JP2006126133A - Radar for sensing object of specific area - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a sensing processing speed of a radar sensing an object of a specific area. <P>SOLUTION: The FM-CW system radar comprises at least a radar receiving part 201 for generating a beat signal by receiving a reflection wave reflected on the object; a filter part 202 for removing a signal except for a sensing area 103 from the beat signal; an A/D conversion part 203 for digitizing the filter-processed beat signal; an FFT processing part 204 for performing FFT processing to the digitized beat signal; and a vehicle detection part 205 for detecting a distance, a relative speed and the like of the object from the FFT data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an FM-CW radar for detecting the position and relative speed of an object in a specific area.

In general, an FM-CW radar is used to detect the position and relative speed of an object.
Such radars are used for infrastructure applications such as traffic monitoring (hereinafter referred to as “infrastructure radars”). For example, vehicle detection infrastructure radars mainly intended for vehicle detection on roads have various shapes. On roads, it is required to detect objects (target vehicles) in the same area as lanes and road shoulders, etc., which are relatively far from the radar installation location to several tens to several tens of meters. The

  For this reason, the antenna has a sharp directivity (beam width) and performs a scanning operation of several degrees to several tens of degrees. Accordingly, the scan angle of the radar is set to include the road that should be the detection area.

FIG. 11 is a block diagram illustrating a conventional example of a receiving unit of a vehicle detection infrastructure radar.
The vehicle detection infrastructure radar shown in the figure is digitized with a radar receiver 1101 that receives a reflected wave reflected by an object and generates a beat signal, and an A / D converter 1102 that digitizes the beat signal. An FFT processing unit 1103 that performs FFT (Fast Fourier Transform) processing on the beat signal, a vehicle detection unit 1104 that detects the distance and relative speed of the object from the FFT data, and the detected vehicle is within the detection area This is an FM-CW radar that includes at least a coordinate determination unit 1105 that discriminates and discards information outside the area, and a scan control / drive unit 1107 for controlling the scan angle of the radar receiver 1101. Data such as the distance and relative speed of the vehicle detected by the detection unit 1104 is the vehicle detection infrastructure. It is sent to a higher-level device connected to.
JP 2003-202373 A

  Since the radar scan angle described above is set so as to include the detection area, the radar signal (reflected wave) irradiated and received by the radar is a structure or moving object in a place other than the detection area. The reflected signal from the signal is also received at the same time.

  As an apparatus for removing and masking a radar signal (reflected wave) outside such a detection area, (1) the range of the detection area is obtained from the road and radar installation coordinates as coordinates, and the position coordinates of the vehicle detected by the radar However, if it is outside the detection area, the vehicle information is discarded and the erroneous detection is reduced, and (2) the accumulated data in which a plurality of scan data is accumulated. Based on this, the moving path of the moving object is estimated to generate mask data, and the scanning data and the mask data are multiplied to discriminate the moving object by targeting only the data corresponding to the desired detection area. There exists a method and an apparatus (patent document 1).

  However, in (1), since the radar signal for detecting the target includes signals outside the detection area, the effect of reducing the false detection is small. In (2), even the information on the position and speed as the target is detected. Since it is necessary to perform mask processing after (calculation), the vehicle detection infrastructure radar performs processing on unnecessary signals in order to further reduce detection errors of the vehicle and further reduce the circuit scale in order to further improve detection performance. Means to avoid are required.

  The present invention has been made in view of the above-described problems, and a problem to be solved is to improve the detection processing speed of a radar whose detection target is a specific area.

  In order to solve the above problems, an FM-CW radar according to the present invention is an FM-CW radar that detects the position and relative speed of an object in a specific area, and transmits a predetermined waveform pattern after frequency modulation. Generating a wave, transmitting the transmission wave at each scan angle, receiving the reflected wave reflected from the object by the transmission wave, mixing the reflected wave and the transmission wave, and generating a beat signal The receiving unit to acquire, the minimum effective frequency corresponding to the minimum distance to the specific area at the scan angle, and the maximum effective frequency corresponding to the maximum distance to the specific area at the scan angle, as the cutoff frequency A filter unit that performs a filtering process on the beat signal, and a distance of the object based on the beat signal that has been subjected to the filtering process by the filter unit; And a, a detection unit for calculating the relative speed.

  By extracting only the signal in the specific area from the beat signal acquired by the reception unit by the filter unit, an effect of facilitating calculation processing of the distance and relative speed of the object by the detection unit is achieved.

Further, since the output of the distance and relative speed of the object in the detection unit can be reduced, the processing speed can be improved and the apparatus configuration can be reduced.
In the FM-CW radar according to the present invention, the beat signal to which the filter unit performs filtering may be an analog signal or a digital signal that has been digitally converted and subjected to FFT processing.

  As described above, according to the present invention, it is possible to improve the detection processing speed of a radar whose detection target is a specific area.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 10.
FIG. 1 is a diagram showing a detection area and a scan range of a vehicle detection infrastructure radar 101 according to an embodiment of the present invention.

  As shown in the figure, the vehicle detection infrastructure radar 101 according to the present embodiment is installed at a high place on the side of the road 102 and detects a target (= vehicle 104) existing in the detection area 103 on the road 102. Therefore, irradiation with radio waves (transmission waves) is always performed at each scan angle of Φ0 to Φn.

FIG. 2 is a block diagram illustrating a configuration example of the receiving unit of the vehicle detection infrastructure radar 101 according to the embodiment of the present invention.
The vehicle detection infrastructure radar 101 shown in FIG. 1 receives a reflected wave reflected by an object and generates a beat signal, and a filter unit 202 excludes signals other than the detection area 103 from the beat signal. An A / D converter 203 that digitizes the beat signal that has been filtered, an FFT processor 204 that performs an FFT process on the digitized beat signal, and the distance and relative speed of the object from the FFT data. An FM-CW radar that includes at least a vehicle detection unit 205 that detects the data, such as the distance and relative speed of the vehicle detected by the vehicle detection unit 205, is connected to the vehicle detection infrastructure radar 101. 206.

  The vehicle detection infrastructure radar 101 shown in the figure includes a reference target determination unit 207 that determines whether the received signal received by the radar receiver 201 is a reflected signal from the reference target, and a detection area 103 at each scan angle. A distance calculation unit 208 that calculates a minimum effective frequency corresponding to the minimum distance and a maximum effective frequency corresponding to the maximum distance; and a detection area information storage unit 209 that stores the maximum / minimum effective frequency at each scan angle. Yes.

Note that the transmission unit of the vehicle detection infrastructure radar 101 according to the present embodiment is configured in the same manner as the transmission unit of a general FM-CW radar, and thus the description thereof is omitted here.
The radar receiving unit 201 controls the scan angle by the scan control / driving unit 210, receives a reflection signal at each scan angle, and generates a beat signal. Then, the generated beat signal is output to the filter unit 202.

  The filter unit 202 performs a beat signal filtering process according to the detection area information (maximum / minimum effective frequency at each scan angle) stored in the detection area information storage unit 209.

  Here, as shown in FIG. 3, the detection area information stored in the detection area information storage unit 209 includes the minimum distance and the maximum distance from the vehicle detection infrastructure radar 101 to the detection area at each scan angle, and the minimum distance. It is composed of a minimum effective frequency that is a corresponding beat frequency and a maximum effective frequency that is a beat frequency corresponding to the maximum distance.

  For example, at the scan angle Φm, the filter unit 202 performs a filter process so that only frequencies in the range of the minimum effective frequency fm (min) to the maximum effective frequency fm (max) pass.

  In the radar scan range (scan angles Φ0 to Φn), as shown in FIG. 1, when a structure 105 or other road outside the detection area 103 runs side by side, radio waves are also transmitted to vehicles outside the detection area. Irradiation is inevitable, the radar will also receive the reflected signal, and the radar received signal obtained by scanning will probably contain unnecessary signal components outside the detection area, In the signal processing after the filter unit 202, only the beat signal obtained from the reflected wave from the object in the range of the minimum distance Rm (min) to the maximum distance Rm (max) is processed by the filter processing described above. It becomes possible.

  4 and 5 show the FFT output when the filter unit 202 is not passed (conventional case) at the scan angle Φm shown in FIG. 1 and the case where the filter unit 202 is passed (in this embodiment). FFT output is shown.

  In FIG. 4, a vehicle (distance Rt, beat frequency ft) within the detection area 103 and a structure 105 (distance Rb, beat frequency fb) outside the detection area 103 are output. In FIG. Since the filter processing is performed in the range of the minimum effective frequency fm (min) to the maximum effective frequency fm (max) by the BPF (Band Pass Filter) or the like in the unit 202, for example, only the object (vehicle) in the detection area 103 is output. Has been.

  The reference target determination unit 207 determines whether the received wave received by the radar receiving unit 201 is a reflected wave from the reference target based on the reception level acquired from the FFT output.

  Here, the reference target is intended to obtain a beat frequency range obtained from the reflected wave of the object in the detection area 103, and is arranged on the boundary of the detection area 103 so as to obtain a predetermined reflected wave (predetermined waveform). Reception level).

  Therefore, it may be installed on the boundary line of the detection area 103 when necessary (for example, when the vehicle detection infrastructure radar 101 according to this embodiment is first installed), and is always installed when it does not interfere with traffic. You may install so that it may move on a boundary line.

  Further, the reference targets may be continuously installed on the boundary line of the detection area 103, or may be installed on the boundary line at equal intervals (in this case, the minimum distance / reference distance shown in FIG. 3 between the reference targets). Since the maximum distance can be obtained by a simple interpolation process, the minimum effective frequency / maximum effective frequency can also be obtained).

FIG. 6A shows a configuration example of the reference target, and FIG. 6B shows an example of the reception level obtained from the reflected wave of the reference target.
A reference target shown in FIG. 6A includes a regular tetrahedral corner reflector antenna 601, a support unit 602 and a table 603 that support the corner reflector antenna 601, a rotation drive unit 604 for rotating the table 603, and a rotation drive unit 604. Including a base 605 including

  By rotating the rotation drive unit 604 in a predetermined pattern, the table 605 attached to the rotation drive unit 604, that is, the corner reflector antenna 601 rotates in a predetermined pattern.

  When the corner reflector antenna 601 rotates in a predetermined pattern, the reflection intensity with respect to the transmission wave also changes in the predetermined pattern. Therefore, the reception level obtained from the reflected wave of the corner reflector antenna 601 also changes in the predetermined pattern. A reception level pattern as shown in FIG. 6B can be obtained.

  Therefore, the reference target determination unit 207 stores the reception level acquired from the FFT output in a storage unit (not shown) at regular intervals. For example, when the received wave matches the pattern shown in FIG. What is necessary is just to judge that it is a reflected wave from a target.

  The distance calculation unit 208 calculates the distance from the beat signal determined by the reference target determination unit 207 as a reflected wave of the reference target, and detects the detection area and effective frequency at the corresponding scan angle shown in FIG. Store in the storage unit 209.

The vehicle detection infrastructure radar 101 according to the present embodiment described above has two operation modes.
That is, the beat signal generated by the receiving unit 201 is filtered by the filter unit 202 in the range of the minimum effective frequency to the maximum effective frequency according to the area information in the detection area information storage unit 209, and the vehicle detection unit 205 detects the vehicle from When the reference target determination unit 207 determines that the reflected wave is from the reference target, the distance calculation unit 208 calculates the distance of the reference target from the beat signal obtained from the reflected wave. This is a detection area information setting mode in which the detection area information stored in the detection area information storage unit 209 is set or updated.

Hereinafter, operations in the vehicle detection mode and the detection area information setting mode will be described with reference to FIGS. 7 and 8.
FIG. 7 is a flowchart showing processing in the vehicle detection mode of the vehicle detection infrastructure radar 101 according to the present embodiment.

  Upon receiving the reflected signal, the radar receiving unit 201 generates a beat signal by mixing the transmission signal generated by the radar transmission unit (not shown) and the received signal, and outputs the beat signal to the filter unit 202 (step S701).

  The filter unit 202 refers to the detection area information storage unit 209, performs a fill process on the beat signal transmitted from the radar receiver unit 201 in the range of the minimum effective frequency to the maximum effective frequency according to the scan angle, and performs A / D The data is output to the conversion unit 203 (step S702).

  The beat signal subjected to the filter processing is converted from an analog signal to a digital signal by the A / D conversion unit 203, and further subjected to FFT processing by the FFT processing unit 204 (steps S703 and S704).

  Data subjected to the FFT processing by the FFT processing unit 204 (hereinafter referred to as “FFT data”) is output to the vehicle detection unit 205 to detect the distance and relative speed of the vehicle (steps S705 and S706).

  In step S707, the reception level is acquired from the FFT data. Then, coordinate data on the detection area 103 (for example, coordinate data in the xy coordinate system corresponding to the detection area 103) is calculated from the distance, speed, and reception level calculated by the processes in steps S705 to S707, and external storage (not shown). Store in the device.

  When a plurality of coordinate data is obtained by repeating the processes in steps S701 to S707 described above a predetermined number of times, the process proceeds to step S708, and the coordinate data grouping (hereinafter, the coordinate data group at this time is referred to as “group”). Data)).

In step S709, it is determined whether or not a vehicle has been detected based on the group data range.
For example, when the range of the group data is compared with a range of coordinate data representing a vehicle prepared in advance (hereinafter referred to as “vehicle reference data”), the comparison results are almost the same (for example, the vehicle reference data It may be determined that the group data is a vehicle (a vehicle is detected) when the occupation ratio of the range of the group data to the range is 70% to 150%.

Further, it may be determined whether the vehicle is a vehicle by tracking whether the group data is moving at a reference speed prepared in advance.
If it is determined in step S709 that the group data is not a vehicle, the data is discarded and the process ends (step S710).

  If it is determined in step S709 that the group data is a vehicle, the process proceeds to step S711, and the detected vehicle information (vehicle position and relative speed) is output to the host device 206, and the process ends.

  As described above, the filter unit 202 can extract only the signal from the object in the detection area 103 from the received wave received by the radar receiving unit 201, so that the subsequent processing unit (A / Load on the D conversion unit 203, the FFT processing unit 204, the vehicle detection unit 205, etc.) can be reduced, the processing speed can be greatly improved, and the apparatus configuration can be reduced.

Furthermore, since the signal from the object outside the detection area 103 is removed by the filter unit 202, it is possible to reduce erroneous detection.
FIG. 8 is a flowchart showing processing in the detection area information setting mode of the vehicle detection infrastructure radar 101 according to the present embodiment.

  When the radar receiver 201 receives the reflected signal, a beat signal is generated by mixing the transmission signal generated by the radar transmitter and the received signal, and is output to the filter unit 202 (step S801).

  In the detection area information setting mode, since the filter processing of the filter unit 202 is in the OFF state, the beat signal generated in step S801 is output to the A / D conversion unit 203 without being filtered (step S802).

  Then, the A / D conversion unit 203 converts the analog signal into a digital signal, and the FFT processing unit 204 performs FFT processing (steps S803 and S804).

  The FFT data is output to the reference target determination unit 207, and the reception level is acquired from the FFT data by the reference target determination unit 207 and stored in the external recording device 701 (steps S805 and S806).

  In order to execute the processes in steps S801 to S806 a predetermined number of times (for example, n times), it is checked in step S807 whether the reception level has been stored continuously n times, and the predetermined number of times (n times). When the reception level is stored, the process proceeds to step S808, and the reception level stored in the external recording device 701 is read.

  The reception level read in step S808 is compared with a predetermined reference pattern (for example, the reference pattern shown in FIG. 6B). If the comparison results do not match, it is determined that there is no reference target and the process ends ( Step S818).

  In step S809, if the comparison results match, it is determined that the received wave received by the radar receiver 201 is from the reference target, and the reference target distance and the reference target distance from the FFT data obtained in step S804 are determined. Relative speed is calculated (step S811, step S812).

In step S813, the distance calculated last time is compared with the distance calculated this time. If the distance is not constant, it is determined that there is no reference target (step S818).
In step S814, the presence / absence of the (relative) speed calculated by the process in step S812 is determined. If the speed is present, the process proceeds to step S818 to determine that there is no reference target.

If it is determined in step S814 that there is a reference target, the distance calculated in step S811 is stored in an external storage device (not shown).
In step S815, the distance calculated in step S811 is compared with the previously calculated minimum distance. If the distance calculated in step S811 is not the minimum, the process proceeds to step S816.

  In step S816, the distance calculated in step S811 is compared with the previously calculated maximum distance. If the distance calculated in step S811 is not the maximum, the process proceeds to step S817, and the data is discarded.

  In step S815, when the distance calculated in step S811 is the minimum, the process proceeds to step S818, the frequency corresponding to the distance is acquired from the FFT data, and the detection area information storage unit 209 illustrated in FIG. The minimum distance and minimum effective frequency of the scan angle corresponding to are stored (step S819).

  In step S816, if the distance calculated in step S811 is the maximum, the process proceeds to step S818, the frequency corresponding to the distance is acquired from the FFT data, and the detection area information storage shown in FIG. The maximum distance and the maximum effective frequency of the corresponding scan angle of the unit 209 are stored (step S819).

Through the above processing, the minimum effective frequency or the maximum effective frequency at each scan angle shown in FIG. 3 is set / updated.
In the above description, the beat signal generated by the radar receiving unit 201 is analog-filtered by the filter unit 202. However, the present invention is not limited to this, and the object distance, relative speed, and the like are detected. What is necessary is just to perform a filter process in front of the vehicle detection part 205 to perform. This is because the processing of the vehicle detection unit 205 has a high load, so that the filtering process is performed before the vehicle detection unit 205 to reduce the input data to the vehicle detection unit 205 as much as possible. This is because it is effective for achieving the above.

FIG. 9 is a block diagram showing a modification of the configuration of the receiving unit of the vehicle detection infrastructure radar according to the embodiment of the present invention.
The vehicle detection infrastructure radar 101 shown in the figure shows an example in which a beat signal generated by a radar receiving unit 201 and FFT processed by an FFT processing unit 204 is digitally filtered by a filter unit 901.

  That is, the vehicle detection infrastructure radar 101 shown in the figure includes a radar receiving unit 201 that receives a reflected wave reflected by an object and generates a beat signal, an A / D conversion unit 203 that digitizes the beat signal, An FFT processing unit 204 that performs FFT processing on the digitized beat signal, a filter unit 901 that excludes signals other than the detection area 103 from the FFT data, and the distance and relative of the object from the filtered FFT data An FM-CW radar that includes at least a vehicle detection unit 205 that detects a speed and the like. Data such as a vehicle distance and a relative speed detected by the vehicle detection unit 205 is connected to the vehicle detection infrastructure radar 101. To the host device 206.

  The vehicle detection infrastructure radar 101 shown in the figure includes a reference target determination unit 207 that determines whether the received signal received by the radar receiver 201 is a reflected signal from the reference target, and a detection area 103 at each scan angle. A distance calculation unit 208 that calculates a minimum effective frequency corresponding to the minimum distance and a maximum effective frequency corresponding to the maximum distance; and a detection area information storage unit 209 that stores the maximum / minimum effective frequency at each scan angle. Yes.

  The filter unit 901 has a minimum effective frequency to a maximum effective frequency range from the FFT data from the FFT processing unit 204 according to the detection area information (maximum / minimum effective frequency at each scan angle) stored in the detection area information storage unit 209. The process which extracts only the data regarding the frequency of is performed.

Note that the processing of blocks other than the filter unit 901 shown in the figure is the same as the processing described in FIG.
FIG. 10 shows a flowchart of processing in the vehicle detection mode of the vehicle detection infrastructure radar shown in FIG.

  Upon receiving the reflected signal, the radar receiving unit 201 generates a beat signal by mixing the transmission signal generated by the radar transmission unit (not shown) and the reception signal, and outputs the beat signal to the A / D conversion unit 203 (step S1001). .

  The A / D conversion unit 203 converts the beat signal from an analog signal to a digital signal, and the FFT processing unit 204 performs FFT processing on the digitized beat signal (steps S1002 and S1003).

  The filter unit 202 refers to the detection area information storage unit 209 and performs a fill process on the beat signal sent from the FFT processing unit 204 in the range of the minimum effective frequency to the maximum effective frequency according to the scan angle, and the vehicle detection unit It outputs to 205 (step S1004).

The vehicle detection unit 205 detects the distance and relative speed of the vehicle from the filtered FFT data (steps S1005 and S1006).
In step S1007, the reception level is acquired from the FFT data. Then, coordinate data on the detection area 103 is calculated from the distance, speed, and reception level calculated by the processes in steps S1005 to S1007 and stored in an external storage device (not shown).

  When the processes in steps S1001 to S1007 described above are repeated a predetermined number of times to obtain a plurality of coordinate data, the process proceeds to step S1008 to group the coordinate data.

In step S1009, it is determined whether or not a vehicle has been detected based on the range of group data.
For example, as described with reference to FIG. 7, the group data range is compared with the coordinate data range that represents a vehicle prepared in advance. It may be determined that it has been detected.

Further, it may be determined whether the vehicle is a vehicle by tracking whether the group data is moving at a reference speed prepared in advance.
If it is determined in step S1009 that the group data is not a vehicle, the data is discarded and the process ends (step S1010).

  If it is determined in step S1009 that the group data is a vehicle, the process proceeds to step S1011. The detected vehicle information (vehicle position and relative speed) is output to the host device 206, and the process ends.

(Supplementary note 1) In an FM-CW radar that detects the position and relative speed of an object in a specific area,
A transmitter that generates a transmission wave by frequency-modulating a predetermined waveform pattern, and transmits the transmission wave at each scan angle;
A receiving unit that receives a reflected wave reflected by the object, and obtains a beat signal by mixing the reflected wave and the transmitted wave;
The beat signal is filtered using the minimum effective frequency corresponding to the minimum distance to the specific area at the scan angle and the maximum effective frequency corresponding to the maximum distance to the specific area at the scan angle as a cutoff frequency. A filter unit for processing;
A detection unit that calculates a distance and a relative speed of the object based on a beat signal that has been filtered by the filter unit;
An FM-CW radar.

(Supplementary note 2) The FM-CW radar according to claim 1, wherein the beat signal that is filtered by the filter unit is an analog signal.
(Supplementary note 3) The FM-CW radar according to claim 1, wherein the beat signal that is filtered by the filter unit is a digital signal that has been digitally converted and subjected to FFT processing.

  (Supplementary Note 4) It is determined whether the beat signal is a reference beat signal composed of a predetermined pattern obtained from a reference target arranged on a boundary of the specific area. The reference target determination unit that calculates an effective frequency corresponding to a distance from a reference beat signal to the specific area at the scan angle, and sets a minimum effective frequency or a maximum effective frequency. FM-CW radar.

It is a figure which shows the detection area and scanning range of the vehicle detection infrastructure radar which concern on the Example of this invention. It is a block diagram which shows the structural example of the receiving part of the infrastructure radar for vehicle detection which concerns on the Example of this invention. It is a figure which shows the detection area information memorize | stored in a detection area information storage part. It is a figure which shows the example of the FFT output at the time of not passing through a filter part in the scan angle (PHI) m shown in FIG. It is a figure which shows the example of the FFT output at the time of passing through a filter part in the scanning angle (PHI) m shown in FIG. 1 (in the case of a present Example). It is a figure which shows the structural example of the reference | standard target which concerns on a present Example. It is a figure which shows the example of the receiving level obtained from the reflected wave of the reference | standard target which concerns on a present Example. It is a flowchart which shows the process at the time of vehicle detection mode of the infrastructure radar for vehicle detection which concerns on a present Example. It is a flowchart which shows the process at the time of the detection area information setting mode of the infrastructure radar for vehicle detection which concerns on a present Example. It is a block diagram which shows the modification of a structure of the receiving part of the infrastructure radar for vehicle detection which concerns on the Example of this invention. FIG. 10 is a flowchart showing processing in a vehicle detection mode of the vehicle detection infrastructure radar shown in FIG. 9. FIG. It is a block diagram which shows the prior art example of the receiving part of the infrastructure radar for vehicle detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Vehicle detection infrastructure radar 102 Road 103 Detection area 104 Vehicle 105 Structure 201 Radar receiving unit 202 Filter unit 203 A / D conversion unit 204 FFT processing unit 205 Vehicle detection unit 206 Host device 207 Reference target determination unit 208 Distance calculation unit 209 Detection area information storage unit 601 Corner reflector antenna 602 Support unit 603 Table 604 Rotation drive unit 605 Foundation 901 Filter unit

Claims (3)

In an FM-CW radar that detects the position and relative speed of an object in a specific area,
A transmitter that generates a transmission wave by frequency-modulating a predetermined waveform pattern, and transmits the transmission wave at each scan angle;
A receiving unit that receives a reflected wave reflected by the object, and obtains a beat signal by mixing the reflected wave and the transmitted wave;
The beat signal is filtered using the minimum effective frequency corresponding to the minimum distance to the specific area at the scan angle and the maximum effective frequency corresponding to the maximum distance to the specific area at the scan angle as a cutoff frequency. A filter unit for processing;
A detection unit that calculates a distance and a relative speed of the object based on a beat signal that has been filtered by the filter unit;
An FM-CW radar.   2. The FM-CW radar according to claim 1, wherein the beat signal that is filtered by the filter unit is an analog signal.   2. The FM-CW radar according to claim 1, wherein the beat signal to which the filter unit performs filtering is a digital signal that has been digitally converted and subjected to FFT processing.

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