JP2010271251A - On-vehicle radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-vehicle radar device that facilitates identification of received waves as the reflected waves of transmitted wave from own vehicle, in an environment where radar waves of identical mode and identical frequency band are mixed with each other, and appropriately maintains required radar functions. <P>SOLUTION: The on-vehicle radar device includes a transmission interval controller 110 for controlling the time as the transmission interval of the transmitted waves transmitted as a time sharing signal of FM-CW mode from a transmission antenna 150 and a time as a transmission stop interval; a power detecting section 240 for detecting power of the received waves received via a receiving antenna 210; and a power-determining section 250 for determining that the received waves as the reflected waves of the transmitted waves, when the duration is received, if the detected power is determined to exceed a threshold set to the possible level of reception processing matches with the time as the transmission interval controlled by the transmission interval controller 110. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an in-vehicle radar device that is mounted on a vehicle and detects a target or the like by FM (frequency modulation) -CW (continuous wave) communication.

  Conventionally, as this type of on-vehicle radar device, for example, a radar device found in Patent Document 1 is known. FIG. 6 shows the frequency transition and transmission timing of the transmission wave according to the radar apparatus described in Patent Document 1, the relationship of the signal waveform before mixing between the transmission wave and the reflected wave (received wave) of the transmission wave, and after mixing. The signal waveform of each beat signal is shown as a time chart.

  First, as shown in FIG. 6 (a), in this time division radar apparatus, transmission sections and transmission stop sections each having a fixed time are alternately provided, and a transmission wave that is frequency-modulated as a triangular wave every time a transmission section is reached. Send. In the transmission stop period, a transmission wave transmitted by itself and a reception wave that is a reflection wave of the transmission wave are mixed, and a so-called beat signal is obtained from a time difference and a frequency difference between the transmission wave and the reception wave. Here, with reference to FIGS. 6B and 6C, the processing mode by the radar apparatus will be specifically described with respect to the transmission wave, the reception wave, and the beat signal.

  As shown in FIG. 6B, the transmission wave transmitted in the transmission section is frequency-modulated as a triangular wave having a period of 1 / fm, a center frequency of f0, and a transition frequency amplitude (frequency modulation width) of ΔF. It is a continuous wave. The received wave, which is the reflected wave of the transmitted wave, has a frequency of ΔD due to ΔT, which is delayed in time according to the distance to the target to be detected, and the Doppler effect generated according to the relative speed between the target and the radar apparatus main body. Have undergone a shift. Based on the time difference and the frequency difference between the transmission wave and the reception wave, a constant value fb1 which is a frequency difference in the frequency increase section of the transmission wave as shown in FIG. A beat signal composed of a constant value fb2 which is a frequency difference is obtained.

  Thereafter, the beat signal is subjected to frequency analysis by FFT (Fast Fourier Transform), and R, which is a relative distance to the target, and V, which is a relative velocity, are calculated using the frequency components obtained thereby. A calculation formula for calculating the relative distance R and the relative speed V can be expressed as follows using the speed of light C.

Relative distance R = C × (fb1 + fb2) / (8 × ΔF × fm) (1)
Relative speed V = C × (fb2−fb1) / (4 × f0) (2)
Next, with reference to FIG. 7, an example of an external radio wave (received wave) received by the radar device of the own vehicle when another vehicle equipped with the radar device of the same type as this radar device comes in the vicinity of the own vehicle. explain.

In a general FM-CW radar device, the frequency of the transmission wave is limited to a band of 76.0 GHz to 77.0 GHz according to the Radio Law, and the transmission wave is modulated with a frequency modulation width of about 50 MHz to 200 MHz. The In addition, when a plurality of radar devices are present close to each other, in order to prevent transmission waves and reflected waves from the devices from interfering with each other, the frequency bands used by the transmission waves are prevented from overlapping. Here, for example, the radar device of the own vehicle transmits a transmission wave having a center frequency f0 of 76.5 GHz and a frequency modulation width ΔF of 150 MHz, and the radar device of the other vehicle close to the own vehicle is delayed by about a half cycle to the center frequency. Assume that a transmission wave having f0 of 76.7 GHz and a frequency modulation width ΔF of 150 MHz is transmitted. In this case, the frequency band upper limit of the transmission wave of the radar device of the own vehicle is 76.575 GHz, and the frequency band lower limit of the transmission wave of the radar device of the other vehicle is 76.625 GHz. 100 MHz. At this time, if the reflected waves of these transmitted waves are subjected to a frequency shift due to the Doppler effect as described above, the margin of 100 MHz is not sufficient, and as shown by arrows in FIG. The frequency bands overlap and interfere with each other, and due to this interference, the values of the frequency differences fb1 and fb2 (FIG. 6C) shift due to the influence of the interference. Therefore, in the radar apparatus described in Patent Document 1, the value of the shifted frequency difference fb1 or fb2 exceeds the threshold value corresponding to each value stored in advance in the storage unit, thereby causing interference. It is judged that the reflected wave by the transmitted wave of another vehicle is received. In such a case, the radar apparatus similarly transmits a transmission wave based on a combination appropriately selected based on a matrix composed of combinations of several frequency bands and several transmission timings stored in advance in the storage unit. Resubmit. Incidentally, the combination of frequency band and transmission timing in this matrix is such that one of them is different from each other, so even if two or more such radar devices are close to each other, There is a high probability of selecting different combinations and retransmitting transmission waves. As a result, the probability that each radar apparatus receives only the reflected wave of its own transmission wave after re-transmission increases, and values such as the time delay ΔT not including interference and the frequency shift ΔD due to the Doppler effect are expressed by the above equation (1). ) And the frequency difference fb1 and fb2 in the equation (2) can be used to calculate an accurate relative distance R and the like.

JP 2008-292264 A

  Thus, in the radar device according to Patent Document 1, even if the radar device of the other vehicle is a radar device of the same specification, if the value of the amplitude of the beat signal exceeds a predetermined threshold value, the reception is performed. It can be determined that there is interference in the waves. When it is determined that there is interference, the frequency of the transmitted wave to be retransmitted, the transmission timing, etc. are appropriately selected so that the received wave becomes only the reflected wave of the transmitted wave of the own vehicle. It created a situation where the reflected waves could be identified.

  However, as there are many other vehicles in the vicinity that have a lot of traffic and are equipped with the same radar equipment as their own radar equipment, the combination of the frequency and timing of the transmitted waves to be retransmitted, as in the radar equipment. Even if selected appropriately, the above-described interference occurs with a high probability. Moreover, in the current situation in which radar waves are often transmitted not only in front radar but also in all directions around the vehicle, similar interference is likely to occur when traveling in a single column or coasting multiple lanes. That is, in such a situation, the probability of occurrence of interference becomes higher and it is difficult to properly enjoy the radar function based on the identification of the received wave that is the reflected wave of the transmission wave of the own vehicle.

  This invention has been made in view of such circumstances, and even in an environment where radar waves of the same method and the same frequency band are mixed, it is easy to identify a received wave that is a reflected wave of a transmission wave from the own vehicle. An object of the present invention is to provide an on-vehicle radar device capable of appropriately maintaining a required radar function.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to the first aspect of the present invention, there is provided a transmission section controller for controlling a transmission period and a transmission stop period of a transmission wave transmitted as a time division signal of the FM-CW method from a transmission antenna, and a reception antenna. A power detection unit for detecting the power of the received wave received via the signal, a duration for which it is determined that the detected power exceeds a threshold set for a possible level of reception processing, and the transmission section controller And a power determination unit that determines that a reception wave, which is a reflection wave of the transmission wave, is received when the time set as the transmission period controlled by the transmission time coincides.

  According to such a radar apparatus, when the duration for which the power detected by the power detection unit continues to be determined to exceed the threshold value coincides with the time set as the transmission section controlled by the transmission section controller, A reception wave that is a reflection wave of a transmission wave of a car can be identified. That is, the time set as the transmission section set by the transmission section controller without the influence of other vehicles is a value obvious to the own vehicle, and the value is used as the identification condition of the received wave that is the reflected wave of the transmission wave of the own vehicle. Therefore, the received wave that is the reflected wave of the transmission wave of the own vehicle can be easily and reliably identified. As a result, even in an environment where radar waves of the same method and the same frequency band coexist, it is easy to identify the received wave that is the reflected wave of the transmitted wave from the own vehicle, and appropriately maintain the required radar function It is possible to provide an on-vehicle radar device that can be used.

  In the invention according to claim 2, the power determination unit sets the duration for which it is determined that the power detected by the power detection unit exceeds the threshold and the transmission interval controlled by the transmission interval controller. The gist is to determine that a received wave, which is a reflected wave of the transmitted wave, is received when the time matches a predetermined number of times.

  According to such a radar apparatus, the duration that continues to be determined to exceed the threshold value and the time that is set as the transmission section coincide with each other even though there is interference due to a received wave caused by another vehicle. As a result, it is possible to reduce the possibility of making an erroneous determination that only the received wave that is the reflected wave of the transmitted wave of the vehicle is identified. That is, by making a determination as to whether or not the duration that continues to be determined to exceed the threshold and the time to be the transmission interval match, the possibility of making an erroneous determination in this way is eliminated, A reception wave, which is a reflection wave of the transmission wave of the own vehicle not receiving interference, can be identified more reliably.

  According to a third aspect of the present invention, the transmission section controller includes a random number generation unit that generates a random number, and controls the time for the transmission period of the transmission wave based on the random number generated from the random number generation unit. The gist.

  According to such a radar apparatus, based on random numbers that are random values, the transmission section controller controls the time to be the transmission section of the transmission wave. It will not be the same fixed time. Therefore, it is possible to further reduce the possibility that the duration that continues to be determined to exceed the threshold and the time set as the transmission interval coincide with each other even though there is interference due to a received wave caused by another vehicle. . As a result, only the received wave that is the reflected wave of the transmission wave of the host vehicle can be more reliably identified.

The block diagram which shows the whole structure about one Embodiment of the vehicle-mounted radar apparatus which concerns on this invention. (A)-(c) is a time chart which shows the operation example by the radar apparatus of the embodiment. The flowchart which shows the transmission processing procedure of the transmission wave performed in the embodiment. The flowchart which shows the process sequence of the received wave performed in the embodiment. The flowchart which shows the process sequence of the received wave performed in the embodiment. Regarding a conventional radar apparatus, (a) is a time chart showing the relationship between the transmission timing of a transmission wave and the frequency transition of the transmission wave, and (b) is a transmission wave transmitted at the transmission timing shown in (a) and its transmission. FIG. 5C is a time chart showing the frequency transition of a received wave that is a reflected wave of the wave, and FIG. 5C is a time chart showing the time difference between the transmitted wave and the received wave and the frequency transition of the beat signal obtained based on the frequency difference. The time chart which shows the state which the received wave which is the reflected wave of the transmission wave by the radar apparatus of the own vehicle, and the received wave which is the reflected wave of the transmitted wave by the radar apparatus of the other vehicle in the vicinity of the own vehicle interfere.

Hereinafter, an embodiment of an in-vehicle radar device according to the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, the on-vehicle radar device according to the present embodiment mainly includes a transmission system 100 for transmitting a transmission wave composed of a time-division signal of the FM-CW method, and reception of the transmission wave as a reflected wave. The receiving system 200 for receiving and processing waves is provided.

  First, the configuration of the transmission system 100 will be described. In this transmission system 100, the transmission section controller 110 is a part that controls the transmission section and the transmission stop section of the transmission wave. In this embodiment, the transmission section controller 110 sets the time to be a transmission section. A random number generation unit 120 that generates a random number for determination at random is incorporated. Further, in the transmission system 100, the transmission wave generating unit 130 is a part that generates the transmission wave, and the switch 140 is only used as a transmission period determined based on the random number. This is a portion that is selectively applied to the transmission antenna 150, and the transmission antenna 150 is a portion that wirelessly transmits the given transmission wave to the outside. As described above, in the present embodiment, the transmission wave generated by the transmission wave generator 130 is controlled based on the time determined randomly based on the random number in the transmission section controller 110. Is transmitted to the outside via the transmission antenna 150 for a period of time.

  Next, the receiving system 200 will be described. In the reception system 200, the reception antenna 210 is a part that receives an external radio wave (reception wave), and the mixer 220 applies the transmission wave received from the transmission wave generator 130 constituting the transmission system 100 and the reception antenna 210. This is the part that mixes the received wave. As described above, a so-called beat signal can be obtained by this mixing. An ADC (analog / digital converter) 230 to which the beat signal is input is a part that converts the beat signal, which is an analog signal, into a digital signal. The power detection unit 240 to which the digital signal is input is input to the beat signal. This is a part for detecting the power (reception power) of the received wave based on the digital signal. Then, the power determination unit 250 to which the power of the received wave detected in this way and the information indicating the time set as the transmission interval from the transmission controller 110 constituting the transmission system 100 is input, the power of the received wave is a predetermined threshold value. This is the part that grasps the time that has continued to exceed the time as the duration of the received wave and compares it with the time for the transmission interval. Incidentally, this threshold value is set as a value by which it can be determined whether or not the power of the received wave is at a level where reception processing is possible, and is stored in advance in a storage unit in the power determination unit 250, for example. Based on such comparison, the power determination unit 250 can identify the reflected wave of the transmission wave from the own vehicle when it is determined that the above-described duration grasped based on the threshold value matches the time set as the transmission section. It is judged that.

On the other hand, in the radar apparatus of the present embodiment, an FFT (Fast Fourier Transform) device 300 is a part that performs a fast Fourier transform on the beat signal (digital signal) given from the ADC 230 and performs frequency analysis. The result of this frequency analysis is sent to the signal processing unit 400. In this signal processing unit 400, for example, the relative distance R and the relative velocity V as the radar device are calculated using the equations (1) and (2). Is done. However, in the present embodiment, such calculation of radar acquisition information is performed only when the power determination unit 250 determines that the reflected wave of the transmission wave from the own vehicle can be identified. ing.

  Next, with reference to FIG. 2, a detailed description will be given of a method by which the radar apparatus of the present embodiment determines that a received wave that is a reflected wave of a transmission wave from the own vehicle can be identified. In the following description, the duration (detection time) of the received wave, which is the time detected by the power determination unit 250 that the power of the received wave has continued to exceed a predetermined threshold, is the time taken as the transmission interval corresponding to the duration. As a condition for determining that the received wave, which is a reflected wave of the transmission wave from the own vehicle, can be identified that the continuous match is repeated twice and a predetermined number of times (n times). Yes.

  Here, as illustrated in FIG. 2A, the time for the first transmission interval is Tx1, the time for the second transmission interval is Tx2, and the length of each transmission stop interval provided between these intervals. Is constant. However, this schedule is obtained by extracting a part of the transmission wave that is continuously transmitted. In practice, the transmission section and the transmission stop section are alternately and continuously provided. In the present embodiment, since the transmission section controller 110 determines the time for each of the transmission sections based on the random number generated from the random number generator 120, the times Tx1 and Tx2 are actually It will be a random time.

  First, consider the case where the power detection unit 240 detects that the power of the received wave transitions in the manner shown in FIG. 2B, for example. Here, the threshold value Pt shown in FIG. 2 is set as a value capable of determining whether or not the power of the received wave is at a level where reception processing is possible, as described above. The unit 250 recognizes and recognizes the time during which the power exceeding the threshold value Pt is continuously detected by the power detection unit 240 as the duration of the received wave. That is, in the example of FIG. 2B, since there are two portions where the power of the received wave is continuously detected as a value greater than the threshold value Pt, the power determination unit 250 calculates the detection times T1 and T2. Recognized as the duration of the received wave. Here, when FIGS. 2A and 2B are compared, the duration (detection time) T1 coincides with Tx1, which is the time set as the first transmission interval, and the duration (detection time) T2 is also equal to the second transmission interval. It can be determined that the time coincides with Tx2, which is the time to perform. If this continuous match is repeated a predetermined number of times, the power determination unit 250 can identify the reflected wave of the transmission wave from the own vehicle based on the received wave whose duration (detection time) is T1 and T2. It is judged that. Thereby, in the signal processing unit 400 as described above, for example, the relative distance R and the relative speed V as the radar device are calculated using the equations (1) and (2). Incidentally, in this case, the power of the received wave that has been detected is P, which is a constant value, and only the received wave that is the reflected wave of the transmitted wave from the vehicle is identified.

Next, consider the case where the power detection unit 240 detects that the power of the received wave transitions, for example, in the manner shown in FIG. In this case, even in the example of FIG. 2C, since there are two portions where the power of the received wave is continuously detected as a value larger than the threshold value Pt, the power determination unit 250 uses the detection times T3 and T4. Is recognized as the duration of the received wave. 2A and 2C, the duration (detection time) T3 coincides with the time Tx1 as the first transmission interval, but the duration (detection time) T4 is It can be determined that the time does not coincide with Tx2, which is the time for two transmission intervals. As a result, the power determination unit 250 determines that the reflected wave of the transmission wave from the own vehicle cannot be identified based on the reception waves whose durations (detection times) are T3 and T4. Therefore, the calculation of the relative distance R and the relative speed V as the radar device is not performed. Incidentally, in this case, the power of the received wave that has been detected fluctuates, and a state in which there is interference from the received wave caused by another vehicle is identified. Duration (detection time) T3 is first
This coincides with Tx1, which is the time set as the transmission interval, but this is the duration that continues to be determined to exceed the threshold value despite the interference from the received wave caused by another vehicle and the time set as the transmission interval. Is coincidentally coincidental. In such a case, as described above, the duration (detection time) T4 is continuously compared with Tx2, which is the time for the second transmission section, to ensure that there is interference from the received wave caused by the other vehicle. Can be identified.

  As a result, even in an environment where radar waves of the same method and the same frequency band are mixed, when the duration of the transmission wave matches the duration of the reception wave, the reception wave that is the reflected wave of the transmission wave from the own vehicle Therefore, it is possible to provide an on-vehicle radar device that can easily maintain the required radar function. Furthermore, it eliminates the possibility of making an erroneous determination that only the received wave, which is the reflected wave of the transmitted wave of the vehicle, is identified despite interference from the received wave caused by another vehicle. The received wave, which is the reflected wave of the transmission wave of the vehicle without interference, can be identified more reliably.

  Further, the duration (detection time) of the received wave as described above coincides with the time set as the transmission interval corresponding to the duration continuously twice, and the continuous coincidence is a predetermined plural times (n times). ) If repeated conditions are used for the above identification, it is possible to more reliably identify the received wave that is the reflected wave of the transmission wave of the vehicle that is not receiving interference.

  Next, with reference to FIG. 3, the process performed in the transmission system 100 with which the radar apparatus of this Embodiment is provided is explained in full detail. Note that this process is repeatedly performed so that each transmission wave is transmitted in a time-division manner so that the time for each transmission section is random.

  As shown in FIG. 3, when the process is started, first, the transmission wave generator 130 generates a transmission wave (step S100). Then, the transmission wave generator 130 transmits the created transmission wave to the mixer 220 (step S101), and the process is terminated as it is. On the other hand, at the same time, the random number generation unit 120 built in the transmission section controller 110 generates a random number (step S102), and based on the random number, the transmission section controller 110 determines Tx as a time to be a transmission section (step S103). ). Next, the transmission section controller 110 transmits the time Tx used as the transmission section to the power determination unit 250 constituting the reception system 200 (step S104), and ends the processing as it is, while simultaneously connecting the switch 140. (Step S105). As a result, the switch 140 gives the generated transmission wave to the transmission antenna 150. The transmission section controller 110 continues to connect the switch 140 until it is determined that the time Tx as the transmission section has elapsed, and when it is determined that the time Tx as the transmission section has elapsed, the connection of the switch 140 is released. (Steps S106 and S107). As a result, the transmission wave generated by the transmission wave generator 130 is transmitted to the transmission antenna 150 only during the transmission period controlled based on the time randomly determined by the transmission period controller 110 based on the random number. It will be transmitted to the outside via. Then, the transmission section controller 110 determines whether or not the time for the transmission stop section has elapsed in order to retransmit the transmission wave after the end of the transmission stop section. This determination is repeated until the transmission section controller 110 determines that the time for setting the transmission stop section has elapsed, and if it is determined that the time has elapsed, the power determination unit 250 constituting the reception system 200 is notified accordingly. Then, the process returns to step S102 to repeat a series of processes (steps S108 and S109).

  Next, with reference to FIG. 4 and FIG. 5, the process performed in the receiving system 200 with which the radar apparatus of this Embodiment is provided is explained in full detail. This process is repeated to determine that a received wave, which is a reflected wave of the transmitted wave transmitted by the process performed in the transmission system 100 of the own vehicle included in the radar apparatus of the present embodiment, is received. To be implemented.

  As shown in FIG. 4, when the processing is started, first, the power determination unit 250 receives from the transmission wave generation unit 130 constituting the transmission system 100 that the time for the transmission stop period has elapsed. (Step S200). Then, as described above, the power determination unit 250 sets i = 0 as the number of times of repeated comparison (number of times of identification) based on the duration (detection time) of the received wave as described above (step S201). ), J, which is the transmission section number for identifying the transmission section corresponding to the transmission section, is set to j = 1 (step S202). Then, the mixer 220 receives a transmission wave from the transmission wave generator 130 constituting the transmission system 100 (step S203), and the power judgment unit 250 obtains a transmission section number from the transmission section controller 110 constituting the transmission system 100. Information indicating the time Txj as the transmission interval corresponding to j is received (step S204). Thereafter, the reception antenna 210 receives the external radio wave (reception wave) (step S205), and the mixer 220 mixes the reception wave and the transmission wave received in step S203 to generate a so-called beat signal (step S206). ). Then, the ADC 230 converts the beat signal, which is an analog signal, into a digital signal (step S207).

Next, processing after the ADC 230 sends a beat signal as a digital signal to the power detection unit 240 will be described.
When the processing is started, first, the power detection unit 240 detects the power of the received wave based on the beat signal that is a digital signal received from the ADC 230, and entrusts all subsequent processing to the power determination unit 250. The detected power of the received wave is sent to the power determination unit 250 (step S208). Then, it is determined whether or not the power P of the received wave is equal to or higher than the threshold value Pt. Here, if it is determined that P is a power less than Pt, it is determined that detection of a received wave that is a reflected wave of the transmitted wave transmitted by the vehicle has failed (steps S209 and S210), and the process returns to step S201. It is. Further, if it is determined that P is a power higher than Pt, it is determined that the reception wave, which is a reflected wave of the transmission wave transmitted by the vehicle, has been successfully detected. Rxj measurement is started (steps S209 and S211).

The process after the measurement of Rxj, which is the duration of the received wave, is started by the power determination unit 250 will be described with reference to FIG.
When this process is started, the measurement of Rxj is continued until it is determined that the power P of the received wave has become a power less than the threshold value Pt, and the measurement is aborted if P becomes a power less than the threshold value Pt, Rxj is determined (steps S300 and S301). Next, in order to determine whether or not the received wave that is the reflected wave of the transmitted wave of the own vehicle can be identified (there is no interference due to the received wave caused by another vehicle), the determined Rxj and step S204 in FIG. The received Txj is compared with the received Txj. If it is determined that Rxj ≠ Txj, it is determined that identification is not possible (interference exists), and the process returns to step S201 in FIG. 4 (steps S302 and S303). If it is determined that Rxj = Txj, it is determined that identification is possible (no interference), and it is subsequently determined whether Rxj and Txj are compared in two consecutive transmission intervals (steps S302 and S304). That is, if it is determined that j as the transmission interval number is j = 1 and only Rxj and Txj are compared in one transmission interval, j = j + 1 is set as j = j + 1. The process proceeds (steps S304 and S305). On the other hand, if the transmission interval number j is j = 2 and it is determined that Rxj and Txj are compared in two consecutive transmission intervals, i = i + 1 is set, and the duration of the received wave (detection time) ) I, which is the number of times of repeating the comparison twice consecutively (number of times of identification), is advanced once (steps S304 and S306). Thereafter, n that is a predetermined number of times or more stored in advance in the previous storage unit is called, and it is determined whether or not i that is the number of times of identification has been performed n times. If it is determined that i <n, the process returns to step S202 of FIG. 4 (step S307), and if it is determined that i = n, there is no interference due to a received wave caused by another vehicle. It is determined that the received wave, which is the reflected wave of the transmitted wave of the car, can be identified (step S308), and the series of processes is terminated.

As described above, according to the in-vehicle radar device according to this embodiment, the effects listed below can be obtained.
(1) As a time for the transmission section, a value obvious for the own vehicle set by the transmission section controller without being influenced by another vehicle is used as a condition for identifying a received wave that is a reflected wave of the transmission wave of the own vehicle. It was decided. As a result, the received wave, which is the reflected wave of the transmission wave of the own vehicle, only when the duration (detection time) of the received wave detected by the power determination unit matches the time set as the transmission section controlled by the transmission section controller. Can be identified. In other words, even in an environment where radar waves of the same method and the same frequency band are mixed, it is easy to identify the received wave that is the reflected wave of the transmitted wave from the own vehicle, and the required radar function can be properly maintained. An in-vehicle radar device capable of being provided can be provided.

  (2) The procedure for continuously determining twice that the duration (detection time) of the received wave detected by the power determination unit coincides with the time set as the transmission interval is taken. As a result, the received wave duration (detection time) detected by the power determination unit and the time set as the transmission section are coincidental even though the received wave receives interference from the received wave caused by another vehicle. By matching, it is possible to reduce the possibility of erroneous determination that the received wave, which is the reflected wave of the transmitted wave of the own vehicle, is identified. That is, it is possible to eliminate as much as possible the possibility of making an erroneous determination as described above, and to more reliably identify a reception wave that is a reflected wave of the transmission wave of the vehicle that is not receiving interference.

  (3) The procedure of continuously determining twice the duration (detection time) of the received wave detected by the power determination unit and the time set as the transmission interval is repeated a plurality of times. . As a result, there is a possibility that an erroneous determination is made that the received wave, which is a reflected wave of the transmission wave of the own vehicle, is identified even though the received wave is receiving interference due to the received wave caused by another vehicle. Therefore, it is possible to further improve the discriminating power of only the received wave that is the reflected wave of the transmission wave of the own vehicle.

  (4) Based on a random number that is a random value, the transmission section controller controls the time to be the transmission section of the transmission wave. As a result, the transmission period of each vehicle does not become the same constant time, so that it is determined that it exceeds the threshold even though the reception wave is receiving interference from the reception wave caused by another vehicle. It is possible to further reduce the possibility that the continuing duration and the time set as the transmission interval coincide with each other. In other words, it is possible to more reliably identify a received wave that is a reflected wave of a transmission wave of the host vehicle that is not receiving interference.

In addition, the said embodiment can also be implemented with the following aspects.
In the above embodiment, when detecting the duration (detection time) of the received wave detected by the power determination unit, the received wave power P (received power) is a threshold set with respect to a level at which reception processing is possible. The condition is that it is Pt or more. Here, the threshold value Pt is not a constant value but can be a value that can be freely set. Thereby, the detection sensitivity of the received wave of this radar device can be freely adjusted based on the surrounding environment where the host vehicle is placed. That is, for example, when traveling in an urban area where there is a lot of traffic, the power of the received wave, which is a reflected wave from a very close measurement object, is strong. Otherwise, the threshold Pt value can be set low to increase the detection sensitivity of the received wave. In this way, even if there are many measurement objects around the vehicle, it is possible to avoid repeating the re-measurement of the received wave, and in other cases, the measurement object exists far away. Even if you are doing it, you will be able to capture it reliably. The amount of traffic depends on the frequency of retransmitting the transmission wave, the traveling speed of the host vehicle, the position information of the car navigation system, and V
It can be determined based on ICS information or the like. In this case, for example, the radar device can compare the acquired traffic volume determination information with the traffic volume stored in advance in the previous storage unit and the correspondence table of the predetermined value to determine the threshold value Pt.

  In the above embodiment, it is assumed that the random number generation unit 120 that generates a random number for randomly determining the transmission period is built in, but based on the random number previously stored in the previous storage unit Thus, the transmission section controller 110 may be set at random. That is, even in this case, it is possible to randomly determine the time to be a transmission section, and it is determined that the threshold value is exceeded even though the reception wave receives interference from the reception wave caused by another vehicle. It is possible to further reduce the possibility that the continuing duration and the time set as the transmission interval coincide.

  The power determination unit 250 receives information indicating the time Tx to be a transmission interval from the transmission interval controller 110. However, even if the data is the time itself, the power determination unit 250 controls the transmission timing used when the power determination unit 250 determines the time. It may be the same signal as the signal. That is, it is only necessary for the power determination unit to be able to grasp Tx, which is the time for the transmission interval. As a result, it becomes possible to compare the duration (detection time) of the received wave detected by the power determining unit with the time set as the transmission section, and the reflected wave of the transmitted wave of the own vehicle not receiving interference. The received wave can be identified.

  In the above embodiment, the transmission section controller 110 includes the random number generation unit 120 inside, and controls the time to be the transmission section of the transmission wave based on the random number generated from the random number generation unit 120. It is not always necessary to set the time during which the transmission wave is transmitted as a random time. That is, even if the transmission wave transmission interval is a fixed time, the received wave duration detected by the power determination unit (detection time) and the transmission interval time are continuously compared twice. It is only necessary to follow the procedure to be performed or to repeat the procedure a predetermined number of times. This makes it possible to identify a received wave that is a reflected wave of the transmitted wave of the vehicle that is not receiving interference.

  -In said embodiment, based on the time made into a transmission area, the procedure which compares twice the duration (detection time) of the received wave which the said power judgment part detects, and the time made into the said transmission area continuously. Although this step is repeated a predetermined number of times, it is not always necessary to do so. That is, even if the procedure itself is not repeated a plurality of times, in the procedure for comparing the duration of the received wave (detection time) and the time used as the transmission interval, the number of comparisons is set to 3 or more instead of 2 However, it is possible to identify a received wave that is a reflected wave of the transmitted wave of the vehicle that is not receiving interference.

-In said embodiment, based on the time used as the 1st transmission section and the 2nd transmission section, the duration (detection time) of the received wave which the said power judgment part detects, and the time used as the said transmission section are continued. We decided to take the procedure of comparing twice. However, it is not always necessary to follow such a procedure. Unless there are many other vehicles in the vicinity, even if the number of comparisons is only one in that procedure, A reception wave that is a reflection wave of the transmission wave can be identified. That is, for example, when traveling in an urban area where there is a lot of traffic, a procedure for comparing the duration (detection time) of the received wave detected by the power determination unit and the time set as the transmission section twice or more in succession. It is only necessary to step on or repeat the procedure a plurality of times. In other cases, there is no problem even if the number of comparisons is made only once in the procedure. Even in this way, it is possible to identify a received wave that is a reflected wave of the transmitted wave of the vehicle that is not receiving interference. Note that the amount of traffic can be determined based on the frequency of retransmitting the transmission wave, the traveling speed of the host vehicle, the position information of the car navigation system, the VICS information, and the like, as described above. In this case, for example, the radar device compares the acquired traffic volume determination information with the correspondence table of the number of comparisons or the number of times of repeating the procedure stored in advance in the previous storage unit, and calculates the number of times. It can be determined as appropriate.

  In the above embodiment, a so-called beat signal is digitally converted by the ADC 230 before being transmitted to the power detection unit. In this case, power detection and reception detection are performed based on the digitally converted data. As a result, an error derived from the sampling rate of the ADC 230 may be included as it is. However, an appropriate margin is set by, for example, doubling the sampling rate when comparing the transmission wave transmission period and the received wave duration (detection time) detected by the power determination unit. This error can be eliminated. Alternatively, this error can be eliminated by setting the fluctuation value of the time Tx determined as the transmission interval of the transmission wave determined by the transmission interval controller 110 to a sufficiently large value from the sampling rate. In addition, if the power detection unit 240 and the power determination unit 250 perform processing, for example, via a detector before digitally converting the beat signal, it is not necessary to consider the influence of the sampling rate. .

  In the above embodiment, the duration of the received wave (detection time) is detected using the value of the power of the received wave as described above. However, any other method can be used as long as this duration can be detected. A detection method may be used.

  DESCRIPTION OF SYMBOLS 100 ... Transmission system, 110 ... Transmission section controller, 120 ... Random number generation part, 130 ... Transmission wave generation part, 140 ... Switch, 150 ... Transmission antenna, 200 ... Reception system, 210 ... Reception antenna, 220 ... Mixer, 230 ... ADC , 240 ... power detection unit, 250 ... power determination unit, 300 ... FFT device, 400 ... signal processing unit.

Claims (3)

A transmission section controller for controlling the time to be the transmission section and the time to be the transmission stop section of the transmission wave transmitted as a time-division signal of the FM-CW scheme from the transmission antenna;
A power detector for detecting the power of the received wave received via the receiving antenna;
When the duration during which the detected power continues to be determined to exceed a threshold set for a possible level of reception processing matches the time set as the transmission interval controlled by the transmission interval controller, A power determining unit that determines that a received wave that is a reflected wave of the transmitted wave is received;
In-vehicle radar device.   In the power determination unit, the duration time during which it is determined that the power detected by the power detection unit exceeds the threshold value matches the time set as the transmission interval controlled by the transmission interval controller a predetermined number of times. The on-vehicle radar device according to claim 1, wherein it is determined that a reception wave that is a reflected wave of the transmission wave is received.   The in-vehicle radar according to claim 1, wherein the transmission section controller includes a random number generation unit that generates a random number, and controls a time period in which the transmission wave is transmitted based on a random number generated from the random number generation unit. apparatus.

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