JP4656146B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar device that detects a target, and more particularly to a radar device that performs detection in two substantially vertical directions using a traveling wave antenna.

  Conventionally, various radar devices that detect and track targets such as other vehicles and obstacles existing around the vehicle have been devised. In many cases, such radar devices usually only detect a target in a direction substantially horizontal to the road surface. However, some radar devices detect not only a direction substantially horizontal to the road surface but also a vertical direction. is there.

  For example, the radar apparatus described in Patent Document 1 performs target detection in the vertical direction (elevation direction) by using a traveling wave antenna as an antenna and radiating pulse signals having different single frequencies. Then, using the frequency corresponding to the direction in which the target is detected as the center frequency, the detection in the horizontal direction is performed by the FMCW method in the narrow frequency band, and detailed information such as the speed and distance of the target is acquired. At this time, the detection in the vertical direction and the detection in the horizontal direction are alternately performed in a time division manner.

In addition, the radar apparatus described in Patent Document 2 uses a traveling wave antenna as an antenna and performs horizontal scanning in the FMCW method at different center frequencies, so that a horizontal direction is obtained at a plurality of vertical angles (elevation angles). Target detection.
JP 2004-101347 A JP 2004-226158 A

  However, the radar devices described in Patent Document 1 and Patent Document 2 adopt an FMCW system based on a narrow frequency band by setting a center frequency corresponding to the angle in the vertical direction for detection. In general, in the FMCW radar device, the distance resolution increases in proportion to the width of the frequency band for modulation. Therefore, if the frequency band is narrow as in these radar devices, the distance resolution decreases. Furthermore, in the millimeter wave radar for automobiles, since the frequency band that can be used originally is narrow, the distance resolution is further deteriorated.

  In addition, since the radar apparatus described in Patent Document 1 alternately performs target detection in the vertical direction and target detection in the horizontal direction in a time-sharing manner, the detection process in the vertical direction is performed in the detection process in the horizontal direction that is the main detection direction. A detection process must be inserted. In addition, since the horizontal detection cannot be performed during the vertical detection process, the horizontal detection interval is widened.

  Therefore, an object of the present invention is to provide a radar apparatus that can simultaneously detect a target in the horizontal direction and the vertical direction.

  The present invention provides an antenna that scans along a predetermined first direction, emits a transmission signal, receives a reflected signal based on the transmission signal, and outputs a reception signal, and performs continuous or intermittent frequency modulation. The transmission signal is generated periodically and given to the antenna by performing every time interval, and the beat signal is generated by mixing the transmission signal and the reception signal. Based on the beat signal, the target signal along the first direction is generated. And a target detection means for performing detection, wherein the antenna is configured by a traveling wave antenna that radiates a transmission signal at a different angle for each frequency with respect to a second direction substantially perpendicular to the first direction. The detecting means detects the target along the first direction and simultaneously detects the azimuth of the target along the second direction based on the time change of the beat signal. That.

  In this configuration, for example, an FMCW transmission signal that is formed by using a traveling wave antenna and periodically or intermittently performing frequency modulation every predetermined time interval is used. Since the frequency of the FMCW transmission signal changes in time series, the direction of the transmission signal radiated from the traveling wave antenna changes in time series.

  Using this, for example, a plurality of traveling wave antennas are arranged in the horizontal direction with the first direction as the horizontal direction. Then, the transmission beam is scanned in the horizontal direction (first direction) by scanning the traveling wave antenna group electronically or mechanically. At this time, since the frequency of the FMCW transmission signal changes with time, the radiation angle of the transmission signal radiated from the traveling wave antenna changes and the transmission beam is scanned in the vertical direction, which is the second direction. .

  By combining the traveling wave antenna and the FMCW transmission signal in this way, scanning in the vertical direction (second direction) is performed while detecting the horizontal direction (first direction). Here, since the vertical direction depends on the frequency change, that is, the time change, the frequency is determined by detecting the time position in the beat signal by the mixing of the transmission signal and the reception signal, and further the vertical direction Is determined.

  In addition, the target detection means of the radar apparatus according to the present invention time-divides one period of the beat signal into a plurality of partial time intervals, and performs FFT processing in each partial time interval, and the FFT processing result. Signal level comparison means for comparing the signal level of the obtained beat frequency in each partial time interval, and detecting the direction of the target along the second direction based on the signal level comparison result in each partial time interval It is a feature.

  Specifically, in this configuration, for example, the radar apparatus stores in advance the relationship between the azimuth in the second direction (vertical direction) and the time position within one cycle of the beat signal. Then, the radar device divides the time interval corresponding to the upstream modulation interval into a plurality of partial time intervals if the transmission signal is an FMCW transmission signal that is frequency-modulated into a triangular wave shape for one cycle of the beat signal. Next, the radar apparatus performs FFT processing on the beat signal in each partial time interval. Here, if the target is present in the first direction corresponding to the beat signal (transmission / reception signal), the peak corresponding to the target is detected at the same frequency in the frequency spectrum for any partial time interval.

  On the other hand, since the signal level at the peak frequency depends on the amount of the reflected signal from the target, the signal level at the peak frequency depends on the position of the target in the second direction. Using this relationship, the signal level of the peak frequency in each partial time interval is compared, and the partial time interval having the highest signal level is detected. And the azimuth | direction in the 2nd direction of a target is obtained by applying the detected partial time area to the relationship between the memorize | stored time position and the azimuth | direction in a 2nd direction.

  At this time, in the detection in the first direction, the beam azimuth moves along the second direction along with the frequency transition, but the azimuth in the first direction is not changed, so that the target detection in the first direction is also performed.

  Further, the target detecting means of the radar apparatus of the present invention samples the beat signal while shifting the sampling start timing in time series in one sampling period shorter than the one period of the beat signal, and performs FFT for each sampling period. FFT processing means for performing processing, and signal level comparison means for comparing the signal level of the beat frequency of each sampling period obtained by the FFT processing result, and the second direction based on the signal level comparison result of each sampling period It is characterized by detecting the orientation of the target along the line.

  In this configuration, the radar apparatus continues to sample the beat signal at a predetermined timing interval, and performs FFT processing for each sampling period having a different start timing and a predetermined time length. Next, the radar apparatus detects the sampling period having the highest signal level by comparing the signal level of the peak frequency of each sampling period. Then, the orientation of the target in the second direction is obtained by applying the detected sampling period to the relationship between the stored time position and the orientation in the second direction.

  The target detection means of the radar apparatus according to the present invention further includes a peak time detection means for detecting a time position at which the amplitude of the beat signal is maximum within one cycle, and is along the second direction based on the detected time position. It is characterized by detecting the orientation of the target.

  In this configuration, the radar apparatus analyzes the amplitude of the acquired beat signal and detects the time position having the largest amplitude. And the azimuth | direction in the 2nd direction of a target is obtained by applying the detected time position to the relationship between the memorize | stored time position and the azimuth | direction in a 2nd direction. In this method, since the azimuth in the second direction can be obtained without performing the FFT process, the processing calculation is omitted.

  The target detection means of the radar apparatus according to the present invention includes an FFT processing means for performing FFT processing on a beat signal for the one period, a peak frequency detection means for detecting a peak frequency of a frequency spectrum obtained by the FFT processing, Inverse FFT processing means for performing inverse FFT processing on a frequency spectrum in a predetermined frequency region including a peak frequency, and peak time detection means for detecting a time position where the amplitude of the restored partial beat signal obtained by the inverse FFT processing is maximum. And detecting the azimuth of the target along the second direction based on the detected time position.

  In this configuration, the radar apparatus performs FFT processing on the beat signal in units of one period (for example, an uplink modulation section of triangular wave modulation), and detects the peak of the frequency spectrum. Next, the radar apparatus extracts a predetermined frequency region whose peak frequency is approximately the center, and performs an inverse FFT process on the frequency spectrum of this frequency region. At this time, if there are a plurality of peaks, the frequency domain is extracted for each and the inverse FFT process is performed. The radar apparatus partially restores the beat signal by this inverse FFT processing, and detects the time position where the amplitude is maximized from each restored partial beat signal. And the azimuth | direction in the 2nd direction of a target is obtained by applying the detected time position to the relationship between the memorize | stored time position and the azimuth | direction in a 2nd direction. By using this method, even if there are a plurality of targets having different distances in the same first direction, the orientation with respect to each second direction can be obtained.

  Also, the target detection means of the radar apparatus of the present invention comprises: filter means for separating the beat signal for each different partial frequency modulation band in the frequency band of the beat signal and generating the partial frequency beat signal; and the partial frequency beat signal And a partial peak time detecting means for detecting a time position at which the amplitude is maximized, and detecting the direction of the target along the second direction based on the detected time position.

  In this configuration, the radar apparatus obtains a partial frequency beat signal by separating the beat signal into a plurality of frequency bands. The radar apparatus detects a time position where the amplitude is maximum from each partial frequency beat signal. And the azimuth | direction in the 2nd direction of a target is obtained by applying the detected time position to the relationship between the memorize | stored time position and the azimuth | direction in a 2nd direction. Thus, by decomposing the beat signal in a plurality of partial frequency bands, the azimuth in the second direction is detected for each distance corresponding to each partial frequency band.

  Further, the target detection means of the radar apparatus according to the present invention is characterized in that the peak frequencies of a plurality of time sections are paired based on the detected direction along the second direction.

  In this configuration, if the target is the same, the detected directions are the same in sections that are close in time, for example, continuous upstream and downstream modulation sections in triangular wave modulation, adjacent upstream and downstream modulation sections, etc. Take advantage of something. When pairing peak frequencies detected in different sections of the transmission signal, the radar apparatus compares detected directions and performs pairing if the directions are substantially the same.

  Further, the target detection means of the radar apparatus according to the present invention is characterized by correcting the time transition of the beat signal level used for pairing.

  In this configuration, even if the beam is scanned during acquisition of the beat signal, the signal level is appropriately corrected, so that the amplitude of the beat signal is stabilized and the FFT processing calculation is stable and accurate. At this time, correction processing is not performed on the beat signal used for the above-described direction detection in the second direction, and only the beat signal used for pairing is corrected. As a result, the orientation detection in the second direction and the stable detection of the peak are compatible.

  According to the present invention, it is possible to simultaneously detect the target in the second direction while performing target detection in the first direction without adding a further configuration from the conventional configuration. For example, target detection can be performed while scanning in the horizontal direction, and the vertical position of the target can be detected simultaneously.

  Further, according to the present invention, highly accurate pairing can be realized by performing pairing using the direction in the detected second direction. Thereby, it is possible to detect in both the first direction and the second direction, and it is possible to realize more accurate target detection in the first direction.

It is a block diagram which shows the structure of the principal part of the radar apparatus of 1st Embodiment. It is a block diagram of the antenna apparatus 1 shown in FIG. It is an external appearance perspective view of the antenna 10 shown in FIG. It is a conceptual diagram which shows the direction of each transmission / reception beam Beam with respect to the vehicle by which the radar apparatus of 1st Embodiment is mounted. The figure which shows the relationship between the transmission signal Stx and the received signal (reflection signal) Srx when the target has a relative speed of 0, and the figure which shows the change in the vertical directivity of the transmission signal Stx due to the frequency change It is. It is a block diagram which shows the main structures of the target detection part of the signal processing part 2 of 1st Embodiment. It is a figure which shows the beat signal waveform after A / D conversion. It is a figure which shows the frequency spectrum formed by carrying out the FFT process of the beat signal shown to FIG. 7 (A)-(E), respectively. It is a figure which shows the relationship of the signal level of the peak spectrum in each division | segmentation time area T1-T4. It is a figure which shows the relationship of the signal level of the peak spectrum in each partial time interval in 2nd Embodiment. It is a block diagram which shows the main structures of the detection function part of the signal processing part 2 of 3rd Embodiment. It is a figure which shows the beat signal waveform in the time interval T, and shows the detection concept of a peak. It is a block diagram which shows the main structures of the target detection part of the signal processing part 2 of 4th Embodiment. It is a figure which shows the beat signal waveform after A / D conversion, and the figure which shows the frequency spectrum after the FFT process of the beat signal shown to FIG. 14 (A). It is a figure which shows the beat signal waveform after carrying out the inverse FFT process only for the peak vicinity in the frequency spectrum of FIG.14 (B). It is the block diagram which shows the main structures of the target detection part of the signal processing part 2 of 5th Embodiment, and the figure which showed the passage characteristic of BPF281-BPF284 shown to FIG. 16 (A). It is a figure which shows the transmission signal Stx 'waveform and reception signal Srx' waveform of an intermittent FMCW system.

Explanation of symbols

  1-antenna device, 2-signal processing unit, 3-VCO, 4-coupler, 5-circulator, 6-mixer, 7-LNA, 8-A / D converter, 10-antenna, 11A-11I-traveling wave antenna 12A-12I-variable phase shifter, 13-branch circuit, 14-transmission / reception unit, 21,21A-21D-FFT processing unit, 211-beat signal time division unit, 212-215-FFT arithmetic unit, 22, 22A- 22D-peak level detector, 23-memory, 24, 24A-24D-elevation angle detector, 25, 25A-25D-peak detector, 26-partial frequency domain extractor, 27-inverse FFT processor, 28-filter bank 29-pairing processing unit, 100-housing, 111A to 111I-horn unit, 112A to 112I-slit, 113A to 113I-waveguide, 900-automobile (own vehicle)

A radar apparatus according to the first embodiment will be described with reference to the drawings. In the present embodiment, an automotive radar apparatus using the millimeter wave band will be described. In the present embodiment, an FMCW radar device using a transmission signal whose frequency changes in a triangular shape in a time series will be described. In the present embodiment, a radar apparatus that electronically scans a transmission / reception beam in the horizontal direction will be described.
FIG. 1 is a block diagram showing the configuration of the main part of the radar apparatus of this embodiment.

  2 is a block diagram of the antenna device 1 shown in FIG. 1, and FIG. 3 is an external perspective view of the antenna 10 shown in FIG.

4A and 4B are conceptual diagrams showing the directions of the transmission and reception beams Beam with respect to the vehicle on which the radar apparatus of the present embodiment is mounted. FIG. 4A is a plan view showing the beam BeamHm in the horizontal scanning direction, and FIG. It is a side view which shows the beam BeamHVmVn.
FIG. 5A is a diagram showing the relationship between the transmission signal Stx and the reception signal (reflection signal) Srx when the target has a relative speed of 0 with respect to the host vehicle, and FIG. It is a figure which shows the change of the vertical directivity of Stx.

  The radar apparatus according to this embodiment includes an antenna apparatus 1, a signal processing unit 2, a VCO 3, a coupler 4, a circulator 5, a mixer 6, an LNA 7, and an A / D converter 8.

  The signal processing unit 2 generates a control voltage for forming a transmission beam based on a detection process to be described later, and applies the control voltage to the VCO 3. The VCO 3 generates a transmission signal Stx in which the frequency is continuously changed in a triangular shape in time series according to a given control voltage. The coupler 4 outputs the input transmission signal Stx to the circulator 5 and provides a part thereof to the mixer 6 as a local signal. The circulator 5 outputs the transmission signal Stx from the coupler 4 to the antenna device 1.

  As shown in FIG. 2, the antenna device 1 includes an antenna 10 in which the individual antennas 11A to 11I are arranged in the horizontal direction, variable phase shifters 12A to 12I connected to the individual antennas 11A to 11I, A branch circuit 13 and a transceiver 14 are provided. The transmission / reception unit 14 gives the transmission signal Stx input from the circulator 5 to the branch circuit 13 and gives the reception signal Srx input from the branch circuit 13 to the circulator 5. The branch circuit 13 distributes and outputs the transmission signal Stx given from the transmission / reception unit 14 to the variable phase shifters 12A to 12I, and gives the reception signal Srx from the variable phase shifters 12A to 12I to the transmission / reception unit 14. . Each of the variable phase shifters 12 </ b> A to 12 </ b> I performs a phase shift process on the input transmission signal Stx in accordance with a transmission beam directivity control command given from the radar apparatus, and outputs it to the antennas 11 </ b> A to 11 </ b> I of the antenna 10. In this way, by performing predetermined phase shift processing on each transmission signal Stx by each variable phase shifter, it is possible to scan the transmission beam in the horizontal direction as indicated by the beams BeamH1 to BeamH7 in FIG. it can. Further, the reflected signals received by the antennas 11A to 11I are phase-shifted in accordance with the received beam directivity control command, and are output to the branch circuit 13 as the received signal Srx. As described above, by performing predetermined phase shift processing on the reflected signal (reception signal) Srx by each variable phase shifter, the reception beam can be scanned in the horizontal direction.

  Each of the antennas 11A to 11I forming the antenna 10 is a so-called waveguide-type leaky wave antenna and has a structure shown in FIG. As a specific structure, as shown in FIG. 3, waveguides 113 </ b> A to 113 </ b> I having the same shape are formed in a substantially flat casing 100 in parallel, and these waveguides 113 </ b> A to 113 </ b> I are formed. Is open to one side surface of the housing 100 (the front surface of the left hand in the figure). This opening is connected to each of the variable phase shifters 12A to 12I. In addition, one main surface (upper surface in the drawing) of the housing 100 has a shape extending along the waveguides 113A to 113I and gradually moves from the inner side (the waveguides 113A to 113I side) of the housing 100 to the surface. Horn portions 111A to 111I having wide opening surfaces are formed. The horn portions 111A to 111I are installed at positions corresponding to the waveguides 113A to 113I, respectively. The horn portions 111A to 111I and the corresponding waveguides 113A to 113I are electrically connected by slits 112A to 112I formed along the extending direction of the waveguides 113A to 113I. The slits 112 </ b> A to 112 </ b> I are formed in a structure that gradually increases from the opening surface side of the waveguides 113 </ b> A to 113 </ b> I along the terminal end side facing the waveguides 113 </ b> A to 113 </ b> I.

  The antenna 10 is installed such that the horn opening surface is in the front direction of the antenna device 1, that is, the front direction of the automobile 900 on which the antenna device 1 is mounted. At this time, the antenna 10 is installed such that the horn opening surface of the antenna 10 is at a predetermined angle substantially perpendicular to the horizontal direction, and the extending direction of the waveguide leaky wave antennas 11A to 11I is along this substantially vertical direction. And if it is such a structure and the frequency of the transmission signal Stx changes, as shown in the beam BeamHmV1 to BeamHmV5 in FIG. For example, the variable phase shifters 12A to 12I are controlled to emit a transmission beam in the BeamH1 direction. At this time, since the transmission signal Stx changes in a triangular wave shape within the frequency band of FMCW modulation, the elevation angle of the transmission beam changes according to this frequency. Thus, in the radar apparatus of the present embodiment, the transmission / reception beam is scanned in the horizontal direction, and the transmission / reception beam is automatically scanned in the vertical direction by the change in the elevation angle of the beam.

  For example, in the case of an antenna using a 76 GHz to 77 GHz band, the waveguide type leaky wave antennas 11A to 11I have a waveguide size of 2.0 mm × 1.27 mm and a length of 50 mm, and slits. Set as appropriate. With such a configuration, as shown in FIG. 5A, the elevation angle of the transmission beam is changed by changing the frequency of the transmission signal from 76 GHz to 77 GHz in a triangular wave shape, as shown in FIG. A beam scan of about 4.7 ° is performed in the vertical direction.

  The reception signal Srx output from the antenna device 1 is given to the circulator 5, and the circulator 5 outputs this reception signal Srx to the mixer 6. The mixer 6 generates a beat signal by mixing the local signal from the coupler 4 and the received signal Srx from the circulator 5 and outputs the beat signal to the LNA 7. The LNA 7 amplifies the beat signal and supplies it to the A / D converter 8. The A / D converter 8 A / D converts the amplified beat signal and gives it to the signal processing unit 2.

  Based on the digitized beat signal, the signal processing unit 2 uses a known FMCW data processing method to detect the target in the horizontal direction, calculate the relative speed of the target, and the distance. Further, the signal processing unit 2 detects the vertical position (elevation angle) of the target from the obtained beat signal using a data processing method described later. That is, the detection in the vertical direction and the detection in the horizontal direction are not performed in a time-sharing manner, and target detection is performed simultaneously in two directions, the horizontal direction and the vertical direction.

Next, a method for detecting a vertical position using a beat signal used for horizontal scanning will be described in detail.
FIG. 6 is a block diagram showing the main configuration of the target detection portion of the signal processing unit 2 of the present embodiment.
FIG. 7 is a diagram showing a beat signal waveform after A / D conversion, where the horizontal axis represents the time axis and the vertical axis represents the amplitude. (A) shows a beat signal waveform in a predetermined time section T (for example, equivalent to the upstream modulation section Tu shown in FIG. 5A), and (B) shows four time sections T shown in (A). The beat signal waveform in the 1st division | segmentation time area T1 of the division | segmentation time area divided | segmented is shown. Similarly, (C) shows the beat signal waveform in the second divided time interval T2 in the time interval T, (D) shows the beat signal waveform in the third divided time interval T3, and (E) shows the fourth signal. The beat signal waveform in divided time section T4 is shown.

  FIG. 8 is a diagram showing frequency spectra obtained by subjecting the beat signals shown in FIGS. 7A to 7E to FFT processing, with the horizontal axis representing FFT bins and the vertical axis representing the signal level. 8A is a frequency spectrum of the beat signal in the time interval T shown in FIG. 7A, and FIG. 8B is a frequency spectrum of the beat signal in the first divided time interval T1 shown in FIG. 7B. It is. 8C shows the frequency spectrum of the beat signal in the second divided time interval T2 shown in FIG. 7C, and FIG. 8D shows the frequency of the beat signal in the third divided time interval T3 shown in FIG. 7D. FIG. 8E shows the frequency spectrum of the beat signal in the fourth divided time interval T4 shown in FIG. 7E.

  FIG. 9 is a diagram showing the relationship between the signal levels of the peak spectrum in each divided time section T1 to T4.

  The signal processing unit 2 includes an FFT processing unit 21, a peak level detection unit 22, a memory 23, and an elevation angle detection unit 24.

  The beat signal dividing unit 211 of the FFT processing unit 21 buffers the input beat signal for a predetermined time interval T and time-divides it into partial beat signals corresponding to the first to fourth divided time intervals T1 to T4, respectively. To do. For example, for the triangular wave FMCW modulated transmission signal as shown in FIG. Then, the time interval T is divided into quarters in time series, and the first divided time interval T1, the second divided time interval T2, the third divided time interval T3, and the fourth divided time interval T4 are set in ascending order of time. Then, the beat signal for the time interval T is time-divided into partial beat signals for the first to fourth divided time intervals T1 to T4, respectively. The beat signal dividing unit 211 outputs the partial beat signal generated in this way to the FFT calculators 212 to 215.

  Each of the FFT calculators 212 to 215 performs FFT processing on each partial beat signal in each divided time interval T1 to T4. By performing FFT processing in this way, frequency spectra as shown in FIGS. 8B to 8E are obtained for the divided time intervals T1 to T4, respectively. The FFT processing unit 21 outputs the frequency spectrum generated in this way to the peak level detection unit 22 together with information on the corresponding divided time intervals T1 to T4.

  The peak level detection unit 22 analyzes each frequency spectrum and detects signal levels A1 to A4 of the peak frequency. The peak frequency signal levels A1 to A4 and the corresponding divided time intervals T1 to T4 are output to the elevation angle detector 24.

  The elevation angle detector 24 detects the elevation angle based on the divided time intervals T1 to T4 and the peak signal levels A1 to A4. Specifically, the memory 23 stores in advance the relationship between the intensity relationship and the elevation angle of the peak signal levels A1 to A4 of the partial time intervals T1 to T4. When the peak signal levels A <b> 1 to A <b> 4 are input, the elevation angle detection unit 24 compares the intensity and calculates the time-series intensity distribution, and compares the intensity comparison and time-series intensity distribution stored in the memory 23. To do. Then, the elevation angle detection unit 24 detects the intensity comparison result and the intensity distribution result with the highest matching degree, and detects the elevation angle corresponding thereto.

  The FFT processing unit 21, the peak level detection unit 22, and the elevation angle detection unit 24 may be configured by individual hardware, but may be configured by software and configured by one semiconductor chip. good.

  Moreover, although the elevation angle detection unit 24 determines the elevation angle based on the intensity comparison result, the intensity distribution, and the like, the elevation angle may be determined based on the divided time interval in which the peak signal level is the highest.

  By using such a configuration and processing, the target position (elevation angle) in the vertical direction can be detected at the same time while performing the target detection in the horizontal direction as in the prior art. This eliminates the need to interrupt the horizontal direction detection process and insert the vertical direction detection process during the horizontal direction detection, thereby simplifying the processing flow.

  Further, by continuously performing the horizontal direction detection while performing the vertical direction detection in this way, the horizontal direction detection cycle is constant, and the vertical direction detection is also executed within this horizontal direction detection cycle. Thereby, a detection cycle can be made faster than the conventional radar apparatus which performs a vertical direction detection and a horizontal direction detection by a time division.

  Furthermore, it is possible to perform detection in two directions, the horizontal direction and the vertical direction, with almost no additional hardware from the conventional radar device that detects only the horizontal direction.

  In the present embodiment, an example is shown in which the time interval T is divided into four (T1 to T4). However, the number of divisions can be set as appropriate according to the detection specifications and the apparatus specifications. Further, in the present embodiment, the FMCW method using a triangular wave-like transmission signal has been described. However, the above-described configuration and effects are also applied to an FMCW method using a sawtooth wave-like transmission signal and an FMCW method having other waveforms. Can do.

Next, a radar apparatus according to a second embodiment will be described with reference to the drawings.
FIG. 10 is a diagram showing the relationship of the signal level of the peak frequency in each partial time section.

  The radar apparatus of this embodiment differs from the radar apparatus of the first embodiment only in the configuration of the signal processing unit 2 and the data processing method, and the other parts are the same. Omitted.

  The FFT processing unit 21 of the signal processing unit 2 of the present embodiment has a circuit configuration that performs sample shift FFT processing.

  The FFT processing unit 21 buffers the input digital beat signal and performs FFT processing on data within a predetermined section length while shifting the start timing of the section. More specifically, nT pieces of sample data are acquired with respect to the sampling time length T of the beat signal corresponding to the upward interval time Tu of the triangular wave, and mT FFT processing corresponding to the partial interval length smaller than nT. A data group is formed. The mT FFT processing data groups are groups whose start timings are sequentially shifted in time, and the same sampling data may exist between neighboring FFT processing groups. Then, the FFT processing is sequentially performed on these mT FFT processing data groups whose start timings are arranged in time series. For example, when there is sampling data from D1 to D1024 in chronological order within the entire sampling section length T, first, FFT processing is performed on the sampling data D1 to D256 as the first partial section Td1. Next, the start timing is shifted by one sample, and FFT processing is performed on the sampling data D2 to D257 as the second partial interval Td2. Next, the start timing is further shifted by one sample, and FFT processing is performed on the sampling data D3 to D258 as the third partial section Td3. In this way, until the last sampling data of the final partial section becomes D1024, the FFT processing is performed with 256 data pieces while sequentially shifting the start timing by one sample.

  When such processing is performed, a frequency spectrum is obtained for each partial section, and a spectrogram of the sample shift FFT is obtained therefrom.

  The peak level detector 22 detects the signal level of the peak frequency from the frequency spectrum of each partial section Td obtained by the above method. The signal level of the detected peak frequency changes in a shape as shown in FIG. The peak level detector 22 discriminates the highest peak signal level value from the transition characteristics of the peak signal level, and detects the corresponding partial section Td.

  The memory 23 stores in advance the relationship between the partial interval Td having the highest peak signal level and the elevation angle. In other words, changes in the partial section Td having the highest peak signal level due to changes in the elevation angle of the target are stored.

  The elevation angle detector 24 collates the partial section Td output from the peak level detector 22 with the relationship stored in the memory 23 to determine the elevation angle.

  By using such a configuration and processing method, the resolution of the elevation angle can be set finely, and more accurate elevation angle detection, that is, vertical direction detection can be performed.

  Next, a radar apparatus according to a third embodiment will be described with reference to the drawings. The radar apparatus according to the present embodiment is the same as the radar apparatus according to the first embodiment except that the configuration of the signal processing unit 2 and the data processing method are the same. To do.

FIG. 11 is a block diagram showing the main configuration of the detection function unit of the signal processing unit 2 of the present embodiment.
FIG. 12 is a diagram showing a beat signal waveform in the time interval T and showing a concept of peak detection.

  The signal processing unit 2 of this embodiment includes a peak detection unit 25, an elevation angle detection unit 24, and a memory 23. As shown in FIG. 12, the peak detection unit 25 acquires a beat signal (sample data) in a predetermined time interval T corresponding to, for example, an upward modulation interval Tu of a triangular wave. The peak detector 25 performs absolute value processing on the amplitude of the acquired sample data and compares the amplitudes. Then, the peak detector 25 extracts sampling data having the maximum amplitude, and acquires the time position of this sampling data. The peak detector 25 outputs the acquired time position to the elevation angle detector 24.

The memory 23 stores in advance the relationship between the time position of the sampling data with the maximum amplitude and the elevation angle.
The elevation angle detector 24 collates the time position information input from the peak detector 25 with the relationship between the time position stored in the memory 23 and the elevation angle, and determines the elevation angle.

  By using such a configuration and processing method, the elevation angle of the target can be detected without performing complicated data processing such as FFT processing.

Next, a radar apparatus according to a fourth embodiment will be described with reference to the drawings.
FIG. 13 is a block diagram showing the main configuration of the target detection portion of the signal processing unit 2 of the present embodiment.
FIG. 14A shows a beat signal waveform after A / D conversion, where the horizontal axis represents the time axis and the vertical axis represents the amplitude. FIG. 14B shows a frequency spectrum after the FFT processing of the beat signal shown in FIG. 14A, where the horizontal axis shows FFTbin and the vertical axis shows the signal level.

  15A and 15B are diagrams showing beat signal waveforms after the inverse FFT processing is performed only on the vicinity of the peak in the frequency spectrum of FIG. 14B. FIG. 15A shows the result for the peak Fpa, and FIG. 15B shows the result for the peak Fpb. Show.

  The signal processing unit 2 of the present embodiment includes an FFT processing unit 21, a peak level detection unit 22, a partial frequency region extraction unit 26, an inverse FFT processing unit 27, a peak detection unit 25, an elevation angle detection unit 24, and a memory 23.

  The FFT processing unit 21 samples the input beat signal (FIG. 14A) over, for example, a predetermined time interval T corresponding to the upstream modulation interval Tu shown in FIG. Perform FFT processing. By this FFT processing, a frequency spectrum as shown in FIG. 14B is obtained. This frequency spectrum data is output to the peak level detector 22.

  The peak level detector 22 analyzes the input frequency spectrum and detects the peak frequency (in bin units) and its signal level. At this time, as shown in FIG. 14B, if there are a plurality of independent peaks separated from each other by a predetermined number of bins or more, these correspond to a plurality of targets having different distances, so that peak frequencies Fpa, Fpb and Detect the signal level. Here, the peak may be detected by setting an appropriate threshold value from the obtained frequency spectrum and detecting a signal level exceeding the threshold value as a peak. The peak level detection unit 22 outputs the detected peak frequencies Fpa and Fpb and the signal level to the partial frequency region extraction unit 26.

  The partial frequency region extraction unit 26 sets predetermined frequency bin ranges FA and FB for the input peak frequencies Fpa and Fpb, respectively. Then, the partial frequency domain extracting unit 26 extracts frequency spectrum data (each bin number and signal level) included in the frequency bin ranges FA and FB. The extracted frequency spectrum data of each frequency bin range FA, FB is output to the inverse FFT processing unit 27.

  The inverse FFT processing unit 27 performs inverse FFT processing on the extracted frequency spectrum data of the frequency bin ranges FA and FB, respectively, each of which includes only a signal in a predetermined frequency range, and the beat signal of the time interval T (FIG. 15 ( A) and FIG. 15B) are generated. These frequency limited restored beat signals are output to the peak detector 25.

  The peak detection unit 25 detects the maximum value of the absolute value of the amplitude for each input frequency-limited restored beat signal as in the above-described embodiment, and the time position TA of the sampling data having this amplitude maximum value TA, TB is detected.

  The memory 23 stores in advance the relationship between the time position of the sampling data with the maximum amplitude and the elevation angle.

  The elevation angle detection unit 24 collates the time positions TA and TB input from the peak detection unit 25 with the relationship between the time position stored in the memory 23 and the elevation angle, and determines each elevation angle.

  As described above, by using the configuration and the processing method of the present embodiment, even when there are a plurality of targets at different distances, the respective elevation angles can be detected individually and simultaneously.

  Note that the peak frequency obtained by the peak level detector 22 is used for pairing in FMCW target detection. That is, the target relative speed, distance, RCS, and the like are calculated by performing pairing based on the peak frequencies detected in successive sections, for example, the upstream modulation section in FIG. 5 and the subsequent downstream modulation section. At this time, pairing can be facilitated by using the elevation angle detected by the elevation angle detector 24. That is, if substantially the same elevation angle is detected in consecutive sections, it can be determined that they are the same target and pairing can be performed. And if there are a plurality of targets at different distances as in this embodiment, by detecting simultaneously the respective elevation angles, that is, the targets existing at a plurality of elevation angles, more precise pairing and target detection can be performed. It can be carried out.

  Next, a radar apparatus according to a fifth embodiment will be described with reference to the drawings.

  FIG. 16A is a block diagram showing the main configuration of the target detection portion of the signal processing unit 2 of this embodiment, and FIG. 16B shows the pass characteristics of the BPF 281 to BPF 284 shown in FIG. FIG.

  The signal processing unit 2 of this embodiment includes a filter bank 28, peak detection units 25A to 25D, elevation angle detection units 24A to 24D, FFT processing units 21A to 21D, peak level detection units 22A to 22D, and a pairing processing unit 29. .

  As shown in FIG. 16B, the filter bank 28 includes BPF 281, BPF 282, BPF 283, and BPF 284 that are adjacent to each other in order in the passband. Each of these BPFs 281 to 284 is constituted by a digital filter, and is set so that the pass band becomes higher in the order of BPF 281, BPF 282, BPF 283, and BPF 284. The beat signal input to the filter bank 28 is separated into signals in each frequency band (partial frequency band beat signals) by the BPFs 281 to 284.

  The peak detection unit 25A detects the maximum absolute value of the amplitude of the first partial frequency band beat signal output from the BPF 281 and outputs time position information corresponding to the maximum value to the elevation angle detection unit 24A. The elevation angle detector 24A collates with the relationship between the time position and the elevation angle stored in a memory (not shown) to determine the elevation angle.

  The FFT processing unit 21A performs FFT processing on the first partial frequency band beat signal output from the BPF 281. The peak level detection unit 22A detects the peak frequency from the frequency spectrum of the first partial frequency band beat signal, and the pairing processing unit 29 Output to.

  The peak detector 25B detects the maximum absolute value of the amplitude of the second partial frequency band beat signal output from the BPF 282, and outputs time position information corresponding to the maximum value to the elevation angle detector 24B. The elevation angle detector 24B collates with the relationship between the time position and the elevation angle stored in a memory (not shown) to determine the elevation angle.

  The FFT processing unit 21B performs FFT processing on the second partial frequency band beat signal output from the BPF 282, the peak level detection unit 22B detects the peak frequency from the frequency spectrum of the second partial frequency band beat signal, and the pairing processing unit 29 Output to.

  The peak detection unit 25C detects the maximum absolute value of the amplitude of the third partial frequency band beat signal output from the BPF 283, and outputs time position information corresponding to the maximum value to the elevation angle detection unit 24C. The elevation angle detector 24C collates with the relationship between the time position and the elevation angle stored in a memory (not shown) to determine the elevation angle.

  The FFT processing unit 21C performs FFT processing on the third partial frequency band beat signal output from the BPF 283, the peak level detection unit 22C detects the peak frequency from the frequency spectrum of the third partial frequency band beat signal, and the pairing processing unit 29 Output to.

  The peak detector 25D detects the maximum absolute value of the amplitude of the fourth partial frequency band beat signal output from the BPF 284, and outputs time position information corresponding to the maximum value to the elevation angle detector 24D. The elevation angle detector 24D collates with the relationship between the time position and the elevation angle stored in a memory (not shown) to determine the elevation angle.

  The FFT processing unit 21D performs FFT processing on the fourth partial frequency band beat signal output from the BPF 284, the peak level detection unit 22D detects the peak frequency from the frequency spectrum of the fourth partial frequency band beat signal, and the pairing processing unit 29 Output to.

  The pairing processing unit 29 appropriately buffers the peak frequency and the signal level information input from each of the peak level detection units 22A to 22D, and performs pairing by comparing with the same information of adjacent modulation sections. . At this time, the pairing processing unit 29 facilitates pairing by referring to the elevation angle information of the target acquired by the elevation angle detection units 24A to 24D. Then, by this pairing operation, the signal processing unit 2 calculates the target orientation, relative speed, distance, RCS, and the like.

  By dividing the frequency of the beat signal in this way, targets existing at different distances can be separated and detected. Thereby, even if there are a plurality of targets, if the distances are different, the elevation angles of these targets can be detected simultaneously.

  In the present embodiment, an example in which a filter bank made of a digital filter is installed at the subsequent stage of the A / D converter is shown, but a filter bank made of an analog filter may be installed before the A / D converter.

  In the present embodiment, an example in which the beat signal is separated into four frequency bands has been described.

  In each of the above-described embodiments, an FMCW transmission signal that performs frequency modulation continuously has been described as an example. However, intermittent FMCW transmission that performs frequency modulation intermittently within a modulation section as shown in FIG. The signal Stx ′ may be used. FIG. 17 is a diagram illustrating a waveform of a transmission signal Stx ′ and a reception signal Srx ′ of the intermittent FMCW method.

  In such an intermittent FMCW method, the time during which the reflected signal (received signal) Srx ′ is obtained changes according to the distance to the target. Therefore, by adjusting the acquisition timing of the received signal Srx ′, targets having different distances can be obtained. It can be detected separately. By using such a method, the elevation angles of targets with different distances can be detected at the same time without using a filter bank as shown in the fifth embodiment.

In each of the above-described embodiments, the beat signal used for target detection is directly subjected to FFT processing. However, only the amplitude level of the target detection beat signal may be adjusted to be constant by AGC or the like. Thereby, even if beam scanning is performed in the horizontal direction during acquisition of a beat signal, expansion of the frequency spectrum after FFT processing can be suppressed, and a plurality of adjacent targets can be reliably separated and detected. In addition, it is possible to prevent a false peak from occurring in a low frequency component close to direct current. As a result, the target detection in the horizontal direction and the vertical direction can be performed more accurately.
In the above-described embodiment, an example in which the horizontal scanning is performed electronically has been described. However, a mechanically configured configuration may be used. In addition, as a traveling wave antenna, a waveguide leakage wave antenna is shown as an example, but another traveling wave antenna may be used.

Claims (8)

An antenna that scans along a predetermined first direction, radiates a transmission signal, receives a reflected signal based on the transmission signal, and outputs a reception signal;
Continuously or intermittently frequency modulation is periodically performed at predetermined time intervals to generate the transmission signal and give it to the antenna, and generate a beat signal by mixing the transmission signal and the reception signal, In a radar apparatus comprising: target detection means for detecting a target along the first direction based on the beat signal;
The antenna is a traveling wave antenna that radiates a transmission signal at a different angle for each frequency with respect to a second direction substantially perpendicular to the first direction;
The radar apparatus characterized in that the target detection means detects the target along the first direction and simultaneously detects the azimuth of the target along the second direction based on a time change of the beat signal. . The target detection means includes
FFT processing means for time-dividing one period of the beat signal into a plurality of partial time sections and executing FFT processing in each partial time section;
Signal level comparison means for comparing the signal level of the beat frequency obtained by the FFT processing result in each partial time interval,
The radar apparatus according to claim 1, wherein the azimuth of the target along the second direction is detected based on a signal level comparison result of each partial time interval. The target detection means includes
FFT processing means for sampling the beat signal while shifting the sampling start timing in a time series in a sampling period shorter than the one period of the beat signal, and performing FFT processing for each sampling period;
Signal level comparison means for comparing the signal level of the beat frequency of each sampling period obtained by the FFT processing result,
The radar apparatus according to claim 1, wherein the direction of the target along the second direction is detected based on a signal level comparison result in each sampling period. The target detection means includes
Peak time detecting means for detecting the time position at which the amplitude of the beat signal is maximum within the one cycle;
The radar apparatus according to claim 1, wherein the direction of the target along the second direction is detected based on the detected time position. The target detection means includes
FFT processing means for performing FFT processing on the beat signal in one cycle;
Peak frequency detection means for detecting the peak frequency of the frequency spectrum obtained by the FFT processing;
An inverse FFT processing means for performing an inverse FFT process on a frequency spectrum in a predetermined frequency region including the peak frequency;
Peak time detection means for detecting the time position at which the amplitude of the restored partial beat signal obtained by the inverse FFT processing is maximized,
The radar apparatus according to claim 1, wherein the direction of the target along the second direction is detected based on the detected time position. The target detection means includes
Filter means for separating the beat signal into different partial frequency modulation bands, and generating a partial frequency beat signal;
A partial peak time detection means for detecting a time position at which the amplitude of the partial frequency beat signal is maximum,
The radar apparatus according to claim 1, wherein the direction of the target along the second direction is detected based on the detected time position.   The radar device according to any one of claims 1 to 6, wherein the target detection unit pairs peak frequencies of a plurality of the time intervals based on the detected direction along the second direction.   The radar apparatus according to claim 7, wherein the target detection unit corrects a time transition of a beat signal level used for the pairing.

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