JP2013096742A - Radar apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately execute switching of range finding systems in accordance with a situation in a radar apparatus for performing range finding by a single-shot range finding system and an integrated range finding system.SOLUTION: Range finding by the single-shot range finding system and range finding by the integrated range finding system are performed in parallel and an intensity parameter P expressing the pulse width of a receiving signal is acquired together with a first range finding value D1 by the single-shot range finding system and a second range finding value D2 by the integrated range finding system (S110). When the intensity parameter P is larger than a determination threshold Pth (S120-YES), the first range finding value D1 is selected as distance information (S130). When the intensity parameter P is the determination threshold Pth or less (S120-NO), the second range finding value D2 is selected as the distance information (S140). Since the intensity parameter P (pulse width of the receiving signal R) having correlation with the intensity of reflected light is used instead of the signal intensity of the receiving signal, the intensity of reflected light can be correctly grasped even when the receiving signal R is saturated, so that a range finding value corresponding to an occasional situation can be accurately selected.

Description

  The present invention relates to a radar apparatus that measures a distance from a target that reflects a transmission wave by transmitting a pulsed transmission wave and receiving the reflected wave.

  A radar device that transmits pulsed laser light, receives the reflected light, and measures the time difference from the transmission timing of the laser light to the reception timing of the reflected light to determine the distance from the target that reflected the laser light It has been known.

  In this type of radar apparatus, as one method for measuring the time difference from the transmission timing to the reception timing (the timing at which the received signal obtained by photoelectrically converting the reflected light reaches the maximum voltage), the received signal is a predetermined signal. Measure the timing difference from the transmission timing to the previous timing, and the timing difference from the transmission timing to the subsequent timing individually with a timer, etc. There is one that estimates the time difference from the transmission timing to the reception timing from the measurement results of these time differences (see, for example, Patent Document 1).

  In addition, every time a laser beam is transmitted, the reception signal is sampled at a predetermined interval for a predetermined period, and based on the result of performing similar sampling for a plurality of transmission waves, the same time with reference to the transmission timing of the transmission waves By adding (integrating) the sampled values sampled at the same time, an integrated sampling value corresponding to the sampling value of the integrated signal (which reduces the noise of the received signal) obtained by integrating multiple received signals is obtained, and the integration is performed. There is also one that obtains reception timing from a sampling value (see, for example, Patent Document 2).

  Furthermore, it is also considered that the former ranging method (hereinafter referred to as a single-range ranging method) and the latter ranging method (hereinafter referred to as an integral ranging method) are used in combination (for example, see Patent Document 3). . However, in Patent Document 3, it is not clarified how to use both of them.

JP-A-9-236661 JP 2005-257405 A Japanese Patent Laid-Open No. 2004-177350

  In the one-shot ranging method, the time resolution (and distance resolution) is determined by the operation clock of the timer that measures the time difference from the transmission timing to the previous timing and the subsequent timing. Therefore, high accuracy is achieved by using a high-speed operation clock. Measurement is possible. However, there is a problem that measurement cannot be performed for a received signal whose signal level does not reach the threshold value.

  On the other hand, in the integral ranging method, the S / N of the received signal can be improved by the integration effect, so that it is possible to obtain a measurement result even for a received signal that is buried in noise. However, the time resolution (and hence the distance resolution) is determined by the sampling interval of the received signal, and the sampling interval cannot be made as high as the operation clock, so that there is a problem that the detection accuracy is inferior compared to the one-shot ranging method. is there.

  Therefore, based on the techniques of Patent Documents 1 to 3, when both methods are used in combination, the integral ranging method is used only when the measurement by both methods is always executed and the measurement result cannot be obtained by the one-shot ranging method. In other words, if the signal level of the received signal is greater than the threshold used in the one-shot ranging method, the one-shot ranging method is used, and if it is less than the threshold, the integral measurement is used. It is conceivable to use a distance method.

  By the way, the intensity of reflected light varies greatly depending on the distance to the target and the type of target (see FIG. 7), and particularly in an in-vehicle radar device that needs to detect various targets over a wide distance range. The difference reaches 10 5 or more. The received signal obtained by photoelectrically converting the reflected light is amplified using an amplifier. Usually, there is no circuit element having such a wide input dynamic range. When the signal has strength, the received signal amplified by the amplifier has a saturated waveform as shown in FIG.

  For this reason, when the received signal is saturated due to the influence of the amplifier, the intensity of the reflected wave cannot be accurately grasped. Therefore, in the conventional method of switching the ranging method based on the signal level of the received signal, There was a problem that it was not possible to carry out accurate switching according to (the intensity of the reflected wave).

  In order to solve the above-described problems, the present invention enables a radar apparatus that performs distance measurement using the one-shot distance measurement method and the integral distance measurement method to accurately switch the distance measurement method according to the situation. With the goal.

  In the radar apparatus according to claim 1, which is an invention made to achieve the above object, the transmission / reception means irradiates a pulsed transmission wave a plurality of times, receives a reflected wave of the transmission wave, and receives a received signal. Generate.

  Then, the first distance measuring unit measures the elapsed time from the transmission timing of the transmission wave to the timing at which the reception signal corresponding to the transmission wave crosses a preset detection threshold for any one of the plurality of transmission waves The first distance value representing the distance to the reflective target that is the target reflecting the transmitted wave is obtained based on the second distance measuring means, and the second distance measuring means transmits each transmitted wave for each of the plurality of transmitted waves. From the timing, the received signal is sampled at a preset sampling interval for the maximum measurement period set longer than the time required for the transmission wave to reciprocate the preset maximum detection distance, and the transmission timing of each transmission wave Based on the integrated sampling value obtained by adding the sampling values sampled at the same time with reference to the second reference value, the second distance measurement value representing the distance to the reflective target is obtained. That.

  Further, the intensity parameter acquisition means acquires an intensity parameter that has a correlation with the intensity of the reflected wave, and becomes a larger value as the intensity of the reflected wave increases, and the distance information selection means obtains the acquired intensity parameter in advance. If it is larger than the set determination threshold value, the first distance measurement value is selected, and if the intensity parameter is equal to or less than the determination threshold value, the second distance measurement value is selected as distance information representing the distance to the reflective target.

  In the radar apparatus of the present invention configured as described above, when selecting a distance measurement value, an intensity parameter having a correlation with the intensity of the reflected wave is used instead of the signal intensity of the received signal. Therefore, even when the received signal is saturated, the intensity of the reflected wave can be correctly grasped, and as a result, the distance measurement value can be accurately selected according to the intensity of the reflected wave. it can.

  In the radar apparatus of the present invention, the intensity parameter acquisition means, for example, the pulse of the received signal measured using a pulse width measurement threshold set to a magnitude equal to or smaller than the detection threshold as described in claim 2. The width may be acquired as an intensity parameter, or the rising edge slope of the received signal may be acquired as an intensity parameter, as described in claim 3.

  In particular, in the former case, it is possible to prevent erroneous detection of noise having a signal level that is instantaneously large as a pulse signal, and in spite of the situation where the second distance value should be selected. It is possible to prevent one distance measurement value from being selected.

  Further, for example, as described in claim 4, the determination threshold value is set to a value such that the accuracy of the distance obtained from the first distance value is equal to or greater than the accuracy of the distance obtained from the second distance value. Alternatively, as described in claim 5, the accuracy of the distance obtained by the first distance measurement value may be set to a value that is equal to or higher than the accuracy required by the application using the distance information.

1 is an overall configuration diagram of a radar apparatus. It is a timing diagram which shows the transmission timing and the operation timing of each part of the apparatus. It is explanatory drawing for demonstrating the operation | movement of a one-shot ranging system and an integral ranging system while illustrating the waveform of the received signal with respect to one pulse signal. It is a flowchart which shows the content of the distance information selection process. It is explanatory drawing which shows the intensity | strength parameter in 1st Embodiment. It is explanatory drawing which shows the intensity | strength parameter in 2nd Embodiment. It is explanatory drawing which shows the intensity | strength of the reflected wave in the radar apparatus which transmits / receives a pulsed laser beam. It is explanatory drawing which shows a mode that a received signal is saturated with an amplifier.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
<Overall configuration>
FIG. 1 is a schematic configuration diagram of a radar apparatus 1 to which the present invention is applied.

The radar device 1 is a device that is mounted on a vehicle, detects various targets existing in front of the vehicle, and generates information (distance, relative speed, etc.) on the detected target.
As shown in FIG. 1, the radar apparatus 1 includes a light emitting unit 10 that irradiates a pulsed laser beam (transmitted wave) toward an irradiation area in front of the vehicle according to a transmission timing signal ST, and a target that reflects the laser beam. Based on a light receiving unit 20 that receives reflected light (reflected wave) from the light and converts it into an electrical signal (received signal), a transmission timing signal ST supplied to the light emitting unit 10 and a received signal supplied from the light receiving unit 20 While controlling the operation of the light emitting unit 10 and the distance measuring unit 30 that measures the distance to the target (reflecting target) that reflects the light by two types of distance measuring methods, And a signal processing unit 40 that detects a target existing in the irradiation region and generates information (distance, speed, etc.) regarding the target.

  Among these, the light emitting unit 10 includes a light emitting element 11 formed of a laser diode (LD) that generates laser light, an LD driving circuit 12 that drives the light emitting element 11 in accordance with a transmission timing signal ST, and a laser emitted from the light emitting element 11. A collimating lens 13 that adjusts the spread of light, a scanner 14 that changes the irradiation direction of laser light by reflecting light incident through the collimating lens 13 by a rotating polygon mirror, and driving from a signal processing unit 40 A motor drive circuit 15 that drives a motor for rotating the polygon mirror according to the signal DR, and a rotational position sensor 16 that detects the rotational position of the polygon mirror and supplies the rotational position signal PO to the signal processing unit 40. Yes.

  The light receiving unit 20 receives the reflected light collected by the light receiving lens 21 and the light receiving lens 21 that collects the reflected light from the front of the vehicle, and generates an electric signal having a voltage value corresponding to the intensity of the reflected light. A light receiving element 22 composed of a photodiode (PD) and an amplifier 23 for amplifying a light receiving signal output from the light receiving element 22 are provided.

  The amplifier 23 is set to an amplification factor such that the reflected light returning from a long distance can be amplified to a size that can be processed by the distance measuring unit 30, and the reflected light returning from a relatively short distance is set. When light is received, the signal level of the output (received signal) R of the amplifier 23 is saturated.

<Operation timing overview>
Here, FIG. 2 is a timing chart showing the transmission timing signal ST and the operation timing of each part of the apparatus.

  As shown in FIG. 2, the signal processing unit 40 generates a periodic signal representing a measurement cycle Tcycl (for example, Tcycl = 33 ms), and generates a transmission timing signal ST in synchronization with the periodic signal. Specifically, the transmission timing signal ST includes N (for example, N = 100) pulse signals that are output every measurement cycle Tcycl. The pulse signal is output at a time interval Tw (for example, Tw = 18 μs) sufficiently longer than the maximum measurement period (for example, 0.33 μs) required for the laser beam to reciprocate the maximum detection distance (for example, 50 m) of the apparatus 1. The However, Tcycl, N, and Tw are not limited to the exemplified values, and may be set to satisfy Tcycl> N × Tw at a minimum.

<Ranging unit>
The distance measuring unit 30 measures the distance using an arbitrary one (for example, the 50th) among the N pulse signals irradiated every measurement cycle Tcycl, and generates the first distance value D1. A first detection circuit 31 that generates an intensity parameter P representing the intensity of the reflected wave, and a second detection circuit 32 that performs distance measurement using all N pulse signals and generates a second distance value D2 are provided. ing. Hereinafter, the distance measuring method in the first detection circuit 31 is referred to as a one-shot distance measuring method, and the distance measuring method in the second detection circuit 32 is referred to as an integral distance measuring method.

  Here, FIG. 3 illustrates the waveform of the received signal R with respect to one pulse signal, and is an explanatory diagram for understanding the operation of the one-shot ranging method and the integral ranging method. FIG. When the signal level of the signal R is such that the distance can be measured by the first detection circuit 31 (larger than the detection threshold), (b) is the magnitude that the distance measurement by the first detection circuit 31 is impossible. The case of (smaller than the detection threshold) is shown.

<First detection circuit: one-shot ranging method>
In the first detection circuit 31, as shown in FIG. 3, the timing when the received signal R exceeds the detection threshold is set as the previous timing, and the timing when the received signal R falls below the detection threshold is set as the subsequent timing. The elapsed time Tf up to and the elapsed time Tb from the transmission timing to the later timing are measured with a timer, and the intermediate timing between the previous timing and the later timing is used as the reception timing (the timing when the received signal R peaks). An average value of the times Tf and Tb is calculated as an elapsed time Tr (= {Tf + Tb} / 2) from the transmission timing to the reception timing. Further, the elapsed time Tr is set as an intensity parameter P, and a value obtained by converting the elapsed time Tr into a distance is output to the signal processing unit 40 as a first distance measurement value D1.

  The first detection circuit 31 includes two timers (first and second timers) that start timing at the transmission timing of the pulse signal to be used (rising edge of the transmission timing signal ST). However, the LSBs of the first and second timers coincide with the cycle of the operation clock for operating the timer, and are set to 0.125 ns in this embodiment. Of these, the first timer stops timing when the received signal R smaller than the detection threshold exceeds the detection threshold, and the second counter counts timing when the received signal R greater than the detection threshold falls below the detection threshold. Is configured to stop.

  When the received signal R exceeds the detection threshold, the strength parameter P (= Tr) and the time value (elapsed time Tf) of the first timer and the time value (elapsed time Tb) of the second timer are used. When the first distance value D1 is obtained and the received signal R is equal to or smaller than the detection threshold (when the first and second timers time out), “no data” is obtained. In this case, the first distance value D1 and the intensity All parameters P are set to zero.

  That is, as shown in FIG. 5, the pulse width of the pulse signal indicated by the received signal R becomes larger as the intensity of the reflected light increases (ie, the reflected signal becomes greater) regardless of whether or not the received signal R is saturated. Since this has a correlation with the intensity of light, this can be used as the intensity parameter P.

  Note that the elapsed time Tr (ie, the intensity parameter P) before conversion into the first distance value D1 is detected by, for example, the received signal R in consideration of distortion that occurs in the received signal R when the amplifier circuit is saturated. The correction may be made according to the length of the period (Tb−Tf) exceeding the threshold.

  A circuit that realizes such a one-shot distance measurement method (excluding the portion related to the intensity parameter P) is described in detail in, for example, Japanese Patent Application Laid-Open No. 9-236661, and therefore, further description is omitted here. .

<Second detection circuit: integral ranging method>
On the other hand, the second detection circuit 32 executes the following processing.
First, for each of the N pulse signals, reception is performed at a predetermined sampling interval Tsmpl (Tsmpl = 25 ns in the present embodiment) until the time required for the laser beam to reciprocate the maximum detection distance from the transmission timing elapses. The signal R is sampled.

An integrated sampling value is obtained by adding the sampling values sampled at the same time with reference to the transmission timing.
Then, a value obtained by multiplying the peak value of the integrated sampling value by a coefficient (0.5 in this embodiment) that is larger than 0 and smaller than 1 is set as a detection threshold (50% threshold), and is set. The same timing as in the case of one-range ranging is detected using the detected threshold, and the sampling value corresponding to the previous timing and the subsequent timing is the number from the transmission timing (the previous timing is the Mfth and subsequent timing). And the elapsed time Tf from the transmission timing to the previous timing and the elapsed time Tb from the transmission timing to the subsequent timing are calculated using the equations (1) and (2).

Tf = Mf × Tsmpl (1)
Tb = Mb × Tsmpl (2)
In the following, as in the case of the first detection circuit 31, the elapsed time Tr from the transmission timing to the reception timing is obtained based on the elapsed times Tf and Tb, the elapsed time Tr is set as the strength parameter P, and the elapsed time Tr is set as the distance. The converted value is output to the signal processing unit 40 as the second distance value D2. A circuit that realizes such an integral distance measuring method is described in detail in, for example, Japanese Patent Application Laid-Open No. 2005-257405, and the description thereof is omitted here.

<Signal processing unit>
Returning to FIG. 1, the signal processing unit 40 is composed of a well-known microcomputer mainly composed of a CPU, a ROM, and a RAM. By controlling with the drive signal DR so as to synchronize with the signal ST, a scan process for performing a scan of laser light within the irradiation region, and an intensity parameter output from the distance measuring unit 30 during the execution of the scan process According to P, at least distance information selection processing for selecting either the first distance value D1 or the second distance value D2 as distance information is executed.

Here, details of the distance information selection processing executed by the signal processing unit 40 will be described with reference to the flowchart shown in FIG.
This process is started every time distance measurement data (first distance value D1, second distance value D2, intensity parameter P) is obtained from the distance measurement unit 30, that is, every measurement cycle Tcycl.

  When this processing is started, first, ranging data is acquired (S110), and a determination threshold value Pth in which an intensity parameter P (that is, a pulse width of a pulse waveform indicated by the received signal R) is preset among the acquired ranging data. It is determined whether it is larger (S120). Note that the determination threshold value Pth is set to a value such that the first distance measurement value D1 has higher distance detection accuracy than the second distance measurement value D2 if P> Pth.

  If the intensity parameter P is larger than the determination threshold Pth (S120: YES), the first distance value D1 obtained by the first detection circuit 31 (one-shot distance measurement method) is selected as distance information (S130). If the intensity parameter P is equal to or less than the determination threshold value Pth (S120: NO), the second distance value D2 obtained by the second detection circuit 32 (integral distance measurement method) is selected as distance information (S140), and this End the process.

The distance information selected by this processing is used in various applications that use the distance to a target existing in front of the vehicle.
<Effect>
As described above, the radar apparatus 1 performs distance measurement by the one-shot distance measurement method (first detection circuit 31) and distance measurement by the integral distance measurement method (second detection circuit 32) in parallel. Which of the first distance value D1 based on the source distance measurement system and the second distance value D2 based on the integral distance measurement system is selected as distance information is correlated with the intensity of the reflected light, not the signal intensity of the received signal R. The determination is made using the intensity parameter P (pulse width Tr of the received signal R).

  Therefore, according to the radar apparatus 1, even when the reception signal R is saturated due to the influence of the amplifier 23, it is possible to correctly grasp the intensity of the reflected light, and as a result, the distance measurement value according to the situation at that time. Can be selected accurately.

  In addition, according to the radar apparatus 1, noise whose signal level is instantaneously large is erroneously detected as a pulse signal, and in spite of the situation where the second distance value D2 should be selected. It is possible to prevent the selection of one distance measurement value D1.

  In this embodiment, the pulse width measured using the detection threshold value in the first detection circuit 31 is used as the intensity parameter P. However, the pulse width obtained from the integrated waveform obtained in the second detection circuit 32 is used as the intensity parameter P. You may comprise so that it may be used as.

  In the present embodiment, the light emitting unit 10 and the light receiving unit 20 are transmission / reception means, the first detection circuit 31 is first distance measurement means and intensity parameter acquisition means, the second detection circuit 32 is second distance measurement means, and distance information selection processing ( The signal processing unit 40 that executes S110 to S140) corresponds to a distance information selection unit.

[Second Embodiment]
Next, a second embodiment will be described.
In the present embodiment, since the intensity parameter P generated by the distance measuring unit 30 is only different from that of the first embodiment, this difference will be mainly described.

<Configuration>
In addition to the first and second timers, the first detection circuit 31 includes a third timer that starts timing at the rising edge of the transmission timing signal ST.

  The third timer is configured to stop timing at a timing when the signal intensity of the reception signal R exceeds the second detection threshold that is set to be smaller than the detection threshold and larger than the noise level.

  Then, using the time measured value (elapsed time Ts) of the third timer and the time measured value (elapsed time Tf) of the first timer, the slope K (= (Tf−Ts) / (TH1−TH2)) of the rising edge is obtained. The slope K is output as an intensity parameter P together with the first distance value D1.

  When the signal level of the received signal R is smaller than the detection threshold and the first timer times out and the time value (elapsed time Tf) of the first timer cannot be obtained, the slope K (that is, the strength parameter P) is Set to zero.

  That is, the slope of the rising edge of the pulse signal indicated by the received signal R becomes larger as the intensity of the reflected wave becomes larger (that is, has a correlation with the intensity of the reflected wave) as shown in FIG. It can be used as the intensity parameter P.

<Effect>
As described above, in the present embodiment, which of the first distance value D1 and the second distance value D2 is selected as distance information is correlated with the intensity of the reflected light, not the signal intensity of the received signal R. Is determined using the intensity parameter P (the slope K of the rising edge of the received signal R).

  Therefore, as in the case of the first embodiment, even when the reception signal R is saturated due to the influence of the amplifier 23, the intensity of the reflected light can be correctly grasped, and as a result, according to the situation at that time. It is possible to accurately select the distance measurement value.

  In the present embodiment, the slope K is obtained, but instead of the slope K, the rise time Tu (= Tf−Ts) is used as the intensity parameter P, or is obtained from the integrated waveform obtained by the second detection circuit 32. The slope or rising time of the rising edge of the pulse signal may be used as the intensity parameter P.

  In the present embodiment, the slope K is obtained based on the time from when the signal strength of the received signal R exceeds the second detection threshold until it exceeds the detection threshold. For example, the slope K exceeds the second detection threshold. Alternatively, the slope K may be obtained based on the time until the saturation level is reached.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can implement in various aspects.

  For example, in the above embodiment, the distance measurement unit 30 obtains the intensity parameter P, but the distance measurement unit 30 outputs data necessary for obtaining the intensity parameter P to the signal processing unit 40, and the signal processing unit 40 You may comprise so that the intensity | strength parameter P may be calculated | required.

  In the above embodiment, if the determination threshold value Pth is P> Pth, the accuracy of the distance obtained from the first distance value D1 is set to a value that is equal to or greater than the distance accuracy obtained from the second distance value D2. However, the accuracy of the distance obtained from the first distance value D1 may be set to a value that is equal to or higher than the accuracy required by the application using the distance information.

  In the above embodiment, the scanning in the irradiation area is performed using the polygon mirror, but the entire irradiation area is irradiated with the laser beam at once, corresponding to each of the plurality of divided areas obtained by dividing the irradiation area. The irradiation area is scanned by a so-called light receiving division method (for example, see Japanese Patent Application Laid-Open No. 6-305383) in which reflected light from the divided areas corresponding to each is received by the provided light receiving elements. Also good.

  DESCRIPTION OF SYMBOLS 1 ... Radar apparatus 10 ... Light emission part 11 ... Light emitting element 12 ... LD drive circuit 13 ... Collimating lens 14 ... Scanner 15 ... Motor drive circuit 16 ... Rotation position sensor 20 ... Light receiving part 21 ... Light receiving lens 22 ... Light receiving element 23 ... Amplifier 30 ... distance measuring unit 31 ... first detection circuit 32 ... second detection circuit 40 ... signal processing unit

Claims (5)

Transmitting / receiving means for irradiating a pulsed transmission wave a plurality of times, receiving a reflected wave of the transmission wave and generating a reception signal;
For any one of the plurality of transmission waves, based on the result of measuring the elapsed time from the transmission timing of the transmission wave to the timing at which the reception signal corresponding to the transmission wave crosses a preset detection threshold, First ranging means for obtaining a first ranging value representing a distance to a reflecting target that is a target reflecting the transmission wave;
For each of the plurality of transmission waves, the transmission timing of each transmission wave is set in advance for a maximum measurement period that is set longer than the time required for the transmission wave to reciprocate a preset maximum detection distance. The received signal is sampled at a sampling interval, and the distance to the reflecting target is calculated based on the integrated sampling value obtained by adding the sampling values sampled at the same time with the transmission timing of each transmission wave as a reference. Second distance measuring means for obtaining a second distance value to be represented;
Intensity parameter acquisition means for acquiring an intensity parameter having a correlation with the intensity of the reflected wave and having a larger value as the intensity of the reflected wave is stronger;
If the intensity parameter acquired by the intensity parameter acquisition means is greater than a preset determination threshold, the first distance value is used. If the intensity parameter is less than or equal to the determination threshold, the second distance value is used. , Distance information selection means for selecting as distance information representing the distance to the reflective target;
A radar apparatus comprising:   The radar apparatus according to claim 1, wherein the intensity parameter acquisition unit acquires a pulse width of the received signal measured using the detection threshold as the intensity parameter.   The radar apparatus according to claim 1, wherein the intensity parameter acquisition unit acquires an inclination of a rising edge of the received signal as the intensity parameter.   The determination threshold value is set to a value at which the accuracy of the distance obtained from the first distance value is equal to or higher than the accuracy of the distance obtained from the second distance value. Item 4. The radar device according to any one of items 3 to 3.   The determination threshold is set to a value at which the accuracy of the distance obtained from the first distance measurement value is equal to or higher than the accuracy required by the application using the distance information. Item 4. The radar device according to any one of items 3 to 3.