JP2874826B2 - Detection state evaluation device for FM-CW radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating an object detection state by an FM-CW radar apparatus.

[0002]

2. Description of the Related Art In recent years, for example, in an automobile, a relative distance and a relative speed of an object such as another vehicle existing in front of or behind the own vehicle with respect to the own vehicle are detected by using a radar device mounted on the own vehicle. In response to this, automatic driving control such as maintaining the inter-vehicle distance, braking, etc., and performing various alarms have been developed. In this type of radar device, detection of a relatively short-distance object is performed. Is possible, and because the system configuration is relatively simple,
Generally, an FM-CW radar device is used.

[0003] The detection of the relative distance and the relative speed of the object by the FM-CW radar apparatus is performed as follows.

That is, for example, as shown in FIG. 2, the frequency is linearly increased or decreased between the frequencies f _X and f _Y.
In other words, a signal obtained by modulating the frequency in the form of a triangular wave as a transmission signal, an electromagnetic wave having the same frequency as the transmission signal is transmitted toward the target, and the reflected wave reflected by the target is transmitted. Receive the wave. At this time, the received wave signal of the reflected wave is frequency-modulated in a triangular wave shape like the transmitted signal, but the time required to reciprocate between the antenna transmitting and receiving the electromagnetic wave and the object. A delay of τ is generated with respect to the transmission signal. Therefore, when the transmission signal and the reception signal are compared on the same time axis, a frequency difference f _B between the two signals is proportional to the delay time τ. Is generated. In this case, since the delay time τ is proportional to the relative distance of the object, the frequency difference f _B is also proportional to the relative distance of the object, and if the relative distance of the object is D, the following equation (1) holds. .

D = k · f _B (1) In equation (1), k is the propagation speed of the electromagnetic wave (= light speed).
And a time constant of the frequency of the transmitted / received signal.

[0006] Based on such a basic principle, FM-C
W radar apparatus, by mixing the transmit signal and the received signal to generate a beat signal having a frequency of the frequency difference f _B of the two signals, to detect the frequency f _B of the beat signal. Detection in this case, the beat signal frequency f _B is
For example the period in which the frequency of both the transmitting signal and the reception signal increases together (in FIG. 2, period denoted by reference numeral T _W) and is carried out in a period in which both the frequency decreases both. Then, from the frequency f _B of the detected beat signal, the above equation (1) is obtained.
To determine the relative distance D of the object. The FM-CW radar device detects the relative distance D by the transmission and reception of each electromagnetic wave while repeating the transmission and reception of the electromagnetic waves as described above, for example, as shown in FIG. 2, and sometimes determines the relative distance D of the target object. Detect every moment.

Since the relative speed of the object is obtained by differentiating the relative speed D with respect to time, if the relative distance D is detected at a sufficiently short time interval, the relative speed of the object is calculated based on the temporal change rate of the relative distance D. Can be detected.

By the way, in such an FM-CW radar device, in order to accurately detect the relative distance of an object, linearity (so-called linearity) of a frequency change of a transmission signal is required, while transmission is required. Due to the heat of the wave signal oscillator and the circuit for modulating and controlling the frequency, etc.
In some cases, the linearity of the frequency change of the transmission / reception signal is reduced. In such a case, it is difficult to accurately detect the relative distance of the target object. Also, even if the linearity of the frequency of the transmission signal is good, for example, when the FM-CW radar device of the own vehicle receives the electromagnetic wave transmitted from the FM-CW radar device mounted on another vehicle, Depending on the transmission timing of the electromagnetic waves, the two electromagnetic waves may interfere with each other, making it difficult to accurately detect the relative distance of the object.

That is, referring to FIG. 11, FIG.
As shown, when the linearity of the frequency of the transmitted signal is good, the linearity of the frequency of the received signal is also good.
In this case, the FM-CW radar apparatus, for example, in the period T _W of the frequency of both the transmitting and receiving wave signal increases together to generate a beat signal by mixing two signals, thereby shown in FIG. (B) Such a beat signal is obtained. At this time, the spectrum distribution (frequency distribution) of the beat signal basically has a steep peak (maximum value) at a frequency f _P corresponding to the relative distance of the target object, as shown in FIG. It becomes such a distribution. Therefore, when the frequency of the beat signal is detected, the detected frequency becomes the frequency f _P corresponding to the relative distance of the target object, and the frequency f _{P
From P} , the relative distance of the target object can be obtained with high accuracy according to the above equation (1).

On the other hand, referring to FIG. 12, if the linearity of the frequency of the transmitted signal becomes poor as shown in FIG. 1A, the linearity of the frequency of the received signal also becomes poor. If the two signals are mixed during a period T _W in which both frequencies of the wave signal increase, a beat signal as shown in FIG. At this time,
Spectral distribution of the beat signal is not the steep distribution as described above, as shown in FIG. (C), becomes a distribution having a spread include frequency f _P corresponding to the relative distance to the object , this beat signal is meant to include many other frequency components other than the frequency f _P components corresponding to the relative distance of the object. Therefore, in such a case, even when detecting the frequency of the beat signal, making it difficult to detect the frequency f _P corresponding to the relative distance to the object, it reduces the detection accuracy of the relative distance of the object easy.

Referring to FIG. 13, for example, FIG.
As shown in (a), transmission of own FM-CW radar device
Transmission of FM-CW radar equipment such as other vehicles to the received signal
When a signal is received, the frequency of its own transmitted / received signal increases.
Addition period T_WIn, mixing the transmitted and received signals
The beat signal becomes a signal as shown in FIG.
You. At this time, the spectrum distribution of the beat signal is as shown in FIG.
As in the case of FIG. 2, the distribution does not become steep, and FIG.
As shown in the figure, the frequency f corresponding to the relative distance of the object _P
And the distribution has a spread. So, like this
In this case, even if the frequency of the beat signal is detected,
Frequency f corresponding to relative distance_PDifficult to detect and
As a result, the detection accuracy of the relative distance of the target decreases. still,
The transmission signal of the FM-CW radar device of such another vehicle is
Interference is caused by the transmission signal of own FM-CW radar device and other vehicles.
Transmission timing with the transmission signal of the FM-CW radar device
In some cases, this does not occur.

As described above, in the FM-CW radar device, when the linearity of the frequency of the transmission signal is reduced or when there is interference of the transmission wave of another FM-CW radar device, the relative distance of the object is detected. It is not preferable to detect the target in such a state, because the accuracy is lowered. In particular, in an FM-CW radar device for an automobile, automatic traveling control such as braking is performed or a warning is issued to a driver or the like in accordance with the detection of the relative distance and relative speed of the target object. Therefore, it is not preferable to continue the detection of the relative distance or the relative speed of the object in the above state, and in the above state, the detection of the relative distance or the relative speed is stopped, or It is desirable to give a warning.

However, in the conventional FM-CW radar device, there is no device capable of detecting a state such as a decrease in the linearity of the frequency of a transmission signal and an interference of a transmission wave of another FM-CW radar device. Therefore, it has been desired to be able to evaluate such a detection state.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing background, and has been made in consideration of the linearity of the frequency of a transmitted signal and other factors.
FM-
An object of the present invention is to provide a detection state evaluation device for an FM-CW radar device that can easily evaluate the quality of a detection state of an object by a CW radar device.

[0015]

In order to achieve the above object, a detection state evaluation apparatus in an FM-CW radar apparatus according to the present invention uses an electromagnetic wave modulated to increase or decrease the frequency in a triangular wave form as an object. Means for transmitting toward;
Means for receiving the reflected wave of the electromagnetic wave, and a beat signal having a frequency corresponding to the relative distance of the object by mixing a part of the transmitted signal of the electromagnetic wave and the received signal of the reflected wave Means for generating, and the beat generated by mixing the transmitted signal and the received signal in a predetermined period predetermined as a period in which both the frequency of the transmitted signal and the frequency of the received signal both increase or decrease. Means for detecting the frequency of the signal as a frequency corresponding to the relative distance of the object, and means for detecting the relative distance of the object from the detected frequency. The predetermined period for detecting the frequency of the beat signal is divided into a plurality of sub-periods, and a frequency distribution of the beat signal in each sub-period is determined. Number analysis means and predetermined characteristics of the spectral distribution of the beat signal in each of the short periods are compared with each other, and when the characteristics substantially match each other, the detection state of the relative distance is determined to be good, and the characteristic is determined. And a determination unit that determines the detection state of the relative distance to be defective when the two do not substantially match each other.

The radar device is a radar device that repeats the transmission of the electromagnetic wave. When the pass / fail determination unit determines that the detection state of the relative distance is bad, the transmission timing of the electromagnetic wave is determined. And a transmission timing changing means for changing the transmission timing.

Further, the characteristics of the spectrum distribution of the beat signal in each of the small periods compared by the pass / fail judgment means include a peak frequency at which the spectrum level in each spectrum distribution has a maximum value, and a spectrum distribution at the position of the peak frequency. The Q value of

Further, the frequency analysis means and the pass / fail judgment means are means for periodically repeating the above-mentioned evaluation processing, and the pass / fail judgment means is arranged so that the spectrum level in the spectrum distribution of the beat signal in each of the short periods is maximized. Means for detecting a peak frequency as a value, and when it is determined that the detection state of the relative distance is bad in the current evaluation processing and the previous evaluation processing, the relative distance is detected in the previous evaluation processing and the current evaluation processing. Means for comparing the peak frequencies with each other, and means for identifying the cause of the detection of the relative distance being determined to be defective based on the result of the comparison.

The predetermined period for detecting the frequency of the beat signal when detecting the relative distance of the object based on the comparison result of the spectrum distribution of the beat signal in each of the small periods by the pass / fail judgment means. And a detection period setting unit that sets a period obtained by combining a plurality of continuous short periods in which the characteristics of the spectral distribution of the beat signal are substantially the same among the short periods. It is characterized in that the predetermined period is set.

[0020]

According to the present invention, when detecting the relative distance of the object, the predetermined period during which the frequency of the beat signal is detected, that is, both the frequency of the transmitted signal and the frequency of the received signal are both increased. Alternatively, in the plurality of sub-periods obtained by dividing a predetermined period predetermined as a decreasing period, a spectrum distribution of each sub-period is obtained by the frequency analysis unit, and the characteristics of the spectrum distribution are determined by the pass / fail judgment unit. Are compared by At this time, the FM-
If the linearity of the transmission signal of the CW radar device is good, and if there is no interference of the transmission signals of other FM-CW radar devices, the spectral distribution of the beat signal in each of the small periods is substantially the same. It is considered to be distribution. Therefore, if the characteristics of the spectral distributions to be compared are appropriately determined, the linearity of the transmission signal of the FM-CW radar device is good when the characteristics of the spectral distributions in each of the short periods substantially match each other. In addition, since it is considered that there is no interference of the transmission signal of another FM-CW radar device, the pass / fail determination means determines that the detection state of the relative distance of the target by the FM-CW radar device is good. On the other hand, in other cases, the linearity of the transmission signal of the FM-CW radar device is poor, or other F
Since it is considered that the interference of the transmission signal of the M-CW radar device has occurred, the pass / fail determination unit determines that the detection state of the relative distance of the target by the FM-CW radar device is bad.

In the case where the FM-CW radar apparatus repeats transmission of an electromagnetic wave, when the pass / fail determination unit determines that the detection state is defective, the transmission timing changing unit determines that the electromagnetic wave is transmitted. The transmission timing is changed, so that when a failure occurs in the detection state due to interference of the transmission signal of another FM-CW radar device, such a state can be resolved. It should be noted that the transmission timing of the electromagnetic wave may be changed regularly or randomly.

Further, as the characteristics to be compared with each other in the spectrum distribution in each of the small periods, it is preferable to use, for example, the peak frequency and the Q value of each spectrum distribution. This is because when the linearity of the transmission signal of the FM-CW radar device is poor or when the transmission signal of another FM-CW radar device interferes, such a state occurs. If the peak frequency (which corresponds to the relative distance of the object) differs between the short period and the short period in the normal state, and the shape of the spectrum distribution at the position of the peak frequency differs. Because it is possible. Note that the Q value generally indicates the sharpness of a signal waveform, and indicates that the linearity of a transmission signal of an FM-CW radar device is poor or that other FM-C
The Q value of the spectrum distribution of the beat signal in the short period in which the interference of the transmission signal of the W radar device occurs is smaller than the Q value of the spectrum distribution in the short period in the normal state.

In general, when the linearity of the transmission signal of the FM-CW radar apparatus is poor, when the above-described evaluation processing is repeated, the peak frequency of each spectrum distribution in each small period is reduced. Is detected, the peak frequency detected in the previous evaluation process and the peak frequency detected in the current evaluation process are almost the same in many cases. Therefore, when the evaluation processing by the frequency analysis means and the pass / fail determination means is periodically repeated, the peak frequency of the spectrum distribution of the beat signal in each of the short periods is detected, and the current evaluation processing and the previous evaluation processing are performed. When a defect in the detection state is determined in the evaluation process, it is possible to identify the cause of the defect by comparing the peak frequencies detected in the previous evaluation process and the current evaluation process with each other. Become.

Further, when the linearity of the transmission signal of the FM-CW radar device is good and there is no interference of the transmission signal of another FM-CW radar device, when detecting the relative distance of the object, It is preferable to detect the frequency of the beat signal during a period in which the frequency of the transmitted / received signal increases or decreases linearly, and it is preferable to set such a period by actually transmitting / receiving electromagnetic waves.
Therefore, based on a comparison result of the spectrum distribution of the beat signal in each of the small periods by the pass / fail judgment means, a period formed by combining a plurality of continuous small periods in which the characteristics of the spectrum distribution substantially match each other is set. The frequency of the beat signal is set as the predetermined period to be detected when detecting the relative distance of the object. In the period set in this way, the characteristics of the spectrum distribution in each of the small periods constituting the period substantially coincide with each other, so that the frequency of the transmission / reception signal of the electromagnetic wave increases or decreases linearly together. Therefore, it is possible to accurately detect the relative distance.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of the present invention will be described with reference to FIGS. FIG. 1 shows an FM including the detection state evaluation device of the present embodiment.
2 is a system configuration diagram of the CW radar device, FIG. 2 is an explanatory diagram showing transmission / reception signals of electromagnetic waves by the radar device of FIG. 1, FIGS. 3 to 5 are flowcharts for explaining the operation of the radar device of FIG. 1, FIG. 10 are explanatory diagrams for explaining the operation of the radar apparatus of FIG.

Referring to FIG. 1, the FM-
The CW radar device is mounted on, for example, an automobile, 1 is an oscillator that generates a transmission signal of an electromagnetic wave, 2 is a modulation control circuit that modulates and controls the frequency of the transmission signal generated by the oscillator 1 over time, 3 is an oscillator 1 to an isolator 4,
An antenna for transmitting an electromagnetic wave having the same frequency as the transmitted signal in response to a transmitted signal provided via the directional coupler 5 and the circulator, and receiving a reflected wave of the transmitted electromagnetic wave; A part of the transmission signal distributed / input via the sexual coupler and the reception signal input via the circulator 6 from the antenna 3 are mixed to have a frequency corresponding to a temporal frequency difference between the two signals. A mixer for generating a beat signal, 8 is an amplifier for amplifying the beat signal generated by the mixer 7, 9 is an A / D converter for A / D converting the beat signal amplified by the amplifier 8, and 10 is A / D conversion. A memory for storing and holding the beat signal A / D-converted by the device 9 in chronological order; and 11 for analyzing the beat signal data stored and held in the memory 10 to detect the relative distance of the target object. A signal processing device 12 for evaluating the detection state and the like is provided with a timing signal defining the timing of storing the beat signal A / D-converted by the A / D converter 9 in the memory 10 and a frequency-modulated electromagnetic wave. A timing signal generation circuit that generates a timing signal that defines a transmission timing according to an instruction from the signal processing device 11 and provides the timing signal to the memory 10 and the modulation control circuit 2;
Is a power supply circuit of the oscillator 1. The antenna 3 has directivity, and transmits an electromagnetic wave toward an object A such as another vehicle existing in front of the own vehicle, for example.

The signal processing device 11 is constituted by an electronic circuit including a microcomputer and the like. The structure of the signal processing device 11 is roughly classified into data processing of a beat signal in order to detect the relative distance D of the object A and the like. , And an evaluation signal processing unit 15 that performs data processing of a beat signal to evaluate the quality of the detection state. Then, the evaluation signal processing unit 15
As its functional configuration, the frequency analysis means 16 for frequency-analyzing the data of the beat signal, and the relative distance D of the object A by the detection signal processing unit 14 based on the spectral distribution of the beat signal obtained by the frequency analysis. Quality judgment means 17 for judging the quality of the detection state, and power supply stop instruction means 18 for outputting a power supply stop command to the power supply circuit 13 of the oscillator 1.
An alarm instruction means 19 for outputting an alarm command to an alarm device such as a buzzer (not shown); a transmission timing instruction means 20 for instructing the modulation control circuit 2 via the timing signal generation circuit 12 on the transmission timing of the electromagnetic wave; There is provided a detection timing instructing means 21 for instructing the memory 10 via the timing signal generating circuit 12 at a timing at which the data of the beat signal is stored and held in the memory 10.

In these configurations, the transmission timing instructing means 20 and the timing signal generating circuit 12 constitute a transmission timing changing means 22, and the detection timing instructing means 21 and the timing signal generating circuit 12 constitute a detecting period setting means 23. I do.

Next, the operation of the apparatus according to the present embodiment will be described together with the detailed description of each part thereof.

First, the basic operation of the FM-CW radar apparatus of the present embodiment (hereinafter referred to as radar processing operation) will be described.

In the FM-CW radar apparatus of the present embodiment, the frequency of the transmission signal generated by the oscillator 1 is modulated and controlled by the modulation control circuit 2 into a triangular waveform as shown by the solid line in FIG. Such modulation control is performed by the timing signal generation circuit 12 according to an instruction from the signal processing device 11.
Is periodically repeated according to the timing signal output from the controller, with a pause period T _{O in the} middle. Then, the transmission signal whose frequency has been modulated and controlled as described above is applied to the antenna 3 via the isolator 4, the directional coupler 5, and the circulator 6, thereby having the same frequency as the transmission signal from the antenna 3. The electromagnetic wave frequency-modulated in a triangular wave is periodically transmitted toward an object A existing in front of the vehicle.

When such an electromagnetic wave is transmitted, the reflected wave from the object A is received by the antenna 3, and the received signal is input to the mixer 7 via the circulator 6. At this time, a part of the transmission signal output from the oscillator 1 is distributed and input to the mixer 7 via the directional coupler 5, and the mixer 7 mixes the transmission signal and the reception signal. I do. As a result, as described above, basically, a beat signal (see FIG. 11B) having a frequency corresponding to the relative distance D of the target A with respect to the own vehicle is generated.

The beat signal generated by the mixer 7 is amplified by a necessary amplitude level by an amplifier 8, A / D converted by an A / D converter 9 at predetermined sampling times, and then digitized. The amplitude data of the beat signal is stored and held in the memory 10 in time series. In this case, the memory 10 chronologically stores and holds the amplitude data of the beat signal in accordance with the timing signal output from the timing signal generation circuit 12 in accordance with the instruction of the signal processing device 11, and transmits and receives the electromagnetic wave frequency-modulated in a triangular waveform. Each time a wave is performed, the amplitude data of the beat signal is stored and retained in a time-series manner within a predetermined period during the transmission and reception of the wave. In this embodiment, as the predetermined period, for example, a period T _W (hereinafter, referred to as a detection period T _W ) in which both frequencies of the transmitted and received signals increase as shown in FIG. 2 is set.

The detection period T _W is determined by the detection period setting means 2 prior to the radar processing operation of the radar apparatus of the present embodiment.
3, which will be described later. Further, the detection period T _W may be set as a period during which both frequencies of the transmission and reception signals decrease.

As described above, based on the beat signal data stored and held in the memory 10, the detection signal processing unit 14 of the signal processing device 11 performs the processing of the object A as described below.
Is detected.

That is, referring to the flowchart of FIG. 3, the detection signal processing section 14 first sets the detection period T _W
In FIG. 3, the frequency analysis of the beat signal data stored and held in the memory 10 is performed to determine the spectrum distribution (FIG. 3).
STEP 1). This frequency analysis is, for example, an FFT (Fast Fourier Transform method) which is an arithmetic processing method of frequency analysis.
This is performed using By such a frequency analysis, basically, as described above, a spectrum distribution as shown in FIG. 11C is obtained. That is, the peak at the frequency f _P corresponding to the relative distance D of the object A (maximum value)
Is obtained.

Next, the detection signal processing section 14 detects a frequency (peak frequency) f _{P at} which the spectrum level has a peak in the obtained spectrum distribution (STEP 2 in FIG. 3). Detection of such a peak frequency f _P
For example, the detection is performed by detecting a frequency at which the spectrum level is equal to or higher than a predetermined threshold value and the change of the spectrum level with respect to the frequency changes from an increasing trend to a decreasing trend.

Then, the detection signal processor 14 sets the detected peak frequency f _P as a frequency corresponding to the relative distance D of the object A, and calculates the above equation (1) from the peak frequency f _P.
, And outputs the obtained relative distance D to an automatic traveling control device (not shown) or the like (STEP 3 in FIG. 3).

In the radar processing operation of the radar apparatus according to the present embodiment, the above-described operation is repeated every time the transmission and reception of the electromagnetic wave whose frequency is modulated in a triangular wave is performed.
The relative distance D of the object A is detected every moment.

Since the value obtained by differentiating the detected relative distance D with respect to time is the relative speed of the object A with respect to the own vehicle, when the relative speed of the object A is also detected, for example, Assuming that the time interval for detecting the relative distance D is Δt and the amount of change in the relative distance D during the time interval Δt is ΔD, the relative speed V of the target A can be obtained by the following equation (2).

V = ΔD / Δt (2) In the apparatus of this embodiment, in parallel with the radar processing operation, the evaluation signal processing section 15 of the signal processing apparatus 11 detects the relative distance D in the detection state. The evaluation is performed. Next, the operation of the evaluation processing will be described.

Referring to FIGS. 4 and 6, the evaluation signal processing unit 15 first _converts the beat signal data of the detection period T _W stored and held in the memory 10 into the frequency analysis means 16 as described above. Thus, the signal is divided into a plurality of (seven in this embodiment) sub-periods T _{S1 to} T _S7 (STEP 1 in FIG. 4), and beat signal data in each of the sub-periods T _{S1 to} T _S7 is subjected to frequency analysis to obtain a spectral distribution. (Step in FIG. 4)
2). Here, the frequency analysis by the frequency analysis means 16 is performed using FFT, similarly to the detection signal processing unit 14.

According to such frequency analysis, as shown in the upper part of FIG. 6, when the linearity of the transmitted / received signal is good, the lower part of the figure is shown corresponding to each of the short periods T _{S1 to} T _S7 . Such a spectral distribution is obtained. In this case, the spectral distribution in each of the small periods T _{S1 to} T _S7 is
It becomes steep spectral distribution as having a peak at a frequency f _P corresponding to the relative distance D of the object A, mutually the same distribution.

As shown in the upper part of FIG. 7, when the linearity of the transmission / reception signal is poor, the lower part of the figure corresponds to each of the short periods T _{S1 to} T _S7 . A spectral distribution is obtained. In this case, some of these spectral distributions do not coincide with each other. For example, comparing the spectral distributions of the short periods T _S1 and T _S6 , they differ from each other in shape, extent of spread, etc., and also in each spectral distribution, the peak frequency f _{P at} which the spectrum level has a maximum value is different from each other. Is different.

As shown in the upper part of FIG. 8, when the linearity of the transmitted / received signal is good and the transmitted signal of the electromagnetic wave is received by the FM-CW radar device of another vehicle or the like, each small period T A spectrum distribution as shown on the lower side of the figure is obtained corresponding to _{S1 to} T _S7 . In this case, as in the case of FIG. 7, some of these spectral distributions do not coincide with each other.

When the spectrum distribution in each of the short periods T _{S1 to} T _S7 is obtained as described above, the pass / fail judgment means 17 sets the spectrum level in each spectrum distribution as a parameter indicating the characteristic of each spectrum distribution. The peak frequency at which the maximum value is obtained and the Q value at the position of the peak frequency are obtained (STEP 3 in FIG. 4).
Here, referring to FIG. 10, detection of peak frequency f _P in each spectrum distribution is performed, as in the case of the above-described radar processing operation, when the spectrum level is equal to or higher than a predetermined threshold and the change in the spectrum level with respect to the frequency is detected. This is performed by detecting a frequency at which the frequency tends to change from increasing to decreasing. The Q value is, for example, a peak frequency f _P ,
1 spectral level S _P in the peak frequency f _P
Using the frequency width Δf of the spectrum distribution at the level of / 2, it is obtained by the following equation (3).

Q = f _P / Δf (3) Next, the pass / fail judgment means 17 determines the peak frequency f obtained for the spectrum distribution in each of the short periods T _{S1 to} T _S7 .
_{The P} and Q values are compared with each other for each spectral distribution, and the quality of the detection state in the radar processing operation is determined based on whether or not they substantially match each other (FIG. 4).
STEP 4). In this case, each difference predetermined value for each spectral distribution of whether the peak frequency f _P and Q values match each other, respectively, for example, the peak frequency f _P and Q values of a set of spectral distribution to be compared with one another Judgment is made based on whether it falls within the range.

In this judgment, when the spectrum distribution as shown in FIG. 6 is obtained, that is, when there is no linearity defect or interference of the transmission signal of another FM-CW radar device, each small period T _S1 for ~T peak frequency f _P and Q values of the spectral distribution in _S7 is substantially coincident with each other, respectively, the detection state by the radar processing operation is judged to be good (Y in STEP4 in FIG
ES).

The evaluation signal processor 15 basically stores the new beat signal data in the memory 10 (each time a triangular frequency-modulated electromagnetic wave is transmitted or received). Then, the above-described evaluation processing operation is repeated.

On the other hand, for example, when the linearity of the transmission / reception signal is poor and the spectrum distribution in each of the short periods T _{S1 to} T _S7 becomes the distribution shown in FIG. 7, the peak frequency f _P and the Q value are reduced. Since a set of mutually different spectral distributions is generated (in the spectral distribution of FIG. 7, for example, the peak frequencies f _P and Q values of the spectral distributions of the short periods T _S1 and T _S6 do not match). It is determined that the detection state by the radar processing operation is defective (NO in STEP 4 of FIG. 4).

Also, when interference occurs in the transmission signal of another FM-CW radar apparatus, and the spectrum distribution in each of the short periods T _{S1 to} T _S7 becomes the distribution shown in FIG. Since a set of spectral distributions in which the frequency f _P and the Q value are different from each other occurs (in the spectral distribution of FIG. 8, for example, the peak frequencies f _P and Q values of the spectral distributions in the short periods T _S1 and T _S3 coincide. No), it is determined that the detection state by the radar processing operation is defective (NO in STEP 4 of FIG. 4).

When it is determined that the detection state is defective, the pass / fail judgment 17 determines whether a defective detection state has occurred in the previous evaluation processing operation. (STEP 5 in FIG. 4).

At this time, in the previous evaluation processing operation,
If the detection state is good (NO in STEP 5 of FIG. 4), the transmission timing instructing means 20 of the evaluation signal processing unit 15
, And instructs the modulation control circuit 2 to change the transmission timing (STEP 6 in FIG. 4). Thereby, the modulation control circuit 2 changes the modulation start timing of the transmission signal and changes the transmission start timing of the electromagnetic wave when transmitting the electromagnetic wave frequency-modulated in a triangular wave next time. Such a change, for example, decreases or increases the pause period T _O of the transmission signal by a predetermined time with respect to the current pause period, or changes the pause period T _O randomly within a predetermined range. This is done by:

When the transmission timing of the electromagnetic wave is changed in this way, in general, the failure of the detection state due to interference of the transmission signal of another FM-CW radar device is often solved.

On the other hand, if the detection state is not good even in the previous evaluation processing operation (YES in STEP 5 in FIG. 4), the pass / fail judgment means 17 determines whether each of the above-mentioned evaluation results obtained in the previous evaluation processing operation has been obtained. a peak frequency f _P of the spectral distribution of the small period T _S1 through T _S7, whether the peak frequency f _P of the spectral distribution of each small period T _S1 through T _S7 obtained by the evaluation processing operation of this time is substantially coincident with each other It is determined whether or not there is (STEP 7 in FIG. 4).

In this case, it is considered that the change in the relative distance D of the object A in the time interval between the previous evaluation processing operation and the current evaluation processing operation is sufficiently small. If the cause of the failure is the poor linearity of the transmitted / received signal, the peak frequency of the spectrum distribution of each of the small periods T _{S1 to} T _S7 obtained by the previous evaluation processing operation is generally obtained by changing the transmission timing. f _P ,
Each small period T _{S1 to} T _S7 obtained by this evaluation processing operation
And the peak frequency f _P of the spectrum distribution of the above. This is because it is considered that the degree of linearity failure of the transmitted / received signal is substantially the same between the previous evaluation processing operation and the current evaluation processing operation.

On the other hand, the cause of the defect in the detection state is other
Is the interference of the transmitted signal of the FM-CW radar device
Is generally the value of each of the
Period T_S1~ T_S7Spectrum distribution and the evaluation process
Each small period T obtained by motion _S1~ T_S7Spectral distribution of
And the peak frequency f_PAre generated. this
Causes interference of the transmission signal of other FM-CW radar equipment.
During the period when the transmission timing is changed or the own FM-CW
The transmission signal is transmitted between the radar device and another FM-CW radar device.
Due to transmission timing differences, etc.
Changes between the current evaluation processing operation and the current evaluation processing operation?
It is.

Therefore, in the apparatus of this embodiment, the peak frequency f _P of the spectral distribution of each of the short periods T _{S1 to} T _S7 obtained in the previous evaluation processing operation and the current evaluation processing operation are obtained. If the peak frequencies f _P of the spectral distributions of the respective small periods T _{S1 to} T _S7 substantially coincide with each other (YES in STEP 7 of FIG. 4), the pass / fail determination means 1
7 identifies the cause of the failure in the detection state as a failure in the linearity of the transmitted / received signal (STEP 8 in FIG. 4). In this case, since the possibility of the linearity defect being eliminated is small, the power supply stop instructing means 18 (see FIG. 1) of the evaluation signal processing unit 15 instructs the power supply circuit 13 of the oscillator 1 to stop the power supply. Thereby, the oscillator 1 is stopped to stop the transmission of the electromagnetic wave. In parallel with this, the alarm instruction means 19 of the evaluation signal processing unit 15 gives an alarm instruction to an alarm device such as a buzzer (not shown), thereby causing a linearity defect and stopping the operation of the radar device. The driver or the like is notified of the fact that he / she is confused (STEP 9 in FIG. 4).

On the other hand, the spectrum distribution of each of the small periods T _{S1 to} T _S7 obtained by the previous evaluation processing operation and the spectrum distribution of each of the small periods T _{S1 to} T _S7 obtained by this evaluation processing operation are shown. If there are peak frequencies f _P that are different from each other (NO in STEP 7 of FIG. 4), the pass / fail determination means 17 determines the cause of the failure in the detection state by another FM-CW.
It is determined that the interference is caused by the transmission signal of the radar device (S in FIG. 4).
(Step 10) In this case, the transmission timing is changed as described above (Step 6 in FIG. 4).

As described above, according to the apparatus of this embodiment, the characteristics of the spectrum distribution in the short periods T _{S1 to} T _S7 obtained by dividing the detection period T _W of the beat signal in the radar processing operation are compared with each other. Thus, the quality of the detection of the relative distance D of the target A by the radar processing operation can be easily evaluated. Then, when a defect in the detection state is continuously detected in the previous evaluation processing operation and the current evaluation processing operation, each short period T obtained in the previous evaluation processing operation and the current evaluation processing operation is obtained. _By comparing the peak frequencies f _P of the spectral distributions of _{S1 to} T _S7 with each other, the cause of the failure can be specified, and appropriate measures can be taken accordingly.

In this embodiment, every time the radar processing operation is performed, the evaluation processing operation is performed in parallel. However, each time the radar processing operation is performed a plurality of times, the evaluation processing operation is performed. It may be performed.

In the apparatus of this embodiment, for example, at the time of initial setting of the apparatus of this embodiment, the detection period T _W of the beat signal for performing the radar processing operation is set. This setting is performed in the following manner under the condition that the linearity of the transmitted / received signal is basically good and the interference of the transmitted signal of another FM-CW radar device does not occur. That is, referring to FIG. 5 and FIG. 9, first, similarly to the above-described radar processing operation and evaluation processing operation,
By transmitting and receiving the frequency-modulated electromagnetic wave, a beat signal having a frequency corresponding to the relative distance of the object is generated, and the data of the beat signal is stored and held in the memory 10 (STEP 1 in FIG. 5). In this case, the detection period in which the beat signal data is stored and held in the memory 10 is arbitrarily initialized in advance, and includes, for example, the entire period in which the frequency of the transmission signal increases as shown in the upper part of FIG. It is set to the period T _W0 .

Next, as in the case of the above-described evaluation processing operation,
To the frequency analysis means 16 of the signal processing unit 15 for evaluation.
From the above, the detection period T_W0To multiple (eg 12) sub-periods
Interval T _S1~ T_S12(STEP 2 in FIG. 5), and each of the
Small period T_S1~ T_S12The beat signal data at
Numerical analysis is performed to obtain a spectrum distribution (STEP in FIG. 5).
3).

At this time, the reception signal as shown in the upper part of FIG.
Is obtained, each small period T_S1~ T _S12Specs in
The vector distribution is as shown in the lower part of FIG. sand
That is, the small period T during which the frequency of the transmitted / received signal increases together_S3~
T_S10In, each small period T_S3~ T_S10Spectrum of
Each distribution has a frequency corresponding to the relative distance of the object.
f_PHas a steep distribution with a peak at
Other small period T_S3~ T_S10At many frequencies
Since the components are mixed, the distribution has a spread. example
If, for a small period T_S1In, because the received signal can not be obtained
In addition, the distribution has a spread as shown in the figure.
For example, small period T_S12In, the frequency of the received signal increases
However, the frequency of the transmitted signal has decreased.
Therefore, the distribution has a spread as shown in FIG.

Next, as in the case of the above-described evaluation processing operation, the evaluation signal processing section 15 uses the pass / fail judgment means 17 to set each of the small periods T _{S3 to} T _S10 as a parameter indicating the characteristic of the spectrum distribution. The peak frequency f _P and Q value of the spectrum distribution are obtained (STEP 4 in FIG. 5), and the peak frequency f _P and Q value are compared with each other (S in FIG. 5).
TEP5).

Here, by the radar processing operation, the target
To accurately detect the relative distance of an object, a beat signal
Frequency distribution corresponding to the relative distance of the object
Number f _PAt which there is a steep distribution with a peak at
While the beat signal has the frequency f_PWith only ingredients
The detection period T_WGood to set as
Good. Therefore, the detection tie of the evaluation signal processor 15 is
The instructing unit 12 (see FIG. 1) performs the comparison (FIG. 5).
Based on STEP 5), each small period T_S1~ T _S12Horse
That is, the peak frequency f of the spectrum level_PAnd Q value
Is composed of successive sub-periods where
Is the detection period T_WAs the memory 10
Set via the timing signal generation circuit 12
(Step 6 in FIG. 5). Specifically, in the case of FIG.
The delay time of the received signal with respect to the transmitted signal
Considering that it changes depending on the relative distance of the object, for example,
Outgoing period T_WAs a continuous small period T_S4~ T_S10Synthesize
Set the period of time.

[0067] Then, in the radar processing operation and evaluation process operation of subsequent processing of the beat signal data using a detection period T _W, which is set as described above is performed.

As described above, in the apparatus of this embodiment, by comparing the characteristics of the spectral distribution of the beat signal in the short periods T _{S4 to} T _S10 with each other, the detection of the frequency of the beat signal during the radar processing operation is performed. The period T _W can be set appropriately.

In the present embodiment, the detection period T _W is set at the time of initial setting of the apparatus of the present embodiment. However, the linearity of the transmitted / received signal is good and other FM
If circumstances as there is no interference of the transmit signal -CW radar device, it is also possible to set the detection period T _W in the course repeating the radar processing operation.

[0070]

As is apparent from the above description, according to the present invention, a predetermined period during which the frequency of a beat signal is detected in order to detect a relative distance of an object, that is, a transmission signal and a reception signal A predetermined period predetermined as a period in which both frequencies increase or decrease is divided into a plurality of sub-periods, the spectral distribution of the beat signal in each sub-period is obtained, and the characteristics of those spectral distributions are mutually determined. By comparing the characteristics of the spectral distributions with each other, whether or not the characteristics of the spectral distributions are substantially the same, whether the linearity of the transmitted / received signal is good or not, the presence or absence of interference with the transmitted signal of another FM-CW radar device, Can easily be evaluated as to whether the detection state is good or bad.

When it is determined that the detection state is defective, the start of transmission of the frequency-modulated electromagnetic wave is changed, so that the cause of the defective detection state is another F.
In the case of interference of the transmission signal of the M-CW radar device, it is possible to eliminate a defect in the detection state due to such interference.

Further, when the characteristics to be compared of the respective spectral distributions in the respective small periods are the peak frequencies and the Q values of the respective spectral distributions, the comparison can be performed easily and accurately.

In the process of repeating the process of evaluating the quality of the detection state, when the evaluation that the detection state is bad is repeated twice consecutively, the peak of the spectrum distribution in each of the small periods obtained in the previous evaluation process is obtained. By comparing the frequency with the peak frequency of the spectrum distribution in each small period obtained in the present evaluation processing, the cause of the failure in the detection state is whether the linearity is poor or another FM-CW radar is used. It is possible to identify whether the interference is caused by a transmission signal of the device, and it is possible to take appropriate measures according to the cause.

Further, the characteristics of the spectral distribution in each of the small periods are compared with each other, and a period formed by combining a plurality of continuous small periods in which the characteristics of the spectral distribution substantially match each other is defined as a relative distance of the object. Is set as a predetermined period for detecting the frequency of the beat signal in order to detect
Under conditions where the linearity of the transmitted and received signals is good and there is no interference of the transmitted signals of other FM-CW radar devices, by detecting the frequency of the beat signal within the period set as described above, The relative distance of the object can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an FM-CW radar device including a detection state evaluation device of the present invention.

FIG. 2 is an explanatory diagram showing transmission and reception signals of electromagnetic waves by the radar device of FIG. 1;

FIG. 3 is a flowchart for explaining the operation of the radar device of FIG. 1;

FIG. 4 is a flowchart for explaining the operation of the radar device of FIG. 1;

FIG. 5 is a flowchart for explaining the operation of the radar device of FIG. 1;

FIG. 6 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 7 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 8 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 9 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 10 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 11 is an explanatory diagram for explaining a conventional technique.

FIG. 12 is an explanatory diagram for explaining a conventional technique.

FIG. 13 is an explanatory diagram for explaining a conventional technique.

[Explanation of symbols]

16: frequency analysis means, 17: pass / fail judgment means, 22: transmission timing changing means, 23: detection period setting means.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsuki Ichinose 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-5-249233 (JP, A) JP-A-6-160513 (JP, A) JP-A-5-142338 (JP, A) JP-A-5-256937 (JP, A) JP-A-5-281335 (JP, A) JP-A-5-297120 (JP, A A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (5)

(57) [Claims] A means for transmitting an electromagnetic wave modulated to increase or decrease the frequency in a triangular wave form toward an object toward an object; a means for receiving a reflected wave of the electromagnetic wave; Means for generating a beat signal having a frequency corresponding to the relative distance of the object by mixing a part of the transmitted signal of the reflected wave and the received signal of the reflected wave ,
As a period during which both frequencies increase or decrease
The transmission signal and the reception signal in a predetermined period.
Means for detecting the frequency of the beat signal generated by mixing the signals as a frequency corresponding to the relative distance of the target, and detecting the relative distance of the target from the detected frequency. In the apparatus for evaluating the quality of the detection state of the relative distance, the predetermined period for detecting the frequency of the beat signal is divided into a plurality of small periods, the frequency spectrum of the beat signal in each small period Frequency analysis means for obtaining a distribution and predetermined characteristics of the spectral distribution of the beat signal in each of the short periods are compared with each other, and when the characteristics substantially match each other, the detection state of the relative distance is determined to be good. And FM / CW determining means for determining the relative distance detection state as defective when the characteristics do not substantially match each other. Detection state evaluation device in radar equipment. 2. The radar device according to claim 1, wherein the radar device repeats the transmission of the electromagnetic wave, and when the pass / fail judgment unit determines that the detection state of the relative distance is bad.
2. An FM-transmission device according to claim 1, further comprising transmission timing changing means for changing the transmission timing of said electromagnetic wave.
A detection state evaluation device in a CW radar device. 3. The characteristics of the spectrum distribution of the beat signal in each of the small periods compared by the pass / fail judgment means are: a peak frequency at which a spectrum level in each spectrum distribution is a maximum value; and a spectrum distribution at a position of the peak frequency. The detection state evaluation device for an FM-CW radar device according to claim 1, wherein the Q value is: 4. The frequency analysis means and the quality judgment means,
Means for periodically repeating the evaluation processing, wherein the pass / fail determination means includes means for detecting a peak frequency at which the spectral level in the spectrum distribution of the beat signal in each of the short periods has a maximum value; Means for comparing the peak frequencies detected in the previous evaluation processing and the current evaluation processing with each other when the detection state of the relative distance is determined to be defective in the previous evaluation processing and the comparison result, 2. A detection state evaluation apparatus for an FM-CW radar apparatus according to claim 1, further comprising: means for specifying a cause of determining that the detection state of the relative distance is defective. 5. The predetermined period in which the frequency of the beat signal is detected when the relative distance of the object is detected based on a comparison result of the spectrum distribution of the beat signal in each of the small periods by the pass / fail determination means. And a detection period setting unit for setting the detection period.
2. The F according to claim 1, wherein a period obtained by synthesizing a plurality of continuous small periods in which the characteristics of the spectrum distribution of the beat signal substantially match each other is set as the predetermined period.
A detection state evaluation device for an M-CW radar device.