112. The display contents of the display 112 include the position, relative speed, danger, and the like of an obstacle in the detection range. The display method is not limited to numerical values or audio. A display method such as showing the front lane on a screen and overwriting the position of an obstacle on the screen may be adopted. The vehicle speed sensor 113 is a sensor that detects the vehicle speed based on the number of revolutions of the wheel shaft, and the like.
The vehicle speed information is sent to the signal processor 110.

FIG. 4 shows the oscillator 1 according to the first embodiment.
6 is a time chart illustrating a relationship between a frequency of a signal oscillated from No. 01 and a timing of detecting a reflected wave. In FIG. 4, R of R1 and R2 indicates an antenna on the right side of the two receiving antennas, and the position of a black circle is a point in time when a reflected wave is collected. Subscripts 1 and 2 indicate frequencies f1 and f2. The same applies to L1 and L2 of the left antenna. R1,
R2, L1 and L2 are before and after the data collection timing,
These are two fixed frequencies, and correspond to data acquisition in the frequency CW method.

On the other hand, R0m and R0p are the timings at which the reflected wave is collected by the right antenna at the f0 frequency at the time of detection and fluctuates with time, and the subscripts m and p are:
Indicates that the slope is negative or positive. Assuming that the modulation time width is Δt and the modulation frequency width is Δf, the slope of the positive frequency change is Δf / Δt, and the slope of the negative frequency change is
−Δf / Δt. L0m and L0p are the same except that the antenna is on the left. The voltage signal applied to the oscillator 101 is generated by the arbitrary waveform generator 111, and the oscillation frequency from the oscillator 101 is controlled based on this waveform.

When collecting reflection data at each black circle position shown in FIG. 4, the arbitrary waveform generator 111 controls an interval ΔT for collecting a series of data, and instructs A / D conversion for collection. , An address at which position in the waveform memory 109 to store the collected data is designated.

The outline of the configuration and operation of the radar apparatus has been described above. Here, the processing contents of the signal processor 110, which is the most important part of the present invention, will be described in detail. First, the characteristics of the sampled waveform are examined, and then, how to detect an obstacle will be described.

First, the characteristics of the sampled waveform are examined. The two-frequency CW method in which the frequencies f1 and f2 do not change within the sampling time and the part in which the frequency changes by Δf at a time Δt around f0 will be described separately. First, a part of the two-frequency CW system in which the frequencies f1 and f2 do not change within the collection time will be described.

The transmission waveform is represented by Expressions 1 and 2 where A is the amplitude.

(Equation 1)

(Equation 2) t is time, and Φ1 and Φ2 are arbitrary initial phases. The reflected signal of the frequency f1 is detected by the left and right antennas. The transmitted signal has a round trip time τR to the reflection target,
Each is detected with a delay of τL, and the amplitude also changes to B. The detection signal becomes Expression 3 for the detection signal of the right antenna, and Expression 4 for the detection signal of the left antenna.

(Equation 3)

(Equation 4) Similarly, the frequency f2 is given by Expressions 5 and 6.

(Equation 5)

(Equation 6) Mixers 105 and 106 detect signals detected by the left and right antennas.
, A low frequency component of the product of the reflected wave and the transmitted wave remains, and a component that changes in a sine wave shape in a short time at the frequencies f1 and f2 is removed.
Expressions 7 and 8 are obtained, and f2 is expressed by Expressions 9 and 10.

Equation 7

(Equation 8)

[Equation 9]

(Equation 10) Here, consider the output from the mixer of data collected from both antennas and two frequencies at a time interval ΔT. The speed of the radio wave is Sc, the relative speed between the radar-equipped vehicle and the detection target is v, and the initial distance from the right antenna to the target is K
Let it be R0. The distance KR changes with time, and the delay time τRi (i = 0, 1,...) Is represented by Expression 11 when the detection target is stationary and the mounted vehicle moves linearly.
Equation 11 corresponds to a case where the mounted vehicle and the target approach each other.

[Equation 11] Substituting τRi of Equation 11 into τR of Equation 7 gives Equation 1
Get 2. Similarly, Equations 8 to 10 also assume that the initial distance from the left antenna to the target is KL0.
It becomes 5.

(Equation 12)

(Equation 13)

(Equation 14)

(Equation 15) In Expressions 12 to 15, the first term in cos is iΔ
Since T corresponds to the elapsed time, it is the Doppler frequency.
In addition, the fact that information about distance is included in the second term is that
Easy to understand. Therefore, when, for example, the fast Fourier transform of the equations (12) and (14) is performed, the Doppler frequency is obtained from the peak frequency, and the distance is obtained from the phase. The score of one waveform to be used for the fast Fourier transform is:
It is predetermined.

FIG. 5 is a diagram showing an example of a frequency analysis result obtained by performing a fast Fourier transform. Since the Doppler frequencies for the same object are the same at f1 and f2, a peak is formed at the same frequency. Since the second term in cos in Expressions 12 and 14 indicates the phase, when the phase difference α between the two at this peak position is obtained, the distance is calculated from the phase difference α by Expression 16
Is required.

(Equation 16) Next, detection of the azimuth angle will be described. Expressions (12) and (13), which are reflection waveforms of the same frequency f1, are used to determine (K
R0−KL0) can be calculated.

(Equation 17) If the distance between the left and right antennas is d and the azimuth angle to be obtained is θ, the distance difference is represented by Expression 18, and therefore, the azimuth angle θ can be easily calculated as in Expression 19. Also, at this stage, the Doppler frequency for a stationary object is calculated from the vehicle speed of the vehicle speed sensor 113, and a peak having a frequency close to this value is searched for, so that the Doppler peak of the stationary object can be accurately obtained.

(Equation 18)

(Equation 19) Up to this point, the two-frequency CW which is a temporally constant modulation frequency
Using the method, it has been described that the distance to the target and the azimuth angle can be detected by the Doppler frequency.

Even if the combination of the detected values is changed, the distance to the target and the azimuth can be similarly detected. That is, Equation 15 is not used in the above calculation. Formula 1
Another combination of the distance to the target and the azimuth angle can be detected by a combination of 5 and another expression. Therefore, if an average of two sets of values is obtained, a plurality of calculation results can be averaged to reduce an error.

The method described above can detect objects having different Doppler frequencies, that is, objects having different relative velocities with respect to a radar-equipped vehicle, even if there are a plurality of objects, because the Doppler frequencies are different.

However, when there are a plurality of stationary objects, it is difficult to separate them. If a plurality of stationary objects are far apart from each other, they can be separated with different Doppler frequencies. When they are close to each other, the Doppler frequencies of a plurality of stationary objects naturally approach each other and may be lower than the frequency resolution of the fast Fourier transform, and one stationary object peak includes a plurality of stationary objects. In this case, the stationary object cannot be separated by the two-frequency CW method which is a temporally constant modulation frequency.

Therefore, in the present invention, a modulation method that changes the frequency over time is used. As shown in FIG. 4, reflection data of the left and right antennas is collected at timings indicated by L0 and R0 of the left and right antennas whose transmission frequency is f0. At this time,
The gradient that changes the frequency over time is Δf / Δt. Δf
In FIG. 4, the value of / Δt is indicated by adding a suffix p such as L0p and R0p when it is in the positive direction, and by adding a suffix m when it is in the negative direction. The transmission waveform is
If the frequency increases with time, the amplitude is represented by Expression 20 as A.

(Equation 20) If the frequency decreases with time, the slope Δf / Δt becomes
−Δf / Δt. When the inclination is positive, the detected waveform of the right antenna is represented by Expression 21, the left antenna is represented by Expression 22, and the mixer output is represented by Expressions 23 and 2.
4. B and C indicate the amplitude.

(Equation 21)

(Equation 22)

(Equation 23)

(Equation 24) Here, the sum and difference between Expressions 23 and 24 are calculated. Since the elapsed time is iΔT, the sum Dsop is given by Expression 25, and the difference Dd0p is given by Expression 26.

(Equation 25)

(Equation 26) In Expressions 21 to 24, when the slope is negative, Δf / Δ
It is sufficient to consider that the portion of t becomes -Δf / Δt. Therefore, the sum Ds0m is given by Expression 27, and the difference Dd0m is
Equation 28 is obtained.

[Equation 27]

(Equation 28) In Equations 25 and 27, when comparing the time change of the first cos term with the time change of the second cos term, the time change of the second term is significantly smaller than that of the first term.
The first term is the Doppler frequency, the sum of the distances between the left and right antennas and the target (KR0 + KL0), (KR0 * KR0 + KL
0 * KL0) and a large value that varies for each wavelength, whereas the second term is the distance difference (KR0−K
L0) and (KR0 * KR0-KL0 * KL0).

For this reason, the result of the fast Fourier transform of Equation 25, which is the sum, indicates the peak frequency at which the first term fluctuates, and the second term indicates a substantially constant amplitude value. In the first cos term of Expressions 25 and 27, the first term can be approximated as Expression 29.

(Equation 29) This is because the third term on the left side of Expression 29 is divided by the square of the radio wave speed Sc, which is a large value, so that it becomes negligibly small compared to the other two terms. For the same reason, the second term of the second cos and sin terms in Equations 25 and 26 can be approximated as in Equation 30.

[Equation 30] Also in Equations 26 and 28, the first sin term indicates the peak position at the same frequency as in Equations 25 and 27, and the second term indicates its amplitude. Further, from Expression 25 to Expression 28
, The change in amplitude with time is small.

FIG. 6 is a diagram showing the relationship between the stationary object Doppler frequency and the peak frequencies of the sum signal and the difference signal. When the slope of the frequency change is positive, the peak frequency in the first term is obtained by subtracting the frequency that changes depending on the distance from the target to the Doppler frequency, as is clear from Expression 29. If the slope is negative, the sum is the sum of the frequencies that change depending on the distance from the Doppler frequency to the target. That is, with respect to a stationary object, the peak positions of the positive and negative signals with respect to the Doppler frequency are symmetrical. In the above portion where the modulation frequency is not changed over time, the vehicle speed sensor and the Doppler frequency can be associated with each other. Therefore, if a peak symmetrical to the Doppler signal with a positive or negative frequency change is searched for a stationary object, Only peaks can be found. Also, from the difference between the Doppler frequency and the peak frequency, for example, the amplitude of the stationary object is the sum of the amplitudes of the fast Fourier-transformed peaks of Equations 25 and 26 where the frequency change is positive, and the sum and the difference are As and Ad, respectively.
Then, since Equation 31 is obtained, the distance difference can be easily obtained.

(Equation 31) This can be calculated even if the frequency change is negative,
An error can be reduced by averaging both. However, As, A
Since d is an amplitude and has no sign, the distance difference obtained from Expression 31 is the absolute value of the distance difference.

Therefore, a code is separately considered. The peak values of the fast Fourier transform results of Equations 25 and 26 are summed and A
sc and Adc (both are complex numbers). Where (Ad
If the angle of c / Ad) / (Asc / As) is obtained and its sign is calculated, the sign of the distance difference can be determined. This is the same even if the slope of the frequency change is negative. As described above, when the signed distance difference can be calculated, the azimuth angle can be obtained in the same manner as in the case of Expression 18. In this case, the peak of the result of the fast Fourier transform is generated according to the distance between the plurality of stationary objects and can be separated from each other. The position of a stationary object can be calculated.

FIG. 7 is a flowchart showing a processing procedure in the signal processor 110. The signal processor 110 captures the data of the reflected wave from the waveform memory 109, and executes analysis and display processing of the captured waveform.

In step 701, it is determined whether or not the waveform of the reflected wave has been completely stored in the waveform memory 109.

At step 702, the vehicle speed sensor 113 collects the vehicle speed data at the time when the waveform of the reflected wave is stored in the waveform memory 109.

In step 703, the waveform data in the buffer area is transferred to the work area for processing.

At step 704, the gradient Δf / Δt and −
The sum and difference are calculated for the left and right antenna signals at the portion where the frequency is temporally changed by Δf / Δt. The calculation formulas are Expressions 25 to 28.

In step 705, equations (12) to (15) are used.
And fast-Fourier-transform operations are performed on the waveforms obtained by Equations 25 and 28. Further, a peak position is obtained from the result of the fast Fourier calculation.

In step 706, the peak position, amplitude, and phase shown in FIG. 5 are calculated. When the peaks obtained from the fast Fourier transform calculations of Expressions 12 to 15 are compared with the vehicle speed data obtained in Step 702 as described above,
The peak of the stationary object is also determined at the same time.

In step 707, the distance to the moving object and the azimuth angle are calculated from the peaks other than the stationary object using Expressions 16 and 19, and the relative speed between the moving object and the radar-equipped vehicle is calculated from the peak position. Is detected.

At step 708, the position of the stationary object is determined. First, the distance is calculated from the difference fd between the Doppler frequency and the peak of the stationary object by using Expression 29, and (2f0 · v−fd ·
C) · Calculated as Δt / 4Δf. Further, the azimuth angle is calculated by Expression 32 and Expression 19. Since these positions can be calculated for each peak of a stationary object, even if there are a plurality of stationary objects, they can be separated.

In step 709, it is determined whether there is an obstacle in the traveling direction, whether there is an approaching object, or the like.
Give an alarm.

The features of the first embodiment are as follows: 1. Use two modulation frequencies that are constant in time and a modulation frequency that changes in time. 2. Receive reflected signals with two antennas. From two temporally constant modulation signals and a vehicle speed signal,
3. Find the position and relative speed of the moving object and the Doppler frequency of the stationary object. That is, a plurality of stationary objects can be separated and their positions can be detected from the reflected signal obtained from the modulation frequency that changes with time and the Doppler frequency obtained in step 3.

With these features, it is possible to provide a vehicle-mounted radar device capable of detecting the positions of a stationary object and a moving object with high accuracy.

[0065]

Second Embodiment FIG. 8 is a block diagram showing a basic configuration of a radar apparatus according to a second embodiment of the present invention. Embodiment 2
Is a radar apparatus provided with a sum-difference calculation circuit 114 for obtaining the sum and difference of high-frequency reflected waves in order to simultaneously sample data of R and L such as R1 and L1 and R0m and L0m.
As the sum-difference calculation circuit 114, for example, a magic tee or a ring-shaped calculation circuit is used.

FIG. 9 is a time chart for explaining the relationship between the modulation frequency and the signal detection timing in the second embodiment. For example, in the part of R1 + L1, the sum of the left and right antennas of the frequency f1 is collected.

In the first embodiment, the signal processor 11
0 is the data R0p + L0p and R0p-L0p and R0 of the portion where the frequency is changed with a temporal gradient.
m + L0m and R0m-L0m were calculated.

On the other hand, in the second embodiment, this is not necessary, and the processing for a stationary object is the same as that in the first embodiment. The difference between the first embodiment and the second embodiment is that the first embodiment can directly collect the detection signals of the left and right antennas in the modulation portion of a temporally constant frequency, whereas in the second embodiment,
It will be collected in the form of sum and difference.

If it is shown that the position and relative velocity of the moving object and the Doppler frequency of the stationary object can be obtained from the sum and difference sampling signals, the object of the present invention can be detected. The sum and difference signals for the frequency f1 are the sum (Dsm1) and the difference (Ddf1) of Equations 7 and 8, and for the frequency f2, the sum (Dsm2) and the difference (Ddf2) of Equations 9 and 10. There are equations 32 to 35.

(Equation 32)

(Equation 33)

(Equation 34)

(Equation 35) Expressions 32 to 35 are derived using Expression 11 and a similar relationship regarding KL0. As can be seen from Equations 32 to 35, Equations 32 and 33 indicate the waveform of the Doppler frequency 2v · f1 / Sc, and Equations 34 and 35 indicate the waveform of 2v · f2 / Sc. From its Doppler frequency as its peak position,
That is, the relative speed between the detection target and the radar-equipped vehicle can be detected. Further, the Doppler frequency for a stationary object can be detected as compared with the vehicle speed data of a vehicle equipped with a radar. The distance is obtained from the phase of each peak. Equation 32 and Equation 35
Let α be the phase difference obtained in step (2), and the distance is (KR0 + K
L0) / 2, which can be calculated by Expression 36.

(Equation 36) Further, the azimuth angle is obtained by calculating the amplitude ratio between Expression 32 and Expression 33 as H
Then, since there is a relationship of Expression 37, (KR
0−KL0), and can be calculated using equation (18).

[Equation 37] In the second embodiment, the method of calculating the position of the stationary object is the same as that of the first embodiment, and there is no significant change in the processing contents of the signal processor 110. In the flowchart of FIG. 7 showing the overall processing procedure of the first embodiment, step 70
4 is the same as that of the first embodiment except that the calculation of the portion for changing the modulation frequency over time is unnecessary, and thus detailed description is omitted.

The feature of the second embodiment is that, in addition to the features of the first embodiment, the sum operation and the difference operation of the signals collected in the portion where the modulation frequency is changed with time required in the first embodiment are performed by hardware. Since the execution is performed, the load on the software is reduced, and the processing can be sped up. Embodiment 2
However, an on-vehicle radar device capable of detecting the positions of a stationary object and a moving object can be provided.

[0071]

[Embodiment 3] Embodiment 3 of the present invention is a portion for changing the frequency over time, in which the slopes Δf / Δt and −Δf / Δt are changed according to the speed of the radar-equipped vehicle or the distance to the object to be observed most. It is characterized by controlling the value. The speed of the radar-equipped vehicle or the distance to the target uses the previous measurement value.

The larger the slope Δf / Δt is, the larger the detected frequency transition becomes, and the higher the detection accuracy is. But,
If Δt is constant, there is a limit to the observable round trip time, that is, the maximum detection distance to the target. On the other hand, when the target is a stationary object, higher detection accuracy is required because the higher the speed of the mounted vehicle and the shorter the distance to the target, the higher the risk.

Therefore, the value of the gradient Δf / Δt is set in advance in accordance with the relationship between the detection accuracy, the detection distance, and the danger, and the signal processing processor 110 sends the arbitrary waveform generator 11
Transfer this value to 1.

In the flowchart, step 7 in FIG.
At the stage where the risk is determined in step 09, Δf / Δt and −Δf / Δt used for the next measurement are set.

The third embodiment has an advantage that the detection accuracy can be adjusted according to the danger of the detection target.

[0076]

Fourth Embodiment A fourth embodiment of the present invention is different from the first, second, and third embodiments in that only a stationary object is detected from information of a reflected wave in a portion whose frequency changes with time. ,
This is an embodiment in which a moving object is detected together with a stationary object. Moving objects can be detected by a method that switches a plurality of modulation frequencies that are constant over time.However, if moving objects are detected from information on reflected waves in the part that changes the frequency over time, moving objects can be compared. Thus, the reliability of detection is improved.

A method for detecting a moving object from information of a reflected wave at a portion where the frequency is temporally changed will be described. Equations (25) to (28), which are the results of calculating the sum and difference of the reflected waves in the part that changes the frequency over time, indicate that there is a frequency peak at a symmetrical position with respect to a certain Doppler frequency as described above. ing. The center Doppler frequency is obtained from a frequency analysis result of a method of switching a plurality of modulation frequencies that are constant over time. These peaks are found not only in stationary objects but also in moving objects. In the first, second, and third embodiments, the stationary object peak is searched for from the peak close to the vehicle speed among the Doppler peaks.

In the fourth embodiment, the peak of the moving object is also used, and a symmetrical one is used in Expressions 25 and 28. The method of calculating the distance and the azimuth angle of the moving object from the peak amplitude and phase is the same as that of the stationary object, and thus the description is omitted. By averaging or comparing the position of a moving object based on the method of switching a plurality of modulation frequencies that are constant over time and the position of a moving object obtained from information on the reflected wave of the portion that changes the frequency over time, the reliability of detection is improved. improves.

[0079]

Embodiment 5 Embodiment 5 of the present invention is different from Embodiments 1, 2, 3, and 4 in that the gradients that change the frequency with time are two, that is, Δf / Δt and −Δf / Δt. On the other hand, there is a feature in using either one. As described above, the Doppler peak of a stationary object can be detected from the result of the two-frequency CW method in which the frequency is not changed with time.

In the fifth embodiment, Δf / Δt and −Δf /
The frequency peak collected at one slope of Δt is tracked during a plurality of measurements to determine the distance to a stationary object. Since this peak approaches a stationary object with the progress of the own vehicle, the distance of the peak is stored and tracked a plurality of times, and an object whose decrease in the distance approaches as the own vehicle advances advances is determined to be a stationary object. Find its position.

In the fifth embodiment, since a stationary object is detected by a plurality of measurements, the position cannot be detected by one measurement as in the first, second, third, and fourth embodiments. In the sense that the number of
There are great benefits.

[0082]

Embodiment 6 FIG. 10 is a time chart for explaining the relationship between the modulation frequency and the timing of signal detection according to Embodiment 6 of the present invention. The sixth embodiment is characterized in that both detection data of the left and right antennas are collected at one sampling timing.

In the sixth embodiment, the A
The / D converters 107 and 108 output, for example, R at the frequency f1.
A / D simultaneously reflected signals from left and right antennas 1 and L1
Convert it. A / D converter to waveform memory 10
Since transfer to 9 cannot be performed at the same time, another data is sent after one is completed. In this way, the data R2 and L2, R0p and L0p, and R0m and L0m can be sampled at the same time, and as shown in FIG. 10, data can be sampled in half the time of the first embodiment, and the speed can be increased.

When the sixth embodiment is applied to the second embodiment, since the sum and difference data can be collected simultaneously, the same effect can be obtained.

[0085]

According to the present invention, the position of a moving object can be detected using two temporally constant frequencies, and the relative speed can be detected using the Doppler frequencies of a moving object and a stationary object. Furthermore, the position of the stationary object can be detected using the detected Doppler frequency of the stationary object and the frequency peak of the modulated wave whose frequency has been temporally changed. Therefore, it is possible to obtain an on-vehicle radar device that can separate the positions of a stationary object and a moving object, which are conventionally difficult, and can detect the positions with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a state where a radar apparatus 100 is installed in front of a vehicle.

FIG. 3 is a diagram showing an example of an appearance of a radar device 100 mounted on a vehicle.

FIG. 4 is a time chart illustrating a relationship between a frequency of a signal oscillated from an oscillator 101 and a timing of detecting a reflected wave in the first embodiment.

FIG. 5 is a diagram illustrating an example of a frequency analysis result obtained by performing a fast Fourier transform in the first embodiment.

FIG. 6 is a diagram illustrating a relationship between a stationary object Doppler frequency and peak frequencies of a sum signal and a difference signal.

FIG. 7 is a flowchart showing a processing procedure in the signal processor 110.

FIG. 8 is a first embodiment of a radar apparatus according to the present invention;
FIG. 2 is a block diagram showing a basic configuration of FIG.

FIG. 9 is a time chart illustrating a relationship between a modulation frequency and a signal detection timing according to the second embodiment.

FIG. 10 is a time chart illustrating a relationship between a modulation frequency and a signal detection timing according to a sixth embodiment.

[Description of Signs] 1 Detection target, 100 Radar device 101 Oscillator 102 Transmit antenna 103 Receive antenna 104 Receive antenna 105 Mixer 106 Mixer 107 A / D converter 108 A / D converter 109 Waveform memory 110 Signal processor 112 Display 111 Arbitrary waveform generator 113 Vehicle speed sensor 114 Sum-difference calculation circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H180 AA01 CC12 CC14 CC15 LL01 LL04 LL07 LL08 5J070 AB08 AC01 AC02 AC06 AD02 AD06 AE01 AF03 AH25 AH31 AH35 AK22 BF03

Claims (9)

[Claims] 1. A radar device for radiating radio waves from a radar device mounted on an own vehicle and processing reflected waves to detect the position and relative speed of another vehicle or a stationary object with respect to the own vehicle. An oscillator having frequency control means for performing frequency modulation during the switching, and a transmission antenna for radiating radio waves from the oscillator to a detection target; and a plurality of detecting antennas detecting reflected waves from the detection target. A receiving antenna, a plurality of mixers for respectively mixing the oscillation signal and each of the received signals, an arithmetic unit for obtaining a sum and a difference of the frequency-modulated mixed signals, and a frequency distribution and a phase distribution of each mixed signal. Analysis means for obtaining the frequency distribution and phase distribution, and peak position determination means for obtaining the frequency at which the amplitude peaks and the phase thereof from the result of obtaining the respective frequency distribution and phase distribution. Distance calculating means for calculating the distance to the target from the phase difference at the two switched frequencies among the peaks of the mixed signal alternately switched at the wave number; and at least one of the mixed signals alternately switched at the two frequencies Azimuth angle determining means for obtaining an azimuth angle from a peak amplitude ratio of a plurality of mixed signals at a frequency; candidate determining means for obtaining a candidate peak of a stationary object among the peaks of the mixed signal alternately switched at two frequencies; Selecting means for selecting a peak corresponding to a stationary object from the peak of the sum or difference signal and the stationary object candidate peak of the mixed signal whose frequency has been changed, and the sum of the stationary object candidate peak and the frequency-modulated mixed signal. Alternatively, distance calculating means for calculating the distance to the detection target from the frequency difference between the peak of the difference signal and the peak corresponding to the stationary object, and a frequency-modulated mixed sum. Azimuth angle calculation means for obtaining an azimuth angle from a peak amplitude ratio between a plurality of signals at a stationary object peak of a difference signal to an object to be detected, and an amplitude ratio of a stationary object peak of a sum or difference signal mixed by frequency modulation. Means for obtaining a sign of the azimuth angle from the sign, and detecting positions and relative velocities of a moving object and a stationary object. 2. A radar device which emits radio waves from a radar device mounted on the own vehicle and processes reflected waves to detect the position and relative speed of another vehicle or a stationary object with respect to the own vehicle. An oscillator having frequency control means for performing frequency modulation during the switching, and a transmission antenna for radiating radio waves from the oscillator to a detection target; and a plurality of detecting antennas detecting reflected waves from the detection target. A receiving antenna, calculating means for calculating a sum and a difference between received signals of the respective receiving antennas, a plurality of mixers for mixing the oscillation signal and the respective received signals, and a sum of the frequency-modulated mixed signal and Calculating means for calculating the difference, analyzing means for determining the frequency distribution and phase distribution of each mixed signal, and amplitude peaking from the result of determining each frequency distribution and phase distribution. Peak position determining means for determining a frequency and its phase; distance calculating means for calculating a distance to a target from a phase difference at the two switched frequencies among the peaks of the mixed signal alternately switched at the two frequencies; Azimuth angle determining means for obtaining an azimuth angle from a peak amplitude ratio of a plurality of mixed signals at at least one of the mixed signals alternately switched at two frequencies; and Candidate determining means for obtaining a candidate peak of a stationary object, and selecting means for selecting a peak corresponding to a stationary object from the peak of the sum or difference signal of the mixed signal of which the frequency is temporally changed and the candidate peak of the stationary object. From the frequency difference between the stationary object candidate peak and the peak corresponding to the stationary object of the sum or difference signal of the frequency-modulated mixed signal to the detection target Azimuth angle calculating means for obtaining an azimuth angle from a peak amplitude ratio between a plurality of signals at a stationary object peak of a frequency-modulated sum or difference signal to an object to be detected; Means for obtaining the sign of the azimuth angle from the sign of the amplitude ratio of the stationary object peak of the sum or difference signal mixed together, and detecting the positions and relative velocities of the moving object and the stationary object. 3. The radar device according to claim 1, further comprising a calculating unit that calculates a distance to the detection target and an azimuth angle using a combination of a plurality of detection signals to obtain an average value. Radar equipment. 4. The radar device according to claim 1, wherein a relationship between time and frequency in frequency modulation of the oscillator is determined in advance according to a distance to a detection target and a vehicle speed. A radar apparatus comprising setting means for setting. 5. The radar device according to claim 1, wherein the frequency control means of the oscillator is a computer. 6. The radar apparatus according to claim 1, wherein said calculating means for calculating the sum and difference of the mixed signals is a computer. 7. The radar apparatus according to claim 1, wherein a position of a moving object obtained by alternately switching an oscillation frequency between two frequencies or a moving object and a stationary object obtained by frequency modulation. A radar device comprising arithmetic means for averaging or comparing the positions of the above to increase the reliability of the measurement. 8. The radar apparatus according to claim 1, wherein the position of a stationary object obtained by frequency-modulating in a positive or negative direction over time is measured over a plurality of times. A radar device provided with a tracking means for tracking. 9. The radar device according to claim 1, wherein the reflected signals obtained by the left and right antennas or the sum and difference signals of the reflected signals obtained by the left and right antennas are simultaneously analog-digital. A radar device comprising an A / D converter for conversion.