JPH11237466A - Radar calibration equipment - Google Patents

Abstract

(57) [Problem] To provide a small and inexpensive radar calibration device capable of accurately calibrating the distance to another vehicle and the relative speed. At the time of calibration, a radio wave propagates like an oscillator 101, a changeover switch 103, a directional coupling element 106, and a waveguide 107, is reflected by a reflector, and propagates backward through the waveguide 107 to perform directional coupling. It flows from 106 to the processing device 105. With the position and speed of the reflector determined in advance,
The detected value, that is, the position and speed obtained from the difference between the frequencies of the transmitted wave and the received wave are compared. The oscillation characteristics are controlled so that they match. This makes it possible to correct fluctuations and distortions in the oscillator oscillation frequency, and correctly detect the distance to the target and the speed of the target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration device for a radar device which detects a reflector with high accuracy by using a continuous signal such as a radio wave, and more particularly to a distance measurement to the reflector and a reflector and a measuring device. Small size that accurately calibrate the relative speed with
The present invention relates to an inexpensive radar calibration device.

[0002]

2. Description of the Related Art Radars using radio waves are sometimes used to prevent collision of automobiles and to ensure safe driving. Regarding the prevention of collision by radar, see, for example, the Journal of the Institute of Electronics, Information and Communication Engineers (October 1996, Vol. 79N).
o. The method and principle are described in detail in “10) Development Trend of Millimeter-Wave Radar for Automobile”. Radar systems are roughly classified into pulse systems and FMCW (Frequency Modulated Con
There are a tinuous wave) system, a two-frequency CW system, and a spread spectrum system, and three systems other than the pulse system use signals that are temporally continuous.

[0003] These radar devices measure the distance to another vehicle and the relative speed between the other vehicle and the own vehicle. However, it is clear that if the transmission frequency, phase characteristics, and the like are different from the initial state due to a change in the temperature or a change with time of the oscillator, a measurement error is caused.

[0004] However, no attention is paid to these points, and measurement values including errors are used, which poses a problem from the viewpoint of risk determination.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art and provides a small and inexpensive radar calibration device capable of accurately calibrating the distance to another vehicle and the relative speed.

[0006]

According to the radar calibration apparatus of the present invention, a waveguide whose propagation speed and length of a radio wave are known is provided.
Utilize the reflected wave inside. That is, a waveguide having a known length and a propagation speed of a radio wave is used, and the reflector is moved in the waveguide. As a result, data of a moving object having a known moving speed at a known position can be obtained from the radar device.
Based on this data, the characteristics of the oscillator are controlled to match the known position and relative speed.

As an example of the present invention, consider the above-mentioned FMCW radar. As shown by the solid line in FIG.
In the FMCW radar, the frequency is modulated in a triangular waveform. As shown by the broken line in FIG. 2A, the frequency of the detection wave is at a position delayed by the round-trip time of the radio wave to the detection target, and
A signal whose frequency fluctuates by the Doppler frequency proportional to the relative speed between the target and the radar is obtained. In the example of FIG. 2A, the center frequency of reception is higher than that of the transmission wave, and the Doppler frequency is positive, that is, the target is closer to the radar side. FIG. 2B shows the frequency difference between transmission and reception. In FIG. 2B, Δf is a frequency change from the transmission wave due to the delay of the round-trip time of the radio wave, and fd is the Doppler frequency, which is proportional to the relative speed.

From the sum and difference of Δf−fd and Δf + fd, Δ
f and fd can be individually detected. However, these detection processes basically assume that the inclination of frequency modulation, the center frequency, and the like are known. When the use of the radar is started, the modulation characteristics cannot be confirmed, and it is not guaranteed that the modulation is performed linearly.

In the present invention, a waveguide having a known length and speed is used in which the reflector is moved. As a result, data of a moving object having a known moving speed at a known position can be obtained. It is characterized in that the characteristics of the oscillator are controlled so as to match the known position and relative speed based on this data.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to embodiments. FIG. 1 is a diagram showing a basic configuration of a radar calibration device according to the present invention. In FIG. 1, a detection target such as a vehicle to be detected is 1, and a radar device 100 obtains a relative speed between the position and a radar. Radar device 10
On the transmitting side of 0, an oscillator 101 having a modulation function and a signal from the oscillator 101 are sent to a transmitting antenna 102,
Alternatively, there is a changeover switch 103 for sending to a calibration device described later, and a radio wave is transmitted from the transmission antenna 102 when a target is detected. The reflected wave of the object 1 is detected by the receiving antenna 104, and the processing device 105 performs processing and displays the result. The oscillator 101, the transmitting antenna 102, the receiving antenna 104, and the processing device 105 described so far are not different from the configuration of a normal CW (Continuous Wave) radar device.

In the present invention, the changeover switch 103 is provided, and the directional coupling element 106 is further added. The directional coupling element 106 has the waveguide 107 coupled thereto and the waveguide 10
At the end of 7, a driving device 10 for the reflector moving in the waveguide
There are eight. Changeover switch 103, drive unit 108
Is controlled by the control device 109, which will be described in detail later. The directional coupling element 106
Known ones can be used.

To explain the flow of radio waves, the oscillator 101 and the changeover switch 10
3. A radio wave is transmitted by the transmitting antenna 102, and the reflected wave is
It flows to the receiving antenna 104 and the processing device 105. On the other hand, the flow of the radio wave at the time of calibration passes through the oscillator 101, the changeover switch 103, the directional coupling element 106, and the waveguide 107, and is reflected by the reflector driven by the reflector driver 108. The directional coupling element 10 propagates in the opposite direction.
6 to the processing device 105.

Here, the waveguide 107 will be described. The waveguide needs to have a certain length, but if it is formed of a general waveguide, there is a problem that the device becomes large. For this reason,
The present invention is characterized in that the waveguide is provided in the case outer wall of the radar case. The radar device is installed in a metal shield case to prevent external noise. In the present invention, a waveguide is provided inside the outer wall of the case in a tunnel shape. This is shown in FIG. A single waveguide 201 is provided inside the outer wall of the case 2 of the radar apparatus as shown in the cross-sectional view of FIG. 3B to reduce the size of the entire apparatus. In addition to a waveguide, a well-known strip line such as a microstrip line or a triplate line can be used for the waveguide.

Next, the operation at the time of calibration, which is the central part of the present invention, will be described in detail. In normal target monitoring situations,
The changeover switch 103 operates so that a radio wave flows out to the transmitting antenna. On the other hand, at the time of calibration, the switch 103 is switched so that a radio wave flows through the directional coupling element 106. FIG. 4 shows an example of the changeover switch 103. FIG.
Shows a cross section of the waveguide 1031. A metal plate 1032 is provided at a branch portion, and switches the direction of radio waves by rotating about a rotation shaft 1033. This rotation is executed by the rotation control mechanism 1034 according to a signal from the control device 109. One of the waveguides 1031 is coupled to the transmission antenna, and the other is coupled to the waveguide provided inside the case.

The radio wave propagates through the waveguide 107 after passing through the directional coupling element 106. A reflector which is moved by a moving mechanism is provided at a known position of the waveguide 107. FIG. 5 shows an example of the moving mechanism and the reflector. The reflector moving mechanism 108 includes a spring 1081 and the end plate 1 coupled thereto.
082 and a reflector 1083 connected to the end plate 1082 and moving in the waveguide 107 are the main constituent elements. In order to connect and move the end plate 1082 and the reflecting plate 1083, a slit is provided in the waveguide 107 in which the connecting portion moves, and the end plate 1082 and the reflecting plate 1083 are connected via this slit. The spring 10 is controlled by a command from the control device 109.
81 is contracted and extended again by the instruction of the control device 109. The contracted position, the extended position, and the speed of the reflector of the spring 1081 are obtained in advance. The position and velocity of the reflector 1083, which have been obtained in advance, and the detected value, that is,
Δ calculated from the sum and difference of Δf−fd and Δf + fd in FIG.
The position and speed obtained from f and fd are compared. For the sake of simplicity, let us consider a part that raises the frequency in the triangular modulation shown in FIG. At this time, if the inclination of the modulation of the oscillator set in advance is α and the time is t, the set oscillation frequency F
(t) is

[0016]

F (t) = α · t (Equation 1) The signal received by the receiving antenna can be considered that the transmitted wave is delayed by a time Δt, and as is well known, by mixing the transmitted wave and the received wave,

[0017]

F (t + Δt) −F (t) = α · Δt ± Fd (Equation 2) Here, Fd is the Doppler frequency.

Α is an assumed value, and Δt is a value determined by the length and speed of the waveguide.

Where

[0020]

Α · Δt = ΔF (Equation 3) Since Δf−fd and Δf + fd shown in FIG. 2 are detected values, Δf and fd can be separately obtained from the sum and difference of the two equations. The set values ΔF, Fd are compared with the detected Δf, fd. Normally, Fd and fd almost coincide with each other in the FMCW radar, but may be different in other types of radars. The value of α is adjusted and the frequency of the oscillator is controlled by the control device 109 so that the two coincide with each other.

The above calibration example is an example in which the inclination α of the oscillator is controlled. On the other hand, not only the inclination α but also the oscillation frequency of the oscillator may change in a non-linear manner. The oscillation frequency at this time is defined as N (t) where the deviation from the straight line is N (t).

[0022]

F (t) = α · t + N (t) (Expression 4) The result of mixing with the received signal is

[0023]

F (t + Δt) −F (t) = α · Δt ± Fd + N (t + Δt) −N (t) ± fd (Equation 5) In this case, the detected α · Δt + N (t + Δt) −
Control is performed so that N (t) and ± Fd ± fd become values set in advance. In some cases, control cannot be performed based on a single detection result, and the oscillation frequency is controlled by the control device 109 by fitting a plurality of results.

The details of the calibration device and the method of calibration have been described above. As a result, the oscillation frequency can be calibrated to a predetermined value even if the oscillation frequency of the oscillator fluctuates due to temperature or the like or is distorted with time. Therefore, when the target is actually detected by the radar, the distance to the target and the relative speed of the target can be accurately detected.

As a modification of the above embodiment, it is conceivable that the reflection plate in the waveguide is not moved, that is, detection is performed at fd = 0. On the other hand, in a modified example, detection is performed by changing fd variously.

Another embodiment is characterized in that a plurality of reflectors in the waveguide are provided. In this case, there is a case where the light passes through a front reflector, and a configuration is required in which the reflector is removed from the waveguide as shown in FIG. In the present invention, the driving mechanism 1
A rotating mechanism 1084 is provided on the spring side of the end plate 1082 to rotate and pull up the reflecting plate 1083 about the rotation axis at the end of the end plate 108 and to disturb the flow of radio waves along the inner wall of the waveguide. Providing a plurality of the driving mechanisms has a feature that calibration can be performed at positions where the lengths of the waveguides are different.

In another embodiment, the inside of the waveguide is filled with a dielectric. Examples of the dielectric used include alumina ceramics and fused quartz. The advantage of using a dielectric is that the wavelength in the waveguide is reduced by the dielectric, and the size of the waveguide can be reduced. Further, there is an advantage that the propagation speed of the radio wave is reduced as compared with the case where no dielectric is inserted, the propagation time of the waveguide is equivalently increased, and there is a margin in selecting the detection time width.

The configuration and operation of the present invention have been described in detail in the embodiments. As a result of the present invention, the oscillation frequency can be set to a predetermined value even when the oscillation frequency of the oscillator fluctuates unexpectedly due to temperature or the like or when the oscillation frequency is temporally distorted. Therefore, when actually detecting the target with radar,
The distance to the target and the relative speed of the target can be accurately detected.

[0029]

According to the present invention, the characteristics such as the oscillation frequency of the radar device are obtained by utilizing the detection gap of another vehicle or the like.
Since a waveguide built in the radar case and having a known length and a propagation speed of radio waves is used, it is possible to avoid an increase in the size of the device. Thus, a small calibration device capable of accurately detecting the distance to another vehicle and the relative speed thereof can be configured, and the engineering effect is large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a radar calibration device according to the present invention.

FIG. 2 is a diagram illustrating a modulation method of an FMCW radar and a frequency of a detection signal.

FIG. 3 is a diagram illustrating a waveguide provided inside a case of the radar device.

FIG. 4 is a diagram illustrating a configuration of a changeover switch.

FIG. 5 is a diagram illustrating a driving mechanism of a reflector in a waveguide.

FIG. 6 is a diagram showing another embodiment of the drive mechanism of the reflector in the waveguide.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Detection object, 100 ... Radar device, 101 ... Oscillator,
102: transmitting antenna, 103: switch, 1
04 reception antenna, 105 processing device, 106 directional coupling element, 107, 1031 waveguide, 108 driving device, 109 control device, 1032 metal plate, 1033
Rotary shaft, 1034: rotation control mechanism, 1081: spring, 108
2 ... End plate, 1083 ... Reflection plate, 1084 ... Rotating mechanism.

Claims (7)

[Claims] 1. A waveguide for transmitting radio waves from an oscillator in a device for radiating radio waves from a radar device mounted on the vehicle and processing reflected waves to detect the position and relative speed of another vehicle or an obstacle, A driving device for moving a movable reflector at a preset position of a waveguide, and means for processing a reflected wave of the reflector to obtain a sum of a distance from an oscillator to a reflector position and a distance from the reflector to the processing device. And a means for determining the moving speed of the reflector, and controlling the oscillation frequency of the oscillator so that the detected distance and the moving speed approach a predetermined value. 2. The radar calibration apparatus according to claim 1, wherein a waveguide for moving the reflector is provided inside an outer wall covering the radar apparatus. 3. The radar calibration apparatus according to claim 1, wherein the plurality of reflective moving bodies inside the waveguide are controlled so as to deform the moving body so that radio waves can pass through the specific moving body. A unique radar calibration device. 4. A radar calibrating apparatus according to claim 1, wherein the moving speed of the reflection movable body inside the waveguide is controllable. 5. A radar calibration apparatus according to claim 1, wherein the waveguide is a waveguide, and the whole or a part of the waveguide is filled with a dielectric. apparatus. 6. A radar calibrating apparatus according to claim 1, wherein said waveguide is a strip line. 7. The radar calibration apparatus according to claim 1, wherein the calibration of the radar and the detection of an object such as another vehicle are executed in a time sharing manner.