JP2012168119A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device that properly detects a target to be traced.SOLUTION: The radar device comprises: transmission means for transmitting a radio wave; receiving means for receiving a reflected radio wave transmitted from the transmission means; reception signal level determining means that distinguishes a signal level of the reflected wave from the others among the signals received by the receiving means, using a threshold; target detecting means that detects a distance or direction to an object on the basis of a signal of the reflected wave distinguished by the reception signal level determining means; target setting means that sets the object to be traced, whose amount of temporal change in distance or direction detected by the target detecting means is equal to or less than a predetermined value, and sets the object not to be traced, whose amount of temporal change exceeds the predetermined value; and threshold changing means that changes the threshold to be used in the reception signal level determining means on the basis of the object to be traced and the object not to be traced set by the target setting means.

Description

  The present invention relates to a radar device, and in particular, by transmitting a radio wave and receiving a reflected wave obtained by reflecting the transmitted radio wave on a target, the distance to the target or the direction of the target is determined. The present invention relates to a radar apparatus suitable for detection.

  Conventionally, a radar device that detects a distance to a target and a direction of a target by transmitting a radio wave to the vicinity of the vehicle and receiving a reflected wave obtained by reflecting the transmitted radio wave on the target is known. (For example, refer to Patent Document 1). In such a radar apparatus, when a reflected wave is received after radio waves are transmitted from a plurality of transmitters, the level of the received signal is detected, and when the level is equal to or greater than a threshold value, the reception timing and transmission timing are The distance to the target is detected based on, and the direction of the target is detected. Then, the temporal change in the distance to the target and the direction of the target is monitored, and a target whose rate of change changes below a predetermined value is set as a tracking target for the host vehicle. Therefore, according to the above-described radar apparatus, the tracking target can be accurately tracked, and the distance and azimuth of the tracking target can be detected with high accuracy.

JP-A-61-259186

  By the way, if the threshold for comparing the level of the received signal is too large, the level of the reflected wave received by the radar device cannot reach the threshold, and as a result, the target cannot be detected. It becomes impossible to specify the tracking target. On the other hand, if the threshold value for comparing the level of the received signal described above is too small, the noise level with a relatively small peak increases the chance of exceeding the threshold value, and as a result, noise is detected as a target, and the tracking target is detected. There is a risk of misrecognition.

  The present invention has been made in view of the above-described points, and an object thereof is to provide a radar apparatus that can accurately detect a target to be tracked.

  The object is to transmit a radio wave, a receiving means capable of receiving a reflected wave of the radio wave transmitted from the transmitting means, and a signal level of the reflected wave among signals received by the receiving means. And a signal level other than the reflected wave are detected by a threshold value, and a distance or direction of the target is detected based on the signal indicating the reflected wave distinguished by the received signal level determining means. A target detection means and a target whose time or amount of change in distance or azimuth detected by the target detection means is a predetermined amount or less and whose target exceeds the predetermined amount. Based on the target setting means for setting the target to be excluded from the tracking target, the target to be tracked set by the target setting means and the target not to be tracked, the reception signal level determination means uses the target. The threshold And threshold changing means for further be achieved by a radar apparatus comprising a.

  In addition, the above-described object is to transmit a radio wave, a reception unit that can receive a reflected wave of the radio wave transmitted from the transmission unit, and a signal of the reflected wave among signals received by the reception unit. Based on the received signal level determination means for distinguishing the signal level and the signal level other than the reflected wave by a threshold, and the signal indicating the reflected wave distinguished by the received signal level determination means, the distance or direction of the target is determined. Target detection means for detecting, pair determination means for pairing targets with the smallest amount of temporal change in distance or azimuth detected by the target detection means for each sampling, and pairing by the pair determination means The threshold value used in the received signal level determination unit is changed based on a proximity pair in which the distance between the target targets is equal to or less than a predetermined distance and a separated pair in which the distance exceeds the predetermined distance. A threshold value changing means is achieved by a radar apparatus comprising a.

  According to the present invention, it is possible to accurately detect a target to be tracked.

It is a block diagram of the radar apparatus which is 1st Example of this invention. It is a flowchart of an example of the control routine performed in the radar apparatus of a present Example. It is a figure showing an example of signal levels, such as noise, a reflected wave, and a clutter. It is a flowchart of an example of the control routine performed in the radar apparatus which is 2nd Example of this invention. It is a figure showing each position of target R1, R2, R3 in the time t-1 and the time t.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a radar apparatus 10 according to a first embodiment of the present invention. The radar apparatus 10 is a periphery monitoring apparatus that is mounted on a moving body such as a vehicle or a flying body, and detects a target (target) existing around the moving body. The radar device 10 is, for example, an FM-CW radar device that detects a target within a predetermined angle range by transmitting a frequency-modulated transmission wave and receiving a reflected wave reflected by the target.

  As shown in FIG. 1, the radar apparatus 10 includes an antenna 12, a high frequency circuit 14, an A / D converter 16, and a control circuit 18. Note that the radar apparatus 10 of this embodiment is mounted on a vehicle, and target data detected by the radar apparatus 10 is an application such as an inter-vehicle control apparatus, a speed control apparatus, and a braking apparatus mounted on the vehicle. Provided and output to the device for use.

  The antenna 12 is disposed on a bumper at the front of the vehicle body. The antenna 12 includes a transmission antenna that radiates a transmission wave to the external space, and a reception antenna that can receive a reflected wave generated by the transmission wave being reflected by a target. The transmission antenna transmits a transmission wave within a predetermined angle range in front of the vehicle (for example, the vehicle traveling direction). Further, a plurality of receiving antennas are provided, and each can receive a reflected wave reflected from within a predetermined angle range.

  The high frequency circuit 14 has an oscillator and a mixer. This oscillator outputs an oscillation signal whose frequency shifts with time. The transmission antenna of the antenna 12 is connected to the oscillator of the high frequency circuit 14. The transmission antenna transmits a transmission wave (for example, a millimeter wave) that is an electromagnetic wave whose frequency shifts with time in response to an oscillation signal supplied from an oscillator.

  In the high-frequency circuit 14, the oscillator and the receiving antenna are connected to the mixer. A mixer is provided for each receiving antenna. The reflected wave received by the receiving antenna is supplied to the mixer as a received signal. Each mixer mixes the oscillation signal output from the oscillator and the reception signal supplied from the reception antenna, and generates a beat signal having the beat frequency of both signals.

  An A / D converter 16 is connected to each mixer of the high-frequency circuit 14. The beat signal generated by each mixer is input to the A / D converter 16. Each A / D converter 16 converts the beat signal supplied from the mixer of the high frequency circuit 14 into a digital signal and supplies the digital signal to the control circuit 18.

  The control circuit 18 obtains frequency spectrum data by performing a fast Fourier transform (FFT) process on the digital signal supplied from each A / D converter 16. Then, frequency components (amplitude and phase) corresponding to the position of the target are extracted based on the frequency spectrum data, and the distance from the host vehicle to the target, the host vehicle and the target are determined based on the extracted frequency component. , And the direction (angle) of the target with respect to the host vehicle. Then, the detected target is recognized as a tracking target, and a data signal corresponding to the recognition result is output to the application device.

  Next, a method for detecting a target in the radar apparatus 10 of this embodiment will be described with reference to FIGS. FIG. 2 shows a flowchart of an example of a control routine executed by the control circuit 18 in the radar apparatus 10 of the present embodiment. FIG. 3 shows an example of signal levels such as noise, reflected waves, and clutter.

  In this embodiment, when the application apparatus or the like is activated and the radar apparatus 10 is activated, an oscillation signal is output from the oscillator of the high-frequency circuit 14 during the activation, whereby the transmission antenna of the antenna 12 at the front of the vehicle body The transmission wave is radiated from the outside to the external space, and reception processing at the reception antenna is performed.

  When the target does not exist within the radiation range of the transmission wave, the transmission wave radiated from the transmission antenna of the antenna 12 is not reflected by the target, so that the reflected wave of the transmission wave is not received by the reception antenna. In this case, the intensity of the received wave received by the receiving antenna is relatively small. On the other hand, when the target exists within the radiation range of the transmission wave, the transmission wave radiated from the transmission antenna is reflected by the target, and the reflected wave is received by the reception antenna. In this case, the intensity of the received wave received by the receiving antenna is relatively high. When the reflected wave of the transmission wave is received by the receiving antenna of the antenna 12, the received signal is supplied to each mixer of the high-frequency circuit 14, so that the frequency from the oscillator shifts with time. Mixed.

  Each mixer generates a beat signal by mixing the received signal from the receiving antenna and the oscillation signal from the oscillator. The frequency of the beat signal represents the distance from the vehicle to the object, and the level of the beat signal represents the intensity of the received reflected wave. Each beat signal generated by each mixer is digitally converted by the A / D converter 16 and then supplied to the control circuit 18.

  The control circuit 18 takes in the digital signal output from the high-frequency circuit 14 every predetermined time (step 100). The control circuit 18 performs FFT processing on each of the captured digital signals and converts the time waveform into frequency spectrum data (step 102). Then, the frequency at which the peak of the signal intensity is equal to or higher than the threshold value THa is extracted from the obtained frequency spectrum data (step 104). The threshold value THa is the minimum signal intensity necessary for detecting a target to be tracked, and is a value that is appropriately changed as will be described later. If there are a plurality of targets within a predetermined angle range, there may be a plurality of frequencies at which the peak of the extracted signal intensity is equal to or higher than the threshold value THa.

  The control circuit 18 detects a distance from the host vehicle to the target (distance detection process) for each frequency at which the peak of the signal intensity extracted as described above is equal to or higher than the threshold value THa, and Processing for detecting the direction from the host vehicle to the target (direction detection processing) is executed (step 106). Note that the frequency of the beat signal exists with a gap corresponding to the frequency difference between the transmitted wave and the received wave, and therefore the distance to the detected target has a certain width.

  Specifically, the control circuit 18 uses the threshold THa to distinguish the signal level of the reflected wave of the transmitted wave and the signal level other than the reflected wave from the received wave to the receiving antenna based on the threshold value THa. It is determined whether or not a frequency at which the peak of the signal becomes equal to or higher than the threshold THa appears, that is, whether or not a signal intensity peak equal to or higher than the threshold THa occurs. As a result, when it is determined that the above-described peak does not occur, it is determined that there is no reflected wave of the transmitted wave in the received wave, and no target is present in the detection range. On the other hand, if it is determined that the above-mentioned peak occurs, it is determined that the reflected wave of the transmitted wave exists in the received wave, assuming that the peak indicates the reflected wave of the transmitted wave, and the peak of the signal intensity is the threshold THa. It is estimated that the target exists at a distance from the vehicle corresponding to the above frequency. Then, an azimuth detection process for detecting the azimuth (angle) of the target with respect to the host vehicle is performed for a frequency at which the peak of the signal intensity is equal to or greater than the threshold THa, that is, for a distance where the target is estimated to exist.

  As the azimuth detection process, the control circuit 18 acquires the amplitude and phase for each channel by a plurality of receiving antennas at a distance corresponding to the frequency at which the peak of the signal intensity in the detection range is equal to or greater than the threshold THa. Then, based on the phase difference between the channels from which the amplitude and phase are acquired, the direction in which the target is present with respect to the host vehicle is detected by arrival direction estimation processing such as digital beam forming.

  When the control circuit 18 detects the distance to the target and the azimuth to the target as described above for each target existing within the predetermined angle range, next, noise or noise is detected from all the detected targets. The processing for accurately detecting the target is executed by eliminating the target such as clutter based on the reflected wave from the road surface or the vehicle that is not the target.

  Specifically, when the control circuit 18 detects the distance to the target and the azimuth to the target in step 106 as described above, first, for each detected target, the change in the distance and the azimuth in a predetermined time. Is measured, and it is determined whether or not the temporal change amount is equal to or less than the threshold value THb (step 108). The threshold value THb may be set for each of the distance and the azimuth, and this step 108 is performed when the temporal change amount of the distance is not more than the threshold value THb and the temporal change amount of the azimuth is not more than the threshold value THb. In this case, an affirmative determination may be made. In general, noise and clutter do not continue to appear at a fixed position with respect to the host vehicle, and therefore the amount of temporal change in the distance and direction of the target related to noise and clutter rarely falls within a narrow range. On the other hand, since a target that is controlled by the host vehicle such as a preceding vehicle continues to appear at a certain position relative to the host vehicle, a range in which the temporal change in the distance and direction of the target vehicle is narrow. Fits within.

  When the control circuit 18 determines that there is a target whose temporal change in distance and direction is equal to or less than the threshold THb among the detected targets, the control circuit 18 sets the target as a tracking target to be tracked by the host vehicle. Then, the number N of observations to be tracked is incremented (step 110). On the other hand, if it is determined that there is a target whose amount of temporal change in distance and direction exceeds the threshold THb among the detected targets, the tracking target that the vehicle should not track such as noise or clutter The number M of observations outside the tracking target is incremented (step 112).

  When the control circuit 18 counts the number of observations N to be tracked and the number M of observations not to be tracked as described above, the control circuit 18 calculates the ratio (= N / M) between the number of observations N to be tracked and the number of observations M to be untracked. Counting is performed to determine whether the ratio N / M is equal to or greater than the threshold value THc (step 114). The threshold value THc is a predetermined value.

  As a result, if it is determined that N / M ≧ THc is established, it is determined that there is a possibility that the target to be tracked may not be detected, and the threshold value of the signal intensity necessary for detection as the target THa is decreased (step 116). The threshold THa may be subtracted by a predetermined amount per time. In this case, the longer the sampling period in which N / M ≧ THc is established, the greater the threshold THa is subtracted as a whole. Become. When the threshold value THa becomes small, the changed threshold value THa is used to detect a target ahead of the vehicle from transmission / reception of radio waves. After reducing the threshold value THa as described above, the control circuit 18 performs tracking filter processing on the N targets detected as tracking targets (step 118). The tracking filter process is a process for detecting a time-series position and speed for each target detected as a tracking target.

  On the other hand, if it is determined that N / M ≧ THc does not hold, it is necessary to detect that there are a number of targets that are not tracking targets, such as noise and cracks, and to detect them as targets. The threshold value THa of the correct signal strength is increased (step 120). The addition of the threshold THa may be performed by a predetermined amount per time. In this case, as the sampling period in which N / M ≧ THc is not established, the addition amount of the threshold THa increases as a whole. Become. When the threshold value THa increases, the changed threshold value THa is used to detect a target ahead of the vehicle from the transmission and reception of radio waves. After increasing the threshold value THa as described above, the control circuit 18 ends the current signal processing.

  As described above, in the present embodiment, the transmission wave is transmitted from the transmission antenna of the antenna 12 and the control circuit 18 performs signal processing on the reception wave received by the reception antenna, whereby the signal intensity peak in the frequency spectrum data is obtained. The distance from the host vehicle to the target can be detected and the azimuth from the host vehicle to the target can be detected based on the frequency at which is equal to or greater than the threshold THa. Then, it is possible to detect the time-series position and speed of the target to be tracked for the host vehicle.

  In the present embodiment, the distance and direction of the target are detected within a predetermined angle range from the host vehicle because a frequency at which the peak of the signal intensity is greater than or equal to the threshold THa appears in the frequency spectrum data obtained by the reception process. In this case, after setting a target whose amount of change in the distance and direction in a predetermined time is equal to or less than the threshold value THb as a tracking target and setting a target whose change amount exceeds the threshold value THb as a tracking target, Based on the relationship between the number N of targets to be tracked and the number M of targets not to be tracked, it is possible to change the threshold THa that the signal intensity peak should satisfy when detecting the target. Specifically, the threshold value THa can be reduced when N / M ≧ THc is satisfied, and the threshold value THa can be increased when N / M ≧ THc is not satisfied.

  If the threshold value THa is reduced, the signal intensity peak will easily reach the threshold value THa thereafter. For example, even when the signal intensity of the reflected wave reflected by the target to be tracked is close to the noise level, The target can be accurately detected as a tracking target. On the other hand, if the threshold value THa is increased, the signal intensity peak will not easily reach the threshold value THa, and therefore noise and clutter detected as a target may be excluded from the detected target. It becomes possible. Further, if the threshold value THa is appropriately changed as described above, even if the signal level or noise level of the reflected wave changes, the threshold value THa is set to an appropriate value according to the change. It is possible to accurately detect the mark.

  Therefore, according to the radar apparatus 10 of the present embodiment, the distance and direction of the target to be tracked can be accurately detected. The detected target data to be tracked is provided to the application device and used. For this reason, it is possible to appropriately carry out inter-vehicle control, speed control, braking control, and the like in the application device based on the distance and direction of the target to be tracked.

  In the first embodiment, the transmitting antenna of the antenna 12 is controlled to the “transmitting means” described in the claims, and the receiving antenna of the antenna 12 is controlled to the “receiving means” described in the claims. It is claimed that the circuit 18 executes the process of step 104 in the routine shown in FIG. 2 in the “received signal level determining means” described in the claims, and the control circuit 18 executes the process of step 106. In the “target detection means” described in the range, the control circuit 18 targets a target whose distance and azimuth change over time are equal to or less than the threshold THb, and the time change over distance and azimuth is the threshold THb. It is necessary for the control circuit 18 to execute the processing of steps 116 and 118 in the “target setting means” described in the scope of claims. To set forth the scope of the "threshold value changing means", it corresponds respectively.

  By the way, in the first embodiment, the threshold THa is changed according to the ratio N / M between the number N of targets set as tracking targets and the number M of targets set outside tracking targets. However, it may be performed based on at least the relationship between the number N of targets set as tracking targets and the number M of targets set outside tracking targets. For example, the threshold value THa may be changed according to M / N, N / (N + M), or M / (N + M).

  The radar apparatus 10 according to the second embodiment of the present invention is realized by causing the control circuit 18 to execute a routine shown in FIG. 4 instead of FIG. FIG. 4 shows a flowchart of an example of a control routine executed by the control circuit 18 in the radar apparatus 10 of the present embodiment. In FIG. 4, steps that execute the same process as the process shown in FIG. 2 are given the same reference numerals, and the description thereof is omitted or simplified. FIG. 5 is a diagram showing the positions of the targets R1, R2, and R3 at time t-1 and time t.

  In this embodiment, when the control circuit 18 executes the distance detection process and the direction detection process for each target in step 106 to detect the distance to the target and the direction to the target, all the detected points at that time are detected. Compare the distance and azimuth (that is, position) for each target with the distance and azimuth (that is, position) for every target that was detected before one sampling. Set as a pair. For example, as shown in FIG. 5, when three targets are detected at time t-1 and time t, three sets of targets that are closest in distance are set.

  When the targets closest to each other as a distance are set as a pair as described above, the control circuit 18 calculates the distance between the targets based on the host vehicle for each pair, and the pair (( Hereinafter, it is referred to as a proximity pair). The threshold THd is the maximum distance at which the targets set in a pair can be determined to be the same target. For example, the subject vehicle has one detection sampling variation in the radar apparatus 10 during one sampling. Or the maximum distance that the target can move is added. Targets in proximity pairs whose distance is equal to or less than the threshold THd are highly likely to be the same target, whereas targets in the pair whose distance exceeds the threshold THd (hereinafter referred to as separated pairs) are the same. It is unlikely that it is a sign.

  The control circuit 18 sets the proximity pairs whose distance is equal to or less than the threshold value THd as the same target, counts the number of the proximity pairs constituting the same target, and for the separated pairs whose distance exceeds the threshold value THd. Is set as a non-identical target, and the number of spaced pairs constituting the non-identical target is counted. Then, the ratio of the number of adjacent pairs whose distance with respect to the total number of pairs is equal to or less than the threshold value THd is calculated, and it is determined whether or not the ratio is equal to or greater than the threshold value THe (step 200). The threshold value THe is a predetermined value.

  As a result, if it is determined that the ratio of the number of adjacent pairs whose distance is equal to or less than the threshold THd with respect to the total number of points paired in two temporally consecutive samplings should be the tracking target It is determined that there is a possibility that the target has not been detected, and the threshold THa of the signal intensity necessary for detecting the target is reduced (step 202). The threshold THa may be subtracted by a predetermined amount per time. In this case, as the sampling period in which the above ratio is the threshold THe is longer, the subtraction amount of the threshold THa is larger as a whole. Become. When the threshold value THa becomes small, the changed threshold value THa is used to detect a target ahead of the vehicle from transmission / reception of radio waves.

  On the other hand, if it is determined that the above ratio is less than the threshold value THe, it may be detected that there are a number of targets that are not subject to tracking, such as noise and cracks, and are detected as targets. The required signal strength threshold THa is increased (step 204). The threshold THa may be added by a predetermined amount per time. In this case, as the sampling period in which the above-mentioned ratio is the threshold THe is longer, the added amount of the threshold THa is larger as a whole. Become. When the threshold value THa increases, the changed threshold value THa is used to detect a target ahead of the vehicle from the transmission and reception of radio waves.

  When the control circuit 18 changes the threshold value THa as described above, the control circuit 18 next executes the processing of steps 108 to 114 described above. If it is determined in step 114 that N / M ≧ THc is established, tracking filter processing is performed on N targets detected as tracking targets (step 118). On the other hand, if it is determined in step 114 that N / M ≧ THc is not established, the current signal processing is terminated without executing the processing in step 118.

  As described above, in the present embodiment, the transmission wave is transmitted from the transmission antenna of the antenna 12 and the control circuit 18 performs signal processing on the reception wave received by the reception antenna, whereby the signal intensity peak in the frequency spectrum data is obtained. The distance from the host vehicle to the target can be detected and the azimuth from the host vehicle to the target can be detected based on the frequency at which is equal to or greater than the threshold THa. Then, it is possible to detect the time-series position and speed of the target to be tracked for the host vehicle.

  In the present embodiment, the distance and direction of the target are detected within a predetermined angle range from the host vehicle because a frequency at which the peak of the signal intensity is greater than or equal to the threshold THa appears in the frequency spectrum data obtained by the reception process. In this case, the targets that are closest in distance from the previous sampling to the current sampling (that is, the targets that have the smallest amount of temporal change in distance and direction) are set as a pair, and among all the pairs, the targets are Based on the relationship between the number of adjacent pairs whose distance is equal to or less than the threshold THd and the number of separated pairs whose distance between the targets exceeds the threshold THd, the peak of the signal intensity should satisfy when detecting the target The threshold value THa can be changed. Specifically, the threshold THa is decreased when the ratio of the number of adjacent pairs in which the distance between the targets with respect to the total number of pairs is equal to or less than the threshold THd is equal to or greater than the threshold THe, while the target with respect to the total points of the pair is reduced. The threshold THa can be increased when the ratio of the number of adjacent pairs whose distance between them is equal to or less than the threshold THd is less than the threshold THe.

  If the threshold value THa is reduced, the signal intensity peak will easily reach the threshold value THa thereafter. For example, even when the signal intensity of the reflected wave reflected by the target to be tracked is close to the noise level, The target can be accurately detected as a tracking target. On the other hand, if the threshold value THa is increased, the signal intensity peak will not easily reach the threshold value THa, and therefore noise and clutter detected as a target may be excluded from the detected target. It becomes possible. Further, if the threshold value THa is appropriately changed as described above, even if the signal level or noise level of the reflected wave changes, the threshold value THa is set to an appropriate value according to the change. It is possible to accurately detect the mark.

  Therefore, also in the radar apparatus 10 of the present embodiment, the distance and direction of the target to be tracked can be accurately detected. The detected target data to be tracked is provided to the application device and used. For this reason, it is possible to appropriately carry out inter-vehicle control, speed control, braking control, and the like in the application device based on the distance and direction of the target to be tracked.

  In the second embodiment, the control circuit 18 pairs targets that are closest in distance from the previous sampling to the current sampling (that is, targets having the smallest amount of temporal change in distance and direction). The setting corresponds to the “pair determining unit” described in the claims, and the control circuit 18 executing the processing of steps 202 and 204 corresponds to the “threshold changing unit” described in the claims. ing.

  By the way, in said 2nd Example, after setting the target nearest in distance from the last sampling to this sampling (namely, the target with the smallest amount of temporal changes of distance and direction) is set as a pair. The threshold THa is changed in accordance with the ratio of the number of adjacent pairs whose distance to the total number of points of the pair is equal to or less than the threshold THd. At least, the number and distance of the adjacent pairs whose distance is equal to or less than the threshold THd What is necessary is just to perform based on the relationship with the score of the separated pair exceeding the threshold value THd. For example, the threshold THa may be changed according to the ratio of the number of adjacent pairs to the number of separated pairs or the ratio of the number of separated pairs whose distance to the total number of pairs exceeds the threshold THd. Specifically, the threshold THa may be decreased when the ratio between the number of adjacent pairs and the number of separated pairs is equal to or greater than a predetermined value, and the threshold THa may be increased when the ratio is less than the predetermined value. .

  In the first and second embodiments, an FM-CW radar device is used as the radar device 10, but the present invention is not limited to this, and a pulse radar device or an AM radar is used. It can be applied to a device, a laser radar device, or the like.

  In the first and second embodiments, the direction of the object relative to the host vehicle is detected using an arrival direction estimation processing method such as digital beam forming. However, it may be performed using a phase comparison monopulse system that detects a phase difference between signals received by a plurality of receiving antennas arranged at different positions.

  In the first and second embodiments, one transmission antenna and a plurality of reception antennas may be provided, but a plurality of transmission antennas may be provided. In addition, when there are a plurality of receiving antennas, a receiving circuit may be provided independently corresponding to each receiving antenna. However, one receiving circuit common to the receiving antenna and each component included in the receiving circuit It is also possible to provide a switch that appropriately switches a receiving antenna to be connected between a plurality of receiving antennas. According to such a modification, it is possible to share a receiving circuit with a plurality of receiving antennas, thereby simplifying the configuration as a radar apparatus.

  In addition, when a plurality of receiving antennas are provided, the receiving antennas may be configured as receiving-only antennas, but at least one of the receiving antennas is also used as a transmitting antenna. A switch for appropriately switching the connection between the transmission circuit side and the reception circuit side may be provided. According to such a modification, it is possible to share the transmission antenna and the reception antenna, thereby further simplifying the configuration of the radar apparatus.

  Furthermore, in the first and second embodiments described above, the detection range from the host vehicle to the target to be detected is one-dimensional, and only one-dimensional scanning is performed for target detection. However, the detection range may be two-dimensional in the front / rear / left / right direction, and a two-dimensional scan may be performed for target detection. A three-dimensional scan may be performed.

DESCRIPTION OF SYMBOLS 10 Radar apparatus 12 Antenna 14 High frequency circuit 16 A / D converter 18 Control circuit

Claims (7)

A transmission means for transmitting radio waves;
Receiving means capable of receiving a reflected wave of the radio wave transmitted from the transmitting means;
A received signal level determining unit that distinguishes between a signal level of the reflected wave and a signal level other than the reflected wave among signals received by the receiving unit by a threshold;
Target detection means for detecting the distance or azimuth of the target based on the signal indicating the reflected wave distinguished by the received signal level determination means;
A target whose temporal or temporal change in distance or direction detected by the target detection means is a predetermined amount or less is a tracking target, and a target whose temporal change exceeds the predetermined amount is excluded from the tracking target. , Target setting means for setting each,
Threshold changing means for changing the threshold used in the received signal level determining means based on the target to be tracked and the target not to be tracked set by the target setting means;
A radar apparatus comprising:   The threshold value changing means determines whether the received signal level determining means is based on the relationship between the number of targets set as tracking targets by the target setting means and the number of targets set outside tracking targets. The radar apparatus according to claim 1, wherein the threshold used is changed.   The threshold value changing means uses the threshold value used in the received signal level determining means as the number N of targets set as tracking targets by the target setting means and the number M of targets set outside tracking targets. 3. The radar apparatus according to claim 2, wherein the ratio is reduced when the ratio (N / M) is greater than or equal to a predetermined value, and is increased when the ratio (N / M) is less than the predetermined value. . A transmission means for transmitting radio waves;
Receiving means capable of receiving a reflected wave of the radio wave transmitted from the transmitting means;
A received signal level determining unit that distinguishes between a signal level of the reflected wave and a signal level other than the reflected wave among signals received by the receiving unit by a threshold;
Target detection means for detecting the distance or azimuth of the target based on the signal indicating the reflected wave distinguished by the received signal level determination means;
Pair determination means for pairing targets with the smallest amount of temporal change in distance or azimuth detected by the target detection means for each sampling;
The threshold value used in the received signal level determination unit is changed based on a proximity pair in which the distance between the targets paired by the pair determination unit is a predetermined distance or less and a separated pair in which the distance exceeds the predetermined distance Threshold changing means for
A radar apparatus comprising:   The radar apparatus according to claim 4, wherein the threshold value changing unit changes the threshold value used in the received signal level determination unit based on a relationship between the number of the adjacent pairs and the number of the separated pairs. .   The threshold value changing means reduces the threshold value used in the received signal level determining means when the ratio between the number of adjacent pairs and the number of spaced pairs is a predetermined value or more, while the ratio is The radar apparatus according to claim 5, wherein the radar apparatus is increased when it is less than a predetermined value. The received signal level determining means detects a frequency at which a peak level of a signal received by the receiving means is equal to or higher than the threshold value as indicating the reflected wave,
The radar according to claim 1, wherein the target detection unit detects a distance or direction of the target based on the frequency detected by the reception signal level determination unit. apparatus.

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