JP2002014160A - Radar apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a radar apparatus from making errors in recognizing a target caused by noise. SOLUTION: Power distribution of beat signals, obtained by separate channels 2-0 to 2-7, is averaged to produce an average power distribution, and power peaks are extracted from the average power distribution. Because the peaks resulting from noises cancel out each other in the average power distribution, only those power peaks which are caused by reflections at the target are extracted. For the frequencies of the power peaks, a DBF compositing process for the beat signals obtained at the channels 2-0 to 2-7 is carried out, whereby accurate recognition of the target is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus for obtaining a target distance based on a frequency of a beat signal obtained by mixing a transmission signal with a reception signal.

[0002]

2. Description of the Related Art A typical example of such a radar apparatus is an FM-CW radar apparatus. The FM-CW radar device uses a transmission signal obtained by applying frequency modulation (FM) to a continuous wave (CW), and is suitable for detecting an object at a relatively short distance as compared with a pulse radar. Therefore, in recent years, research and development of an FM-CW radar device as a means for detecting a position and a relative speed of a preceding vehicle mounted on the vehicle have been promoted.

In an FM-CW radar apparatus, a continuous wave subjected to a triangular wave modulation in which the frequency is alternately increased and decreased alternately is used as a transmission signal, and the beat frequency and the modulation in a modulation frequency increasing section (hereinafter simply referred to as an up section) are used. The distance and speed of the target in the beam direction are calculated from the beat frequency in the frequency reduction section (hereinafter simply referred to as the down section). By executing this processing for all the beams in the scanning range, information on targets existing in the scanning range is obtained.

[0004]

However, FM-CW
In a radar apparatus such as a radar apparatus that obtains a target distance based on the frequency of a beat signal, it is necessary to increase S / N in a power distribution (frequency spectrum) using the frequency of the beat signal as a parameter. That is, it is required to make the difference between the peak due to the noise floor level and the power peak due to the target reflection as large as possible.

In a target having a large reflectivity or a target at a short distance, the level of the signal itself reflected by the target is high, so that the difference between the noise and the power peak is large. Mistakes are less likely to occur. Here, the term “pairing” refers to a combination of a power peak in an up section and a power peak in a down section that are considered to be caused by the same target.

On the other hand, in the case of a target having a low reflectance or a distant target, the signal level reflected by the target is low, so that the S / N ratio deteriorates, and the target reflection signal peak and the noise peak are erroneously distinguished. Is likely to occur, and a target misrecognition due to a pairing mistake is induced.

[0007]

The radar apparatus according to the present invention comprises:
In order to solve the above problem, a radar apparatus that obtains a target distance based on a beat signal obtained by mixing a transmission signal with a reception signal has a power distribution that uses the frequency of the beat signal as a parameter. An average power distribution generating means for averaging a plurality of beat signals to generate an average power distribution; extracting a power peak frequency which is a frequency indicating a peak of the average power distribution; A target recognizing means for calculating a distance.

[0008] By averaging the power distributions of a plurality of beat signals in the average power distribution generating means, noise peaks in each power distribution cancel each other out. The difference from the noise peak increases. Therefore, it is easy to accurately extract the power peak frequency based on the target reflection.

The target recognizing means performs a distance calculating operation by narrowing down to the power peak frequency when calculating the target distance based on the beat signal generated based on the received signal. Thereby, the recognition failure caused by noise is eliminated.

[0010] The plurality of beat signals for obtaining the average power distribution may be a plurality of beat signals acquired at different timings in time. If the time interval of the acquisition timing of the beat signal is sufficiently short that the moving speed and the distance of the target can be regarded as not changing, the frequency of the power peak based on the target reflection does not substantially change. Therefore, the frequency of the power peak based on the target reflection can be extracted from the average power distribution.

When the radar device has an array antenna including a plurality of element antennas as a receiving antenna,
The plurality of beat signals can be a plurality of beat signals obtained from a plurality of reception signals received at the same timing by a plurality of element antennas.

Since the noise level floor is different for each element antenna, if an average power distribution is obtained for the beat signal obtained for each element antenna, the peak due to noise is canceled out, and the power peak based on target reflection is emphasized. Can be.

The radar apparatus of the present invention can be applied to an FM-CW radar apparatus from the viewpoint of a method of acquiring the distance and relative speed of a target, and can be applied to a DBF radar apparatus using an array antenna from the viewpoint of a scanning method. Application is conceivable.

The radar apparatus according to the present invention employs an FM-CW type D
In the case of a BF radar device, a plurality of beat signals are generated from a reception signal passing through a reception channel having the highest sensitivity among reception antennas corresponding to each element antenna, and are acquired at different timings in time. It is desirable to include a plurality of beat signals.

The S / N of a received signal passing through a receiving channel with high sensitivity is the S / N of a receiving signal passing through another receiving channel.
Since the average power distribution is higher than N, if the average power distribution is generated including a plurality of beat signals generated from the reception signal passing through the reception channel with high sensitivity, the S / N of the power peak becomes high.

The radar apparatus according to the present invention employs an FM-CW type D
In the case of a BF radar device, the plurality of beat signals may include beat signals for a plurality of reception channels obtained at a plurality of acquisition timings. By generating an average power distribution for the various beat signals,
The noise peak canceling effect can be enhanced.

Even in such a case, by including a plurality of beat signals generated from a received signal passing through a highly sensitive receiving channel, a power peak based on target reflection can be emphasized.

[0018]

FIG. 1 is a block diagram showing the configuration of a radar apparatus according to an embodiment of the present invention. This radar device is an FM-CW radar device using a continuous wave obtained by performing frequency modulation on a transmission signal, and a DBF radar device that forms and scans an antenna beam by digital signal processing.

The receiving array antenna 1 comprises eight element antennas 1-0 to 0-7 corresponding to the respective receiving channels 2-0 to 2-7.
1-7. Each element antenna 1-0 to 1-7
Correspond to the respective mixers 11-0 to 11-7 via the individual isolators constituting the isolator group 12.
It is connected to the.

The mixers 11-0 to 11-7 mix a part of the transmission signal with the reception signals arriving at the element antennas 1-0 to 1-7 to obtain a beat signal. Transmission signal components provided as local signals to mixers 11-0 to 11-7 are provided from voltage controlled oscillator (VCO) 14 via branch circuit 15 and isolator group 13.

The oscillator 14 is a varactor-controlled gun oscillator having a center frequency f0 (for example, 76 GHz). The frequency is f0 ± (1/2) ΔF by a control voltage output from a control voltage output circuit 22 for modulation. And outputs a modulated wave that changes in a triangular waveform between the two.

Here, the FM modulation is a triangular wave modulation in which a frequency increasing section (up section) and a frequency decreasing section (down section) are alternately continuous, and the frequency is f in the up section.
It increases linearly from 0- (1/2) ΔF to f0 + (1/2) ΔF, and in the down section, the frequency changes from f0 + (1/2) ΔF to f0- (1/2) Δ in the same time as the up section.
It decreases linearly to F.

This FM modulated wave is supplied to the transmission antenna 21 via the branch circuit 15 and is radiated as a transmission signal. As described above, the FM modulated wave is branched into eight channels as a local signal. At 11-7, the received signals of the eight channels 2-0 to 2-7 are mixed with each other to generate a beat signal for each channel.

Mixer group 11, isolator group 12, 1
3, a low-noise amplifier 24, a high-speed A / D converter 25, a signal processing unit 26, and a complex FFT operation unit 27 are provided downstream of the high-frequency circuit 10 including the oscillator 14, the branch circuit 15.

The low noise amplifier (amplifier) 24 is a mixer 1
This is to amplify the 8-channel beat signals output from 1-0 to 11-7 in parallel. The amplifier 24
Has a cutoff frequency of 77 for anti-aliasing.
A low-pass filter of kHz is built in.

The high-speed A / D converter 25 is a circuit for performing A / D conversion of each beat signal of eight channels in parallel and simultaneously, and performs sampling at 200 kHz. At this sampling frequency, sampling is performed at 128 points in each of the up section and the down section of the triangular wave in the FM modulation. The output signal of the control voltage output circuit 22 is used for synchronization control with the sampling of the FM modulation.

The signal processing unit 26 includes a high-speed A / D converter 25
, A digital beat signal for each channel is obtained, and various signal processes are performed according to the flowchart shown in FIG. 2 to perform a target (target) recognition process.

The complex FFT operation unit 27 includes a signal processing unit 26
Is a computing unit that executes the complex FFT operation in the series of processes in the processing of FIG.
The T operation is performed, and the result is returned to the signal processing unit 26.

Next, the operation procedure of the present apparatus will be described with reference to the flowchart shown in FIG.

First, in step S10, a digital beat signal for each channel is fetched. Since the digital beat signal for each channel is obtained by sampling 128 points in the up section and the down section for each channel, a total of 128 (points) × 2 (section) × 8 (channels) = 2048 points Of data. Then, based on these data, FFT (Fast Fourier Transform processing) is executed for each channel, and beat frequency information for each channel is obtained. Furthermore, based on this beat frequency information,
The power distribution of the beat signal using the frequency as a parameter, that is, the frequency spectrum of the beat signal is obtained for each channel.

The beat frequency information and power distribution obtained here are all stored in a storage unit in the signal processing unit 26. Note that the beat frequency information, which is the basic data of the power distribution for each channel, includes phase information necessary for the subsequent DBF processing.

In step S11, it is determined whether the various processes to be executed are for up section data or down section data. If the determination is affirmative, that is, if the subsequent processing is for the up-section data, the process proceeds to step S12, where the digital beat frequency information of the up-section stored in step S10 is read, and the DBF processing is performed. Prepare. If a negative decision is made in step S11, the operation proceeds to step S13,
The digital beat frequency information of the down section stored in step S10 is read to prepare for the subsequent DBF processing.

In step S14, each channel 2-0
An average power distribution is generated by averaging the power distribution (frequency spectrum) of the beat signal acquired for each of 2-7.
Then, in step S15, a power peak is extracted from the average power distribution. In the average power distribution, the peaks due to noise cancel each other out, so the power peaks extracted here do not include the power peaks due to noise, and only the power peaks due to target reflection are extracted. Have been.

This will be described in more detail with reference to the graph of FIG. FIG. 3 is a graph showing the power distributions of beat signals acquired in four channels 2-0 to 2-3 and their average power distributions. The power distributions of the channels 2-0 to 2-3 are respectively represented by solid lines,
It is drawn with a dashed line, a dotted line, and a dashed line. The average power distribution is depicted by a solid bold line. In this example, it is assumed that a peak 38 due to target reflection is formed at a frequency point 39, and all other peaks are due to noise.

As can be seen from this graph, in the power distribution for each channel, it is clear that there is a power peak 38 at the frequency point 39, but a waveform that can be recognized as a peak at other frequencies is sometimes found. be able to. Therefore, when trying to extract a power peak using the power distribution for each channel, a peak due to noise may be extracted in addition to a peak due to target reflection.

However, in the average power distribution, a clear power peak 38 can be found only at the frequency point 39. That is, since there is no clear power peak at frequencies other than the frequency point 39, the power peak 38 at the frequency point 39 is outstanding.
Therefore, only peaks due to target reflection can be extracted.

The word power in the power distribution is
Here it is used in a broad sense: amplitude, power in a narrow sense,
Alternatively, it is a concept including both a decibel conversion value and the like of power in a narrow sense. Therefore, as a power distribution averaging method, a method of averaging amplitude, a method of averaging power in a narrow sense, a method of averaging a decibel conversion value of power in a narrow sense, and the like are considered.

In the method of averaging amplitudes, A (n) = SRQT (Re (n) ² + Im (n) ² ) is calculated and averaged. Here, n is the sequence number assigned to the beat frequency of the FFT result, A (n) is the amplitude value of the FFT result at frequency number n, and Re (n) is the frequency number n
, The real part of the FFT result, Im (n) is the frequency number n
Is the imaginary part of the FFT result in.

In the method of averaging the amplitude, the square root calculation (S
RQT) is required, but since the magnitude of the numerical value can be suppressed as compared with a method of averaging power in a narrow sense described later, a large dynamic range can be obtained for the same number of bits.

In the method of averaging power in a narrow sense, Pow (n) = A (n) ² = Re (n) ² + Im (n) ² is calculated and averaged. This method has the advantage that the calculation is simple.

In the method of averaging the decibel conversion value (dB conversion value) of the power in a narrow sense, the following calculation is performed: dB conversion value = 10 Log (Pow (n)) = 10 Log (Re (n) ² + Im (n) ² ) And average. According to this method, calculation of logarithm (Log) is required, but the dynamic range can be maximized as compared with the other methods described above. Incidentally, the graph of FIG. 3 shows the result calculated by this method.

In the example of FIG. 3, averaging is performed on four channels for simplicity, but in this embodiment, averaging is performed on all channels (eight channels). The averaging may be performed on a plurality of appropriately selected channels instead of all channels.

As described above, as a pre-process of the DBF synthesizing process, the power distribution of the beat signal for each channel is averaged, and the power peak is extracted to remove the power peak caused by noise. Can be.

Next, the DBF combining process using the beat signal for each channel is executed only for the power peak frequency resulting from the target reflection thus obtained.

In step S16, the power peak frequency obtained in step S15 and its neighboring frequencies are selectively phase-rotated by digital signal processing on the digital beat signal for each channel. By appropriately setting the amount of phase rotation at this time for each channel, -10
A beam is formed in one of the scanning angle directions, which is obtained by dividing the range from degrees to +10 degrees at intervals of 0.5 degrees in 41 directions. When performing beam forming in a desired direction, how to perform phase rotation for each channel may be in accordance with ordinary digital beam forming processing, and a detailed description thereof will be omitted.

In step S17, D in step S16
BF processing is performed in all directions, that is, from -10 degrees to +
It is determined whether or not the processing has been completed for 41 directions up to 10 degrees. When the extraction of the power peaks by scanning direction has been completed for all directions, the process proceeds to step S18.

In step S18, power peaks in the scanning direction adjacent to each other in the scanning direction and having substantially the same value are grouped to generate a power peak group.

FIGS. 4A and 4B are graphs showing the state of grouping. FIG. 4A shows the state of grouping in the up section, and FIG. 4B shows the state of grouping in the down section. In the figures (a) and (b), the horizontal axis represents the scanning angle,
The vertical axis represents the beat frequency. Further, the power peak is indicated by a point, and the height of the power peak is indicated by the size of the point. The higher the power peak, the larger the dot size.

Now, it is assumed that the up section is being processed.
Referring to FIG. 4A, at the power peak frequency f1, a plurality of power peaks for each scanning angle continuously exist in a scanning angle range centered on the scanning angle θ1. Step S1
In 7, these power peaks are grouped into one power peak group 31. Similarly, the power peak for each scanning angle of the power peak frequencies f3 and f4 is the scanning angle θ, respectively.
Since there are a plurality of scan peaks continuously in the scan angle range centered at 2, θ3, these are grouped into power peak groups 33 and 34, respectively.

When the grouping of the power peaks is completed, a representative scanning angle is extracted in step S19. In this embodiment, the scanning angle of the power peak indicating the highest level in the power peak group is set as the representative scanning angle.
Referring to FIG. 4A, the representative scanning angle of the power peak group 31 is θ1, and the representative scanning angles of the power peaks 33 and 34 are θ2 and θ3, respectively.

Subsequently, in step S20, an edge scanning angle of each power peak group is extracted. The edge scanning angle is
This is a scanning angle that is lower than the maximum level (level at the representative scanning angle) of the power peak group by a predetermined value. In the example of FIG.
The scanning angles of the power peaks located at the left end and the right end of 33 and 34, respectively.

In step S21, the power peak distribution width of each power peak group, that is, the angle range from the left edge scanning angle to the right edge scanning angle of each power peak group is checked. It is determined whether or not there is. If this determination is affirmative, the process proceeds to step S23 via step S22.

In step S22, a new power peak group is generated by subtracting the standard power peak distribution (hereinafter simply referred to as the standard distribution) from the power peak distribution of the power peak group whose power peak distribution width is equal to or greater than the predetermined value. In step S23, a representative scanning angle of the new power peak group generated in step S22 is extracted.

FIG. 5 is a graph for explaining the processing in steps S22 and S23. FIG. 11A shows the power peak distribution of the power peak group before the subtraction processing, FIG. 10B shows the standard distribution, and FIG. 10C shows the new power peak distribution generated after the subtraction processing. In each graph, the horizontal axis indicates the scanning angle, and the vertical axis indicates the peak level.

The power peak distribution 41 shown in FIG.
Are grouped in step S18, the representative scanning angle θ41 is extracted in step S19,
It is determined in step S21 that the distribution width W41 is equal to or greater than a predetermined value.

The power peak distribution 42 shown in FIG.
Is a standard distribution for the power peak distribution 41. This standard distribution is normalized so that the representative scan angle of the power peak distribution for a standard single target and the peak level at the representative scan angle match the representative scan angle of the power peak distribution 41 and the peak level at the representative scan angle. It was done. The power peak distribution for a standard single target is measured and stored in advance.

The power peak distribution 43 shown in FIG.
Shows a result obtained by subtracting such a standard distribution 42 from the power peak distribution 41.

A power peak distribution having a distribution width exceeding a predetermined value is considered to be based on reflected waves from a plurality of targets. The power peak distribution 43 is based on reflected waves from two targets arranged at the same distance and at the same speed, and the representative scanning angle θ41 is based on the reflected waves from one target. The standard distribution 42 is obtained by estimating the power peak distribution based only on the reflected wave from one of the targets, and by subtracting this from the power peak distribution 41, the power peak distribution based on only the reflected wave from the other target is estimated. it can. The power peak distribution 43 is the representative scanning angle θ4.
Numeral 3 indicates the orientation of the other target. In addition,
The representative scanning angle θ42 of the standard distribution 42 is the same as the representative scanning angle θ41 of the power peak distribution 43 by definition.

Subsequently, the flow shifts to step S24. In step S24, it is determined whether or not the above-described series of processing from step S12 to step S23 has been performed for both the up section and the down section. If the determination is negative, the process returns to step S11. If the determination is positive, the process proceeds to step S25.

When returning from step S24 to step S11, the series of processing from step S14 to step S23 based on the beat frequency data in the up section is completed, and the same processing based on the beat frequency data in the down section is still executed. Since this is not the case, a negative determination is made in step S11. Then, step S1
Then, the process proceeds to step S3, where the beat frequency data of the down section calculated and stored in step S10 is read, and the processing from step S14 to step S23 is executed based on the read data. At this point, when the process proceeds to step S24, the determination is affirmed, and the process proceeds to step S25.

In step S25, the power peak group in the up section and the power peak group in the down section are paired. Pairing refers to combining power peak groups estimated to be based on the same target, and the method will be described with reference to FIG.

The representative scanning angle of each power peak group indicates the center azimuth of the target. Therefore, in order to combine power peak groups based on the same target, those having the same representative scanning angle may be combined.

In FIG. 4, the power peak group 31 in the up section has a representative scanning angle θ1 and can be combined with the power peak group 35 in the down section having the representative scanning angle θ1. For the representative scanning angle θ2, the power peak group 33 in the up section and the power peak group 37 in the down section are paired, and for the representative scanning angle θ3, the power peak group 34 in the up section and the power peak group 36 in the down section are paired. Pair.

When the pairing in step S25 is completed as described above, the process proceeds to step S26, and the processing and speed of the target are obtained by calculation using the beat frequency of the paired power peaks. This operation is FM
-It is based on the basic principle of a CW radar device.

Here, the detection principle of the FM-CW radar device will be briefly described just in case.

The center frequency of the transmission signal is f0, the frequency modulation width is ΔF, the FM modulation frequency is fm, and the beat frequency (beat frequency in a narrow sense) when the relative speed of the target is zero is based on fr and the relative speed. Assuming that the Doppler frequency is fd, the beat frequency in the up section is fb1, and the beat frequency in the down section is fb2, fb1 = fr-fd (1) fb2 = fr + fd (2) holds.

Therefore, if the beat frequencies fb1 and fb2 in the up and down sections of the modulation cycle are measured separately, fr and fd can be obtained from the following equations (3) and (4). fr = (fb1 + fb2) / 2 (3) fd = (fb2-fb1) / 2 (4)

Once fr and fd are determined, the target distance R and velocity V can be determined by the following equations (5) and (6). R = (C / (4 · ΔF · fm)) · fr (5) V = (C / (2 · f0)) · fd (6) where C is the speed of light.

Taking FIG. 4 as an example, in the combination of the power peak group 33 and the power peak group 37, f3 and f7 are fb1 in the above equations (1) to (4), respectively.
And fb2.

In step S27, the target distance R and velocity V obtained in this way are combined with past target information to detect the time-series movement of the target. More detailed target recognition is performed by predicting target types and future movements.

Next, a second embodiment of the present invention will be described. The hardware configuration of the second embodiment is the same as that of the first embodiment, and is as shown in FIG.

FIG. 6 is a flowchart showing the operation of the second embodiment. This embodiment is different from the first embodiment in D
Only the method of extracting the power peak before the BF synthesis processing is different. That is, the flowchart of FIG. 6 differs only in that steps S61 and S62 are executed instead of steps S14 and S15 of the flowchart of the first embodiment shown in FIG.

In step S61, attention is paid to a received signal received by an appropriate element antenna, for example, an element antenna 1-4 located substantially at the center of the array antenna 1, and the beat signal obtained in the current up section or down section is focused on. The power distribution and the power distribution of the beat signal in the same kind of section received by the same element antenna in the past three times are averaged.

FIG. 7 is a transmission signal timing chart. The transmission signal frequency is plotted on the vertical axis and time is plotted on the horizontal axis.
The up section and the down section are continuously and alternately repeated, and section 4 shows the current time, that is, the latest up section and down section. Section 3 is an immediately preceding up section and a down section, section 2 is an immediately preceding up section and a down section, and section 1 is an immediately preceding up section and a down section.

Now, assuming that the up section is being processed by the determination in step S11, in step S61, the power of the beat signal based on the received signal in each of the up sections of section 1 to section 4 received by the element antenna 1-4. Average the distribution.

FIG. 8 is a graph showing the power distribution of beat signals acquired in each of the up sections of section 1 to section 4 and their average power distribution. The power distributions of the sections 1 to 4 are drawn by solid lines, broken lines, dotted lines, and thin dashed lines. The average power distribution is depicted by a solid bold line. In this example, at frequency point 89, a peak 88 due to target reflection
Is formed, and all other peaks are caused by noise.

Since the status (distance, relative speed) of the target in section 1 to section 4 changes every moment, the power peak frequency due to target reflection also changes. However, if the period of each section is sufficiently short with respect to a change in the situation of the target, power peaks due to target reflection in each section substantially overlap. For example, in an on-vehicle radar device for recognizing a preceding vehicle, when the modulation frequency is set to several hundred Hz, the distance and relative speed of the preceding vehicle are substantially changed over a period of about four modulation periods from section 1 to section 4. Can be regarded as not changing.

In step S62, a power peak 88 is extracted from the average power distribution thus obtained, and its frequency 89 is obtained.

The procedure after obtaining the power peak frequency thus obtained is the same as that of the first embodiment, and the description is omitted.

Next, as a third embodiment, a case where a switch-switching type DBF radar device is used will be described.

FIG. 9 is a block diagram of a switch-switching DBF radar device. As in the above two embodiments, this radar device is also an FM-CW radar device. However,
In this switch-switching DBF radar device, the nine element antennas Rx1 to Rx9 of the array antenna 102 do not simultaneously receive the received signals,
03, one element antenna is selected from the element antennas Rx1 to Rx9, and the reception signal there is selectively taken into the reception unit 104. The element antennas are switched at a high speed by the changeover switch 103, and as a result, the signals received by all the element antennas are obtained. With such a configuration, expensive RF amplifiers and mixers can be reduced.

The transmitting section 101 includes a voltage controlled oscillator 111, a buffer amplifier 112, and a transmitting antenna 11
3, an RF amplifier 114, and a coupler 115. The changeover switch 103 includes a three-to-one changeover switch 13.
By combining 1 to 134, a 9: 1 changeover switch is configured. The receiving unit 104 includes the RF amplifier 1
41, a mixer 142, an amplifier 143, a filter 144, and an A / D converter 145. The DBF processor 105 receives the digital beat signal from the A / D converter 145, and performs target recognition by beat signal averaging and DBF combining.

As a switching method of the changeover switch 103, by repeating the switching of all the element antennas many times in one section (one set of the up section and the down section), one section substantially regarded as simultaneous reception for all the element antennas A multi-section scheme that achieves reception of all element antennas by grouping several sections by repeating switching between several element antennas in the first section and repeating switching of different element antennas in the next section. There is.

In the case of the multi-section system, the element antenna to be selected in each section is determined, and in the sections other than the first section, reception of other element antennas by the amount of change of the received signal by the common element antenna is performed. By correcting the signals, the reception signals of all the element antennas are substantially in the same section (first section).
It can be treated as if it had been obtained in.

In the present embodiment, a multi-section system is adopted. As shown in the timing chart of FIG. 10, element antennas Rx5, Rx4, Rx6 are selected in the first section, and element antennas Rx5, Rx3 in the second section. , Rx7
Is selected, and in the third section, the element antennas Rx5 and Rx
2, Rx8 is selected, and in the fourth section, the element antenna Rx
5, Rx1 and Rx9 are selected.

In each section, the selected three element antennas are repeatedly switched at a high speed.
Connected to. The switching frequency of the changeover switch is, for example, a carrier frequency of several tens of GHz and a modulation frequency of several hundred Hz.
Is set to several MHz to several hundred MHz.

The operation of this embodiment will be described with reference to the flowchart of FIG. 2 showing the operation of the first embodiment.
In the first embodiment, the capture of the digital beat signal for each channel in step S10 is achieved in one section (one up section and one down section), but in this embodiment, from the first section to the fourth section shown in FIG. Achieve with. By using four sections, the element antenna R
A beat signal can be obtained for a reception signal for each element antenna channel received by all element antennas from x1 to element antenna Rx9.

Thereafter, as in the case of the first embodiment,
Based on these data, FFT is performed for each channel, and beat frequency information for each channel is obtained. Further, based on the beat frequency information, the power distribution of the beat signal using the frequency as a parameter, that is, the frequency spectrum of the beat signal is obtained for each channel.

The beat frequency information and the power distribution obtained here are all stored in the storage unit in the DBF processor 105.

When step S10 is completed, step S
Through the steps 11 to S13, the power distribution of the beat signal for each channel in the steps S14 and S15 is averaged to obtain an average power distribution. Then, in step S15, a power peak is extracted from the average power distribution.

The same processing as that of the first embodiment is executed in step S16 and subsequent steps, and finally target recognition is performed.

In the present embodiment, the element antennas Rx1 to Rx1
Although the power distribution of all channels corresponding to x9 has been averaged, an appropriate channel may be selected to shorten the calculation time for averaging. For example, in the radar apparatus having the changeover switch 103 as in this embodiment, the channel path of the element antenna Rx5 is the shortest, the sensitivity is the highest, and the beat signal is provided in all of the first to fourth sections. Can be obtained, so that only the element antenna Rx5 may be averaged.

Further, one section, for example, the first to fourth sections
Focusing on the newest fourth section in the section, element antenna Rx5 connected to receiving section 104 in the fourth section,
The power distribution may be averaged for the Rx1 and Rx9 beat signals.

Alternatively, two or three of the four sections may be selected, and the power distribution of the beat signal acquired during the section may be averaged.

[0095]

As described above, according to the radar apparatus of the present invention, the power distribution is averaged for a plurality of beat signals to generate an average power distribution, and the power peak frequency is referred to to determine the target power from the beat signal. Calculate the distance and the like.
As described above, since the distance calculation is performed by narrowing down to the power peak frequency of the average power distribution, recognition failure due to noise is eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a radar device of the present invention.

FIG. 2 is a flowchart showing the operation.

FIG. 3 is a graph showing power distributions of beat signals acquired in four channels of channels 2-0 to 2-3 and their average power distributions.

FIG. 4 is a graph for explaining pairing of a power peak group.

FIG. 5 is a graph for explaining a process of subtracting a standard distribution from a power peak distribution.

FIG. 6 is a flowchart showing the operation of the radar device according to the second embodiment.

FIG. 7 is a timing chart of a transmission signal subjected to triangular wave frequency modulation.

FIG. 8 is a graph showing power distributions of beat signals acquired in a section 1 to a section 4 and their average power distributions.

FIG. 9 is a configuration diagram of a switch-switching DBF radar device according to a third embodiment.

FIG. 10 is a timing chart of a transmission signal subjected to triangular wave frequency modulation.

[Explanation of symbols]

1, 102: array antenna, 10: high frequency circuit, 11
... mixer group, 14 ... voltage controlled oscillator, 15 ... branch circuit,
22: control voltage output circuit, 24: low noise amplifier, 25:
High-speed A / D converter, 26: signal processing unit, 27: complex FF
T calculation unit, 101: transmission unit, 103: changeover switch, 1
04: receiving unit, 105: DBF processor, 111: voltage-controlled oscillator, 113: transmitting antenna, 141: RF
Amplifier, 142 mixer, 145 A / D converter.

Claims (8)

[Claims] 1. A radar apparatus for obtaining a target distance based on a beat signal obtained by mixing a transmission signal with a reception signal, wherein a power distribution using a frequency of the beat signal as a parameter is averaged over a plurality of beat signals. Average power distribution generating means for generating an average power distribution by extracting a power peak frequency which is a frequency indicating a peak of the average power distribution, and calculating a target distance from the beat signal with reference to the power peak frequency. A radar device comprising: target recognition means. 2. The radar apparatus according to claim 1, wherein the plurality of beat signals are a plurality of beat signals acquired at different timings in time. 3. An array antenna comprising a plurality of element antennas as a receiving antenna, wherein the plurality of beat signals are a plurality of beat signals obtained from a plurality of reception signals received at the same timing by the plurality of element antennas. The radar device according to claim 1, wherein: 4. The radar device according to claim 2, wherein the radar device is an FM-CW radar device. 5. The radar device according to claim 4, wherein the radar device is a DBF radar device. 6. The plurality of beat signals are generated from received signals passing through the most sensitive receiving channel among respective receiving channels for a plurality of element antennas, and are acquired at different timings. The radar apparatus according to claim 5, wherein the radar apparatus includes a plurality of beat signals. 7. The plurality of beat signals are beat signals generated from reception signals passing through respective reception channels for a plurality of reception antennas, and the beat signals for a plurality of reception channels obtained at a plurality of acquisition timings. The radar device according to claim 5, further comprising a signal. 8. The apparatus according to claim 7, wherein the plurality of beat signals include a plurality of beat signals generated from a reception signal passing through a reception channel having the highest sensitivity and acquired at different timings in time. The described radar device.