JP2008045987A - Radar device, and detection method of short-distance target of radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive radar device capable of recognizing both targets at a short distance and at a long distance, and a detection method of a short-distance target of the radar device. <P>SOLUTION: When a transmission switch 16 is switched off, a leakage signal is output from the transmission switch 16. A leakage radio wave is transmitted from a transmission antenna 17 by the leakage signal, and the short-distance target 20 is detected. When the transmission switch 16 is switched on, a high-frequency signal is output to the transmission antenna 17, and a long-distance target 20 is detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radar apparatus and a method for detecting a short-range target of the radar apparatus. Specifically, the present invention relates to a radar device that recognizes both short-range and long-range targets.

  In general, a long-distance millimeter-wave radar device is mounted on an automobile or the like to recognize (detect) a long-distance target. It would be convenient if such a radar apparatus could be used to recognize not only a long distance but also a short distance target.

  However, a long-distance radar apparatus has a strong transmission output power so that radio waves reach a long-distance target. Therefore, the level of the received signal is too high for a short-range target, and a so-called “saturation” state occurs.

  In order to avoid such a state, for example, it is conceivable to adjust the transmission output power by lowering, but gain adjustment in a high-frequency circuit is difficult and is not generally performed.

  On the other hand, it is conceivable to adjust the gain according to the reception level on the receiving circuit side. However, due to the isolation by the reception antenna and the circuit on the reception side, the transmission signal wraps around the reception signal and the noise level of the reception signal increases. For this reason, it becomes difficult to recognize a target at a short distance.

As a conventional technique of such a radar device, for example, periodicity is detected from a received signal, and if there is periodicity, a transmission signal attenuated by an attenuator (attenuator) is output, so that even a short distance can be measured with high accuracy. A possible microwave level meter is disclosed (Patent Document 1 below).
JP 2004-301617 A

  However, in Patent Document 1, an attenuator that electrically adjusts the amount of attenuation is very expensive. Therefore, the entire apparatus becomes expensive.

  It is also conceivable to provide a radar device that uses both a short distance and a long distance by providing a radar device for short distance measurement. However, it is necessary to provide a separate radar device for short distance, and the entire device becomes expensive.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an inexpensive radar apparatus capable of recognizing both short-range and long-distance targets, and a short-range target detection method of the radar apparatus. There is.

  In order to achieve the above object, according to one embodiment of the present invention, an antenna that transmits a transmission wave to a long-distance target and receives a reflection wave from the long-distance target, and a reception signal by the reflection wave are used. A signal processing circuit that detects the target; and a transmission switch that switches on and off transmission of the transmission wave under the control of the signal processing circuit, and leakage that is output from the antenna when the transmission switch is turned off. The radar apparatus detects a target at a short distance by radio signals using the signal processing circuit.

  In order to achieve the above object, according to another embodiment of the present invention, an antenna that transmits a transmission wave to a long-distance target and receives a reflection wave from the long-distance target, and the reflection wave A signal processing circuit that detects the target from a received signal, and a transmission amplifier that switches on and off transmission of the transmission wave under the control of the signal processing circuit, and outputs from the antenna when the transmission amplifier is turned off. A radar apparatus that detects a target at a short distance by the signal processing circuit based on a leaked radio wave.

  Furthermore, according to another embodiment of the present invention, when the transmission of the transmission wave is turned off in the radar apparatus, the leakage signal from the transmission switch or the transmission amplifier is subjected to FM modulation and the leakage is performed. It is characterized by transmitting radio waves.

  Furthermore, according to another embodiment of the present invention, in the radar apparatus, the signal processing circuit alternately switches on and off the transmission switch or the transmission amplifier, so that the long distance target and the short distance And detecting a target.

  Furthermore, according to another embodiment of the present invention, the radar apparatus further includes a transmission circuit that outputs a transmission signal having a constant frequency, and the signal processing circuit turns off the power of the transmission circuit. Then, transmission of the leaked radio wave is stopped, and interference by another radar apparatus is detected.

  Furthermore, according to another embodiment of the present invention, in the radar device, the signal processing circuit detects a distance and a relative speed of the long distance or the short distance target from the received signal. To do.

  Furthermore, in order to achieve the above object, according to another embodiment of the present invention, an antenna for transmitting a transmission wave to a long-distance target and receiving a reflection wave for the long-distance target, and reception by the reflection wave In a method for detecting a short-range target of a radar apparatus comprising a signal processing circuit for detecting the target from a signal, when the transmission wave transmission is switched on and off by the control of the signal processing circuit, A short-range target is detected by the signal processing circuit based on a leaked radio wave output from an antenna.

  According to the present invention, it is possible to provide an inexpensive radar apparatus capable of recognizing both short-range and long-distance targets, and a short-range target detection method in the radar apparatus.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of a radar apparatus 10 to which the present invention is applied. The radar apparatus 10 can detect the distance and speed of the target 20 at a long distance (relative speed between the target 20 and the radar apparatus 10), and can also detect the distance of the target 20 at a short distance.

  As shown in FIG. 1, the radar apparatus 10 includes a receiving antenna 11, a mixer (MIX) 12, an amplifier (AMP) 13, a signal processing circuit 14, a VCO (Voltage Controlled Oscillator) 15, a transmission switch (SW). ) 16 and a transmission antenna 17.

  The receiving antenna 11 receives a reflected wave (received wave) reflected from the target 20 and outputs a received signal. The mixer 12 mixes the reception signal and the transmission signal from the VCO 15 and outputs the mixed reception signal. The amplifier 13 increases the level of the mixed received signal and outputs it.

  The signal processing circuit 14 performs various signal processing on the received signal from the amplifier 13 to detect the target 20 and the like. Further, the signal processing circuit 14 outputs a control voltage to the VCO 15. Further, the signal processing circuit 14 also outputs a control signal for controlling on / off of the transmission switch 16.

  The VCO 15 outputs a transmission signal (for example, a high frequency signal) having a constant oscillation frequency based on the control voltage from the signal processing circuit 14.

  The transmission switch 16 is controlled to turn on / off the switch 16 based on a control signal from the signal processing circuit 14. When ON, a transmission signal from the VCO 15 is output to the transmission antenna 17. When it is off, the transmission signal from the VCO 15 is not output.

  The transmission antenna 17 outputs a transmission wave based on the transmission signal from the transmission switch 16. This transmitted wave is reflected by the target 20, and this reflected wave is received by the receiving antenna 11.

  Here, attention is paid to the transmission switch 16. Even when the transmission switch 16 is off, if the radar apparatus 10 is powered on, a leakage signal is output from the transmission switch 16. This leakage signal is output to the transmission antenna 17, and a weak leakage radio wave is output from the transmission antenna 17.

  FIG. 2 is a diagram illustrating a configuration example of the radar apparatus 10 when the transmission switch 16 is off. For example, if the transmission power before the transmission switch 16 is “0 dB”, the output of the transmission radio wave is “−3 dB” due to insertion loss when the switch is on (see FIG. 1), but “−40 dB” when the switch is off. It becomes. In this way, when the switch is off, the transmission radio wave is not transmitted at all from the transmission antenna 17, but a weak radio wave is transmitted.

  When such a weak leak signal (or leak radio wave) is used, since the output of the transmit radio wave is very small, the isolation which is a problem on the receiving antenna 11 side does not become a problem. Therefore, the noise level does not increase on the receiving side, and the short distance target 20 can be detected.

  In the present embodiment, it is possible to detect the short-range target 20 by using the weak leak signal generated even when the transmission switch 16 is off and the leaked radio wave due to this leak signal.

  When the transmission is turned off, the leak signal may be subjected to FM modulation so that the target 20 as a stationary object can be detected by the signal processing circuit 14, the VCO 15, the transmission antenna 17, and the like.

  In this manner, the short-range target 20 can also be detected using the radar apparatus 10 configured to detect (recognize) the long-range target 20. Therefore, it is not necessary to separately use a dedicated circuit for a short-distance target, the circuit configuration can be simplified, the cost of the entire apparatus can be reduced, and an inexpensive short-distance and long-distance radar apparatus 10 can be provided.

  The transmission switch 16 in FIG. 3 is an example of a transistor (for example, a MESFET (Metal Semiconductor Field Effect Transistor), which is a kind of FET. Of course, it may be composed of other FETs) and an example of an equivalent circuit thereof. FIG.

3A shows a switch-on state, and FIG. 3B shows a switch-off state. As shown in FIG. 3A, when the voltage V _GS applied between the source and the gate is sufficiently high in the positive direction (for example, V _GS = 0V), the transistor 161 has a resistance of “0. 162 and becomes a low impedance state. At this time, transmission power is output from the source to the drain, that is, from the VCO 15 to the transmission antenna 17. Therefore, the switch is turned on.

  On the other hand, when the voltage VGS applied between the source and the gate is sufficiently increased in the negative direction, the transistor 161 is equivalent to a parallel circuit of a resistor 162 of “several kΩ” and a capacitor 163 of “0 to several pF”. The switch is turned off with high impedance. Therefore, transmission power is not output from the VCO 15 to the transmission antenna 17, and the switch is turned off.

  However, in this case, since an equivalent circuit is configured by the resistor 162 and the capacitor 163, transmission power is not output at all even in the switch-off state, and the loss is large compared to FIG. A signal is output.

  Therefore, similarly to the above-described example, the target 20 at a short distance can be detected by the leaked radio wave using the leak signal. Therefore, it is not necessary to separately provide a short-distance radar device, and the radar device 10 that can be used for both long-distance and short-distance can be provided at low cost. When the transmission amplifier 22 is turned off, it is possible to detect the target 20 stopped by applying FM modulation to the leakage signal by the signal processing circuit 14 or the like as in the above example.

  Note that the voltage applied to the gate of the transistor 161 is controlled by a control signal from the signal processing circuit 14. That is, by this control signal, the impedance to the high frequency signal from the VCO 15 to the transmission antenna 17 changes, and the transmission switch 16 is controlled to be turned on / off.

  FIG. 4 shows an example in which on / off is controlled by an LNA (Low Noise Amp) instead of the transmission switch 16. That is, a reception amplifier (AMP) 21 is provided between the reception antenna 11 and the mixer 12, and a transmission amplifier (AMP) 22 is provided between the VCO 15 and the transmission antenna 17 to control on / off of the reception amplifier 21. This is an example of detecting a target 20 at a long distance and a short distance.

  The transmission amplifier 22 is controlled to be turned on and off by a control signal from the signal processing circuit 14. Even in this case, a weak leak signal is output from the transmission amplifier 22 when it is off, and a leak radio wave is output from the transmission antenna 17. For example, the output of the transmission wave in the on state is “10 dB”, and the output of the transmission wave in the off state is “0 dB”. Even when the amplifier is off, it does not mean that there is no output at all.

  Therefore, similarly to the above-described example, the target 20 at a long distance can be detected when the transmission amplifier 22 is on, and the target 20 at a short distance can be detected by using a leaked radio wave when the transmission amplifier 22 is off. Therefore, the circuit configuration can be simplified, and the radar apparatus 10 that can detect both the long-distance and short-distance targets 20 can be provided at low cost.

  FIG. 5 is a principle diagram for calculating the distance and speed of the target 20 (relative speed between the target 20 and the radar device 20) from the transmitted wave and the reflected wave (received wave), in particular, FMCW (Frequency Modulated Continuous Wave: transmitted wave). A principle diagram based on a method of frequency modulation with a triangular wave is shown.

  FIG. 5A is a diagram showing the relationship between the transmitted wave and the reflected wave. The horizontal axis indicates time, and the vertical axis indicates frequency. With respect to the transmission wave indicated by the solid line, the reflected wave is slightly delayed as indicated by the broken line due to the time delay due to the distance to the target 20 and the speed difference from the target 20 (the relative speed difference between the target 20 and the radar apparatus 10). Detected.

  As shown in the figure, the two frequency differences between the transmitted wave and the reflected wave are “Fu” and “Fd”. FIG. 5B shows the relationship between the two frequencies with the horizontal axis as time. Fu and Fd are detected alternately.

  FIG. 6 is a diagram illustrating the operation of the radar apparatus 10. 6A is operating only at a long distance, FIG. 6B is detecting both a long distance and a short distance, FIG. 6C is detecting both but transmitting off. It is an example in the case of including the state of. Each is an example of a received wave.

  As shown in FIG. 6A, when a long-distance target 20 is detected, received waves are detected at regular intervals. In this case, the signal processing circuit 14 is in a state where the switch 16 is kept on. In the detection of a long distance, the recognition cycle (detection cycle) may be long because of its usage characteristics. For example, it may be about “100 ms”.

  As shown in FIG. 6B, when both the long-distance target 20 and the short-distance target 20 are detected, a reception wave from the long-distance target 20 is detected and then received from the short-distance target 20. A wave is detected. Compared to FIG. 6A, the signal processing circuit 14 detects the short-distance target 20 by using the idle time during which long-distance detection processing is not performed. In this case, the signal processing circuit 14 switches the switch 16 from on to off during this idle time.

  Note that such on / off switching (switching between a long distance and a short distance) is calculated from the received wave as shown in FIG. 5, and can be switched according to the calculated distance.

  Of course, it is possible to improve the performance of the radar apparatus 10 by alternately switching on and off. In the case where the signals are alternately switched, efficient processing can be performed if the reception signals can be sequentially transferred to the signal processing circuit 14 like a pipeline. In FIG. 4, the reception amplifier 21 is provided as an example. For example, a plurality of reception amplifiers 21 may be connected.

  Further, as shown in FIG. 6C, the power of the configuration on the transmission side of the radar apparatus 10 may be turned off to stop the output of the leaked radio wave itself. For example, the power to the VCO 15 is turned off. This can be implemented under the control of the signal processing circuit 14.

  When the received wave is received in this transmission-off state, it is a state in which the received wave is received from another radar device, so that it can be detected that it is receiving so-called interference. As described above, the radar apparatus 10 can repeat the three states of long-distance detection, short-distance detection, and interference detection, and can detect the target 20 with higher accuracy.

  In any of the above-described examples, the radar apparatus 10 in which the transmission antenna 17 and the reception antenna 11 are separately configured has been described as an example. Needless to say, even if the radar apparatus 10 is configured by one antenna that serves both as a transmission antenna and a reception antenna, the radar apparatus 10 can be implemented in the same manner and has the same effects.

  FIG. 7 is a diagram illustrating an example in which the radar apparatus 10 is mounted on the vehicle 100. In the example shown in FIG. 7, the radar apparatus 10 is mounted in front of the vehicle 100, but of course, it may be mounted in any position of the vehicle 100 such as behind. In either case, the same effects as the above-described example are achieved.

It is a figure which shows the structural example of the radar apparatus with which this invention is applied. It is a figure which shows the structural example of a radar apparatus. It is a figure which shows the example of the structural example of a switch circuit, and the example of the equivalent circuit. It is a figure which shows the other structural example of a radar apparatus. It is a figure which shows the relationship between a transmission wave and a reception wave, and the relationship between Fu and Fd. It is a figure which shows operation | movement of this radar apparatus. It is a figure which shows the example of the vehicle carrying this radar apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 radar apparatus, 11 receiving antenna, 12 mixer, 13 amplifier (AMP), 14 signal processing circuit, 15 VCO, 16 transmission switch (SW), 17 transmitting antenna, 20 target, 21 receiving amplifier (AMP), 22 transmitting amplifier ( AMP), 161 transistor, 162 resistor, 163 capacitor

Claims (7)

An antenna for transmitting a transmission wave to a long-distance target and receiving a reflected wave for the long-distance target;
A signal processing circuit for detecting the target from a reception signal by the reflected wave;
A transmission switch that switches on and off transmission of the transmission wave under the control of the signal processing circuit;
A radar apparatus, wherein a short-range target is detected by the signal processing circuit based on a leaked radio wave output from the antenna when the transmission switch is turned off. An antenna for transmitting a transmission wave to a long-distance target and receiving a reflected wave for the long-distance target;
A signal processing circuit for detecting the target from a reception signal by the reflected wave;
A transmission amplifier that switches on and off transmission of the transmission wave under the control of the signal processing circuit;
A radar apparatus, wherein a short-range target is detected by the signal processing circuit based on a leaked radio wave output from the antenna when the transmission amplifier is turned off.   3. The radar apparatus according to claim 1, wherein when the transmission of the transmission wave is turned off, the leakage radio wave is transmitted by performing FM modulation on a leakage signal from the transmission switch or the transmission amplifier. .   3. The signal processing circuit according to claim 1, wherein the long distance target and the short distance target are detected by alternately switching on and off the transmission switch or the transmission amplifier. Radar device. Furthermore, a transmission circuit that outputs a transmission signal having a certain frequency is provided,
The radar apparatus according to claim 1, wherein the signal processing circuit stops transmission of the leaked radio wave by turning off the power of the transmission circuit and detects interference by another radar apparatus.   The radar apparatus according to claim 1, wherein the signal processing circuit detects a distance and a relative speed of the target at the long distance or the short distance from the reception signal. A near-field target of a radar apparatus comprising: an antenna that transmits a transmission wave to a long-distance target and receives a reflected wave with respect to the long-distance target; and a signal processing circuit that detects the target from a reception signal by the reflected wave In the detection method of
According to the control of the signal processing circuit, the transmission of the transmission wave is switched on and off, and when the signal is turned off, a target in a short distance is detected by the signal processing circuit based on a leaked radio wave output from the antenna. Method for detecting a short-range target of a radar device.

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