JP2016125945A - Radar signal processor and radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar signal processor detecting a specific target located in a short range of a radar device mounted on a vehicle and a radar device having the radar signal processor incorporated therein, which can surely detect an object that moves at low speed and an object that stays still and slightly moves.SOLUTION: A radar signal processor processing a radar signal arriving at a radar mounted on a vehicle, and detecting a target which is located in a prescribed short range and is displaceable at slow speed, and with which the vehicle is possible to come in contact at a speed higher than a prescribed speed, comprises: period specification means that specifies a period for which the speed of the vehicle can be accelerated at the speed equal to or higher than the prescribed speed; and target identification means that identifies presence of the target as a distribution of a Doppler component of the radar signal within the short range during the period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radar signal processing device that detects a specific target located within a near range of a radar device mounted on a vehicle, and a radar device incorporating the radar signal processing device.

  Radar devices include on-vehicle radars mounted on vehicles. The in-vehicle radar is used by being attached to a front bumper or a rear bumper of the vehicle. The in-vehicle radar receives a reflected wave of the transmitted radio wave, and detects an object such as a vehicle or a person existing in front, side or rear of the vehicle based on the reflected wave (see, for example, Patent Document 1). .) The in-vehicle radar outputs an alarm when it detects an object.

  Such a conventional in-vehicle radar is shown in FIG. This in-vehicle radar includes a transmission unit 100, a first reception unit 200, a second reception unit 300, and an angle extraction unit 400. That is, the in-vehicle radar is provided with two reception systems.

  The transmission unit 100 of the in-vehicle radar is a part that transmits radio waves to detect an object, and includes a signal generation unit 101 and an antenna 102.

The signal generator 101 generates a transmission signal having a frequency sweep. The state of this frequency sweep is shown in FIG. The frequency sweep shown in FIG. 9 includes a first period MFCW1 and a second period MFCW2. The first period MFCW1 has a time width of about 0.1 s, and the M ₁ sweep is performed with the time width of 0.1 s. Further, the M ₁ sweep consists of a plurality of N ₁ steps. Each _{N 1} step, stepwise frequency width of 180MHz gradually changed.

Following the first period MFCW1, there is a second period MFCW2. Second period MFCW2 is the time width of about 0.1s, _{M 2} sweep is performed in the time width of this 0.1s. Furthermore, the M ₂ sweep consists of multiple N ₂ steps. Each N ₂ steps, separated in frequency by the width of 180 MHz, stepwise frequency is gradually changed. At this time, each N ₂ step of the M ₂ sweep is different from the N ₁ step of the M ₁ sweep in the following points. That is, in the N ₂ step, the frequency is divided narrower than in the N ₁ step, and the frequency is finely changed stepwise.

Signal generating unit 101 sends a transmission signal and _{M 2} sweep _{M 1} sweeps the second period MFCW2 first period MFCW1 followed alternately to the antenna 102. The antenna 102 radiates the transmission signal subjected to frequency sweeping into the air as a transmission wave in the air.

  The first receiving unit 200 of the in-vehicle radar receives the radio wave from the transmitting unit 100 reflected by the object, for example, on the right side of the rear bumper of the vehicle. For this purpose, the first receiving unit 200 includes a receiving circuit 210, an ADC (analog / digital conversion) unit 220, a detection circuit 230, a switching circuit 240, and a speed correction circuit 250.

  The receiving circuit 210 of the first receiving unit 200 is a part that receives a radio wave reflected by an object, and includes an antenna 211, a mixer 212, and an LPF (low-pass filter) 213. When the antenna 211 receives a radio wave, that is, a reflected wave, the antenna 211 generates a reception signal. The mixer 212 receives the reception signal from the antenna 211 and a part of the transmission signal output from the signal generation unit 101 of the transmission unit 100. The mixer 212 mixes the transmission signal and the reception signal, generates a beat signal, and outputs it. The beat signal is also an analog signal, and includes a distance component (distance to the object) corresponding to the time difference between the transmission signal and the reception signal, and a Doppler component (speed of the object) corresponding to the frequency shift of the reception signal. The LPF 213 receives the beat signal output from the mixer 212. The LPF 213 removes a high frequency noise component from the beat signal and outputs it.

  The ADC circuit 220 of the first receiving unit 200 receives the beat signal from which the high frequency component from the LPF 213 has been removed. The ADC circuit 220 converts an analog beat signal into a digital beat signal and outputs the digital beat signal.

  The detection circuit 230 of the first receiving unit 200 receives the beat signal from the ADC circuit 220 as an input. The detection circuit 230 extracts a distance component included in the beat signal and a velocity component (Doppler component) included in the beat signal. For this purpose, the detection circuit 230 includes an FFT (Fast Fourier Transform) unit 231, a buffer 232, an FFT unit 233, and a target detection unit 234.

The FFT unit 231 receives the digital beat signal from the ADC circuit 220 as an input. The FFT unit 231 performs signal processing for fast Fourier transform of the beat signal, and obtains a frequency spectrum of the beat signal by this signal processing. At this time, FFT section 231, and the signal processing of the first period MFCW1 the _{N 1} steps and the second period MFCW2 the _{N 2} beat signals corresponding to the steps of (Fig. 9) (FIG. 9) . The frequency spectrum obtained by the signal processing includes data on the distance component to the object. The FFT unit 231 extracts the data of the distance component to the object from the data of the frequency spectrum. This distance component data is also data representing a frequency spectrum, that is, spectrum data.

The buffer 232 temporarily accumulates the distance component data extracted by the FFT unit 231. At this time, the buffer 232 accumulates data of distance components corresponding to two periods of each N ₁ step of the first period MFCW1 (FIG. 9) and each N ₂ step of the second period MFCW2 (FIG. 9). To do. Further, after the first first period MFCW1, the buffer 232 has the same distances corresponding to two periods of each N ₂ step of the _second period MFCW2 and each N ₁ step of the _first period MFCW1. Accumulate component data. That is, the buffer 232 accumulates data of distance components including the movement of the object that occurs during an integration time of about 0.2 s.

  The FFT unit 233 performs signal processing by fast Fourier transform on the accumulated data of the distance component accumulated by the buffer 232. The FFT unit 233 examines the Doppler component from the frequency spectrum data generated by the signal processing of the accumulated data. Then, the FFT unit 233 extracts the velocity component data of the object from the Doppler component distribution. At this time, the FFT unit 233 detects the object based on the movement of the object between the first period MFCW1 and the second period MFCW2, that is, the movement of the object during about 0.2 s (FIG. 9). Extract the velocity component data.

  The target detection unit 234 detects the target based on the velocity component data extracted by the FFT unit 233. For example, the target detection unit 234 determines that an object has been detected when the velocity component data is equal to or higher than a preset peak. When the target detection unit 234 detects the object, the target detection unit 234 outputs the velocity component data detected in the first period MFCW1 and the second period MFCW2 to the switching circuit 240.

  The switching circuit 240 of the first receiving unit 200 is for switching the speed component data from the target detection unit 234. That is, the switching circuit 240 switches the output destination of the speed component data according to whether the reception signal in the reception circuit 210 is the first period MFCW1 or the second period MFCW2.

  The speed correction circuit 250 of the first receiving unit 200 corrects the speed of the object based on the speed component data from the switching circuit 240. For this purpose, the speed correction circuit 250 includes target modulation units 251 and 252 and a speed correction circuit 253. The target modulation unit 251 receives the velocity component data from the target detection unit 234 when the reception signal in the reception circuit 210 is in the first period MFCW1, and the target modulation unit 252 receives the first signal in the reception circuit 210. In the second period MFCW2, the velocity component data from the target detection unit 234 is input. The target modulation unit 251 modulates and outputs the velocity component data in the first period MFCW1, and the target modulation unit 252 modulates and outputs the velocity component data in the second period MFCW2. The speed correction circuit 253 corrects the speed of the object based on data from the target modulation unit 251 and the target modulation unit 252.

Here, the length of the first period MFCW1 and second periods MFCW2 described above, depending on the setting of the sweep time _{(N 1} step and _{N 2} steps), governs the upper limit of the measurable maximum speed. The speed exceeding the upper limit is measured by going around the speed axis. For example, when the upper limit speed of the first period MFCW1 is 30 km / h and the upper limit speed of the second period MFCW2 is 40 km / h, the object having the speed of 70 km / h A measurement result of 10 km / h is obtained in the period MFCW1 and 30 km / h is obtained in the second period MFCW2. The speed correction circuit 253 obtains a correct speed by using the difference in speed during these periods.

  The second receiving unit 300 of the in-vehicle radar receives the radio wave from the transmitting unit 100 reflected by the object on the left side of the rear bumper of the vehicle, for example, and receives the receiving circuit 310 and ADC (analog / digital conversion). A circuit 320, a target detection circuit 330, a switching circuit 340, and a speed correction circuit 350 are provided. The reception circuit 310, the ADC circuit 320, the target detection circuit 330, the switching circuit 340, and the speed correction circuit 350 are the reception circuit 210, the ADC circuit 220, the detection circuit 230, the switching circuit 240, and the speed correction circuit of the first reception unit 200. Since this is the same as 250, a description thereof will be omitted. Here, the second receiving unit 300 and the first receiving unit 200 described above are located at positions separated from each other by about a half wavelength in order to be able to specify the arrival direction of the radio wave that is reflected from the object. Be placed.

  The in-vehicle radar angle extraction unit 400 identifies the arrival direction of the corresponding signal from the phase difference of the signals in the detection information output from the speed correction circuit 250 and the speed correction circuit 350. In such an arrival direction, for example, when the receiving units 200 and 300 are arranged at a half-wave distance, the range is specified within a range of ± 90 degrees from the front of the radar based on the phase difference.

  The angle extraction unit 400 outputs the angle of the target object as the extraction result as target information.

  When such an on-vehicle radar is used, the detection of the object is performed by the movement of the object between the first period MFCW1 and the second period MFCW2, that is, the object with a time width of about 0.2 s (FIG. 9). It is based on the movement of things. As a result, for example, a child playing near the bumper in a parking lot may not be detected because the distance to the radar is closer than the resolution. In this case, an accident may occur without the vehicle driver noticing.

  The reason why the detection cannot be performed is that the component of the signal arriving from the child is generally included in “a component of a large level whose distance is zero” in the radar signal processing target and cannot be separated.

  In radars that measure distance and speed, the component of the signal coming from the child is generally included in the “component with zero distance and zero velocity”, but the distance resolution is made smaller than the distance to the child. Or, by making the speed resolution smaller than the minute speed at which children play, they can be detected separately. The distance resolution is determined by the frequency shift width, but in practice, it cannot be made very small due to limitations of the Radio Law. On the other hand, the speed resolution is determined by the integration time, but there is no legal limit.

  In order to prevent the accident, there are the following methods. That is, in order to observe the very vicinity of the vehicle like the shadow of the car bumper, the band of the in-vehicle radar is widened and the distance resolution is reduced. However, there is a limit to the frequency band that can be used due to the legal provisions (Radio Law). For this reason, sonar using a sound wave is used for such a short-distance monitoring instead of a radar using a radio wave.

JP 2009-244136 A

  However, using sonar to detect children in the immediate vicinity of the vehicle has the following problems. A conventional in-vehicle radar is a device that transmits radio waves, and the radio waves are reflected by the object and return to the in-vehicle radar. However, sonar is a device that transmits sound waves, and if an object is wrapped with a soft object such as a cloth, it is difficult to generate a reflected wave. Further, if the object is planar, a reflected wave is likely to be generated, but depending on the shape of the object, it is difficult to generate a reflected wave. For this reason, in sonar, the accuracy of detection of an object may be reduced.

  The object of the present invention is to solve the above-mentioned problems and reliably detect an object that moves at a low speed or an object that is stationary and has a slight movement that cannot be detected by a conventional apparatus. It is an object of the present invention to provide a radar signal processing apparatus and a radar apparatus that can achieve the above.

  The invention of claim 1 processes a radar signal that has arrived at a radar mounted on a vehicle, is located within a specified near range, can be displaced at a very low speed, and the vehicle can contact at a specified speed or higher. A radar signal processing device for detecting a target. The period specifying means specifies a period during which the speed of the vehicle can be accelerated more than the specified speed. The target identifying means identifies the presence of the target as the Doppler component distribution of the radar signal within the near range during the period.

  In other words, the identification of the existence of a specific target that is located within the near range and can be displaced at a slow speed is based on the frequency analysis of the radar signal to be performed for the identification, and the vehicle speed exceeds the prescribed speed described above. This is accomplished by starting with a period that can be accelerated and completing with high accuracy.

According to a second aspect of the present invention, in the radar signal processing device according to the first aspect, the speed of the vehicle is given as a ground speed detected by the radar.
That is, the speed of the vehicle is measured by utilizing a ranging function provided in the radar to which the present invention is applied.
A third aspect of the present invention is the radar signal processing device according to the first or second aspect, wherein the period specifying means includes an operation performed on the vehicle by an operator, and a state of the vehicle. Based on all or part of the behavior of the vehicle, the period includes a period preceding the start of the vehicle.

  That is, the above-described frequency analysis of the radar signal is started prior to the time when the vehicle travels or accelerates.

  A fourth aspect of the present invention is the radar signal processing device according to any one of the first to third aspects, wherein the compensation means is transmitted by a temperature of a predetermined portion of the radar and the radar. The frequency drift of the transmission wave transmitted by the in-vehicle radar is compensated by feedback control or feedforward control based on all or part of the number of pulses and the time elapsed since the radar was started.

  That is, the frequency analysis of the radar signal described above is not hindered by the frequency drift that can accompany the transmission wave in such a process even when the radar apparatus is in a steady operation state after starting. Realized accurately and stably.

  The invention according to claim 5 is a radar device for detecting a target mounted on a vehicle and located in the vicinity of the vehicle, wherein the period specifying means is located within a specified near range and can be displaced at a slow speed. A period during which the speed of the vehicle can be accelerated above a specified speed that should not be exceeded when contacting a specific target is specified. The target identifying means identifies the presence of the specific target as a Doppler component distribution in the near range of the radar signal that has arrived at the radar during the period.

  In other words, the identification of the existence of a specific target that is located within the near range and can be displaced at a slow speed is based on the frequency analysis of the radar signal to be performed for the identification, and the vehicle speed exceeds the prescribed speed described above. This is accomplished by starting with a period that can be accelerated and completing with high accuracy.

  According to the present invention, since the length of the period during which the frequency analysis of the radar signal is to be performed is ensured longer than before, the presence of a target that is located in the near range and can be displaced at a very low speed has high accuracy and accuracy. Can be identified.

  Further, according to the present invention, the desired performance is improved and maintained at a low cost without complicating the configuration.

  Furthermore, according to the present invention, the presence of the specific target can be identified with high accuracy and accuracy.

  Further, according to the present invention, the presence of the specific target can be determined stably and accurately.

  Therefore, in the vehicle to which the present invention is applied, the occurrence of an accident that may have occurred in the past when starting or accelerating can be avoided with high accuracy, and the safety can be greatly improved.

It is a block diagram which shows the radar apparatus by Embodiment 1 of this invention. It is a figure explaining the frequency sweep of the electromagnetic wave which a radar apparatus transmits. It is a figure for demonstrating the detection of a target object. It is a figure for demonstrating the detection of a target object. It is a figure for demonstrating the detection of a target object. It is a block diagram which shows the radar apparatus by Embodiment 2 of this invention. FIG. 10 is a configuration diagram showing a configuration by switching in a second embodiment. It is a block diagram which shows the conventional vehicle-mounted radar. It is a figure explaining the frequency sweep of the electromagnetic wave which a vehicle-mounted radar transmits.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1 is a block diagram showing a radar apparatus according to Embodiment 1 of the present invention. The radar apparatus includes a transmission unit 10 and a reception unit 20, and detects an object in the vicinity of the rear part of the vehicle.

  The transmission unit 10 of the radar apparatus is a part that transmits radio waves in order to detect an object, and includes a signal generation unit 11 and an antenna 12.

The signal generator 11 generates a transmission signal having a frequency sweep. FIG. 2 shows the frequency sweep according to the first embodiment. The frequency sweep shown in FIG. 2 consists of the first period MFCW1. The first period MFCW1 has a time width of about 0.1 s, and the M ₁ sweep is performed with the time width of 0.1 s. Further, the M ₁ sweep consists of a plurality of N ₁ steps. Each _{N 1} step, stepwise frequency is changed in the width of 180 MHz. In this embodiment, the signal generation unit 11 sends a transmission signal that has been subjected to the M ₁ sweep of the first period MFCW ₁ to the antenna 12. The antenna 12 is the same as the antenna 102 of FIG. The antenna 12 is installed at the rear of the vehicle.

  The receiving unit 20 of the radar apparatus receives the radio wave from the transmitting unit 10 reflected by the object, for example, on the rear side of the vehicle, and outputs target information indicating the presence or absence of the object. For this purpose, the reception unit 20 includes a reception circuit 21, an ADC circuit 22, and a detection circuit 23.

  The receiving circuit 21 of the receiving unit 20 is a part that receives radio waves reflected by an object, and includes an antenna 21A, a mixer 21B, and an LPF 21C. The antenna 21A is installed at the rear of the vehicle. The mixer 21B and the LPF 21C are the same as the mixer 212 and the LPF 213 of the receiving circuit 210 in FIG. 8, and a description thereof will be omitted.

  Similarly to the ADC circuit 220 in FIG. 8, the ADC circuit 22 of the receiving unit 20 receives the beat signal from which the high frequency component from the LPF 21 </ b> C has been removed. The ADC circuit 220 converts the beat signal, which is an analog signal, into a digital beat signal and outputs the digital beat signal.

  The detection circuit 23 of the receiving unit 20 extracts the distance component included in the beat signal from the ADC circuit 22 and the velocity component (Doppler component) also included in the beat signal, and detects the object based on the extraction result. Part. For this purpose, the detection circuit 23 includes an FFT unit 23A, a distance limiting unit 23B, a buffer 23C, an FFT 23D, and a target detection unit 23E.

The FFT unit 23A of the detection circuit 23 receives the digital beat signal from the ADC circuit 22 as an input. The FFT unit 23A performs signal processing for fast Fourier transform of the beat signal, and obtains a frequency spectrum of the beat signal by this signal processing. At this time, FFT section 23A is in the signal processing of the beat signal corresponding to the reflection of the _{N 1} steps of the first period MFCW1 (Figure 2). Such an FFT unit 23A is the same as the FFT unit 231 in FIG. The FFT unit 23A extracts the data of the distance component to the object from the data of the frequency spectrum obtained by the signal processing of the beat signal. This distance component data is also data representing a frequency spectrum, that is, spectrum data.

  The distance limiting unit 23B of the detection circuit 23 receives distance component data extracted by signal processing by the FFT unit 23A. The distance limiter 23B passes only the data of the distance component corresponding to the short distance within 2 m in this embodiment, in which the peak is not less than a predetermined value set in advance in the input distance component data.

The buffer 23C of the detection circuit 23 receives distance component data corresponding to the short distance from the distance limiter 23B. The buffer 23C temporarily stores the input distance component data. That is, the buffer 23C stores the data of the distance component corresponding to each of _{N 1} steps of the first period MFCW1 (Figure 2). At this time, the buffer 23C accumulates the first period MFCW1 of about 0.1 s for a period of 1000 to 3000 ms. In this embodiment, the buffer 23C accumulates distance component data of about 1.5 s, that is, spectrum data. As a result, the buffer 23C accumulates the data of the distance component including the movement of the object that occurs in the integration time of about 1.5 s, which is longer than the conventional integration time of about 0.2 s. After the first period MFCW1, that is, after about 0.1 s, the buffer 232 similarly stores a series of distance component data corresponding to each N ₁ step of the next first period MFCW1. Thus, the buffer 232 sequentially accumulates the distance component data as accumulated data with an integration time of about 1.5 s.

The FFT unit 23D of the detection circuit 23 performs signal processing by fast Fourier transform on the accumulated data accumulated in the buffer 23C. The FFT unit 233 examines the Doppler component from the frequency spectrum data generated by the signal processing of the accumulated data. Then, the FFT unit 233 extracts the velocity component data of the object from the Doppler component distribution. At this time, the FFT unit 23 </ b> D determines the target based on the movement of the target in the first period MFCW <b> 1 corresponding to 1.5 s, which is longer than 0.2 s (conventional predetermined period) that is conventionally used. Extract speed. That, FFT section 23D, based on the distribution of Doppler components contained in each N ₁ steps of M ₁ sweep in the integration time of about 1.5s, detects the speed of the data of the moving object the rear side of the vehicle at a low speed To do. As a result, the speed resolution in the FFT unit 23D is higher than that in the normal time.

  The target detection unit 23E of the detection circuit 23 detects the object based on, for example, whether the speed level is equal to or higher than a predetermined level based on the speed data extracted by the FFT unit 23D. Then, the target detection unit 23E outputs the detected result as target information.

Next, the operation of the radar apparatus according to this embodiment will be described. This radar device is attached to the rear of the vehicle and used for rearward confirmation. The transmission unit 10 radiates a transmission signal having a frequency sweep as a radio wave. At this time, the first period MFCW1 is about 0.1 s, and this 0.1 s period consists of M ₁ sweeps. Further, in each sweep, the frequency is changed stepwise with a width of 180 MHz. Then, the transmission unit 10 radiates radio waves having a frequency sweep in which the first period MFCW1 continues.

  On the other hand, the receiving circuit 21 of the radar apparatus receives the radio wave from the transmitting unit 10 reflected by the object behind the vehicle. The reception circuit 21 generates a beat signal by mixing the received signal based on the received radio wave and the transmission signal of the transmission unit 10. Further, the receiving circuit 21 removes the high frequency component from the beat signal and outputs it.

  The ADC circuit 22 converts the analog beat signal from the receiving circuit 21 into a digital beat signal and outputs it.

  The detection circuit 23 extracts the distance component data included in the beat signal from the ADC circuit 22 and the velocity component data included in the beat signal, and detects the object based on the extraction result. At this time, the distance limiting unit 23B of the detection circuit 23 has data whose peak is not less than a predetermined value in the distance component data from the FFT unit 23A, that is, frequency component data corresponding to a short distance within 2 m. Only pass through. Thereby, the detection range of the object is limited to 2 m or less.

  Thereafter, the data of each distance component in the first period MFCW1 of about 0.1 s is accumulated for about 1.5 s by the buffer 23C of the detection circuit 23. As a result, the distance component data including the movement of the object generated in the integration time of about 1.5 s, which is longer than the conventional integration time of about 0.2 s, is accumulated in the buffer 23C. Then, the FFT unit 23D of the detection circuit 23 performs signal processing based on the fast Fourier transform on the distance component data accumulated in the buffer 23C, and extracts the velocity data of the object from the frequency spectrum generated by the signal processing. The At this time, the data of the speed of the object is extracted based on the movement of the object in the first period MFCW1 for 1.5 s which is longer than the conventional 0.2 s.

  This state is shown in FIGS. FIG. 3 shows a state of detection in a state where there is no pedestrian as an object. FIG. 4 shows a state of detection in a state where a pedestrian is stationary. Furthermore, FIG. 5 shows a state of detection when the pedestrian moves his hand. Thus, compared with the case where the pedestrian is stationary (circle in FIG. 4), the FFT unit 23D detects a slight movement (arrow in FIG. 5) of about 0.07 km / h.

  Thereafter, the target detection unit 23E of the detection circuit 23 detects the object based on the speed data extracted by the FFT unit 23D. Then, the detected result is output as target information. Thereafter, the detection result sounds, for example, an alarm device installed in the driver's seat to notify the driver that there is an object such as a child in the immediate rear of the vehicle.

  According to this embodiment, since the reflected wave of the radio wave is used and the data stored in the buffer is increased, the object can be reliably detected. Moreover, according to this embodiment, it is possible to detect a pedestrian or the like walking at a low speed within 1 km / h within a range of 2 m from the vehicle. In addition, it is possible to detect a person such as a child who has a slight movement such as an arm even when stationary. Furthermore, the object can be detected even at a speed that is low enough that the accuracy of the measurement performed by the vehicle does not satisfy the prescribed standard.

(Embodiment 2)
FIG. 6 is a block diagram showing a radar apparatus according to Embodiment 2 of the present invention. In this embodiment, components that are considered to be the same as or the same as those in the first embodiment and the in-vehicle radar in FIG. 8 are given the same reference numerals, and the description thereof is omitted. The radar apparatus in FIG. 6 detects an object at the rear of the vehicle according to the start of the vehicle.

  The radar apparatus according to this embodiment includes a transmitter 10 similar to that of the first embodiment. The radar apparatus includes a receiving unit 20 and a receiving unit 30. The receiving unit 20 includes the same antenna 21A, mixer 21B and LPF 21C as those in the first embodiment, an ADC circuit 22, an FFT unit 23A to a target detection unit 23E. It has. The receiving unit 20 includes a switching circuit 240 and a speed correction circuit 250 similar to those in FIG. On the other hand, the receiving unit 30 includes an antenna 31A, a mixer 31B and an LPF 31C, an ADC circuit 32, and an FFT unit 33A to a target detection unit 33E. The receiving unit 30 includes a switching circuit 340 and a speed correction circuit 350 similar to those in FIG. The radar apparatus includes an angle extraction unit 400 similar to that shown in FIG.

  An FFT unit 23A, a distance limiting unit 23B, a buffer 23C, and an FFT unit 23D are connected to the switching circuit 25 of the receiving unit 20. The switching circuit 25 receives as input vehicle data indicating vehicle gear switching and speed. When the vehicle data is switched to the back, the switching circuit 25 switches the connection of the FFT unit 23A, the distance limiting unit 23B, the buffer 23C, and the FFT unit 23D, and detects the connection state shown in FIG. Put it in a state. This state is the same as in FIG. 1, and the target detection unit 23E outputs target information. Further, when the vehicle data is switched to the drive, the switching circuit 25 switches the connection between the FFT unit 23A, the distance limiting unit 23B, the buffer 23C, and the FFT unit 23D, so that the connection state shown in FIG. Set to the detection state.

  The switching circuit 35 of the receiving unit 30 switches the connection of the FFT unit 33A, the distance limiting unit 33B, the buffer 33C, and the FFT unit 33D based on the vehicle data from the vehicle, like the receiving unit 20. The detection state in the vicinity is the same as that in FIG. 7, but in this embodiment, the target detection unit 33E does not output target information.

  According to this embodiment, when the vehicle is going to move forward, it has the same function as the conventional in-vehicle radar shown in FIG. It has a function to detect moving objects. That is, according to this embodiment, it is possible to perform two functions with one device according to the start of the vehicle.

(Embodiment 3)
In this embodiment, the switching circuits 25 and 35 of the second embodiment are as follows. In this embodiment, components that are considered to be the same as or the same as those in the first embodiment and the in-vehicle radar in FIG. 8 are given the same reference numerals, and the description thereof is omitted.

  A speed threshold value is set in advance in the switching circuits 25 and 35 of the radar apparatus according to this embodiment. Then, for example, until the speed indicated by the vehicle data exceeds the threshold value, or until the relative speed extracted by the FFT units 23D and 33D exceeds the threshold value, the switching circuits 25 and 35 include the FFT unit 23A, the distance limiting unit 23B, and the buffer 23C. And the FFT unit 23D are switched to the connection state shown in FIG.

  According to this embodiment, the function similar to the on-vehicle radar shown in FIG. 8 and the function of detecting an object moving at a low speed in the vicinity of the rear of the vehicle are switched according to the speed of the vehicle. That is, according to this embodiment, it is possible to perform two functions with one device according to the speed of the vehicle.

(Embodiment 4)
In this embodiment, temperature drift compensation is performed such that the frequency of the transmission signal in the transmitter 10 of the radar apparatus changes. That is, the transmission unit 10, for each M ₁ sweep, or at a predetermined frequency, performing a sequence of correction of the transmission and the temperature drift of the transmitted signal alternately. Then, a correction sequence is realized as feedback control or feedforward control based on any of the following.
a. The temperature of a given part of the vehicle radar,
b. The number of pulses transmitted,
c. Time that has elapsed since the on-vehicle radar was started

Thus, according to this embodiment, the sequence of transmission and correction is alternately performed for each M ₁ sweep or at a predetermined frequency, so that the frequency correction sequence due to temperature drift affects the transmission. Can be suppressed.

  As mentioned above, although each embodiment of this invention has been described in detail, the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the scope of this invention, It is included in this invention. For example, the radar device according to the present invention is not limited to being mounted on a vehicle, but can be used for situations to be prevented, such as material management including theft prevention.

  In each of the above-described embodiments, in order to correct the frequency of the transmission signal by the feedback control method, transmission of the transmission signal is intermittently performed as long as integration necessary for detecting a minute speed of a child or the like is not hindered. It is desirable that the transmission signal is monitored by being performed or being thinned out in units of a predetermined period.

  For example, when the period in which such integration is to be performed is as long as 1000 ms to 3000 ms, the frequency of the transmission signal is monitored after the integration in that period is completed or the frequency at which a large error does not occur in the integration result. It may be done during the period.

  In addition, as described above, the frequency of the transmission signal may be monitored by any trigger as long as integration necessary for detecting a minute speed of a child or the like is not hindered.

  Further, in such a case, the above monitoring results are accumulated in a time series (cyclically) in a memory or the like, and the integration process is performed based on the moving average method or the exponential smoothing method. The maximum speed of the target is reduced, but if the maximum is within the speed of the target to be detected, it is avoided that the frequency at which the frequency of the transmitted signal is monitored is unnecessarily reduced. Is possible.

  Further, in each of the above-described embodiments, “Fast Fourier Transform” is replaced by Fourier transform performed in various forms such as DFT (Discrete Fourier Transform) if frequency analysis is realized with desired accuracy and responsiveness. May be.

DESCRIPTION OF SYMBOLS 10 Transmission part 11 Signal generation part 12 Antenna 20 Reception part 21 Reception circuit 22 ADC circuit 23 Detection circuit 23A FFT part 23B Distance restriction part 23C Buffer 23D FFT part 23E Target detection part

Claims (5)

Radar signal processing that detects radar signals that arrive at radar mounted on a vehicle, detects a target that is located within a specified near range, can be displaced at a very low speed, and that the vehicle can contact at or above a specified speed A device,
A period specifying means for specifying a period during which the speed of the vehicle can be accelerated above the prescribed speed;
A radar signal processing apparatus comprising: target identification means for identifying the presence of the target as a Doppler component distribution of the radar signal within the near range during the period. The radar signal processing apparatus according to claim 1,
The radar signal processing apparatus, wherein the speed of the vehicle is a ground speed detected by the radar. The radar signal processing device according to claim 1 or 2,
The period specifying means includes
Including a period preceding the start of the vehicle in the period based on all or part of the operation performed on the vehicle by the operator, the state of the vehicle, and the behavior of the vehicle. A characteristic radar signal processing apparatus. A radar signal processing device according to any one of claims 1 to 3,
By feedback control or feedforward control based on all or part of the temperature of a predetermined part of the radar, the number of pulses transmitted by the radar, and the time elapsed since the radar was started, A radar signal processing apparatus comprising compensation means for compensating for a drift in frequency of a transmitted transmission wave. A radar device for detecting a target mounted on a vehicle and located around the vehicle,
A period specifying means for specifying a period during which the speed of the vehicle can be accelerated above a specified speed that should not be exceeded when contacting a specific target that is located within a specified near range and can be displaced at a slow speed;
A radar apparatus comprising: target identification means for identifying the presence of the specific target as a distribution of Doppler components in the near range of a radar signal arriving at the radar during the period.

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