JP2008286696A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar device allowing concurrent observation in a short distance and a far distance by one radar, capable of dispensing with a mode switch, while using one radar, and capable of restraining the number of part items from increasing. <P>SOLUTION: The radar device includes a signal processing part 20 applied with a digital beam forming antenna to a reception antenna constituted of a plurality of antenna elements, and for outputting an observation result of a target 2 by executing multibeam forming processing and frequency analytical processing to a digital base band reception signal based on a reception signal obtained by reflection of a transmission signal emitted from a transmission antenna 14 on the object 2, and the signal processing part 20 is constituted to make at least either of the multibeam forming processing or the frequency analytical processing variable in response to an observation-objective distance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radar apparatus that measures the distance and speed of a moving object, in particular, an obstacle mounted in front of an automobile or another automobile.

  As a fail-safe function of an automobile, an automatic driving control system and a driver assistance system have been studied, and some have been put into practical use. These systems are often equipped with a radar device that observes the situation around the vehicle in order to supplement the driver's perception and feeling.

  As such a radar system for mounting on an automobile, a transmission signal is pulsed by a pulse radar, a pulse compression radar, an FMCW (Frequency Modulated Continuous Wave) radar, a multi-frequency CW (Continuous Wave) radar, an FMCW radar or a multi-frequency CW radar. Various schemes such as FMICW (Frequency Modulated Interrupted Wave) radar and multi-frequency ICW (Interrupted Continuous Wave) radar have been proposed.

  A radar device that is installed in front of a vehicle body and that observes obstacles and other automobiles (hereinafter simply referred to as targets) at a distance of about 100 to 200 m in front of the vehicle uses radio waves as radiated electromagnetic waves. A millimeter wave having a frequency of about 76 to 77 GHz is used.

  When observing a wide distance range from several meters ahead to about 100 to 200 m, for example, different radar modes are used for short distance and long distance, or different sensors are used for short distance observation and long distance observation. Often used (see, for example, Patent Document 1).

Special table 2003-526792 gazette

However, the prior art has the following problems.
When using different radar modes or different sensors at short distance and long distance, the reaction time is reduced due to switching between modes or sensors, or by integrating the observation results of multiple sensors. There was a problem that would be long.

  Moreover, when using another sensor, the subject which requires the fusion process of the data which these sensors output occurred. In addition, there is a problem that the number of parts increases by using a plurality of sensors.

  The present invention has been made in order to solve the above-described problems. It is possible to simultaneously observe a short distance and a long distance with one radar, and it is not necessary to have mode switching with one radar, and the parts An object of the present invention is to obtain a radar apparatus capable of suppressing an increase in the number of points.

  The radar apparatus according to the present invention applies a digital beamforming antenna to a reception antenna composed of a plurality of antenna elements, and a digital base based on a reception signal obtained by reflecting a transmission signal radiated from the transmission antenna to a target. A radar apparatus including a signal processing unit that outputs an observation result of a target by performing multi-beam forming processing and frequency analysis processing on a band reception signal, and the signal processing unit is configured to perform multi-beam forming processing or frequency The process setting condition of at least one of the analysis processes is made variable according to the observation target distance.

  According to the present invention, a digital beam forming antenna is used as a receiving antenna, and at least one of multi-beam forming processing and frequency analysis processing is appropriately set according to the observation target distance, so It is possible to prevent the reaction time from becoming longer due to switching modes and observing, and it is possible to observe short distance and long distance simultaneously with one radar, and mode switching with one radar It is possible to obtain a radar apparatus which is not necessary and can suppress an increase in the number of parts.

  A preferred embodiment of a radar apparatus according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a radar apparatus according to Embodiment 1 of the present invention. The radar device 1 according to the first embodiment includes a signal generator 11, a transmission signal converter 12, a pulse converter 13, a transmission antenna 14, and P element antennas 15 (1) to 15 (P is an integer of 2 or more). 15 (P), P mixers 16 (1) to 16 (P), P A / D converters 17 (1) to 17 (P), and a signal processing unit 20.

  The signal generator 11 generates a transmission signal from the radar apparatus 1. The transmission signal converter 12 converts the signal generated by the signal generator 11 into a high frequency signal. The pulse generator 13 pulses the high frequency signal output from the transmission signal converter 12. The transmission antenna 14 radiates the high frequency signal pulsed by the pulse generator 13 into the air as the transmission wave 3.

  In the first embodiment, the directivity of the transmission antenna 14 is wide. That is, the high frequency signal radiated in the air as the transmission wave 3 is radiated at a wide angle. The transmission wave 3 radiated from the radar device 1 into the air is reflected by the target 2 and taken into the radar device 1 again as the target reflected wave 4.

  P element antennas 15 (p) (p = 1, 2,..., P) are element antennas that receive the target reflected wave 4 as a high-frequency signal, and constitute a reception antenna. The element antenna 15 (p) may be composed of a plurality of antennas. Each of the P mixers 16 (p) (p = 1, 2,..., P) has a high-frequency signal received by the corresponding element antenna 15 (p) and a pulse before being transmitted as a transmission signal. The high frequency signal generated by the transmission signal converter 12 is mixed and frequency-converted to baseband.

  Each of the P A / D converters 17 (p) (p = 1, 2,..., P) time-discretizes (samples) the output signal of the corresponding mixer 16 (p) and sets the level. Discretize and convert to digital signal. Then, the signal processing unit 20 calculates the relative speed and distance to the observed target 2 from each digital received signal sampled by the P A / D converters 17 (p).

  Although not shown in FIG. 1, an amplifier, an AGC (Automatic Gain Control) circuit, or the like may be further used as the radar apparatus 1 as necessary.

  Next, a series of operations of the radar apparatus 1 of the first embodiment will be described based on the configuration of FIG. Here, a case where a multi-frequency ICW signal obtained by pulsing a continuous wave (multi-frequency CW) having a constant amplitude and a stepwise increase in frequency will be described as a transmission signal. FIG. 2 is a diagram schematically showing a multi-frequency ICW transmission signal according to Embodiment 1 of the present invention.

Signal generator 11 has a frequency (the N 2 or more integer) stepwise N at regular intervals Δf type increases (refer to this period modulation period represents a period in T _P) of the base band repeating the multi A frequency CW signal is generated. If the duration of one frequency is T _PRI , the modulation period is T _P = N · T _PRI . The baseband multi-frequency CW signal is converted into a high-frequency signal by the transmission signal converter 12.

As shown in FIG. 2, the frequencies of the multi-frequency CW signal are f ₁ , f ₂ ,..., F _N. The frequency f _n (n = 1, 2,..., N) is expressed as f _n = f ₁ + (n−1) Δf. f ₁ is the minimum carrier frequency. The interval corresponding to the signal of a certain frequency f _n to be referred to as n-th step. The m-th modulation cycle (m is an integer equal to or greater than 1) is referred to as an m-th modulation process.

  The multi-frequency CW signal converted to a high frequency is pulsed by the pulse generator 13 to become a multi-frequency ICW signal. FIG. 2A schematically shows a transmitted pulse, and the vertical axis indicates frequency. The pulsed multi-frequency ICW signal is radiated into the air as the transmission wave 3 via the transmission antenna 14.

The reflected wave 4 reflected by the target 2 is received as a received wave via the P element antennas 15 (p), and each is sent to the corresponding mixer 16 (p). In the mixer 16 (p), the reception wave from the element antenna 15 (p) and the high-frequency multi-frequency CW signal that is the output of the transmission signal converter 12 are mixed and frequency-converted, and then used as a baseband reception signal. Each is output to the A / D converter 17 (p). Each received baseband signal, A / D converter 17 at (p) is sampled at a sampling interval T _s, is converted into a digital signal.

Here, the sampling period T _s is a time shorter than the pulse width. Further, it referred to as a digital baseband received signal the output signal of the A / D converter 17 _(p), expressed by u p (m, n, k ). The digital baseband reception signal u _p (m, n, k) is input to the signal processing unit 20.

Here, m represents the m-th modulation process, n represents the transmission frequency is f _n , and k is the range bin number. As shown in FIG. 2B, the range bin number is a sample point number when the received signal is sampled at the sampling interval T _s within the duration T _PRI of one frequency equal to the pulse repetition period.

FIG. 2B illustrates a case where the sampling interval T _s is equal to the pulse width and the number of range bins is K. The number of modulation periods required to output one set of target detection results is M (M is an integer equal to or greater than 1). The time corresponding to this is an output period of target detection data (hereinafter referred to as observation values) of target distance, relative speed, and angle as observation values. The multi-frequency ICW signal is continuously transmitted beyond the observation value output period.

In the configuration of FIG. 1, the digital baseband received signal u _p (m, n, k) is a real number, but the digital in-phase (I) signal is obtained by frequency-converting the high-frequency signal received by the element antenna 15 (p). The quadrature (Q) signal may be obtained. In this case, the digital baseband received signal u _p (m, n, k) is treated as a complex digital signal having the real part as an in-phase signal and the imaginary part as a quadrature signal.

Next, specific processing in the signal processing unit 20 will be described.
FIG. 3 is an internal configuration diagram of the signal processing unit 20 of the radar apparatus according to Embodiment 1 of the present invention. The signal processing unit 20 includes a digital multi-beamformer 21, a Doppler frequency analyzer 22, a frequency analyzer 23, and a target detector 24.

Here, a process for one observation value output period will be described. For the digital baseband received signal u _p (m, n, k), the digital multi-beamformer 21 performs the beam forming process of the following equation (1).

Here, the multi-beam number for first k range bin and Q _k. W _k is a digital multi-beam forming weight matrix of Q _k rows and P columns for the signal of the k-th range bin. U (m, n, k) is a vector composed of a digital baseband received signal u _p (m, n, k) that is an input signal of the digital multi-beamformer 21. X (m, n, k) is the output signal of the digital multibeam former 21 (hereinafter, referred to as beam signals) number of elements made of is a vector of Q _k. The element x _q (m, n, k) (q = 1, 2,..., Q _k ) of the vector X (m, n, k) is the q-th beam signal of the digital multi-beamformer 21.

The characteristic point of the present invention is that the multi-beam forming weight matrix W _k and the number of multi-beams Q _k are changed according to the range bin number k, that is, the observation target distance. Setting of the coverage according to the observation target distance is performed by setting the multi-beam forming load matrix W _k and the multi-beam number Q _k . Extremely speaking, the multi-beam forming weight matrix W _k and the multi-beam number Q _k can be changed for each range bin number k. That is, the coverage can be changed according to the range bin number k.

In actual applications, especially in automotive radar, the observation range related to distance is divided into two parts, short distance and long distance, or short distance, medium distance, and long distance. Will change. Accordingly, the multi-beam forming weight matrix W _k and the number of multi-beams Q _k are changed, and the number of types is equal to the number of divisions of the observation range related to the distance.

  FIG. 4 is a diagram schematically showing an example of the coverage and multi-beam set by the digital multi-beam former 21 in Embodiment 1 of the present invention. In FIG. 4, the observation distance range is divided into two, short distance and long distance. In general, an in-vehicle radar requires a wide coverage area for a short distance and a narrow coverage area for a long distance. In FIG. 4, a vehicle equipped with a radar is represented as a vehicle 100.

The difference between FIG. 4 (a) and FIG. 4 (b) is that FIG. 4 (a) covers a wide range of a short distance with a large number of narrow multi-beams 101, whereas FIG. ) Is such that a short covered area is covered with a smaller number of multi-beams 102 than in the case of FIG. The multi-beam 103 is a small number of multi-beams with a narrow angle that covers a long-angle narrow angle coverage. In either case, the types of the multi-beam forming load matrix W _k and the number of multi-beams Q _k are two types, short distance and long distance.

Next, the Doppler frequency analyzer 22 performs Doppler frequency analysis of the beam signal x _q (m, n, k). Specifically, frequency analysis regarding m of the beam signal x _q (m, n, k) is performed for each of q, n, and k. As a frequency analysis method, discrete Fourier transform or fast Fourier transform is generally used. If the discrete Fourier transform is used, the output signal y _q (m ′, n, k) of the Doppler frequency analyzer 22 is expressed by the following equation (3). Here, m ′ is a variable corresponding to the Doppler frequency.

Next, the frequency analyzer 23 performs frequency analysis on the variable n of the output signal y _q (m ′, n, k) of the Doppler frequency analyzer 22. The means for frequency analysis is the same as that in the Doppler frequency analyzer 22. If the discrete Fourier transform is used, the output signal z _q (m ′, n ′, k) of the frequency analyzer 23 is represented by the following expression (4).

The target detector 24 searches for a peak with respect to the absolute value | z _q (m ′, n ′, k) | of the output signal z _q (m ′, n ′, k) of the frequency analyzer 23 or its square value. I do. This generally involves setting an appropriate threshold and exceeding it, k = 1, 2,..., K, q = 1, 2,..., Q _k , m ′ = 1,2. ,..., M, n ′ = 1, 2,.

  The relative speed with respect to the target is obtained from m ′ that gives the extracted peak. The search range related to the angle (beam number q) generally differs depending on the range bin number k. In the example of FIG. 4 described above, the search range related to the angle changes with a certain range bin number as a boundary and nearer and farther than that.

Here, for simplicity, it is assumed that the number of targets is one, the distance at time t = 0 is R, and the relative speed in the line-of-sight direction with the radar is v. Let m ′ _peak be the value of m ′ that gives the maximum value of | z _q (m ′, n ′, k) |. A frequency f _peak corresponding to m ′ _peak is a measured Doppler frequency. Accordingly, the measured relative speed v is expressed by the following formula (5).

Here, λ is a wavelength corresponding to any one of f ₁ , f ₂ ,..., F _N. Strictly speaking, the wavelengths corresponding to f ₁ , f ₂ ,..., F _N are different, but if they are to be used as automotive radars, they can be regarded as the same in practical use.

The distance R is the frequency number m ′ _peak that gives the maximum value of | z _q (m ′, n ′, k) |, the target existence range bin k _peak , and the beam number q _peak before the frequency analysis by the frequency analyzer 23. Is obtained from the phase difference of the received signal between any two transmission frequencies. Or the distance R is calculated | required from the average of the phase gradient between N frequency, or the phase difference between several sets of 2 frequency like the following Formula (6).

  Here, c is the speed of light, and arg [·] is the complex argument.

For the measurement of the angle of the target, the beam center direction of the beam number _{q peak,} or corresponding to the next beam number of the beam number _{q peak | z qpeak +1 (m} 'peak, n' peak, k peak) | or _{What is necessary is just} to measure by a monopulse method from the ratio of | z _{qpeak −1} (m ′ _peak , n ′ _peak , k _peak ) | and | z _qpeak (m ′ _peak , n ′ _peak , k _peak ) |.

n ′ _peak is a value of n ′ that gives the maximum value of | z _q (m ′, n ′, k) |. In addition, a well-known angle measurement method such as a MUSIC (multiple signal classification) method can be used. The relative speed v, distance R, and angle obtained as described above are the output of the target detector 24.

In the configuration of FIG. 3, the digital baseband received signal u _p (m, n, k) is subjected to beam forming processing by the digital multi-beam former 21 and then subjected to Doppler frequency analysis. Yes. However, these two orders may be interchanged. That is, the digital multi-beam forming process may be performed after performing the Doppler frequency analysis on the variable m with respect to the digital baseband received signal u _p (m, n, k).

Further, at this time, a peak search is performed with respect to the frequency variable m ′ with respect to the absolute value of the signal after the Doppler frequency analysis of the digital baseband received signal u _p (m, n, k), and a frequency giving several peaks is obtained. The digital multi-beam forming process may be performed only on the number.

  Further, in FIG. 4 showing an example of the coverage set by the digital multi-beam former 21 and the multi-beam, the coverage is formed almost symmetrically with respect to the front of the automobile. However, when the road is curved, it is conceivable to shift the coverage area accordingly.

FIG. 5 is a diagram schematically showing an example of a coverage and a multi-beam set by the digital multi-beam former 21 when the road is curved in the first embodiment of the present invention. As shown in FIG. 5, in particular, the load matrix W _{k of the} digital multi-beamformer 21 is set so that the far-field observation coverage 103b is slightly shifted from the front according to the curve of the road 110 (asymmetric with respect to the front). May be set.

  The curve of the road can be detected by, for example, a yaw rate sensor, a steering sensor, or a camera. It is also possible to detect from the observation result of the roadside object by the radar itself.

  Although the case where a multi-frequency ICW signal is used as a radar transmission wave has been described, it is possible to form a multi-beam so that the coverage is changed according to the range bin number for other pulse signals. For example, the present invention can be applied to a case where an FMICW signal, a pulse compression method, a pulse train that is neither frequency-modulated nor compressed is transmitted.

  As described above, according to the first embodiment, the function of the signal processing unit applies the digital beam forming antenna to the receiving antenna, and the appropriate coverage according to the observation distance as the processing setting condition in the multi-beam forming process. Can be set. As a result, short-range observation and long-distance observation can be performed by one radar, and it is not necessary to have a short-distance mode and a long-distance mode separately. As a result, the number of parts can be reduced, and since there is no mode switching, the reaction time can be shortened.

Embodiment 2. FIG.
In the first embodiment, the range covered by the multi-beam is set by changing the range bin number, that is, the target observation distance. However, on the other hand, signal integration time other than beam forming, that is, the discrete Fourier transform point M of the above equation (3) in the Doppler frequency analyzer 22 and the discrete Fourier transform point of the above equation (4) in the frequency analyzer 23. N was set to the same value regardless of the range bin number k.

  These values M and N are the integral numbers of the received signal. The greater the number of integrations, the longer the integration time, and generally the greater the signal to noise power ratio of the received signal. However, since a reflected signal from a short-range target generally has a large signal-to-noise power ratio, the target can often be detected without any trouble even if the integration time of the received signal is reduced. Therefore, it is conceivable to change the number of discrete Fourier transform points in frequency analysis including Doppler frequency analysis according to the range bin number k.

More specifically, the number of discrete Fourier transform points may be smaller than M or N as the short range bin (the smaller k). The peak search range for m ′ and n ′ of | z _q (m ′, n ′, k) | in the target detector 24 varies depending on the short distance and the long distance. Note that changing the integration time of the received signal in accordance with the range bin is disclosed as a conventional technique.

Here, for the sake of simplicity, the observation range is divided into two, short distance and long distance. In short distance, it is assumed that the discrete Fourier transform points, the number M smaller value M _c of the modulation period corresponding to the observed value output period of the above equation (3) in the Doppler frequency analyzer 22. Since the integration time is shortened at a short distance, the period for outputting the observation value can be shortened accordingly.

FIG. 6 is a diagram showing observed value output when the number of discrete Fourier transform points M is varied between short distance and long distance in the radar apparatus according to Embodiment 2 of the present invention. More specifically, it shows the intervals at which observation values can be output when M = 8 for a long distance and M _c = 2 for a short distance.

  For a long distance, an observation value is output every 8 modulation periods, whereas, for a short distance, an observation value can be output every two modulation periods. In an automotive radar, the reaction time in short-distance observation is required to be short, but in the second embodiment, this requirement can be satisfied by reducing the number of discrete Fourier transform points.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, as a processing setting condition in the frequency analysis processing, discrete in frequency analysis including Doppler frequency analysis is performed according to the target observation distance. By changing the number of Fourier transform points, the integration time at a short distance can be shortened, and the period of outputting the observation value can be shortened accordingly.

Embodiment 3 FIG.
In the first and second embodiments, the case where there is one transmission antenna has been described. On the other hand, this Embodiment 3 demonstrates the case where it has multiple transmission antennas.

  FIG. 7 is a configuration diagram of the radar apparatus according to Embodiment 3 of the present invention. As a configuration having a plurality of transmission antennas, for example, as shown in FIG. 7, two transmission antennas 14a and 14b are arranged outside P reception array antennas 15 (p), and switched to time division. It is conceivable to transmit. By taking such an arrangement, an effect of widening the antenna aperture can be obtained.

  The switch 18 is a switch that supplies the high-frequency multi-frequency ICW signal pulsed by the pulse generator 13 to the two transmission antennas 14a and 14b in a time division manner. The switch 18 switches and supplies a transmission signal to one of the transmission antennas 14a and 14b at a certain timing.

  As an example of the switching method, the odd-numbered (first, third, fifth,...) Modulated signal of the modulation process shown in FIG. 2 is transmitted from the transmission antenna 14a, and the even-numbered (second, fourth, 6,...) May be transmitted from the transmission antenna 14b. Therefore, a case where a signal is transmitted based on such switching will be described.

  In FIG. 7, the transmission wave 3a is radiated in the air from the transmission antenna 14a, and the transmission wave 3b is radiated in the air from the transmission antenna 14b. These transmission waves 3a and 3b are reflected by the target 2, and are received antennas composed of P element antennas 15 (p) as the target reflected wave 4a by the transmitted wave 3a and the target reflected wave 4b by the transmitted wave 3b. And received in time division.

  Each signal received by the element antenna 15 (p) is supplied to the signal processing unit 20b in the same manner as in the first embodiment. The signal processing unit 20b performs signal processing similar to that in the first embodiment to detect the target 2, and outputs the distance, relative speed, and angle that are observation results. However, the processing in the digital multi-beamformer 21 is different from that in the first embodiment, and the details will be described below.

A weight matrix W _{1, k} for the corresponding digital baseband reception signal to the transmitting wave 3a from the transmitting antenna 14a, weight matrix W _{2, k} for the corresponding digital baseband received signal to a transmission wave 3b from transmitting antenna 14b is In general, the values are different. By applying different loads to these two types of received signals, beam forming / signal combining processing assuming that the number of elements is 2P is performed as shown in the following equations (7) and (8).

  In this way, beam formation equivalent to the case where the antenna aperture is widened is possible. X (m ″, n, k) in the above equation (8) becomes an output signal (beam signal) of the digital multi-beamformer 21. Hereinafter, the processing is the same as in the first embodiment, but m ″. = 1, 2,..., M / 2 (M is an even number).

  As described above, according to the third embodiment, in addition to the effects of the first and second embodiments, a plurality of transmission antennas that output transmission signals in a time division manner are provided, and these multiple types of transmission signals are supported. An effect of widening the antenna aperture can be obtained by performing beam forming and signal synthesis processing by applying different values of load to each received signal.

Embodiment 4 FIG.
In the first embodiment, the range covered by the multi-beam is set by changing the range bin number, that is, the target observation distance. On the other hand, in the fourth embodiment, the coverage at the time of multi-beam formation is the same in the entire observation range, and the output signal z _q (m ′, n ′, k) of the frequency analyzer 23 in the target detector 24. In the peak search for the absolute value | z _q (m ′, n ′, k) | of), the search range for the beam number q is changed according to the range bin number k.

  FIG. 8 is a diagram schematically showing an example of the coverage and multi-beam set by the digital multi-beam former 21 in the fourth embodiment of the present invention. In FIG. 4 in the first embodiment, taking the automobile radar as an example, the observation distance range is divided into two, short distance and long distance, so that the short distance covers a wide covered area and the long distance covers a narrow covered area. The case where the multi-beams 101 and 103 or 102 and 103 are formed has been described.

On the other hand, in the fourth embodiment, even for a long distance, not the multi-beam 103 in FIG. 4 but the short-distance multi-beam 101 in FIG. A multi-beam 104 covering a wide angle range is formed in advance. In this case, it is desirable that the individual beam width is narrow. In the peak search of the absolute value | z _q (m ′, n ′, k) | of the output signal z _q (m ′, n ′, k) of the frequency analyzer 23 in the target detector 24, the beam number q is related. The search range is wide in the short range bin and the range is narrowed in the long range bin.

  As described above, according to the fourth embodiment, the beam formation is the same for all range bins. However, as a process setting condition in the final stage of the frequency analysis process, the search range related to the beam in the target detector is The effect similar to that of the first embodiment can be obtained by widening and narrowing the long distance.

It is a block diagram of the radar apparatus in Embodiment 1 of this invention. It is the figure which represented typically the transmission signal of the multifrequency ICW system in Embodiment 1 of this invention. It is an internal block diagram of the signal processing part of the radar apparatus in Embodiment 1 of this invention. It is the figure which represented typically an example of the coverage and the multi-beam which are set with the digital multi-beamformer in Embodiment 1 of this invention. In Embodiment 1 of this invention, when the road is curving, it is the figure which represented typically an example of the coverage and multibeam which are set with a digital multibeam former. In the radar apparatus of Embodiment 2 of this invention, it is the figure which showed the observation value output at the time of making a discrete Fourier-transform point number differ by a short distance and a long distance. It is a block diagram of the radar apparatus in Embodiment 3 of this invention. It is the figure which represented typically an example of the coverage and multi-beam which are set with the digital multi-beamformer in Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Radar apparatus, 11 Signal generator, 12 Transmission signal converter, 13 Pulse converter, 14, 14a, 14b Transmission antenna, 15 (1) -15 (P) Element antenna (reception array antenna), 16 (1)- 16 (P) mixer, 17 (1) to 17 (P) converter, 18 switch, 20, 20b signal processing unit, 21 digital multi-beamformer, 22 Doppler frequency analyzer, 23 frequency analyzer, 24 target Detector.

Claims (17)

A digital beam forming antenna is applied to a reception antenna composed of a plurality of antenna elements, and a multi-band digital baseband reception signal based on a reception signal obtained by reflecting a transmission signal radiated from the transmission antenna to a target A radar apparatus including a signal processing unit that outputs an observation result of the target by performing beam forming processing and frequency analysis processing,
The radar apparatus according to claim 1, wherein the signal processing unit makes a process setting condition of at least one of the multi-beam forming process and the frequency analysis process variable according to an observation target distance. The radar apparatus according to claim 1, wherein
The radar apparatus according to claim 1, wherein the signal processing unit variably sets a coverage area formed by the multibeam by the digital beamforming antenna according to the observation target distance as the processing setting condition in the multibeam forming process. The radar apparatus according to claim 2, wherein
The signal processing unit divides an observation distance range into a predetermined number, and variably sets the coverage according to each divided distance range. The radar apparatus according to claim 3, wherein
The radar apparatus according to claim 1, wherein the signal processing unit presets the predetermined number dividing the distance range as 2 or 3. The radar apparatus according to any one of claims 2 to 4,
The signal processing unit is configured to set, according to the observation target distance, a coverage area formed when the observation target distance is short than a coverage area formed when the observation target distance is far. Radar device. The radar apparatus according to any one of claims 2 to 5,
The signal processing unit sets the number of multi-beams to be formed when the observation target distance is short according to the observation target distance as the processing setting condition in the multi-beam forming process, when the observation target distance is long. Radar apparatus characterized by setting more than the number of multi-beams to be formed. The radar apparatus according to any one of claims 2 to 5,
The signal processing unit, as the processing setting condition in the multi-beam forming process, determines the width of each beam in the multi-beam formed when the observation target distance is close according to the observation target distance, and the observation target distance is A radar apparatus characterized in that it is set wider than the width of a beam formed when it is far away. The radar device according to any one of claims 2 to 7,
The signal processing unit sets the integration time in the frequency analysis processing set when the observation target distance is short according to the observation target distance as the processing setting condition in the frequency analysis processing, and the observation target distance is long A radar apparatus characterized in that it is set shorter than an integration time in the frequency analysis processing set in the case. The radar apparatus according to any one of claims 2 to 8,
The signal processing unit sets the output period of the observation result of the target set when the observation target distance is short according to the observation target distance as the processing setting condition in the frequency analysis process, The radar apparatus is set shorter than the output cycle of the observation result of the target set when the distance is far. The radar apparatus according to claim 1, wherein
The signal processing unit variably sets an angle range in peak detection processing after frequency analysis of the digital baseband reception signal according to the observation target distance as the processing setting condition in the frequency analysis processing. Radar device. The radar apparatus according to claim 10, wherein
The radar apparatus according to claim 1, wherein, in the multi-beam forming process, the coverage area covered by the multi-beam formed by the digital beam forming antenna is the same in all observation areas. The radar apparatus according to any one of claims 1 to 11,
The signal processing unit, when obtaining a target angle as an observation result of the target, obtains the target angle using output signals of adjacent beams. The radar apparatus according to any one of claims 1 to 12,
A radar apparatus comprising: a plurality of transmission antennas, wherein a plurality of transmission antennas are switched to time division to emit a signal, and a reception signal is received in time division. The radar apparatus according to any one of claims 1 to 13,
The radar apparatus according to claim 1, wherein the transmission signal is a signal obtained by pulsing a frequency modulation signal. The radar device according to any one of claims 1 to 14,
The signal processing unit variably sets the multi-beam direction according to the shape of the road when outputting the observation result of the target on the road. The radar apparatus according to claim 15, wherein
The radar apparatus according to claim 1, wherein the signal processing unit estimates a shape of the road based on an observation result of the target and variably sets the multi-beam direction. The radar apparatus according to claim 15, wherein
The radar apparatus, wherein the signal processing unit estimates the shape of the road based on a detection result of an external sensor for detecting the shape of the road, and variably sets the multi-beam direction.

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