JP2778864B2 - Millimeter wave radar distance / velocity measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a millimeter-wave radar distance / velocity measuring device for frequency-modulating a transmission signal of a continuous wave radar and simultaneously receiving a reflected signal from a target to measure a distance and a speed. In particular, the present invention refers to a signal processing device for a plurality of targets.

[0002]

2. Description of the Related Art Conventionally, as a technique relating to a millimeter wave radar distance / velocity measuring apparatus in such a field, "Radar technology" is known.
(Institute of Electronics, Information and Communication Engineers). When the frequency of the transmission signal of the continuous wave radar is modulated and appropriately repeated, and the beat is taken with the reception signal, the beat frequency f can be expressed as f = 4R · fm · Δf / c. Here, R is the distance to the target, fm is the repetition frequency of frequency modulation, Δf is the frequency shift width, and c is the speed of light. Therefore, when the beat frequency f is obtained, the distance to the target is obtained.

[0003] Next, when the target is moving, the beat signal frequency f is superimposed on the beat signal frequency f in the case of a fixed target in the relationship between the transmission signal and the reception signal due to the Doppler effect. Since the direction alternates between ascending (up) and descending (down) for each modulation cycle, it is given by the following equation. When the Doppler frequency fp is obtained, the speed with respect to the target is obtained.

Fu (up) = f-fp fd (down) = f + fp Therefore, for each half cycle of modulation, fu (up) and f
If d (down) is measured separately, the signal is processed as f = {fu (up) + fd (down)} / 2 fp = {fu (up) −fd (down)} / 2, that is, the target Distance and speed can be obtained separately.

[0005]

In the conventional millimeter-wave radar distance / velocity measuring apparatus, when the target is a single target, the beat signal has a sine wave, so that the beat signal is pulse-counted. Distance, etc. were measured. However, if the conventional millimeter-wave radar distance / velocity measuring device is used by mounting it on an automobile, for example, when there are a plurality of targets, the waveform of the beat signal is displaced from the distorted sine wave, so that even if pulse counting is performed as in the related art, Counting becomes inaccurate. For this reason, the beat signal is subjected to frequency analysis by an FFT (Fast Fourier Transformer), and the above fu (up) for each target is analyzed.
It is conceivable to obtain the distance and the like by obtaining fd (down) and fd (down). However, if this combination is incorrect, an accurate distance and speed to the target cannot be obtained, so that means for determining these combinations must be established. There are issues.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a millimeter-wave radar distance / velocity measuring apparatus capable of measuring speed and distance even for a plurality of targets.

[0007]

The present invention SUMMARY OF] In order to solve the above problems, a frequency modulation to the transmission signal of a continuous wave radar
It was repeated to apply those, in the millimeter-wave radar range rate measurement device for determining the distance and velocity relative to the target from the beat signal between the received signal and the transmission signal, the frequency of the beat signal
Analyze the frequency modulation frequency for multiple targets
The frequency to find the peak frequency on the rising side and the falling side respectively
A number analysis unit, and an ascending side obtained by the frequency analysis unit.
And descending peak frequencies in order of frequency magnitude.
An aligning part aligned in the beginning, and an ascending side aligned in the aligning part
Generated by noise for the peak frequency on the lower side
Lack of peak frequency, not be affected by additional
In addition, a pair of ascending and descending peaks
For calculating distance and speed by combining
A millimeter-wave radar range,
Provided is a separation velocity measuring device. Further, the combination unit
Is the combination of the pair of rising and falling peak frequencies.
Ascending and descending sides of the closest pair
Combined frequency. Further, the combination unit
At the closest rising and falling peak frequencies.
Exclude from the combination if the difference is larger than the specified value
You.

[0008]

According to the millimeter-wave radar distance / velocity measuring apparatus of the present invention, the beat signal is subjected to frequency analysis to determine a plurality of peak frequencies, and the peak frequencies are respectively determined on the rising and falling sides of the frequency modulation frequency. When arranged in the order of the frequency magnitude, the corresponding peak frequency of each pair corresponds to each of the plurality of targets, so that the peak frequencies on the ascending side and the descending side are combined in pairs in correspondence with the order and each The distance and speed to the target will definitely be determined. Also, by combining only the closest ones of the plurality of peak frequencies on the rising side and the falling side, an error occurs in the combination even if noise is added to the alignment of the peak frequencies or the peak frequency is missing due to the noise. Disappears. Further, even if only the closest one of the plurality of peak frequencies on the ascending side and the descending side is combined, if the difference between the two is greater than a predetermined value, it is excluded from the combination, thereby causing a mistake in combination. It is small.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a millimeter wave radar distance / velocity measuring apparatus according to an embodiment of the present invention. The millimeter-wave radar distance / velocity measuring apparatus shown in FIG. 1 transmits a triangular-wave modulated continuous wave signal, and mixes this with a received signal reflected by a target to form a beat signal. A low-pass filter 2 that removes a folded signal due to a contained harmonic, and an A / D (Analog to Digital) that converts an analog signal from the low-pass filter 2 into a digital signal.
Converter) and a beat signal converted into a digital signal from the A / D converter 3 by frequency analysis, and a DSP (Digital Sign) for processing into a distance and speed signal.
al Processor), a controller 5 for controlling the display of the distance and speed data obtained by the signal processor 4, and a display for displaying the data controlled by the controller 5. Unit 6.

FIG. 2 shows the formation of the output signal of the sensor of FIG. As shown by the solid line in FIG.
, A continuous transmission signal of triangular wave modulation is transmitted, and the signal reflected by the target is received by the sensor 1 as shown by the dotted line. Further, as shown in FIG. 2B, a beat signal fu on the rising side of the triangular wave modulation and a beat signal fd on the falling side are formed by a mixer (not shown).

FIG. 3 is a diagram showing the frequencies of the rising and falling beat signals when there are two targets. As shown in FIG. 3A, a signal is sent from a sensor 1 of a vehicle 100 equipped with the millimeter-wave radar distance / velocity measuring device to a target 1 which is a motorcycle and a target 2 which is a vehicle at a certain distance from the vehicle 100. Is transmitted, beat signals fu1 and fu2 are generated on the ascending side and fd1 and fd2 are generated on the descending side, respectively, as shown in FIGS. Although the above description has been made with respect to two targets, a beat signal generated in a similar manner is detected in a plurality of cases.

FIG. 4 is a diagram showing a configuration of the signal processing unit of FIG. As shown in the figure, the signal processing unit 4 includes a frequency analysis unit 41 that analyzes the frequency of a beat signal using an FFT (Fast Fourier Transformer) and a beat signal that is analyzed and obtained by the frequency analysis unit 41. , An ascending beat signal and an ascending beat signal separately arranged as described later, and an ascending beat aligned by the aligning unit 42 to calculate a distance and a speed to each target. And a combination unit 43 that combines the signal and the downbeat signal.

FIG. 5 is a diagram showing the processing of a beat signal in the alignment unit of FIG. In the alignment unit 42 shown in FIG. 4, as shown in FIG. 5, a plurality of beat signals detected at the time of rising of the triangular wave modulation signal are, for example, fu1 <f in descending order of frequency.
A plurality of beat signals detected at the time of descent are similarly arranged in the order of u2 <... <fum, and similarly in the order of low frequency, for example, fd1 <fd2 <... <fdm.

FIG. 6 is a diagram showing the processing of the beat signal in the combination section of FIG. As shown in FIG. 4, in the combination unit 43 shown in FIG. 4, the beat signals on the ascending side and the descending side aligned by the alignment unit 42 correspond to the order, for example, fu1 and fd.
1, fu2 and fd2,..., Fum and fdm. The reason for such a combination will be described. The frequencies fn and fpn corresponding to the distance and the speed for each target n are obtained as follows.

For target 1, f1 = (fu1 + fd1) / 2 fp1 = (fu1-fd1) / 2 For target 2, f2 = (fu2 + fd2) / 2 fp2 = (fu2-fd2) / 2... For the target n, the following processing is performed: fn = (fun + fdn) / 2 fpn = (fun−fdn) / 2.

By the way, when a vehicle which is a target n advances in the same direction as a vehicle equipped with the present apparatus and is located ahead of the vehicle, a measurement frequency fn which indicates a relative distance from the target n.
In contrast, the measurement frequency fpn representing the relative speed with respect to the target is usually very small. For example, if the frequency between channels in the FFT is set to Δf = about 1.5 KHZ in consideration of its resolution, this becomes about 2 m in terms of relative distance and about 9 Km / h in terms of relative speed. Therefore, the relative distance is 100
m and the relative speed is 9 km / h, fn = (100
m / 2m) × 1.5 KHz = 50 × 1.5 KHz = 75
KHZ, fpn = (9 km / h / 9 km / h) × 1.5
KHZ = 1 × 1.5 = 1.5KHZ, usually fpn
≪fn is established. On the other hand, if the relative distance is 4 m in a normal slowing state in the city, the relative speed becomes fn = (4
m / 2m) × 1.5 KHZ = 2 × 1.5 KHZ = 3 KH
Z, and the relative speed is 9 km / h or less.
n ≒ 0KHZ. However, stationary objects and accidents are excluded. For an oncoming vehicle, when the oncoming vehicle is far away, the above relationship is established. When the oncoming vehicle is approaching, this relationship is not established. . Therefore, the relationship between the fum on the ascending side and the fdm on the descending side shown in FIG. fum
And fdm. Thus, the relative distance and the relative speed can be obtained from fn and fpn represented by the above equations without mistake in the combination of fum and fdm.

In the above description, the number of beat signals is the same on the ascending side and the descending side. However, the beat signal may be missing or added on either the ascending side or the descending side due to noise. is there. In this case, if the combination is simply performed in the order of lower frequency as described above, the combination with the different target is erroneously performed, and the distance and the speed cannot be accurately obtained. Therefore, a combination in such a case will be described below.

FIG. 7 is a diagram for explaining a combination of beat signals when a rising or falling beat signal is missing or added. As shown in the figure, first, fu1 and fd1 are compared with each other to obtain Δf1-1, and then fu1 and fd2 are compared with each other to determine Δf1-2.
If 1 <Δf1-2, it is determined that the combination of fu1 and fd1 is correct. Next, Δf2 is compared with fu2 and fd2.
1 and then compare fu2 and fd3 to determine Δf2-2. If Δf2-1> Δf2-2, it is assumed that the combination of fu2 and fd2 is incorrect and that the combination of fu2 and fd3 is correct. That is, it is assumed that fd2 is generated by noise or a signal of the corresponding rising frequency is lost by noise. In the same manner, a pair of mutually close up and down beat signals having a similar frequency can be combined.

FIG. 8 is a diagram showing a first specific example of FIG. As shown in the figure, the numerical value is the peak frequency of the rising and falling beat signals measured by FFT, and multiplying this by 1.5 KHZ gives the actual frequency.
And 4.3, 7.6 and 7.4 are correct combinations, but 12.5 on the descending side is regarded as noise, and an example in which noise occurs on the side where the beat frequency is higher is shown.

FIG. 9 is a diagram showing a second specific example of FIG. As shown in the figure, 4.9 on the rising side represents noise, and 10.3 and 9.9, 14.0 and 14.3 are correct combinations, and noise occurred on the side with the lower beat frequency. shows the example. FIG. 10 shows a third specific example of FIG.
FIG. As shown in the figure, 2.8 and 4.0 are correct combinations, but the difference between 10.0 and 30.0 is 2
Converting this to a difference in relative speed at 0.0 gives 20 × 9
Km / h = 180 Km / h, and since such a thing is unlikely among those usually running on the ground, these data are regarded as noise. That is, this is an example in which the number of data on both the ascending and descending sides is the same, but there is one noise on each side.

[0021]

As described above, according to the present invention, the beat signal is subjected to frequency analysis to obtain a plurality of peak frequencies, and the peak frequencies are respectively increased on the rising and falling sides of the frequency modulation frequency. And the corresponding pair of peak frequencies corresponds to each of the plurality of targets, and only the closest ones of the ascending and descending peak frequencies are combined. If it is larger than the predetermined value, by excluding it from the combination, the distance and the speed for each of the plurality of targets can be definitely obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a millimeter wave radar distance / velocity measuring apparatus according to an embodiment of the present invention.

2 shows the formation of the output signal of the sensor of FIG. 1;

FIG. 3 is a diagram showing frequencies of rising and falling beat signals when there are two targets.

FIG. 4 is a diagram illustrating a configuration of a signal processing unit in FIG. 1;

FIG. 5 is a diagram illustrating processing of a beat signal in an alignment unit in FIG. 4;

FIG. 6 is a diagram illustrating processing of a beat signal in the combination unit of FIG. 4;

FIG. 7 is a diagram illustrating a combination of beat signals when a rising or falling beat signal is missing or added;

FIG. 8 is a diagram showing a first specific example of FIG. 7;

FIG. 9 is a diagram showing a second specific example of FIG. 7;

FIG. 10 is a diagram illustrating a third specific example of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sensor 2 ... Low-pass filter 3 ... A / D converter 4 ... Signal processing part 5 ... Controller 41 ... Frequency analysis part 42 ... Alignment part 43 ... Combination part

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 13/34

Claims (3)

(57) [Claims] The method according to claim 1 frequency modulated transmission signal of a continuous wave radar
It was repeated to apply those, in the millimeter-wave radar range rate measurement device for determining the distance and speed from the beat signal between the received and transmitted signals, prior to a plurality of targets said beat signal and frequency analysis
The rising and falling sides of the frequency
Frequency analysis section for determining the peak frequency , and the rising and falling peaks obtained by the frequency analysis section.
Are arranged in the order of magnitude of frequency
An aligning section, and the rising and falling peak frequencies aligned by the aligning section.
Number of peak frequencies missing due to noise
The same goal so that no additional
Combining a pair of rising and falling peak frequencies
Providing a combination unit for determining distance and speed
A millimeter-wave radar distance / velocity measuring device characterized by the above-mentioned . 2. The pair of ascending sides are connected to each other.
And the closest combination of peak frequency on the downside
Combines the rising and falling peak frequencies of
It characterized that, millimeter wave radar range rate measurement apparatus according to claim 1, wherein the causing. 3. The combination section according to claim 1, wherein said combination section includes a nearest ascending side and
Even at the falling peak frequency, the difference between the two is greater than the specified value
If not, it is excluded from the combination.
The millimeter wave radar distance / velocity measuring apparatus according to claim 1.