JP2002277536A - Frequency-modulated continuous wave radar device, reflector device, and radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome the problem that a target object can not be discriminated from the other objects when reflected waves from a plurality of objects are detected. SOLUTION: A reflector antenna 9 receives radio waves from an FMCW(frequency-modulated continuous wave) radar device 100. Only when received power is connected to a reflector 12 by a switch 10 that repeats switching at the repeating frequency of a clock generator 13, the reflected waves are returned to the reflector antenna 9 and again emitted into the air. In the radar device 100, the reflected waves are received by a radar antenna 4 and detected by a detector 5. Then, the waves are frequency-analyzed by a frequency analysis part 6 and stored in a memory 7. With respect to the waveform data stored in the memory 7, a change detecting and signal processing part 8 cancels reflected waves from the other objects than a reflector device 200 by finding the difference between data on the reflected state and data on the terminal state and thus only the reflected wave from the target object is extracted, thereby detecting the target object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting a signal which is frequency-modulated by a modulation signal having a predetermined repetition frequency, receiving a signal obtained by reflecting the transmission signal on a target, and comparing the reflected signal with the transmission signal. The present invention relates to a frequency-modulated continuous wave (FMCW) radar device, a reflector device, and a radar system that detect a target using a beat signal generated therebetween.

[0002]

2. Description of the Related Art Conventionally, an FMCW radar system for detecting a distance to a target and a relative speed is disclosed in JP-A-6-9 / 1994.
What is described in 4829 gazette is known. In a block diagram 7 showing the configuration of a conventional FMCW radar system and a signal waveform diagram 8 in the conventional FMCW radar system, a sweep oscillator 71 generates a transmission wave whose frequency wave number changes at a predetermined repetition frequency as shown in FIG. appear. The generated transmission wave passes through the directional coupler 72 and the circulator 73 and is radiated from the radar antenna 74. The reflector unit 79 mounted on the target is attached to the target when the reflection cross-sectional area of the target is small, so that the FMCW radar apparatus can easily receive the target.

[0003] A received wave reflected back from a target or a reflector unit 79 passes through a circulator 73 from a radar antenna 74, and a part of a transmission wave from a sweep oscillator 71 is detected by a directional coupler 72 by a detector 75. It is mixed with the branched power and detected to obtain a detection waveform as shown in FIG.
The circulator 73 shares the radar antenna 74 for transmission and reception, and is used for separating a transmission wave and a reception wave. The signal detected by the detector 75 is frequency-analyzed by the frequency analysis unit 76 to obtain a waveform as shown in FIG.

[0004] As an example, the frequency analysis unit 76 performs frequency analysis by A / D converting a signal detected by the detector 75 and performing fast Fourier cosine sine transform (hereinafter, referred to as FFT). The signal processing unit 78 analyzes the data stored in the memory 77, and if there is a received signal larger than a preset threshold value, determines that a target exists, and calculates the distance and speed from the frequency and the change in the frequency. As described above, since the target is detected by a simple reflected wave from the object, there is essentially no difference in characteristics between the reflected wave from the target and the reflected waves from other objects.

[0005]

SUMMARY OF THE INVENTION Such a conventional FM
The CW radar system has a problem that a target object cannot be distinguished from other objects when reflected waves from a plurality of objects are detected.

The present invention has been made to solve such a problem, and provides a frequency modulation continuous wave radar device, a reflector device, and a radar system for selectively detecting a target.

[0007]

SUMMARY OF THE INVENTION A frequency-modulated continuous wave radar apparatus according to the present invention comprises a transmitting means for transmitting a radio wave whose frequency is modulated at a constant repetition frequency, a reflected wave of a radar beam radiated from the transmitting means and a transmitting means. A configuration including a detection unit that outputs a beat signal with a radio wave to be transmitted, and a signal processing unit that analyzes a beat signal and performs signal processing for detecting a target, and extracts periodic change information of the target from the reflected wave. have. With this configuration, the target can be selectively detected.

Further, in the frequency modulation continuous wave radar apparatus according to the present invention, the signal processing means extracts a periodic change in the reflectance, and further detects the target by summing the extracted periodic change information. have. With this configuration, it is possible to detect the target even when the reflected radio waves from the target are weak.

Further, in the frequency modulation continuous wave radar apparatus according to the present invention, the signal processing means extracts a periodic change in the reflectance, and further detects the target by taking a majority decision of the extracted periodic change information. have. With this configuration, the detection probability of the target can be improved even when the state of reflection from the target changes or when the signal intensity changes.

Further, the reflector device of the present invention is provided with a reflector device for reflecting a radar beam radiated by a frequency-modulated continuous wave radar device on a target, and a means for periodically changing the reflectance of the reflector. have. With this configuration, a reflected wave capable of selectively detecting a target can be emitted.

Further, the reflector device of the present invention has a structure in which a radio wave absorbing means, a radio wave reflecting means, and a switching means are provided, and the reflectance of the reflector is changed by switching the radio wave absorbing means and the radio wave reflecting means by the switching means. are doing. With this configuration, the reflectance of the reflector can be easily changed.

Further, in the reflector device of the present invention, the switching means has a function of a radio wave reflecting means. With this configuration, the reflectance of the reflector can be changed at low cost.

Further, the radar system of the present invention has a configuration including a frequency-modulated continuous wave radar device for detecting a target from a periodic power change of a reflected wave and a reflector device for periodically changing the reflectance of the reflector. Have. With this configuration, a radar system that can selectively detect a target can be constructed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to these embodiments at all, and can be implemented in various modes without departing from the gist thereof.

FIG. 1 shows a first embodiment of the present invention.
FIG. 10 is a block diagram showing configurations of an FMCW radar device, a reflector device, and an FMCW radar system according to the third to third embodiments. As shown in FIG. 1, the FMCW radar system according to the first embodiment of the present invention
A reflector device 200 including a radar device 100 and a reflector device 200, wherein a radar wave radiated from the FMCW radar device 100 is attached to a target.
And the reflected wave is received by the FMCW radar apparatus 100, and a target is detected based on a beat signal generated between the FMCW radar apparatus 100 and a transmission signal.

That is, the FMCW radar system of the present invention
A swept oscillator 1 having a first repetition frequency, a directional coupler 2 for branching a part of power, a circulator 3 for sharing transmission and reception antennas and separating transmission and reception waves, and a radar antenna 4 for transmitting and receiving radar waves A detector 5 for mixing the received wave returned from the radar antenna 4 through the circulator 3 with the power obtained by branching a part of the transmitted wave from the sweep oscillator 1 by the directional coupler 2 and detecting the mixed wave, A / D conversion FMCW radar comprising a frequency analysis unit 6 composed of a filter and an FFT circuit, a memory 7 for storing waveform information, and a change detection & signal processing unit 8 for detecting a periodic power change of a reflected wave and further analyzing and processing the waveform information. A reflector antenna 9 for receiving the transmission wave radiated from the radar antenna 4 and transmitting a reflected wave, a switch 10 for switching the reflectance, Terminator 11 as a radio wave absorbing means for absorbing a radar wave, a reflector 12 as a radio wave reflecting means for reflecting a received radar wave, and a clock generator 13 for determining a switching frequency (second repetition frequency) of the switch 10. And a reflector device 200.

Next, the operation of the FMCW radar system according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a signal waveform diagram according to the first embodiment of the present invention. The sweep oscillator 1 generates a transmission wave whose frequency changes at the first repetition frequency as shown in FIG.

The generated transmission wave passes through the directional coupler 2 and the circulator 3, and is radiated from the radar antenna 4. The circulator 3 shares the radar antenna 4 for transmission and reception and is used for separating a transmission wave and a reception wave. The vertical axis in FIG. 2A is the frequency of the transmission wave and the horizontal axis is time, and is swept at the first repetition frequency.
Periods (4) to (4) show the time when the reflector device 200 is in the reflection state, and periods (5) to (8) show the time when the reflector device 200 is in the terminal state. (9) The subsequent steps are repeated.

The reflector antenna 9 of the reflector device 200 receives a radio wave from the FMCW radar device 100,
This received power is guided to the terminator 11 or the reflector 12 by the switch 10. Here, the switch 10 repeats the switching with the clock of the second repetition frequency from the clock generator 13, and when the received power is connected to the reflector 12, most of the power except for some power lost in the path is received. The received power is reflected, returns to the reflector antenna 9 through the switch 10, and is radiated again into the air. On the other hand, when the received power is connected to the terminator 11, most of the received power is consumed by the terminator 11 and is hardly radiated into the air again.

The reflected wave from the reflector device 200 is received by the radar antenna 4, passes through the circulator 3, and is detected by the detector 5 by mixing with the power partially branched from the swept oscillator 1 by the directional coupler 2. . Figure 2 shows the detection signal.
As in (B), the vertical axis is the received power and the horizontal axis is the time, which changes according to the state of reflection or termination of the reflector device 200. When the reflector device 200 is in the reflection state, the detection signal becomes large like V11 to V14, and when the reflector device 200 is in the terminal state, the switch 10 is switched to the terminator 11, so that the F signal received by the reflector antenna 9 is received.
Most of the radio waves from the MCW radar device 100
Are not reflected, and the detection signal becomes small as V21 to V24, and the reflected wave from other than the target and the ambient noise become the majority. After V31, the above is repeated.

The detected signal is subjected to frequency analysis by a frequency analysis unit 6 and stored in a memory 7. The frequency analysis in the frequency analysis unit 6 is performed by, for example, performing A / D conversion and FFT of the received signal. The frequency-analyzed signal is as shown in FIG. 2 (C), the vertical axis represents the received power, and the horizontal axis represents the frequency change for each sweep period. When the reflector device 200 is in the reflecting state, the reflected wave from the reflector and other objects There is a reflected wave from the object, and only a reflected wave from an object other than the reflector exists in the terminal state.

The data stored in the memory 7 detects a target by detecting and analyzing a periodic power change contained in the reflected wave by the change detection & signal processing unit 8. FIG.
(D) is a diagram illustrating the processing of the change detection & signal processing unit 8. In the change detection & signal processing unit 8, the frequency analysis data when the reflector device 200 is in the reflection state is represented by F11,
F12, F13, F14, F21, F22, F23, F in terminal state
When expressed as 24, (F11-F21), (F12-F2
2) By taking the difference between the data in the reflection state and the data in the terminal state as in (F13-F23) and (F14-F24),
Since a reflected wave from an object other than the reflector device 200 can be canceled and only a reflected wave from the reflector device 200 can be detected, even if another object that is easily confused with the target object is present near the target object, the target object can be detected. Only can be detected.

As described above, the FMCW radar device, the reflector device, and the FMCW radar system according to the first embodiment of the present invention transmit the radio wave from the FMCW radar device by using the terminator and the reflector of the reflector device in a periodic manner. The target object can be distinguished from other objects and detected by subjecting the reflected wave received by the FMCW radar device to signal processing.

(Second Embodiment) The FMCW radar device, the reflector device and the FMCW radar system according to the second embodiment of the present invention have the same configurations as those of the first embodiment shown in FIG. Since only the processing and operation related to the change detection & signal processing unit 8 are different from those of the first embodiment, the following description will focus on the differences in processing and operation with reference to FIGS. The operation of the FMCW radar system according to the second embodiment will be described. FIG. 3 is a signal waveform diagram of the FMCW radar system according to the second embodiment of the present invention.

First, the detected signal is the same as that of the first embodiment until the frequency is analyzed by the frequency analyzer 6 and stored in the memory 7, so that the detailed description is omitted. The data stored in the memory 7 is analyzed by the change detection & signal processing unit 8 to detect a target. In the change detection & signal processing unit 8, when the frequency analysis data when the reflector device 200 is in the reflection state is represented as F11, F12, F13, F14, and when the reflector device 200 is in the termination state, as F21, F22, F23, F24, F11-F21), (F12-F22), (F13-F2
3) By taking the difference between the data in the reflection state and the data in the terminal state as in (F14-F24), the reflection wave from an object other than the reflector device 200 is canceled and only the reflection wave from the reflector device 200 is detected. And only the target can be detected.

The processing methods of FIGS. 3A to 3D are basically the same as those of the first embodiment.
2 (A) to 2 (D).
However, when the frequency sweep of the sweep oscillator 1 is not synchronized with the switching timing of the switch 10 by the clock generator 13 of the reflector device 200 as shown in FIG. 3A, the reflection state of the reflector device 200 changes. By the way, since the received power of the target decreases, the target may not be correctly detected only by the processing shown in FIG. The present embodiment has been made to solve this problem. As shown in FIG. 3E, a sweep transmission is performed by adding data obtained by taking a difference between the data in the reflection state and the data in the terminal state. Sweep and reflector device 200
Is not synchronized with the switching timing of the switch 10 by the clock generator 13 of FIG.
The target can be correctly detected even in a state where the reception power of the target decreases when the reflection state of the target changes.

As described above, the FMCW radar device, the reflector device, and the FMCW according to the second embodiment of the present invention.
In the MCW radar system, the operation of the signal processing unit in the first embodiment is further added to the data obtained by taking the difference between the data in the reflection state and the data in the termination state. Targets can be detected wherever they change.

(Third Embodiment) An FMCW radar device, a reflector device, and an FMCW radar system according to a third embodiment of the present invention have the same configurations as those of the first embodiment shown in FIG. Since only the processing and operation related to the change detection & signal processing unit 8 are different from those of the first embodiment, the differences in processing and operation will be mainly described with reference to FIG.
FM according to the third embodiment of the present invention with reference to FIG.
The operation of the CW radar system will be described. FIG. 4 is a signal waveform diagram of the FMCW radar system according to the third embodiment of the present invention.

First, the detected signal is the same as that of the first embodiment until it is subjected to frequency analysis by the frequency analysis unit 6 and stored in the memory 7, so that the detailed description is omitted. The data stored in the memory 7 is analyzed by the change detection & signal processing unit 8 to detect a target. In the change detection & signal processing unit 8, when the frequency analysis data when the reflector device 200 is in the reflection state is represented as F11, F12, F13, F14, and when the reflector device 200 is in the termination state, as F21, F22, F23, F24, F11-F21), (F12-F22), (F13-F2
3) By taking the difference between the data in the reflection state and the data in the terminal state as in (F14-F24), the reflection wave from an object other than the reflector device 200 is canceled, and only the reflection wave from the reflector device 200 is detected. And only the target can be detected.

Referring to FIG. 4, FIG. 3 (A) and (B)
Although the signal waveform corresponding to is omitted, the processing method is basically the same as in the second embodiment, and is as described in FIGS. 3A and 3B. Similarly, FIG.
The processing methods of (A) and (B) are basically the same as in the second embodiment, and are as described in FIGS. 3 (C) and (D). However, as shown in FIG. 4A, the frequency sweep of the sweep oscillator 1 and the reflector 200
Is not synchronized with the switching timing of the switch 10 by the clock generator 13 of FIG.
Since the received power from the target decreases as shown in F11, F21, and F31 when the reflection state of 00 changes, FIG.
May not be able to detect the target.
Further, when there is a change in the signal strength due to the movement of the radar apparatus 100 or the reflector apparatus 200, FIG.
In the addition processing according to the second embodiment, the detection of the target may be uncertain. The present embodiment has been made to solve these problems. As shown in FIG. 4C, majority decision processing is performed on data obtained by taking a difference between the data in the reflection state and the data in the termination state.

As described above, the FMCW radar device, the reflector device, and the FMCW according to the third embodiment of the present invention.
In the MCW radar system, the operation of the signal processing unit in the first embodiment is configured to further perform a majority decision process on data obtained by taking a difference between the data in the reflection state and the data in the termination state. Even when the reflection state changes or the signal strength fluctuates, the detection probability of the target can be improved.

(Fourth Embodiment) FIG. 5 is a schematic view showing a configuration of a switch, a reflector and a terminator of a reflector device according to a fourth embodiment of the present invention. In FIG. 5, the waveguide antenna connection port 575 is connected to the switch A 520 and the switch B 530 by performing impedance matching between the distribution matching section 540, the terminator B541, and the shape of the waveguide 570. The reflector 512 is configured by closing one opening of the switch B530. The terminator A 511 is mounted close to the switch A 520, grounds one side of the triangular resistive film 515 having a thickness to the closed waveguide 570, and sets the grounded side to the base of the triangle.
5 is configured to protrude into the inner space of the waveguide 570. The terminator B541 has the same configuration. Switch A
520 is one or more suitable number of switching diodes 52
5 are connected in parallel, the cathode side is installed at the bottom of the waveguide 570, and the anode side is capacitively coupled to the waveguide 570, and has a direct current through a small hole opened in the ceiling of the waveguide 570. Are insulated, and the operation thereof is switched by the bias circuit 550. The switch B530 has the same configuration.

Next, the operation of the thus configured reflector device of the present embodiment will be described. In FIG. 5, the distribution matching unit 540 and the terminator B 541 are configured to transmit a radio wave from the waveguide antenna connection port 575 into a T-shaped waveguide 57.
0 for the switch A 520 and the switch B 530 for impedance matching in two directions, and for distribution.
The bias circuit 550 energizes the switch B 530 and the switching diode 535 is turned on, and the switch A
The switching diode 525 is in an off state while no power is supplied to 520. In this state, the radio wave input from the reflector antenna (not shown) to the waveguide antenna connection port 575 does not proceed to the switch B side where the switching diode 535 is on, and passes through the waveguide 570 to switch the switching diode 525. Passes through the switch A520 in the OFF state, reaches the terminator A511, and the radio wave is absorbed by the resistive film 515 and is not reflected.

Next, the bias circuit 550 is switched to energize the switch A 520 to turn on the switching diode 525, and the switch B 530 is turned off without energizing the switch B 530. In this state, the radio wave input from the reflector antenna to the waveguide antenna connection port 575 does not proceed to the switch A side where the switching diode 525 is on, and the switching diode 535 goes off via the waveguide 570. After passing through B and reaching the reflector 512, the radio wave is reflected and again transmitted through the waveguide 570 to the reflector antenna from the waveguide antenna connection port 575 and transmitted. Here, the switching of the bias circuit 550 is repeated with a clock of a second repetition frequency from a clock generator (not shown), and the other operations are the same as those of the first embodiment.

As described above, in the reflector device according to the fourth embodiment of the present invention, the terminator and the reflector are periodically switched by two switches and reflected.
The reflectance can be easily changed periodically.

Although the above embodiment has been described with reference to the case of a waveguide, the present invention is not limited to a waveguide and a diode switch and a terminator configured in the waveguide, but may be applied to a printed circuit board. A similar effect can be obtained even if the distribution circuit, the diode switch, and the terminating resistor are used. The same effect can be obtained even if the polarity of the anode and cathode of the diodes constituting the switches A and B and the polarity of the bias circuit are reversed.

(Fifth Embodiment) FIG. 6 is a schematic view showing the configuration of a switch and a terminator of a reflector device according to a fifth embodiment of the present invention. In FIG.
Numeral 0 indicates that one or more appropriate number of switching diodes 625 are connected in parallel, and the cathode side is a waveguide 67.
The bottom of the waveguide 670 is grounded, the anode side is capacitively coupled to the waveguide 670, and is insulated DC from a small hole formed in the ceiling of the waveguide 670, and its operation is switched by the bias circuit 650. The waveguide antenna connection port 675 is connected to the switch 620. The terminator 611 is mounted close to the switch 620, grounds one side of the thick triangular resistive film 615 to the closed waveguide 670, and sets the grounded side to the base of the triangular resistive film 615. Waveguide 67 at the top
It is configured to protrude into the internal space of 0.

Next, the operation of the thus configured reflector device of the present embodiment will be described. In FIG. 6, the bias circuit 650 does not energize the switch 620, and the switching diode 625 is off. In this state, a radio wave input from the reflector antenna (not shown) to the waveguide antenna connection port 675 reaches the terminator 611 through the switch 620 in which the switching diode 625 is off, and the radio wave is transmitted to the resistive film 615. It is not reflected by being absorbed by. Next, the bias circuit 650 is switched to energize the switch 620, and the switching diode 625 is turned on. In this state, the waveguide antenna connection port 5
The radio wave input to the reflector antenna 75 is set so that the switching diode 625 is turned on and the interval and position of the diodes are set so as to form a grid-like reflector. Is transmitted to the reflector antenna and transmitted. Here, switching of the bias circuit 650 is performed by a second signal from a clock generator (not shown).
The switching is repeated with a clock having a repetition frequency of, and the other operations are the same as those of the first embodiment.

As described above, the reflector device according to the fifth embodiment of the present invention is configured such that the switch has the function of a reflector. The device can be configured.

Although the above embodiment has been described with reference to a waveguide, the present invention is limited to a waveguide, a diode switch and a terminator formed in the waveguide, as in the fourth embodiment. Even if a distribution circuit, a diode switch, a terminating resistor, and the like are provided on a printed wiring board, the same effect can be obtained. The same effect can be obtained even if the polarity of the anode and cathode of the diodes constituting the switches A and B and the polarity of the bias circuit are reversed.

[0041]

As described above, according to the present invention, the reflector reflectivity of the reflector device is periodically changed, and the frequency-modulated continuous wave radar device is used for the reflector device based on the power change of the reflected wave from the target. By extracting a periodic change in reflectivity, even if a plurality of objects are present, a frequency-modulated continuous-wave radar device having an excellent effect of being able to distinguish between a target object and other objects,
A reflector device and a radar system can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing configurations of an FMCW radar device, a reflector device, and an FMCW radar system according to a first embodiment to a third embodiment of the present invention.

FIG. 2 is a signal waveform diagram of the FMCW radar system according to the first embodiment of the present invention.

FIG. 3 is a signal waveform diagram of an FMCW radar system according to a second embodiment of the present invention.

FIG. 4 is a signal waveform diagram of an FMCW radar system according to a third embodiment of the present invention.

FIG. 5 is a schematic view showing a configuration of a switch, a reflector, and a terminator of a reflector device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic view showing a configuration of a switch and a terminator of a reflector device according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional FMCW radar system.

FIG. 8 is a signal waveform diagram of a conventional FMCW radar system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sweep oscillator 4 Radar antenna 5 Detector 6 Frequency analysis part 7 Memory 8 Change detection & signal processing part 9 Reflector antenna 10,620 Switch 11,511,541,611 Terminator 12,512 Reflector 100 FMCW radar apparatus 200 Reflector apparatus

Claims (7)

[Claims] A transmitting means for transmitting a radio wave frequency-modulated at a constant repetition frequency; and a detecting means for outputting a beat signal of a reflected wave of a radar beam emitted from the transmitting means and the radio wave transmitted from the transmitting means. Signal processing means for analyzing the beat signal and performing signal processing for target detection, and detecting the target by extracting periodic change information of the target from the reflected wave. Characteristic frequency modulated continuous wave radar device. 2. The method according to claim 1, wherein the signal processing unit detects the target by extracting a periodic change in the reflectance and further taking a sum of the extracted periodic change information. Frequency modulated continuous wave radar device. 3. The method according to claim 1, wherein the signal processing means detects the target by extracting a periodic change in the reflectance and taking a majority decision of the extracted periodic change information. Frequency modulated continuous wave radar device. 4. The reflector device according to claim 1, further comprising a reflector mounted on the target object for reflecting a radar beam emitted by the frequency-modulated continuous wave radar device, and comprising means for periodically changing the reflectance of the reflector. . 5. The reflector device includes a radio wave absorbing unit, a radio wave reflecting unit, and a switching unit, and the reflectance is changed by switching the radio wave absorbing unit and the radio wave reflecting unit by the switching unit. The reflector device according to claim 4, wherein: 6. The reflector device according to claim 5, wherein said switching means has a function of said radio wave reflection means. 7. A radar system comprising a combination of the frequency-modulated continuous wave radar device according to any one of claims 1 to 3 and the reflector device according to any one of claims 4 to 6.