JP2008058165A - On-board radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ease detection of the presence of a self vehicle by a radar in other vehicle by improving recognizability by a radar in other vehicle. <P>SOLUTION: The radar device includes a unit that receives transmission waves transmitted from other radar device and a unit that sends the received waves from a self radar in a vehicular radar system that receives reflection waves reflected from a target by outputting transmission waves from a transmitting unit and detects the distance to a target and a relative speed based on the reflection waves. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an on-vehicle radar device.

  In recent years, an inter-vehicle distance warning system that informs the driver of the vehicle danger by warning lights, warning sounds, etc. when the distance between the vehicle and the target in front of the vehicle (vehicles, obstacles, etc.) is too close. An adaptive cruise control system that controls the distance so that it is maintained at a predetermined interval, and when a collision with a target approaching the host vehicle from the front, side, rear, etc. of the host vehicle cannot be avoided. Various driving support systems have been put into practical use, such as the collision damage reduction system that reduces the impact of collision by operating the brakes and reduces the impact on the passengers due to collision by properly tightening the seat belt. Yes.

  When constructing the driving support system as described above, as a sensor that measures the distance to the target, relative speed, etc., it emits radio waves and receives reflected waves from targets such as vehicles and obstacles. A vehicle-mounted radar device that detects time, reflected wave signal intensity, frequency Doppler shift, and the like, and measures the distance to the target and the relative speed based on such information is used.

  Such an on-vehicle radar device is premised on the fact that the radiated radio wave is reflected by a target (vehicle, obstacle, or structure) to be detected and returned as a reflected wave having a predetermined radio wave intensity. . Therefore, by scanning at least one of the transmitter and the receiver within a predetermined range on the left and right, an area in which a radio wave is radiated to a wider range and a reflected wave with a radio wave intensity of a predetermined level or higher can be expected to return. Expansion is considered (Japanese Patent Laid-Open No. 6-273512).

JP-A-6-273512

  However, the intensity of the radio wave emitted by the on-vehicle radar device differs depending on the distance from the radar device and the azimuth angle, so depending on the positional relationship between the own vehicle and the other vehicle, the own vehicle may be scanned even if the transmitter or the receiver is scanned. In some cases, the intensity of the transmitted radio wave from the radar device reaching the point is not sufficient. Also, depending on the shape and orientation of the host vehicle, the reflected cross-sectional area where the radio wave is reflected is small, and the reflected wave with sufficient radio wave intensity may not return to the radar device. In such a case, even if the reflected signal is received by the radar apparatus, information on the host vehicle may not be extracted because the radio wave intensity is attenuated.

  In order to solve such problems, it is essential to improve the on-vehicle radar device itself, but on the other hand, it is also necessary to make the target easy to be recognized by the radar device. Therefore, the present invention improves the ease of recognition (recognition or visibility) by the radar device of another vehicle, and the radar device of the other vehicle can easily detect the presence of the own vehicle even in the above situation. The purpose is to do.

  In order to solve the above-described problem, an on-vehicle radar in which a receiving unit receives a reflected wave reflected from a target by outputting a transmission wave from the transmitting unit, and detects a distance and a relative speed from the target based on the reflected wave. The apparatus includes a means for receiving a transmission wave transmitted from another radar apparatus and a means for transmitting the reception wave from the own radar.

  Preferably, the in-vehicle radar device includes means for amplifying the power of the received wave. Alternatively, in the in-vehicle radar device, the receiving unit may include a discriminating unit that distinguishes a reflected wave transmitted from the transmitting unit from a reflected wave and a transmitted wave transmitted from another radar device. It is set as the structure provided.

  ADVANTAGE OF THE INVENTION According to this invention, the recognizability of the own vehicle by the radar apparatus of another vehicle can be improved.

  An in-vehicle radar device according to an embodiment of the present invention will be described below with reference to the drawings.

  Before describing a specific configuration of the on-vehicle radar device, characteristics of target recognition by the on-vehicle radar device will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a diagram illustrating an example of a relationship between a direction in which radio waves are irradiated and a reflection cross-sectional area of a vehicle. The concentric circular graph indicates that the reflection cross-sectional area of the vehicle is larger toward the outside of the circle. From this figure, it can be seen that the reflection sectional area from the front or side of the vehicle increases, but the reflection sectional area from the oblique direction decreases. Therefore, depending on the orientation of the target with respect to the on-vehicle radar device, the signal intensity of the reflected wave necessary for detecting the target may not be obtained.

  FIG. 2A is a diagram illustrating an example of the positional relationship between the in-vehicle radar device and the target when the target is present at the end of the transmission wave. This is a frequently occurring situation when the vehicle is traveling.

  FIG. 2B is a diagram illustrating an example of the relationship between the antenna angular direction and the antenna gain. The horizontal axis is the angular direction, and the vertical axis is the antenna gain. From this figure, it can be seen that when the target is present at the end of the transmission wave, both the transmission antenna gain and the reception antenna gain are reduced.

  In general, the signal intensity of the reflected wave, the reflection cross-sectional area, and the antenna gain have a relationship represented by Expression (1). Therefore, when the reflection cross-sectional area is small and the antenna gain is small, the signal strength of the reflected wave is reduced. Therefore, when the target is present at the end of the transmission wave, the signal strength of the reflected wave may not be sufficiently obtained.

ここで、Ｐｒは受信電力（反射波の信号強度）、Ｐｔは送信電力、Ｇｔは送信アンテナゲイン、Ｇｒは受信アンテナゲイン、σは反射断面積、Ｒａｎｇｅは距離、Ｋは比例係数である。

Here, Pr is the received power (signal intensity of the reflected wave), Pt is the transmission power, Gt is the transmission antenna gain, Gr is the reception antenna gain, σ is the reflection cross section, Range is the distance, and K is the proportional coefficient.

  From the above characteristics, it can be seen that there is a region where sufficient reflected wave intensity cannot be secured only by passive reflection. In view of this point, embodiments of the present invention are as follows, for example.

  FIG. 3 is a diagram showing a block configuration of the in-vehicle radar device according to the first embodiment of the present invention.

  In FIG. 3, the on-vehicle radar device includes a modulation processing unit 301, a signal generation device 302, a transmission side changeover switch 303, a power amplifier 304, a transmission antenna 305, a reception antenna 306, and a reception side changeover switch 307. , A mixer 308, a demodulation processing unit 309, an A / D converter 310, a signal processing unit 311, and a switch switching processing unit 312.

  Hereinafter, the role of each block and the like will be described by taking as an example the case where the radar method is a two-frequency CW (Continuous Wave) method.

  The switch switching processing unit 312 performs processing for switching between two different functions inside the radar, a target detection function and a received wave retransmission function. Switching between the two functions is executed by a signal input from the outside of the switch switching processing unit 312. When a signal indicating the presence of an interference wave is input, the received wave retransmission function is executed for a certain period of time, and then the target detection function is switched.

  It should be noted that switching between the two functions can be performed by alternately switching in time without using an externally input signal.

  Hereinafter, the target detection function and the received wave retransmission function will be described.

  First, the target detection function will be described. The modulation processing unit 301 applies two different voltages v 1 and v 2 to the signal generator 302. The signal generator 302 generates high-frequency signals having two different frequencies f1 and f2 corresponding to the voltages v1 and v2. This high frequency signal is input to the power amplifier 304 through the transmission side changeover switch 303, amplified to a signal of an appropriate size, and then input to the transmission antenna 305, and the transmission radio waves of the frequencies f1 and f2 are radiated into the space. The The transmission radio wave is reflected by a target such as a vehicle or an obstacle (not shown) and input to the reception antenna 306 as a reception radio wave.

  At this time, the Doppler frequency (fd) generated by the relative speed with respect to the target is added to the transmission high-frequency signal (hereinafter referred to as the transmission signal) to the reception high-frequency signal (hereinafter referred to as the reception signal). Therefore, the frequency of the received signal is f1 + fd and f2 + fd, respectively.

  The reception signal input to the reception antenna 306 is input to the mixer 308 through the reception side changeover switch 307, mixes the transmission signal and the reception signal, generates an intermediate frequency signal, and then inputs this to the demodulation processing unit 309. . The signal demodulated by the demodulation processing unit 309 is input to the A / D converter 310 and input to the signal processing unit 311. The signal processing unit 311 is a processor such as a DSP, for example.

  Second, the received signal retransmission function will be described. When a transmission wave (hereinafter referred to as an interference wave) from another radar apparatus (not shown) is irradiated to the own radar apparatus, the interference wave is received from the reception antenna 306. This interference wave is input to the power amplifier 304 through the reception side changeover switch 307 and the transmission side changeover switch 303. After being amplified to a signal of an appropriate size by the power amplifier 304, it is input to the transmitting antenna 305 and re-radiated into space. The power amplifier 304 may perform retransmission by giving an amplitude equivalent to the amplitude of the received interference wave. This is because when other radars have a mechanism for obtaining some information based on the radio wave intensity of the reflected wave, a signal may be amplified and retransmitted, which may cause erroneous recognition. Therefore, when the radio wave intensity of the interference wave is greater than or equal to a predetermined value, the signal is retransmitted with the same amplitude, and when the radio wave intensity of the interference wave is less than the predetermined value, it may be amplified and retransmitted. In this way, by amplifying and retransmitting the transmission wave from another radar device as it is, when viewed from the other radar device, it appears as if the reflection of sufficient radio wave intensity is returning from the target. Can do. Therefore, the host vehicle can be easily recognized by other radar devices.

  As shown in the present embodiment, since the waveform of the received signal is amplified and retransmitted as it is, there is no need to recognize or acquire another radar modulation method. Therefore, the visibility of the host vehicle can be improved not only for the radar device of the same modulation method as the device itself but also for the radar device of another method.

  Next, specific processing of the signal processing unit 311 included in the in-vehicle radar device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart of a routine executed by the signal processing unit 311 and is repeated at predetermined time intervals.

  When the routine is started, first, the FFT processing in step 100 is executed, and an FFT signal including frequency spectrum information is generated.

  Note that the FFT processing can be selected from processing by software or processing by a dedicated circuit such as an ASIC.

  Next, the interference wave confirmation process in step 101 is executed. In the interference wave confirmation, the presence of the interference wave is confirmed from the FFT signal.

  Here, an example of the interference wave confirmation method will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of a frequency spectrum generated by FFT processing. The horizontal axis represents the frequency of the received signal, and the vertical axis represents the signal strength of the received radio wave. This example shows a case where a reflected wave and an interference wave from the target are received simultaneously. The band to which the reflected wave from the target belongs can be known in advance from the modulation method of the own radar apparatus. In the two-frequency CW method used for the on-vehicle radar device, the signal is about 0 to 30 kHz. For this reason, the peak in the own radar use band is determined to be a peak due to a reflected wave from the target. On the other hand, since the interference wave often exists outside the band used by the radar, it can be determined that the interference wave exists when there is a certain peak or more in this band.

  Next, step 102 is executed, and when the presence of the interference wave is confirmed, the notification process of step 103 is started, and when the presence of the interference wave is not confirmed, the physical value conversion process of step 104 is started.

  When the presence of the interference wave is confirmed, first, the notification process in step 103 is executed, and a signal is sent to the notification device 313 to notify the driver vehicle that the interference wave exists.

  Next, switch switching processing in step 104 is executed, and a signal is sent to the switch switching processing unit 312 to switch between two different functions inside the radar described above, thereby a function of amplifying and retransmitting the interference wave. validate.

  If the presence of the interference wave is not confirmed, the physical value conversion process of step 105 is executed, and the target distance is calculated by the equation (2) based on the FFT signal.

ここで、Range は距離、Ｃは光速度、φは受信電波におけるｆ１とｆ２の位相差、Δｆはｆ１とｆ２の周波数差である。

Here, Range is the distance, C is the speed of light, φ is the phase difference between f1 and f2 in the received radio wave, and Δf is the frequency difference between f1 and f2.

  Further, the relative speed of the target is calculated by Expression (3).

ここで、Ｒａｔｅは相対速度、Ｃは光速度、ｆｄはドップラ周波数、ｆは送信周波数である。

Here, Rate is a relative speed, C is a speed of light, fd is a Doppler frequency, and f is a transmission frequency.

  FIG. 6 is a diagram illustrating a block configuration of the in-vehicle radar device according to the second embodiment of the present invention.

  In FIG. 6, the on-vehicle radar device includes a modulation processing unit 301, a signal generation device 302, an adder 314, a power amplifier 304, a transmission antenna 305, a reception antenna 306, a mixer 308, and a received synthesized wave separation. A processing unit 315, a demodulation processing unit 309, an A / D converter 310, and a signal processing unit 311 are provided.

  Hereinafter, the role of each block and the like will be described by taking as an example the case where the radar method is a two-frequency CW (Continuous Wave) method.

  The modulation processing unit 301 applies two different voltages v 1 and v 2 to the signal generator 302. The signal generator 302 generates high-frequency signals (hereinafter referred to as modulated transmission waves) having two different frequencies f1 and f2 corresponding to the voltages v1 and v2. This modulated transmission wave is input to the adder 314, combined with the output of the reception combined wave separation processing unit 315 (hereinafter referred to as a transmission combined wave), input to the power amplifier 304, and converted into a signal of an appropriate size. After being amplified, it is input to the transmitting antenna 305 and radiated into the space. The transmitted combined wave is reflected by a target such as a vehicle or an obstacle (not shown) and input to the receiving antenna 306.

  At this time, the Doppler frequency (fd) generated by the relative velocity with the target is added to the transmission composite wave, so that the components of the modulated transmission wave in the transmission composite wave are f1 + fd and f2 + fd (hereinafter referred to as target reflection). And is received from the receiving antenna 306. At this time, when a transmission wave (hereinafter referred to as an interference wave) from another radar apparatus (not shown) is irradiated to the own radar apparatus, the interference wave is received from the reception antenna 306. Therefore, the radio wave received by the receiving antenna 306 is a radio wave (hereinafter referred to as a received combined wave) in which either one of the target reflected wave and the interference wave or both are combined.

  The received combined wave input to the receiving antenna 306 is input to the mixer 308 and mixed with the modulated transmission wave to generate an intermediate frequency signal, which is then input to the received combined wave separation process. The received combined wave input to the received combined wave separation processing unit 315 is separated into an interference wave and a target reflected wave, and then the interference wave is input to the adder 314 and the target reflected wave is input to the demodulation processing unit 309. . The signal demodulated by the demodulation processing unit 309 is input to the A / D converter 310 and input to the signal processing unit 311. The signal processing unit 311 is a processor such as a DSP, for example.

  Next, specific processing of the signal processing unit 311 included in the in-vehicle radar device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a flowchart of a routine executed by the signal processing unit 311 and is repeated at predetermined time intervals.

  When the routine is started, first, the FFT processing in step 110 is executed, and an FFT signal including frequency spectrum information is generated.

  Note that the FFT processing can be selected from processing by software or processing by a dedicated circuit such as an ASIC.

  Next, the physical value conversion process in step 111 is executed. When the physical value conversion process is executed, the target distance is calculated by the above equation (2) based on the FFT signal. Further, the relative speed of the target is calculated by the above equation (3).

  Next, a configuration method of the reception synthesized wave separation processing unit 315 included in the in-vehicle radar device according to the second embodiment of the present invention will be described with reference to FIGS. 8 (a) and 8 (b).

  FIG. 8A is a diagram illustrating an example of a frequency spectrum of a received synthesized wave. The horizontal axis represents the frequency of the received combined wave, and the vertical axis represents the signal intensity of the received combined wave.

  The band in which the target reflected wave is detected can be known in advance from the modulation method of the own radar device. In the two-frequency CW method used for the on-vehicle radar device, a target reflected wave is detected in a band of about 0 to 30 kHz.

  FIG. 8B is a diagram illustrating an example of frequency characteristics of the low-pass filter and the high-pass filter. The horizontal axis is frequency and the vertical axis is gain. By appropriately using the low-pass filter 316, the band including the target reflected wave can be separated from the received combined wave. Further, by appropriately using the high-pass filter 317, it is possible to separate the band including the interference wave from the received combined wave.

  As described above, the received combined wave separation processing unit 315 that separates the interference wave and the target reflected wave from the received combined wave can be configured.

  FIG. 9 is a diagram showing a block configuration of an in-vehicle radar device according to Embodiment 3 of the present invention.

  The present embodiment is characterized in that the received combined wave separation processing unit 315 is installed in a high frequency band (hereinafter referred to as an RF band) when compared with the configuration of the on-vehicle radar device of the above-described second embodiment. The difference from the second embodiment is the configuration method of the received combined wave separation processing unit 315. Hereinafter, a configuration method of the received combined wave separation processing unit 315 in this configuration will be described with reference to FIGS.

  FIG. 10A is a diagram illustrating an example of a frequency spectrum of a received synthesized wave. In this example, there is an interference wave having a frequency higher than the transmission frequency of the own radar apparatus and an interference wave having a frequency lower than the transmission frequency of the own radar apparatus. The horizontal axis represents the frequency of the received combined wave, and the vertical axis represents the signal intensity of the received combined wave.

  The band in which the target reflected wave is detected can be known in advance from the modulation method of the own radar device. In the two-frequency CW method used in the on-vehicle radar device, a target reflected wave is detected in a band of about 76.5 GHz ± 30 kHz.

  FIG. 10B is a diagram illustrating an example of frequency characteristics of the bandpass filter and the band elimination filter. The horizontal axis is frequency and the vertical axis is gain. By appropriately using the bandpass filter 318, a signal in a band including the target reflected wave can be separated from the received combined wave. Further, by appropriately using the band elimination filter 319, it is possible to separate both the band (1) including the interference wave and the band (2) including the interference wave from the received combined wave.

  As described above, the received combined wave separation processing unit 315 that separates the interference wave and the target reflected wave from the received combined wave can be configured.

  Needless to say, the band-pass filter and the band elimination filter can be realized by appropriately combining a low-pass filter and a high-pass filter.

  In the first to third embodiments described above, the modulation processing unit 301 can identify a modulated transmission wave transmitted by the own radar apparatus by adding a special code. As a result, the target reflected wave is received in a state where special code information is added, and is decoded by the demodulation processing unit 309, so that the influence of the interference wave can be further reduced. It becomes possible to further improve the reliability of.

  In the above-described first to third embodiments, the characteristics of these filters so that the inter-vehicle distance warning system, the adaptive cruise control system, the pre-crash system, and the like can realize appropriate control characteristics according to road conditions and the surrounding environment. By switching between, it is possible to provide a more comfortable and reliable system.

  In the first to third embodiments described above, the two-frequency CW method is particularly described as an example. However, for example, the same effect can be obtained with other modulation methods such as an FMCW method that modulates the frequency of a radio wave into a triangle in terms of time. It is done.

  In the first to third embodiments described above, the 76 GHz band is particularly described, but the same effect can be obtained at other frequencies.

  As described above, when the signal strength of the reflected wave is not sufficiently obtained due to the direction of the target, it is difficult for the radar device to detect the target, or the target exists at the end of the transmission wave. Even when it is difficult to detect the target by the own radar device when the signal strength of the reflected wave is not sufficiently obtained, by making the other radar device detect the presence of the own vehicle, it is possible to It is possible to provide an in-vehicle radar device that can reduce the possibility of being involved in an accident.

The figure which shows an example of the relationship between the direction where the electromagnetic wave was irradiated, and the reflective cross-section of a vehicle. The figure which shows an example of the positional relationship of a vehicle-mounted radar apparatus and a target, and the relationship between the angle direction of an antenna, and antenna gain. 1 is a block diagram of an in-vehicle radar device according to a first embodiment of the present invention. The flowchart of the signal processing in the vehicle-mounted radar apparatus which concerns on 1st embodiment of this invention. The figure which shows the frequency spectrum in 1st embodiment of this invention. The block diagram of the vehicle-mounted radar apparatus which concerns on 2nd embodiment of this invention. The flowchart of the signal processing in the vehicle-mounted radar apparatus which concerns on 2nd embodiment of this invention. The figure which shows the frequency spectrum in 2nd embodiment of this invention, and the frequency characteristic of a low-pass filter and a high-pass filter. The block diagram of the vehicle-mounted radar apparatus which concerns on 3rd embodiment of this invention. The figure which shows the frequency spectrum in 3rd embodiment of this invention, and the frequency characteristic of a low-pass filter and a high-pass filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 301 ... Modulation process part, 302 ... Signal generator, 303 ... Transmission side changeover switch, 304 ... Power amplifier, 305 ... Transmission antenna, 306 ... Reception antenna, 307 ... Reception side changeover switch, 308 ... Mixer, 309 ... Demodulation process part 310 ... A / D converter, 311 ... signal processing unit, 312 ... switch switching processing unit, 313 ... notification device, 314 ... adder, 315 ... received synthesized wave separation processing unit, 316 ... low pass filter, 317 ... high pass filter, 318 ... Band pass filter, 319 ... Band elimination filter, 320 ... FFT processing unit, 330 ... Interference wave confirmation processing unit, 340 ... Notification processing unit, 350 ... Physical value conversion processing unit.

Claims (11)

In the in-vehicle radar device that receives the reflected wave reflected from the target by outputting the transmission wave from the transmission means, and detects the distance and relative speed with the target based on the reflected wave,
When a transmission wave transmitted from another radar apparatus is received, a signal having substantially the same waveform as the reception wave is transmitted from the transmission unit. In claim 1,
A vehicle-mounted radar device comprising means for amplifying the power of the received wave. In claim 1 or 2,
The in-vehicle radar device characterized in that the receiving means includes a discriminating means for distinguishing between a reflected wave transmitted from the transmitting means and reflected from a target and a transmitted wave transmitted from another radar apparatus. . In claim 3,
The on-vehicle radar device, wherein the discrimination means is a band limiting filter. In claim 3,
The discriminating unit adds a modulation code to the transmission wave transmitted from the transmission unit, and determines whether the modulation wave is detected when the received signal is demodulated. A vehicle-mounted radar device that distinguishes from a transmission wave. In any one of Claims 3 thru | or 5,
An on-vehicle radar device comprising amplification means for amplifying the amplitude of a transmission wave of another radar device discriminated by the discrimination means. In claim 6,
A vehicle-mounted radar device comprising means for synthesizing a transmission wave transmitted from the transmission unit and the amplified transmission wave of another radar device.   8. The on-vehicle radar device according to claim 7, further comprising means for transmitting the combined wave. In claim 1 or 2,
Switching between the function of detecting the distance and relative velocity with respect to the target based on the reflected wave reflected from the target by the transmitted wave transmitted from the transmitting means, and the function of retransmitting the transmitted wave transmitted from another radar device An on-vehicle radar device comprising switching means. The on-vehicle radar device according to claim 9, wherein the function switching unit is a switching circuit. In any one of Claims 1 thru | or 10,
An in-vehicle radar device comprising: a notification unit that notifies a driver that a transmission wave of another radar device has been received.

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