JPS62100673A - Fm-cw apparatus - Google Patents

Abstract

PURPOSE:To enable the detection of relative velocity every second, by performing a frequency modulation so that the period during which a transmitting frequency changes linearly with respect to time and the period during which it is constant may appear alternately. CONSTITUTION:First, in the transmitting system, an oscillation frequency of an oscillator 4 is modulated with a modulator 5 which performs a frequency modulation so as to alternately repeat the period during which the transmission signal frequency changes linearly with respect to time and the period during which it is constant, and the oscillation output is transmitted into space from an antenna 1 via a directional coupler 3 and a circulator 2. Then, in the receiving system, a receiving signal from a target is mixed by a receiving mixer 6 with a part of the transmission signal passing via the couple 3, and an output of the mixer 6 is processed by a signal processing section 7. Here, the mixer 6 alternately outputs a frequency f1 of a difference during the period in which the frequencies of the transmitting signal and the receiving signal both changes linearly and a frequency f2 of a difference during the period wherein the frequencies of the transmitting signal and the receiving signal are both constant. Then, a processing section 7 receives the signal with the frequency of f1 and the signal with the frequency of f2 to calculate the relative distance and velocity directly.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides an FM-C for detecting relative distance and relative velocity.
W (Frequency Modulation-C
(Arrier l/ave) radar device.

(Prior Art) Regarding a conventional FM-CW radar device, a functional block diagram thereof is shown in FIG. The relationship between the output frequency and time of the receiving mixer 6 is shown in FIG.
In the conventional FM-CW I/-der device shown in FIG. 4, first, in the transmission system, the modulator 5' adjusts the oscillation frequency of the oscillator 4' so that the transmission frequency becomes a triangular wave as shown in FIG. 5 with respect to time. , and its oscillation output is sent to the directional coupler 3. Next, in the receiving system, the received signal reflected from the target and returned from the antenna 1 is mixed with a part of the transmitted signal that has passed through the directional coupler in the receiving mixer 6. Then, the output signal of the reception mixer 6 is processed by a signal processing section 7'. Here, the reception mixer 6 outputs a signal having a difference frequency between the transmission signal and the reception signal, as shown in FIG. Since this frequency difference is proportional to the relative distance, the relative distance can be determined by a signal processing circuit.

Furthermore, if it is necessary to know the relative speed to the target, it can be determined from the amount of change over time in the obtained relative distance, so conventionally a relative distance time differentiation circuit was provided in the signal processing section. .

(Problems to be Solved by the Invention) The conventional FM-CW radar device described above requires a complex circuit for time differentiation in the signal processing section in order to determine the relative velocity from the relative distance. In addition, there is a problem that a target whose relative distance changes, that is, whose relative velocity is not zero, has a Doppler shift, which causes an error in the relative distance.

Further, in order to reduce these errors through multiple measurements, more complicated signal processing is required, and when the target moves rapidly, it is extremely difficult to reduce the errors.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, an object of the present invention is to provide an FM-CW radar device that can detect momentary relative speed without using a differentiating circuit or a complicated signal processing circuit. shall be.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following configuration. That is, the FM-CW radar device of the present invention has a frequency that changes linearly with respect to time. Transmitting means for transmitting a frequency-modulated high-frequency signal so as to alternately repeat one period and a constant period; A coupling means for branching and extracting a part of the high-frequency signal; The high-frequency signal is transmitted to a target. a receiver that receives both the received signal reflected and returned by the receiver and the high-frequency signal taken out from the coupling means, and outputs a signal having a frequency that is the difference between the frequencies of the two signals;
Of the output signals of the mixer, the relative distance to the target is calculated from a signal during a period in which the frequencies of the received signal and the high-frequency signal from the coupling means are both changing linearly, and the frequency of both signals is The present invention is characterized by comprising: two signal processing means for calculating a relative velocity with respect to a target object from a signal of a constant period; and;

(Function) The transmitting means of the FM-CW radar device of the present invention transmits a high-frequency signal modulated such that a period in which the frequency changes linearly with respect to time and a period in which the frequency is constant are alternately repeated. Then, the received signal reflected from the target object and a part of the high frequency signal (transmitted signal) taken out from the coupling means are mixed by a mixer, and a signal having a difference frequency between the two signals is taken out.

Here, as in the conventional device, the difference frequency during the period in which the frequencies of the received signal and the transmitted signal both increase and decrease linearly in the same direction is proportional to the relative distance between the radar device and the target. , the relative distance is determined from this difference frequency.

Next, the frequency difference during a period in which the frequencies of the received signal and the transmitted signal are both constant has a value proportional to the moving speed of the target object due to the Doppler effect.

Therefore, the moving speed of the target can be directly determined from the frequency difference between the two signals. The signal processing means receives the signals of these two types of difference frequencies and directly calculates the relative distance and relative velocity from these frequencies. Therefore, there is no need for a circuit that calculates relative velocity by differentiating relative distance with respect to time, or for complex signal processing to correct relative distance errors caused by Doppler shift due to target movement, as in conventional devices. It is possible to detect accurate relative speed even when the movement is rapid.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional 11312 diagram of an embodiment of the present invention. In the FM-CW radar device of the present invention shown in FIG. 1, first, in the transmission system, the transmission signal frequency is
As shown by the solid line in the figure, the oscillation frequency of the oscillator 4 is modulated by the modulator 5, which generates a modulation signal that modulates the frequency so that linearly changing periods and constant periods are alternately repeated, and the oscillation output is Directional coupler 3. It is transmitted into space from the antenna 1 via the circulator 2.

Next, in the receiving system, the received signal reflected from the target and returned is mixed with a part of the transmitted signal that has passed through the directional coupler 3 in the receiving mixer 6, and the output of the receiving mixer 6 is subjected to signal processing. Processing is performed in section 7.

Here, as shown in FIG. 3, the reception mixer 6 uses the difference frequency f1 in a period in which the frequencies of the transmission signal and the reception signal both change linearly, and the difference frequency f1 in a period in which the frequencies of the transmission signal and the reception signal both change linearly. The difference frequency f2 is output alternately.

Further, fl is proportional to the relative distance, and fl is proportional to the relative velocity.

The signal processing unit 7 receives the signal with the frequency fl and the signal with the frequency fl and directly calculates the relative distance and relative velocity.

(Effects of the Invention) As explained above, in the FM-CW radar device of the present invention, the frequency is modulated so that periods in which the transmission frequency changes linearly with respect to time and periods in which it is constant appear alternately. Therefore, by mixing the transmitted signal and the received signal at an appropriate level, a signal with a frequency proportional to the relative distance to the target object and a signal with a frequency proportional to the relative speed of the target object can be obtained alternately. Velocity can be directly determined, and a relative distance time differentiator circuit for determining relative velocity,
There is an advantage that accurate relative distance and relative velocity can be directly determined without providing a complicated signal processing circuit for correcting relative distance errors due to Doppler shift of the moving target.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure shows the frequency versus time relationship of the transmitting signal and the received signal in the receiving mixer 6 of the present invention, FIG. 3 shows the frequency versus time relationship of the output signal of the receiving mixer 6, and FIG. 4 shows the conventional A block diagram showing an example of the configuration of an FM-CW radar device. FIG. 5 is a diagram showing the frequency versus time relationship of a transmitting signal and a receiving signal in the receiving mixer 6 of a conventional FM-CW radar device. FIG. 3 is a diagram showing the relationship between frequency and time of the output signal of mixer 6. FIG. 1... Antenna, 2... Circulator, 3... Directional coupler, 4.4'...
...Oscillator, 5.5'...Modulator, 6...
...Reception mixer, 7.7'...Signal processing section. Agent Patent Attorney Yoshi Hachiman Hiromoto Yosho's History Example No. 1 Figure Reception Mi Kakiiri Ka Isa No. Zhou Tire A Jou I L Half 2 Zu Uke 1 Goose Mikichim Power Signal Me Frequency - Figure 3 Follower car - FM-C-V Toda L, groove 71 2' No. 4 Reception, double mixer No. 5 - 7 Drop fLTIL fixed/brush
5 Fig. 6. Fig. 6. Fig. 6. Fig. 6.

Claims (1)

[Claims] a transmitting means for transmitting a frequency-modulated high-frequency signal such that a period in which the frequency changes linearly with respect to time and a period in which the frequency is constant; and a coupling means for branching and extracting a part of the high-frequency signal. and; Receives both the received signal from which the high-frequency signal was transmitted and returned after being reflected by the target object, and the high-frequency signal taken out from the coupling means, and outputs a signal having a frequency that is the difference in frequency between the two signals. a mixer that calculates the relative distance to the target from the output signal of the mixer during a period in which the frequencies of the received signal and the high-frequency signal from the coupling means both change linearly; An FM-CW radar device comprising: signal processing means for calculating a relative velocity with respect to a target object from signals during a period in which both frequencies of the FM-CW radar device are constant.