JP4098311B2 - Electronic scanning millimeter wave radar apparatus and computer program - Google Patents

Description

  The present invention relates to an electronic scanning millimeter-wave radar apparatus and a computer program used therefor, and more particularly to an electronic scanning millimeter-wave radar apparatus and a computer program that effectively removes incoming waves from other than a target object.

  2. Description of the Related Art Conventionally, in-vehicle electronic scanning millimeter-wave radar devices have a mechanical scanning method in which a single beam is mechanically scanned in a lateral direction and a plurality of beams in a lateral direction. A scanning electric type (for example, refer to Patent Document 1) is known. However, in any method, in order to remove the influence of the incoming wave component from the obstacle other than the target object, it is necessary to narrow the beam width transmitted from the transmission antenna.

For example, FIG. 16 shows a transmission wave transmitted from a transmission antenna of an electronic scanning millimeter-wave radar device mounted on a rear vehicle to two front vehicles, and an incoming wave from the front vehicle is a three-channel reception antenna. Shows the case of receiving. In this case, when the beam width of the transmitted wave is wide, for example, when the obstacle on the side side of the front of the vehicle is present, as shown in FIG. 16 (b), the portion of the right side of the beam reaches this obstacle Therefore, there is a problem that the incoming wave (received wave) received by the receiving antenna includes an unnecessary component other than the radio wave from the object (vehicle in the case of FIG. 16 ).

Therefore, in order to solve the above problem, as shown in FIG. 16 (a), by narrowing the beam width of the transmitted wave, it is necessary so as not to reach the beam obstruction lateral side . However, in order to realize this, it is necessary to increase the areas of the transmission antenna and the reception antenna (see, for example, Non-Patent Document 1).
JP-A-6-88869 Antenna Engineering Handbook, edited by the Institute of Electronics and Communication Engineers, published on September 30, 1991, P188-P191

  As described above, to prevent unnecessary components from being included in the incoming wave (received wave), it is effective to increase the area of the transmitting antenna and the receiving antenna and reduce the beam width. On the other hand, when the area of the antenna and the receiving antenna is increased, there is a problem that it is difficult to reduce the size or cost of the entire apparatus.

  Therefore, the present invention has been made in view of the above-described problems, and even when an unnecessary component is included in an incoming wave, an electronic scanning millimeter-wave radar device and a computer program that effectively remove the unnecessary component The purpose is to provide.

The invention according to claim 1 is received by each of the plurality of receiving antennas that receive an incoming wave from an object, a transmission wave generating unit that generates a transmission wave, a transmission antenna that transmits a transmission wave, and each of the reception antennas. Mixing the received wave and the transmitted wave to generate a beat signal, an A / D converter for converting the beat signal into a digital signal, and associating the digitized beat signal with each receiving antenna Storage means for storing, Fourier transform means for Fourier transforming the stored beat signal, digital beam forming means for generating a beam signal at a predetermined pitch angle based on the Fourier transformed signal, and the generated Direction detecting means for detecting the direction of the object from the obtained beam signal, and distance detecting means for detecting the distance from the generated beam signal to the object. Removing means for removing unnecessary signal components from the beat signal corresponding to each receiving antenna Fourier-transformed by the Fourier transform means; and inverse Fourier transform of the beam signal corresponding to each receiving antenna from which the unnecessary component has been removed. An inverse Fourier transform means, and a signal separation processing means for performing a separation process on the beat signal based on the azimuth and distance of the detected object from the beat signal corresponding to each receiving antenna subjected to the inverse Fourier transform. In the electronic scanning millimeter-wave radar apparatus, the signal separation processing unit determines whether or not to perform the separation process based on a determination result of whether or not the angle of the arrival direction of the received wave is wider than a predetermined angle. of the performed determination, when it is determined that the separation process, of the complex number data for each receiving antenna which is generated at the Fourier transform means, Number parts or by using only the imaginary part, performs a separation process of the signal by the maximum entropy method, the removing means includes a wherein said signal separation means performs the removal process when it is determined that the separation process An electronic scanning millimeter-wave radar device is proposed.

According to the present invention, even when an unnecessary component is included in the incoming wave, there is an effect that the unnecessary component can be effectively removed.
In addition, since it is not necessary to narrow the beam width transmitted from the transmission antenna in order to prevent unwanted components from entering the incoming wave, there is an effect that the entire apparatus can be downsized and the cost can be reduced.

  Hereinafter, an electronic scanning millimeter wave radar apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 1, the electronic scanning millimeter wave radar apparatus according to the present embodiment includes receiving antennas 1a to 1i, mixers 2a to 2i, a transmitting antenna 3, a distributor 4, filters 5a to 5i, SW 6, A / D converter 7, control unit 8, triangular wave generation unit 9, VCO (Voltage Controlled Oscillator) (transmission wave generation means) 10, and signal processing unit 20. , Memory (storage means) 21, Fourier transform processing section (Fourier transform means) 22, DBF (Digital Beam Forming) processing section (digital beam forming means) 23, distance detection section (distance detection means) 24, speed A detecting unit 25, an azimuth detecting unit (azimuth detecting unit) 26, an unnecessary component removing unit (removing unit) 27, and an inverse Fourier transform. A processing unit (inverse Fourier transform unit) 28, and a separation processing unit (signal separation means) 29..

  The receiving antennas 1a to 1i are antennas that receive a received wave coming from an object. In the present embodiment, the receiving antennas 1a to 1i are configured by nine receiving antennas. The mixers 2a to 2i mix the transmission waves transmitted from the transmission antenna 3 and the signals received by the reception antennas 1a to 1i and amplified by the amplifiers to generate beat signals.

  The transmission antenna 3 transmits a transmission signal obtained by frequency-modulating the signal generated in the triangular wave generation unit 9 by the VCO 10 to the object. The distributor 4 distributes the frequency modulation signal from the VCO 10 to the mixers 2 a to 2 i and the transmission antenna 3. The filters 5a to 5i perform band limitation on beat signals of channels corresponding to the reception antennas 1a to 1i generated in the mixers 2a to 2i.

  The SW 6 sequentially switches the signals of the channels corresponding to the receiving antennas 1 a to 1 i that have passed through the filters 5 a to 5 i and supplies them to the A / D converter 7. The A / D converter 7 converts the beat signal for each channel corresponding to each of the receiving antennas 1a to 1i input via the SW 6 into a digital signal. The control unit 8 controls the entire apparatus based on a control program stored in a ROM (not shown) or the like.

  Next, the memory 21 in the signal processing unit 20 stores the digital signal digitally converted by the A / D converter 7 for each channel corresponding to each of the receiving antennas 1a to 1i. The Fourier transform processing unit 22 performs a Fourier transform process on the signals for each channel corresponding to the receiving antennas 1 a to 1 i stored in the memory 21. The DBF processing unit 23 performs digital beam forming processing (DBF) on each signal subjected to Fourier transform in the Fourier transform processing unit 22 to generate a beam having a predetermined angular pitch.

  The distance detection unit 24 detects the distance from the signal subjected to the digital beam forming process (DBF) to the object. The speed detection unit 25 detects the speed of the object from the signal subjected to the digital beam forming process (DBF). The azimuth detecting unit 26 detects the azimuth with respect to the object from the signal subjected to the digital beam forming process (DBF).

  The unnecessary component removing unit 27 detects a road condition where the target vehicle is traveling, and removes an incoming wave component from a region other than the lane region of the road. Alternatively, a predetermined threshold is set for the reception level of the channel corresponding to each receiving antenna, and the incoming wave component of the channel below the threshold is removed.

  The inverse Fourier transform processing unit 28 performs an inverse Fourier transform process in order to convert the signal from which the unnecessary component is removed by the unnecessary component removing unit 27 into a signal that can be processed by the separation processing unit 29. The separation processing unit 29 performs separation processing on the beat signals corresponding to the reception antennas 1 a to 1 i that have been subjected to inverse Fourier transform in the inverse Fourier transform processing unit 28. In the present embodiment, the maximum entropy method is used for the separation process.

Next, processing of the electronic scanning millimeter wave radar apparatus according to the present embodiment will be described with reference to FIG.
When the triangular wave generating unit 9 generates a triangular wave by the control signal from the control unit 8 and outputs the triangular wave to the VCO 10, the VCO 10 frequency-modulates the triangular wave signal to generate a transmission signal. This transmission signal is supplied to the mixers 2a to 2i or the transmission antenna 3 via the distributor 4, and the transmission antenna 3 transmits the transmission signal forward as a radio wave.

  When this transmission wave is reflected by an object such as an oncoming vehicle and is received as a reception signal by the reception antennas 1a to 1i, the mixers 2a to 2i mix the reception signal and the transmission signal from the VCO 10 to perform a Doppler frequency. A beat signal including a component is generated. The generated beat signal passes through the filters 5a to 5i for each channel corresponding to the receiving antennas 1a to 1i and is band-limited, and then input to the SW 6. The SW 6 inputs signals corresponding to the reception antennas 1 a to 1 i that have passed through the filters 5 a to 5 i by sequentially switching the switches at a predetermined timing to the A / D converter 7.

  The signal input to the A / D converter 7 is converted into a digital signal, and the converted digital signal is rearranged for each channel corresponding to each of the receiving antennas 1a to 1i and stored in a predetermined area of the memory 21. (Step 101). Next, the digital signals stored in the memory 21 are sequentially read out, and Fourier transform processing is performed in the Fourier transform processing unit 22 (step 102). At this time, the Fourier transform processing unit 22 executes real Fourier transform that inputs only the real part of the data stored in the memory 21.

  Subsequently, the data subjected to the actual Fourier transform in the Fourier transform processing unit 22 is output to the DBF processing unit 23, where digital beam forming processing is executed (step 103). The digital beam forming process forms a beam having an arbitrary pitch by further Fourier-transforming the received signal of each receiving antenna subjected to Fourier transform in the spatial axis direction for each predetermined frequency point.

  The distance detection unit 24 and the speed detection unit 25 select beat frequencies on the ascending part side and the descending part side of the beat signal on which the digital beam forming process is executed in the DBF processing unit 23, and use these beat frequencies. The distance and relative speed are calculated by a predetermined arithmetic expression (step 104). Further, the azimuth detection unit 26 detects the azimuth with respect to the object based on a beam signal having a predetermined angular pitch generated by performing the digital beam forming process in the DBF processing unit 23 (step 105).

  Next, the separation processing unit 29 is based on the distance to the object detected by the distance detection unit 24, the speed of the object detected by the speed detection unit 25, and the direction with respect to the object detected by the direction detection unit 26. Then, it is determined whether or not the angle of the incoming direction of the received wave is wider than a predetermined angle, and it is determined whether or not separation processing is to be performed (step 106). When the separation processing unit 29 determines that the separation process is to be performed, the unnecessary component removal unit 27 performs a process of removing the incoming wave component from outside the control target area (step 107).

  Then, the signal from which unnecessary components are removed is output to the inverse Fourier transform processing unit 28, and an inverse Fourier transform process is performed to convert the signal into a signal that can be processed by the separation processing unit 29 (step 108). In the inverse Fourier transform processing unit 28, the signal subjected to the inverse Fourier transform process is output to the separation processing unit 29, the separation process by the maximum entropy method is executed, and the directions of a plurality of objects are output (step 109).

  In the present embodiment, the maximum entropy method is used for the separation processing in the separation processing unit 29. The maximum entropy method estimates a high resolution spectrum from a finite measurement waveform by estimating an autocorrelation function having a large lag that cannot be measured by itself so that the information entropy is maximized.

  This outline will be described with reference to FIG. For example, consider representing a beat signal with an autoregressive model. If the beat signal waveform is assumed to be Equation 1, this cosine wave can be expressed as the sum of two attenuation signal waveforms according to Euler's formula.

Equation 2 is expressed as shown in FIG. 3, where t is the horizontal axis. Here, the autoregressive model is a current value (X (n) in FIG. 3) and a time value before that (X (n-1), X (n-2) in FIG. 3). It is a model expressed by Therefore, when this is applied to an autoregressive model of a single cos signal waveform, Equation 3 is obtained. In Equation 3, a ₁ and a ₂ are autoregressive coefficients.

  Here, when m wave sources are used, a single cos wave becomes a second-order autoregressive model as shown in Equation 3, and therefore the sum of m cos wave components is a 2m-order self-regression model. It can be represented by a regression model.

Therefore, when the beat signal is two wave sources, the signal vector Rx _i (i = 0 to 8) at each receiving antenna is expressed by a determinant of 4 × 4 matrix as shown in Equation 4. For this determinant, the autoregressive coefficient a _i is obtained by using the least square method or the Burg method as shown in Equation 5, and the signal vector Rx _i (i = 0 to 8) of each receiving antenna is obtained. The damping constant and vibration frequency can be estimated.

  That is, by using the maximum entropy method, peaks of frequency components that cannot be separated by FFT can be clearly separated. Therefore, in the present embodiment, for example, as shown in FIG. 16B, the object can be clearly separated even when there is no level difference between the channels.

  Further, the separation processing unit 29 performs processing by the maximum entropy method using only the real part or the imaginary part of the complex number data for each of the receiving antennas 1a to 1i generated in the Fourier transform processing unit 22. . Specifically, an example in which calculation is performed using only the real part of complex number data will be described with reference to FIGS.

  The calculation is performed using only the real part of the complex number data in order to simplify the calculation process and shorten the processing time. However, when the calculation is performed using only the real number part of the complex number data, FIG. As shown, since the signal vectors (CH0 to CH4 in the figure) at each receiving antenna are collected on the real axis, it becomes impossible to determine the direction using the processing result by the maximum entropy method.

  Therefore, the process of sequentially shifting the phase by 90 degrees with respect to the signal vector at the adjacent receiving antenna, that is, as shown in FIG. 5, CH1 * i is obtained by shifting the phase of CH1 by 90 degrees with respect to CH0. The orientation can be discriminated by sequentially performing processing such as CH2 * i * i by shifting the phase of CH2 by 90 degrees with respect to * i.

  As a result, as shown in FIG. 6, the azimuth detection range is narrower to −90 deg to 90 deg than −180 deg to 180 deg when the complex number calculation is performed, but there is no problem in the determination of the azimuth. An operation using only the imaginary part of the complex data can be performed in the same manner.

  Further, apart from the above method, the same processing can be performed even if the real part and the imaginary part of the complex data are alternately used for each signal vector in the adjacent receiving antenna. In this case, the process of shifting the phase by 90 degrees is not necessary, so that the calculation process can be simplified and the processing time can be shortened.

Next, the removal of unnecessary components will be described below with reference to specific examples using FIGS. 9 to 17.
<First embodiment>
The first embodiment will be described with reference to FIGS.
The first embodiment 1 is a target object by detecting a road condition on which the target vehicle is traveling and determining whether the road on which the vehicle is traveling is a straight road or a curve. An incoming wave (received wave) component from other than the vehicle is removed.

  In FIGS. 9 and 10, the portion indicated by a broken line indicates a lane, and the millimeter wave radar device is located at the center between the lanes. Further, the distance from the millimeter wave radar device to one lane is W, and the distance between the lanes is 2 W, so that incoming waves from other than the portion surrounded by the square are removed. FIG. 10 shows a case where the road is a curve, and the radius of curvature at this time is R.

  The electronic scanning millimeter-wave radar device according to the present embodiment has a road on which a target vehicle is traveling based on a yaw value that is output from a yaw rate sensor (not shown) and the own vehicle speed obtained from a speedometer or the like. It is determined whether the road is a straight road or a curve.

  A processing method when the road on which the vehicle that is the object is traveling is a curve will be described with reference to FIGS. 11 and 12. In FIG. 11, arbitrary two points on the lane are designated as A point and B point, and from the intersection of a line segment connecting A point and B point and a straight line extending in the front direction of the millimeter wave radar device, A point, B The distances to the points are YA and YB, respectively. The distance from the millimeter wave radar apparatus to the intersection is X, the distance from the center of the lane to the right lane is WR, and the distance from the center of the lane to the left lane is WL.

From FIG. 11, when the road is a right curve, YA and YB are respectively expressed as follows.
YA = R-SQRT (R-WR) ^ 2-X ^ 2 (1)
YB = R-SQRT (R-WL) ^ 2-X ^ 2 (2)
Similarly, when the road is a left curve, YA and YB are expressed as follows.
YA = R + SQRT (R-WR) ^ 2-X ^ 2 (3)
YB = R + SQRT (R-WL) ^ 2-X ^ 2 (4)

Here, θ (A) and θ (B) represent angles formed by a straight line extending in the front direction of the millimeter wave radar apparatus and a line segment connecting the millimeter wave radar apparatus and the point A or B, respectively. Use X, YA, YB,
θ (A) = ATAN (YA / X) (5)
θ (B) = ATAN (YB / X) (6)
It is expressed.

  Therefore, θ (A) and θ (B) can be calculated by using the above equations (1) to (6). On the other hand, the directivity directions of the receiving antennas used in the millimeter wave radar apparatus are determined in advance. Therefore, when θ (A) and θ (B) are obtained, a reception antenna from which the reception signal should be deleted is obtained as shown in FIG. 12 in order to remove unnecessary components from the respective directivity directions of the reception antenna. .

<Second embodiment>
A second embodiment will be described with reference to FIGS. 13 and 14.
The method in this embodiment sets a predetermined threshold for the reception level of each channel corresponding to the reception antenna, uses only the incoming wave (received wave) component of the channel exceeding this threshold, and does not exceed this threshold. The unnecessary component is removed by removing the incoming wave (received wave) component of the other low channel. This method uses the property that the level of the incoming wave (received wave) coming from other than the target is lower than the level of the incoming wave (received wave) coming from the vehicle that is the target.

  FIGS. 13 and 14 show the reception level in each channel when the number of channels corresponding to the reception antenna is fifteen. Of these, FIG. 13 shows the case of a straight road. In this case, signals exceeding the threshold value are concentrated in the vicinity of the central portion where the target vehicle is present, and other signals are to be removed.

  FIG. 14 shows a case where the road on which the target vehicle is traveling is a right curve. In this case, since the road that is running is a right curve, the signals that exceed the threshold are concentrated in the middle and slightly to the right where the target vehicle is present. Subject to removal. According to the method as described above, the reception level of each channel corresponding to the reception antenna is discriminated by a predetermined threshold value, and based on the result, the incoming wave component is removed. Since it is not necessary to calculate road conditions by calculation, the processing time can be shortened.

  Therefore, according to this embodiment, even when an unnecessary component is included in the incoming wave, this can be accurately removed, and the orientation of the object can be accurately obtained. That is, in the case shown in FIG. 16B, if unnecessary components are not removed in the present invention, a signal indicating a false orientation appears even if the separation process is executed as shown in FIG. End up. However, if unnecessary component removal in the present invention is performed as shown in FIG. 15A, it is possible to prevent generation of false orientation information based on unnecessary components as shown in FIG. 15B. Therefore, highly accurate azimuth detection is possible.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and includes design changes and the like within a scope not departing from the gist of the present invention. It is.

1 is a configuration diagram of an electronic scanning millimeter wave radar device according to an embodiment. FIG. It is a processing flow of the electronic scanning type millimeter wave radar apparatus concerning this embodiment. It is a figure which shows the concept of the autoregressive model in the maximum entropy method. It is a figure which shows each signal vector at the time of processing using only the real part among the complex number data obtained from each receiving antenna. FIG. 5 is a diagram illustrating each signal vector when a process of sequentially shifting the phase by 90 degrees is added to FIG. 4. It is a figure which shows the detection range at the time of processing using only a real part, and the detection range at the time of processing using complex number data. It is a figure which shows the conventional problem. It is the figure which showed the received wave spectrum at the time of performing the signal separation process using the maximum entropy method. It is a figure for demonstrating the 1st Example regarding the removal of an unnecessary component. It is a figure for demonstrating the 1st Example regarding the removal of an unnecessary component. It is a figure for demonstrating the 1st Example regarding the removal of an unnecessary component. It is a figure for demonstrating the 1st Example regarding the removal of an unnecessary component. It is a figure for demonstrating the 2nd Example regarding the removal of an unnecessary component. It is a figure for demonstrating the 2nd Example regarding the removal of an unnecessary component. It is a figure which shows the effect of this embodiment. It is a figure regarding a prior art example. It is a figure regarding a prior art example.

Explanation of symbols

1a to 1i ... receiving antennas 2a to 2i ... mixer 3 ... transmitting antenna 4 ... distributors 5a to 5i ... filter 6 ... SW
7 ... A / D converter 8 ... control unit 9 ... triangular wave generation unit 10 ... VCO (transmission wave generation means)
20 ... Signal processing unit 21 ... Memory (storage means)
22 ... Fourier transform processing unit (Fourier transform means)
23 ... DBF processing unit (digital beam forming means)
24 ... Distance detection unit (distance detection means)
25... Speed detection unit 26... Direction detection unit (direction detection means)
27 ... Unnecessary component removing unit (removing means)
28: Inverse Fourier transform processing unit (inverse Fourier transform means)
29... Separation processing unit (signal separation processing means)

Claims (1)

A plurality of receiving antennas for receiving incoming waves from the object;
A transmission wave generating means for generating a transmission wave;
A transmission antenna for transmitting a transmission wave;
A mixer that mixes the received wave and the transmitted wave received at each receiving antenna to generate a beat signal;
An A / D converter for converting the beat signal into a digital signal;
Storage means for storing the digitized beat signal in association with each receiving antenna;
Fourier transform means for Fourier transforming the stored beat signal;
Digital beam forming means for generating a beam signal at a predetermined pitch angle based on the Fourier transformed signal;
Azimuth detecting means for detecting the azimuth of the object from the generated beam signal;
Distance detecting means for detecting a distance from the generated beam signal to the object;
Removing means for removing unnecessary signal components from the beat signal corresponding to each receiving antenna Fourier transformed by the Fourier transform means;
An inverse Fourier transform means for performing an inverse Fourier transform on a beam signal corresponding to each receiving antenna from which the unnecessary component has been removed;
Signal separation processing means for performing separation processing on the beat signal based on the direction and distance of the detected object from the beat signal corresponding to each reception antenna subjected to the inverse Fourier transform;
In an electronic scanning millimeter-wave radar device comprising:
When the signal separation processing unit determines whether to perform the separation process based on the determination result of whether the angle of the arrival direction of the received wave is wider than a predetermined angle, and determines to perform the separation process In the complex number data for each receiving antenna generated in the Fourier transform means, using only the real part or the imaginary part, the signal is separated by the maximum entropy method,

The electronic scanning millimeter-wave radar apparatus according to claim 1, wherein the removing unit executes a removing process when the signal separating process unit determines to perform the separating process.

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