JP2679907B2 - 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 reflection signal from a target to measure a distance and a velocity. In particular, the present invention refers to interpolation when the peak frequency of the beat signal measured with respect to the target is missing.

[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"
(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 (1). 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.

Next, when the target is moving, the beat signal frequency f is superposed by the Doppler frequency fp on the beat signal frequency f in the case of a fixed target due to the relationship between the transmission signal and the reception signal due to the Doppler effect. However, fp can be expressed as fp = 2 · f0 · V / c (2) Here, f0 is the transmission center frequency. The direction of the frequency of the combined beat signal of f and fp alternates between rising (up) and falling (down) for each modulation cycle, and is therefore given by the following equation.

Fu (up) = f−fp (3) fd (down) = f + fp (4) Accordingly, fu (up) and f (fp) are set every half cycle of modulation.
If d (down) is measured separately, these are combined as follows and f = {fu (up) + fd (down)} / 2 (5) fp = {fu (up) -fd (down) } / 2 (6), the distance R and the velocity V are obtained from these f and fp.

[0005]

However, in the conventional millimeter-wave radar range velocities measuring apparatus, as shown by the above equation, the beat signal is normally observed in pairs on the rising side and the falling side, but at the target. There is a case where one of the ascending side and the descending side does not exist due to noise due to the poor reflection state of the received signal, and in this case, the frequencies f and fp theoretically corresponding to the target distance and speed can be obtained. There is a problem that there is no.

Therefore, in view of the above problems, it is an object of the present invention to provide a millimeter wave radar range velocity measuring device capable of measuring velocity and range even when there is no beat signal on either the rising side or the falling side.

[0007]

In order to solve the above-mentioned problems, the present invention performs frequency modulation on a transmission signal of a continuous wave radar and repeats it appropriately, and a plurality of beat signals of a reception signal and a transmission signal are used. In a millimeter-wave radar range-velocity measuring device that obtains the distance and velocity of each target,
Frequency analysis of the beat signal to
Find the peak frequency on the rising and falling sides of the key respectively
Fourier transformer and up and down for multiple targets
Align the peak frequencies in frequency order on each side and
The corresponding peak frequencies on the rising and falling sides are paired in order.
The distance to each target for each peak frequency.
And an aligning unit for determining the separation and velocity,
Is in the same order as the peak frequency measured this time
Take the difference in rank with the peak frequency from the previous measurement,
Moreover, the peak frequency and the order of alignment are determined by the above measurement.
The difference between the peak frequency and the next rank was determined by the previous measurement.
If the difference in equal rank is greater than the difference in adjacent rank,
Next to the peak frequency measured this time,
Detects frequency deficiency when there is a deficiency and detects the current deficiency peak
Interpolate the frequency with the corresponding previous peak frequency
You . The peak frequencies on the rising side or the falling side corresponding to the defective peak frequencies are excluded and other peak frequencies are rearranged. The missing peak frequency is interpolated by the current peak frequency predicted using the speed and the distance and the peak frequencies of the ascending side and the descending side obtained last time while obtaining the distance to the target while keeping the speed at the target constant. . The distance is obtained by linearly predicting the speed.

[0008]

According to the millimeter wave radar range velocity measuring apparatus of the present invention, the beat signals are frequency-analyzed with respect to a plurality of targets, and the peak frequencies are obtained and analyzed on the rising side and the falling side of the frequency of the frequency modulation. Whether or not there is a peak frequency deficiency for each target is confirmed for each target, and even when the deficiency is detected, the distance and speed can be obtained by performing interpolation using the past data. For intermittent deficiency, the previous peak frequency was used as the current peak frequency, and for continuous deficiency, the speed was kept constant and the previously obtained rising and falling peak frequencies were used as the current peak frequency. Taking into account the variation in the distance, etc., linearly predict the current distance and speed from the past multiple distance and speed data, calculate the peak frequency on the ascending side and the descending side from the predicted distance and speed, and calculate the peak frequency at this time. As a result, more stable distance and speed can be obtained.

[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 device shown in the figure is a sensor 1 that transmits a continuous wave signal of triangular wave modulation and mixes the continuous wave signal with a reception signal reflected by a target to form a beat signal; Low pass filter 2 which removes high frequency band from the output of the filter and prevents aliasing due to sampling, and A / D (Analog to Digital Converter) which converts an analog signal from the low pass filter 2 into a digital signal. Converter 3
A signal processing unit 4 constituted by a DSP (Digital Signal Processor) for frequency-analyzing the beat signal converted into the digital signal from the A / D converter 3 and processing it into a distance and velocity signal; The controller 5 includes a controller 5 that performs control for displaying the distance and speed data obtained by the signal processing unit 4, and a display unit 6 that displays the data controlled by the controller 5.

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 configuration of the signal processing unit shown in FIG. As shown in this figure, a fast Fourier analyzer (FF
T), which analyzes the frequency of the signal from the A / D converter 3, and a plurality of peak-side and peak-side peak frequencies analyzed by the frequency-analyzing unit 41, which are aligned and peaked according to the target. When there is a frequency deficiency, the aligning unit 42 for detecting it, the storage unit 43 for storing the peak frequency aligned by the aligning unit 42 for each analysis, and the peak frequency aligned by the aligning unit 42 are missing. If there is, the storage unit 4
The estimation unit 44 that estimates the missing peak frequency from the past data stored in 2 and the peak frequency on the ascending side or the descending side aligned by the aligning unit 42 are combined, and further, when the peak frequency is missing. Supplements the peak frequency estimated by the estimation unit 44 and calculates the distance and speed from the above equations (5) and (6).

FIG. 4 is a diagram showing the data processing of the alignment section of FIG. 3, and FIG. 5 is a diagram showing the combination of peak frequencies. As shown in FIG. 4, when the peak frequencies of the beat signals on the ascending side and the descending side are arranged in ascending order from low to high with respect to a plurality (m) of targets, for example, fu on the ascending side is fu.
1 <fu2 <... <fum, fd1 <fd2 on the descending side
<... <fdm. From the above formulas (3) and (4), fp
Since very small with respect to f, ignoring the relative velocity in the item (5) and (6) fu (Stay up-) and fd (d
own) can be combined. That is, as shown in FIG. 5, the distances and the velocities with respect to the respective targets can be obtained from the expressions (3) and (4) by combining them in the order of arrangement.

However, if even one of the peak frequencies shown in FIG. 5 is missing due to noise or the like, the above combination becomes impossible. Therefore what peak frequency will be described below a method of detecting whether deficiency. FIG. 6 is a diagram illustrating a method of finding a defect by comparing the peak frequencies of this time and the previous time. The aligning unit 42 reads the previous peak frequency on the rising side from the storage unit 43 and aligns it so as to compare with the peak frequency obtained this time. In this figure, focusing on the present data, for example, fu1 (T-1) and fu
1 (T) has the smallest peak frequency of the previous time and this time
The difference between fu1 (T) and fu1 (T-1) is larger than that of fu1 (T) and fu2 (T-1). T-
When 1) is compared and then fu3 (T) and fu2 (T-1) are compared, the difference becomes smaller, which makes it clear that fu2 (T) is defective. Thus, by examining this difference, the missing peak frequency can be easily detected. Therefore, fu2 corresponding to such a missing peak frequency
Exclude (T-1) and rearrange for other peak frequencies to form a combination. In addition, the previous data is used as the center, and the same arrangement is performed again to form a combination.
The above description is for the ascending side, but it can be similarly detected for the descending side. It is confirmed that there is no mistake in the combination by confirming that the difference between the two thus recombined is smaller than a predetermined value. In this way, it can be detected that the peak frequency corresponding to the excluded peak frequency has a peak frequency loss.

FIG. 7 is a diagram for explaining a method of finding a defect by comparing peak frequencies on the rising side and the falling side. The peak frequency on the falling side is found on the rising side in the same manner as described above, and the missing peak frequency is found. The above description will be described with reference to the drawings. FIG. 8 is a diagram showing a temporal change in peak frequency and a missing peak frequency for each target. As shown in this figure, the combination of the peak frequencies on the ascending side and the descending side with respect to the closest first target is calculated by the method shown in FIG.
i, yi) and the next closest second target is (a
i, xi), for the third goal is (ci, z
i), where i indicates that it was measured at time Ti. Every hour, it is checked whether or not each peak frequency is missing by the method shown in FIG. 6 or 7, and, for example, the rising time T4 in FIG.
Then, the defect of the peak frequency b4 is detected in the first target.
If there is such a missing frequency, the velocity and distance of the first target cannot be calculated. Therefore, the estimation unit 44 interpolates the peak frequency b4 in the following manner when the presence of the defective peak frequency is notified from the alignment unit 42 via the storage unit 43.

This interpolation method will be described below. In the first method, since the processing time interval is sufficiently short, it is assumed that the target does not change abruptly during this period, and the missing peak frequency b4
Interpolate with the previous peak frequency instead of. This interpolated value is output to the alignment unit 42 via the storage unit 43, combined with another normal value such as y4 in FIG. 8, and used in the distance / speed processing unit 45 for speed and distance processing.

Next, when the peak frequency loss occurs intermittently, the above method is sufficient, but when the loss occurs continuously, the change from the target becomes large, and the one before loss is used. The error may increase. Therefore, the peak frequency to be interpolated is predicted and calculated. The second method of calculating and interpolating the predicted peak frequency will be described below.

The following is a direct calculation of the distance and velocity from the above equations (1), (2), (5) and (6). R = (c / (8 · fm · Δf)) · (fu + fd) (7) V = (c / (4 · f0)) · (fu−fd) (8) This is simplified as follows. To do.

R = a (fu + fd) (9) V = b (fu-fd) (10) where a and b are constants obtained from the equations (9) and (10). a = (c / (8fmΔf)) (11) b = (c / (4f0)) (12) Therefore, assuming that the velocity V is constant, the measurement time from the previous time to this time is Δt. Then, the distance R0 can be expressed by the following formula.

R0 = VΔt + R (13) Therefore, assuming that the rising and falling peak frequencies obtained this time are fu1 and fd1, respectively, R0 and V are given by the following equations. R0 = a · (fu1 + fd1) (14) V = b · (fu1-fd1) (15) From this, (fu1 + fd1) = R0 / a (16) (fu1-fd1) = V / b (17) ) Here, R0 = a (fu + fd) + Δtb (fu-fd) (18) Therefore, from equations (18) and (19), fu1 = 1 / 2 (R0 / a-V / b ) = 1/2 * (fu + fd + (b / a) * [Delta] t * (fu-fd)-(fu-fd)) = fu + (b / 2a) * [Delta] t * (fu-fd) (19) fd1 = 1 / 2 · (R0 / a + V / b) = 1/2 · (fu + fd + (b / a) · Δt · (fu−fd) + (fu−fd)) = fd + (b / 2a) · Δt · (fu− fd) (20) In the case of the missing peak frequency in FIG. 8, instead of the missing peak frequency b4 Using those obtained by serial formula (19) is interpolated.

In the above interpolation, prediction is performed using the data before the peak frequency is lost, but the result of the FFT usually varies, and if it is used as it is, the prediction error may increase. Therefore, a third interpolation method for reducing the influence of FFT variation will be described below. In addition, from the above equations (9) and (10), the distance speed processing unit 45
The distance and speed are previously stored in the storage unit 43 via the estimation unit 44.
To memorize it. The relevant distance and speed are read from the storage unit 43, and the estimation unit 44 removes the influence of the above-mentioned variations from the distance and speed in the past data.

FIG. 9 shows a circuit for forming distance data to be interpolated using the distance data obtained from the equation (9). The circuit shown in this figure (a) is composed of an FIR filter, and as an example, four delay units connected in series for delaying signals by unit time 1 / fm and a delay unit of the first stage from the input side are provided. It is composed of a multiplier connected to the output and the output of the delay device at the final stage and having respective counts −1/3 and 4/3, and an adder for adding the outputs of the respective multipliers. ), It is assumed that the data by the past distance signal has linearity in a short time, and the past time T-
Distance data at T can be predicted from velocity signals of 4, T-3, T-2 and T-1.

FIG. 10 shows a circuit for forming speed data to be interpolated using the speed data obtained from the equation (10).
The circuit shown in this figure (a) is composed of an FIR filter,
By way of example, four delay units connected in series to each delay the signal by a unit time 1 / fm, a multiplier connected to the output of each delay unit and having a respective count of 1/4, It consists of an adder that adds the outputs, and as a result, as shown in this figure (b), the past times T-4, T-3, T-
The velocity data at T can be predicted from the velocity signals of 2 and T-1.

The distances and velocities obtained in FIGS. 9 and 10 are substituted into equations (9) and (10) to obtain fu and fd, and these are substituted into equations (19) and (20) to obtain fu1 and f1.
Find d1. In the case of loss of peak frequency in FIG.
Interpolation is performed using the one obtained as described above instead of the missing peak frequency b4.

[0024]

As described above, according to the present invention, the beat signals are frequency-analyzed with respect to a plurality of targets, peak frequencies are obtained on the rising side and the falling side of the frequency of the frequency modulation, and the peak frequencies are calculated for each analysis. Confirm the presence or absence of peak frequency loss for each target, and if the loss is detected,
By using the past data to interpolate, the distance and velocity can be obtained. It has become possible to obtain more stable distances and velocities even in the case of intermittent defects and continuous defects, taking into account variations in FFT and the like.

[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 a configuration of a signal processing unit in FIG.

FIG. 4 is a diagram showing data processing of the alignment unit of FIG.

FIG. 5 is a diagram showing a combination of peak frequencies.

FIG. 6 is a diagram illustrating a method of finding a defect by comparing the current peak frequency with the previous peak frequency.

FIG. 7 is a diagram illustrating a method of finding a defect by comparing peak frequencies on the rising side and the falling side.

FIG. 8 is a diagram showing a temporal change in peak frequency and a missing peak frequency for each target.

FIG. 9 shows a circuit that forms distance data to be interpolated using the distance data obtained from equation (9).

FIG. 10 shows a circuit that forms velocity data to be interpolated using the velocity data obtained from the equation (10).

[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 ... Storage part 44 ... Estimating part 45 ... Distance speed processing part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-94183 (JP, A) JP-A-49-128771 (JP, A) JP-A-52-16995 (JP, A) JP-B-38- 5454 (JP, B1)

Claims (4)

(57) [Claims] 1. A millimeter-wave radar range-velocity measuring device for obtaining a distance and velocity to a plurality of targets from beat signals of a reception signal and a transmission signal by performing frequency modulation on a transmission signal of a continuous-wave radar and appropriately repeating the modulation . , Frequency-analyzing the beat signal for multiple targets
The peak frequency on each of the rising and falling sides of frequency modulation
The Fourier transformer for calculating the number of peaks and the peak
The wave numbers are arranged in order of frequency, and the corresponding rising side in that order.
And the peak frequency on the falling side as a pair, and each peak
Find distance and velocity for each target for wave number
For aligning the peak frequency and the order of alignment in this measurement.
Equal to the peak frequency from the previous measurement
Take the difference and adjust the peak frequency by the measurement this time.
The order of the columns is next to the peak frequency according to the previous measurement.
The difference in rank is larger than the difference in rank next to each other.
In case of a peak, the peak is next to the peak frequency measured this time.
There is a loss of frequency
The missing peak frequency corresponds to the previous peak frequency
Millimeter-wave radar range-velocity measuring device characterized by interpolating with . 2. The rising side corresponding to the missing peak frequency
Or other peak frequency excluding the peak frequency on the falling side
2. The millimeter according to claim 1, characterized in that
Wave radar distance velocity measuring device. 3. The missing peak frequency corresponds to the target.
The speed for
Speed and distance and peaks on the ascending and descending sides obtained last time
Frequency and is interpolated with the peak frequency of this time predicted using
The millimeter-wave radar range rate measurement apparatus according to claim 1. 4. The distance is obtained by linearly predicting the velocity.
The millimeter-wave radar range according to claim 3, characterized in that
Speed measuring device.