JPH05249233A - Millimeter-wave radar equipment - Google Patents

Abstract

PURPOSE:To prevent millimeter-wave radar equipment from becoming unstable in distance and speed due to the fluctuation of the peak frequency of measured beat signals caused by noise, etc. CONSTITUTION:The radar equipment which finds the distance to a target and moving speed of the target from transmitted and received signals of continuous- wave radar which are frequency-modulated with triangular waves is equipped with storing sections 55 and 59 which store the ascending- and descending-side frequencies of past beat signals. In addition, the radar equipment is also equipped with reference value forming sections 56 and 60 which use the mean values of the frequencies of the beat signals stored in the sections 55 and 59 and comparing sections 57 and 61 which discriminate whether or not the frequencies of the beat signals fall in a prescribed range against the reference values from the sections 56 and 60 so as to eliminate fluctuating data.

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 device for measuring the distance and speed by subjecting a transmission signal of a continuous wave radar to frequency modulation and simultaneously receiving a reflection signal from a target. In particular, the present invention has an object to prevent the peak frequency of the beat signal measured by noise or the like from fluctuating, and thus the distance and speed from becoming unstable.

[0002]

2. Description of the Related Art Conventionally, as a technology relating to a millimeter wave radar device in such a field, there is one described in "Radar Technology" (Institute of Electronics, Information and Communication Engineers). this is,
Frequency modulation is applied to the transmission signal of the CW continuous wave radar to increase (UP) or decrease (DO) the frequency of the received signal.
WN) and a transmission signal are beat | beated, the frequency of each beat signal is combined, and the distance and relative velocity with an object were calculated | required continuously.

[0003]

However, in the conventional millimeter wave radar device, in order to obtain the distance and velocity, basically, the calculation processing is performed by considering only the data for one time, and the obtained result is obtained. Although it was made to correspond to the distance and the speed, this method cannot suppress the variation in the distance and the speed due to the variation in the measurement result of the frequency of the received signal on the rising side (UP) and the falling side (DOWN). There was a problem.

Therefore, in view of the above problems, it is an object of the present invention to provide a millimeter wave radar device which does not affect the distance and speed even if the frequency of the received signal varies.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a millimeter range for obtaining distance and velocity from beat signals of a transmission signal and a reception signal of a continuous wave radar which is frequency-modulated with a triangular wave. The wave radar device is provided with a storage unit, a reference value formation unit, and a comparison unit. The storage unit stores the rising and falling frequencies of the past beat signal, the reference value forming unit uses the average value of the frequencies of the beat signals stored in the storage unit as a reference value, and the comparison unit varies. In order to remove the data, it is determined whether the frequency of the beat signal is within a predetermined range with respect to the reference value from the reference value forming unit. The reference value forming unit may form the reference value by weighting the frequency of the beat signal close to the present time. Further, the reference value forming unit includes an average reference value forming value unit that uses the average value of the frequencies of the beat signals as a reference value, and a weight reference value forming unit that forms a reference value by weighting the frequencies of the beat signals that are close to the present time. Regarding the frequency of the past beat signal, the average value far away from the present time and the average value close to the present time are compared, and when the difference is small, the average reference value forming value portion, and when the difference is large, A judgment unit for supplying the reference value from the weight reference value forming unit may be provided.

[0006]

According to the millimeter-wave radar device of the present invention, the storage unit stores the frequencies on the rising side and the falling side of the past beat signal, and the reference value forming unit stores the beat signal stored in the storage unit. The average value of the frequencies is used as a reference value, and the comparing unit removes the variation data by determining whether the frequency of the beat signal is within a predetermined range with respect to the reference value from the reference value forming unit. Further, the reference value forming unit may form a reference value that weights the frequency of the beat signal close to the present time.
This improves the accuracy of the reference value when the relative speed with the object changes. Further, the reference value forming unit includes an average reference value forming value unit that uses the average value of the frequencies of the beat signals as a reference value, and a weight reference value forming unit that forms a reference value by weighting the frequencies of the beat signals that are close to the present time. Comparing the average value of the past beat signal frequency far away from the present time and the average value close to the present time, if the difference is small, from the average reference value forming value part, the difference is In the case of a large value, the weight reference value forming unit is provided with a determination unit for supplying the reference value, so that the advantages of each other are brought out, so that the reference value closer to the next data is shown.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outline of a millimeter wave radar device which is a premise of the present invention. The millimeter-wave radar device shown in this figure transmits the continuous wave (CW) signal to the target object, and at the same time, receives the reflected signal from the target object and the antennas 1 and 2 for transmitting the continuous wave signal to the antenna 1. CW transmitter 3
And a mixer 4 for mixing the continuous wave signal of the CW transmitter 3 and the received signals of the frequency rising side (UP) and the frequency falling side (DOWN) at the antenna 2 to form a beat signal, and the mixer. A signal processing unit 5 for obtaining a distance and a speed from a beat signal formed by 4, and a device for performing device control based on the distance data and the speed data obtained by the signal processing unit 5 and displaying them. The control / display unit 6 is included.

FIG. 2 is a diagram showing the relationship between frequency band times when a reflected signal from a moving target is received by the millimeter wave radar device. As indicated by the solid line in this figure (a), CW
The transmitter 3 repeatedly transmits a triangular wave of frequency modulation (FM). On the other hand, in the antenna 2, this figure (b)
As shown by the dotted line in FIG. 3, if a frequency-modulated signal of repeating triangular waves is received, and the frequency of the rising beat signal in the mixer 4 is fd and the frequency of the falling beat signal is fu, then The formula holds.

Fd = fr + fp fu = fr-fp Here, it can be expressed as fr = 4R · fm · Δf / c. Here, R is the distance to the target, fm is the frequency modulation repetition frequency, Δf is the frequency shift width, and c is the speed of light.

Fp = 2f0V / c where f0 is the transmission center frequency, and V is the relative speed to the target. FIG. 3 is a diagram showing a configuration of a signal processing unit of the millimeter wave radar device according to the embodiment of the present invention. The signal processing unit 5 shown in the figure is an A / D converter 51 (Analog to Digital Co) that converts an analog signal from the mixer 4 into a digital signal.
nverter), a fast Fourier transform unit 52 (FFT) that analyzes the frequency of the beat signal from the A / D converter 51,
A switch unit 53 that distributes the frequency data obtained by the fast Fourier transform unit 52 between the rising side and the falling side of the frequency of the triangular wave, and a variation removing unit 54 that is connected to the switching unit 53 and removes the variation data. 58, storage units 55 and 59 connected to the switch unit 53 to store frequency data of beat signals, and the storage units 55 and 59.
If the input data is not within the predetermined range, the reference value forming units 56 and 60 for forming the reference value from the past data from the above and the reference value data of the reference value forming units 56 and 60 are compared with the input data. Comparing units 57 and 61 for outputting identification signals as variation data to the variation removing units 54 and 58, and a distance velocity deriving unit for deriving the distance and velocity based on the data without variation from the variation removing units 54 and 58. 62 is included.

Next, the operation of each main part will be described. FIG. 4 shows the frequencies (fd, f) of the beat signal stored in the storage unit of FIG.
u) is a diagram showing data. As shown in the figure, the current time T is stored in the storage units 55 and 59 as, for example, past T-
Frequency data (fd, fu) of beat signals 1, T-2, T-3, T-4, and T-5 are sequentially stored and updated.

In the reference value forming units 56 and 60, the storage unit 5
Based on the data of 5 and 59, the data are averaged to obtain the reference values fdref (T), furef at time T as follows.
(T) is formed. fdref (T) = {fd (T-1) + fd (T-2) +
… + Fd (T-5)} / 5 furef (T) = {fu (T-1) + fu (T-2) +
… + Fu (T−5)} / 5 Until the previous data is accumulated, the average value of existing data may be calculated and used as a reference value, or even when the value is skipped several times. The average value of the data being processed may be used as the reference value. Furthermore, the number of times of the above average is shown as an example and is not limited to this.

FIG. 5 is a diagram showing the comparison between the reference value and the input data in the comparing section of FIG. As shown in the figure, in the comparison units 57 and 61, fdref (T) ± w with respect to the reference value.
d, furef (T) ± wu, and fdref (T) -wd ≤ fd (T) ≤ fdref (T) +
wd furef (T) −wu ≦ fu (T) ≦ furef (T) +
wu If the input data at time T falls within this width, it is judged that the data is normal. Based on this determination, the variation removing units 54 and 5
8 removes the abnormal variation data. Comparison unit 57
The reason for making such determinations in 61 and 61 is that the relative distance and relative velocity with respect to the same object do not change abruptly. That is, this is because the measurement time interval is as short as 10 ms, and the stationarity during that time is guaranteed. In addition, since the values of the past several times are very short, the relative distance and the relative speed do not change suddenly.

FIG. 6 is a diagram showing frequency data of a beat signal obtained by this embodiment. As shown in this figure,
Since the reference value is taken from the average value of the past several times, it is possible to perform stable association even if there is a value that has abruptly changed due to noise. Further, since the rising side and the falling side are obtained separately, even if there is a slight difference between the rising side and the falling side, the reference values close to each other will be shown.

When data is removed by the variation removing units 54 and 58, the previous data may be used instead of the removed data. In the distance velocity deriving unit 62, the distance R from fr (T) = {fd (T) + fu (T)} / 2 fp (T) = {fd (T) −fu (T)} / 2 to the object (T) and velocity V (T) are obtained as R (T) = fr (T) · c / (4 · fm · Δf) V (T) = fp (T) · c / (2 · f0) ..

Thus, it becomes possible to easily make a judgment for interpolating the frequency value of the beat signal whose value has been greatly removed due to the influence of noise. That is, the frequency data for the same object must be associated as continuous data. For that reason, the reference value for searching the next data for the same object should be closer to the next data, and the stability of the result is improved by reducing the error between this reference value and the next data. To do.

Although the case where the relative speed is constant has been described above, the case where the relative speed changes will be described below. FIG. 7 is a diagram showing a modification of the reference value formation when the relative speed changes. First, in the storage unit 59, fd (T-
n), fd (T-n + 1), ..., fd (T-2), fd
(T-1) and fd (T) are stored, and fu is stored in the storage unit 55.
(T-n), fu (T-n + 1), ..., fu (T-
2), fu (T-1), fu (T) are stored. As shown in the figure, for example, when the frequency of the rising beat signal changes, as described above, the reference value forming units 56 and 60.
When the past data is averaged to form a reference value, an error occurs. Therefore, in order to prevent this, the reference value forming units 56 and 60 use the reference values fdref (T) and furef.
(T) is formed as follows.

Fdref (T) = fd (T-1) + {fd (T-1) -fd (T)} / 2+ {fd (T-2) -fd (T-1)} / 4 + ... + { fd (T- n + 1) -fd (T-n + 2)} / 2 n-1 + {fd (T- n) -fd (T-n + 1)} / 2 n furef (T) = fu (T-1) + {Fu (T-1) -fu (T)} / 2+ {fu (T-2) -fu (T-1)} / 4 + ... + {fu (T-n + 1) -fu (T-n + 2)} / 2 ^n-1 + {fu (T-n) -fu (T-n + 1)} / 2 ^{n In} this way, by weighting the portion near the current time T, the relative velocity can be changed rapidly. Even this will be able to cope with this.

FIG. 8 is a diagram showing a reference value switching configuration. As shown in the figure, the reference value forming units 56 and 60 are
Average reference value forming units 561 and 601 which form the above-mentioned average reference value from the frequency data fu and fd of the beat signal,
The weight reference value forming unit 562 that makes the weight large at the above-mentioned present time point
And 602, and determination units 563 and 603 that determine whether the reference value should be based on the average value or the weighted reference value.
The average reference value forming units 561 and 601 or the weight reference value forming units 562 and 60 are determined by the determining units 563 and 603.
2 includes switch units 564 and 604.

FIG. 9 is a diagram showing the reference value switching judgment of the judgment unit in FIG. As shown in this figure, the average values furef1 and fdref1 of fu and fd near the present time point T and the average values furef2 and fdref2 of fu and fd at the far point are separated. furef1 (T) = {fu (T-1) + fu (T-2) +
... + fu (T-n)} / n furef2 (T) = {fu (T-n-1) + fu (T-n)
-2) + ... + fu (T-2n)} / n fdref1 (T) = {fd (T-1) + fd (T-2) +
… + Fd (T−n)} / n fdref2 (T) = {fd (T−n−1) + fd (T−n)
-2) + ... + fd (T-2n)} / n Furthermore, as δu (T) = furef1 (T) -furef2 (T) δd (T) = fdref1 (T) -fdref2 (T), ± w10, ± By setting w11, it is determined whether -w10≤δu (T) ≤ + w10-w11≤δd (T) ≤ + w11.

FIG. 10 is a diagram showing a comparison of average values of beat signal frequencies at the present time point and the far point and the near point in terms of time. At point (1) shown in this figure, it is assumed that the above inequality is satisfied and the change amount of the reference value is small, so that the average reference value forming unit 5
Reference values are supplied from 61 and 601. At point (2) shown in the figure, the above inequality is not satisfied, and it is determined that the amount of change in the reference value is large, and the weight reference value forming units 562 and 6 are provided.
The reference value is supplied from 02.

Thus, the advantages of the case where the reference value is the average value and the case where the weight is placed at the present time are brought out, so that the reference value closer to the next data is shown.

[0023]

As described above, according to the present invention, the average value of the frequencies of the past beat signals is used as the reference value, and the reference value obtained by weighting the frequency of the beat signal at the present time is used as a reference value. The variation data is removed by determining whether it is within a predetermined range. Regarding the frequencies of past beat signals, the average value far away from the present time and the average value near the present time are compared, and if the difference is small, the average reference value is set.If the difference is large, the weight reference value is set. Since they are supplied, the advantages of each other will be brought out, and the reference value closer to the next data will be shown.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a millimeter wave radar device which is a premise of the present invention.

FIG. 2 is a diagram showing a relationship between frequency and time when a millimeter wave radar device receives a reflection signal from a moving target.

FIG. 3 is a diagram showing a configuration of a signal processing unit of the millimeter wave radar device according to the embodiment of the present invention.

FIG. 4 is a diagram showing frequency (fd, fu) data of beat signals stored in a storage unit of FIG.

5 is a diagram showing a comparison between a reference value and input data in a comparison unit of FIG.

FIG. 6 is a diagram showing frequency data of a beat signal obtained according to this embodiment.

FIG. 7 is a diagram showing a modification of reference value formation when the relative speed changes.

FIG. 8 is a diagram showing a configuration for switching reference values.

9 is a diagram showing reference value switching determination of the determination unit in FIG.

FIG. 10 is a diagram showing a comparison of average values of beat signal frequencies at a current time point, a far point, and a near point in terms of time.

[Explanation of symbols]

 1, 2 ... Antenna 3 ... CW transmitter 4 ... Mixer 5 ... Signal processing unit 6 ... Equipment control / display unit 54, 58 ... Variation removing unit 55, 59 ... Storage unit 56, 60 ... Reference value forming unit 57, 61 … Comparison unit 62… Distance velocity derivation unit

Claims (3)

[Claims] 1. A millimeter-wave radar device for obtaining a distance and a velocity from beat signals of a transmission signal and a reception signal of a continuous wave radar that is frequency-modulated with a triangular wave. Storage unit (55, 59) for storing the frequency, and a reference value forming unit (56, 60) having an average value of the frequencies of the beat signals stored in the storage unit (55, 59) as a reference value
And a comparing section (57, 61) for judging whether or not the frequency of the beat signal is within a predetermined range with respect to the reference value from the reference value forming section (56, 60) in order to remove the variation data. A millimeter-wave radar device characterized by comprising. 2. The millimeter wave radar device according to claim 1, wherein the reference value forming unit (56, 60) forms a reference value by weighting the frequency of the beat signal close to the present time. 3. The reference value forming unit (56, 60) includes an average reference value forming value unit (561, 601) having an average value of frequencies of beat signals as a reference value, and a beat signal frequency close to the present time. A weighting reference value forming unit (562, 602) that weights and forms a reference value, and an average value far from the present time and an average value near the present time with respect to the frequencies of past beat signals are compared and the difference therebetween is calculated. Is smaller, the average reference value formation value part (56
1. The millimeter wave radar device according to claim 1, further comprising: a determining unit (563 and 603) for supplying a reference value from the weighting reference value forming unit (562, 602) when the difference is larger than that of the first and the first. ..