JPH0431782A - Microwave circuit device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave circuit device for detecting the speed of a traveling vehicle and the presence of a vehicle when the traveling vehicle has stopped.

[Conventional technology]

FIG. 6 is a block diagram showing an example of a conventional microwave circuit device for a Doppler radar that measures the speed of a running vehicle.
FIG. 7 is a diagram showing changes in the amplitude fluctuation period of the Doppler signal. In the figure, (1) is the oscillator, (2) is the oscillator (1
) is an isolator to stabilize the output and oscillation frequency, (8) is a circulator to switch the path of the transmitted wave and reflected wave, and (9) is a circulator that emits the transmitted wave into space and receives the reflected wave from the target object. A common transmitting and receiving antenna for
(11 is a mixer for extracting the Doppler frequency shift from the reflected wave, (14) is a directional coupler for extracting a part of the transmitted wave as a local signal of the mixer aω.

Next, the operation will be explained. As is well known, two frequencies f0
When the transmitted wave is reflected by a target object moving at a relative velocity vr, the reflected wave undergoes a Doppler frequency shift ft shown in equation (1) below.

2v.

f reef = ro, - (it (C = 3 x 10'm /s) The output waveform of the mixer scream of the reflected wave that has undergone the Doppler frequency shift fa is as shown in Figure 7, and the Doppler The frequency shift f can be measured.

The relative velocity (2) of the target object can be determined from the following equation (2).

[Problem to be solved by the invention]

When a conventional Doppler radar microwave circuit device that operates as described above is used as a traffic information service device for road congestion, etc., when there is no Doppler frequency shift, it may be caused by congestion or no traffic volume. There was a problem in that it became difficult to determine whether the

This invention is as described above! The purpose of this invention is to provide a microwave circuit device that can determine, even when there is no Doppler frequency shift, whether it is due to congestion or no traffic at all. do.

[Means to solve the problem]

The microwave circuit device according to the present invention pulse-modulates the transmitted wave with a high-speed high-frequency switch and detects the level of the reflected wave during the reception period, thereby identifying whether the transmitted wave is a reflected wave from a vehicle or a road surface. This is how it was done.

[Effect]

The microwave circuit device according to the present invention can determine the relative speed of a traveling vehicle by measuring the Doppler frequency shift, and even when there is no Doppler frequency shift, it is possible to determine whether it is due to congestion or there is no traffic at all. [Embodiment] Fig. 1 is a block diagram showing the configuration of a microwave circuit device according to the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, and Figs. The figure is a block diagram showing the circuit configuration related to the improvement of the present invention, and FIG. 5 is an explanatory diagram of the operation of FIGS. 3 and 4.

In the figure, (3) is the first high-speed high-frequency switch for pulse modulating the output of the oscillator (11), and (4) is the terminator.

(5) is a transmitting circuit, (6) is a first directional coupler for extracting a part of the transmitted wave from the transmitting circuit (5) as a mixer local signal, and (7) is a reflected wave from a target object. (11) is a high frequency amplifier to amplify the reflected wave from the target to a predetermined level.

(12) is a detector for detecting the reflected wave from the target and extracting it as a video signal; (13) is a second high-speed high-frequency switch that is turned off during the transmission period and turned on during the reception period.

Next, the operation will be explained. In FIG.

The output waveform of the transmission line (5) pulse-modulated by the first high-speed high-frequency switch (3) is the second rI! It becomes like J(a).

In FIG. 2(,), To is the period during which the first high-speed high-frequency switch (3) is in the ON state (transmission period), and T2 is the period in which the first high-speed high-frequency switch (3) is in the OFF state (reception period). This pulse modulated wave is radiated into space by the transmitting/receiving antenna (9), reflected by the traveling vehicle, and received again.The output waveform at the reflected wave nomimixer a is shown in Fig. 2 (b), and its envelope is The Doppler frequency shift can be measured using the line, and the relative speed of the vehicle can be determined.

On the other hand, detection! At the input end of (12), there are leakage waves of transmitted waves such as reflected waves due to mismatching of the transmitting/receiving antenna (9) as shown in Fig. 2(c), and the target object shown in Fig. 2(a). The reflected wave from the detector (12) is input as 11 tatami, and the output waveform of the detector (12) becomes as shown in Fig. 2(e).
By sampling and holding the level of the output wave at the vehicle and determining whether the level is higher or lower than the level of the reflected wave from the road surface, it is possible to identify whether the reflected wave is caused by the vehicle or the road surface. Therefore, even when there is no Doppler frequency shift, it is possible to determine whether it is due to congestion or no traffic at all.

In addition, the level of the leakage wave during transmission shown in FIG. 2(c) is large, and the high frequency amplifier (11) or the detection It! (12)
When the subsequent receiving circuits become saturated, the recovery time becomes longer depending on their circuit configuration or the circuit elements used, and reflected waves from nearby vehicles may not be detected during the receiving period. An example of the output of the receiving circuit after the detector (12) in this case is shown in FIG. 2(f).

FIGS. 3 and 4 are block diagrams showing circuit configurations for solving the above problem. Second high speed high frequency switch (
13) is turned off during transmission and turned on during reception to suppress the level of leakage waves during transmission, thereby avoiding saturation of the receiving circuit after the high frequency amplifier (11) 4 or the detector (12). . Figure 5(a) shows the transmitting circuit (5
) is detected in Figure 5(b)! (12) An example of the output of the receiving circuit after that is shown. In addition, the high frequency amplifier (11
) If the glue recovery time is not a problem, the high frequency amplifier (11
), the output power is limited by the saturation level of the second high-speed high-frequency switch (13), so there is an advantage that the isolation level when the second high-speed high-frequency switch (13) is turned off can be reduced.

Furthermore, if it is possible to quickly switch between operation and non-operation of the high-frequency amplifier (11), the second high-speed high-frequency switch (13) can be omitted and the high-frequency amplifier (11) can be directly turned on and off. You can.

〔Effect of the invention〕

According to the microwave circuit device according to the present invention.

A microwave circuit device that can determine the relative speed of a traveling vehicle by measuring Doppler frequency shifts, and even when there is no Doppler frequency shift, can determine whether it is due to congestion or no traffic at all. It has the effect of being able to provide

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a microwave circuit device according to the present invention, FIG. 2 is an explanatory diagram of the operation of FIG. 1, and FIGS. , FIG. 5 is an explanatory diagram of the operation of FIGS. 3 and 4, FIG. 6 is a block diagram showing an example of a conventional microwave circuit device for a Doppler radar that measures the speed of a running vehicle, and FIG. FIG. 3 is a diagram showing changes in the amplitude fluctuation period of a signal. In the figure, (1) is an oscillator, (2) is an isolator, (
3) is the first high speed high frequency switch, (4) is the terminator, (
5) is a transmitting circuit, (6) is a first directional coupler, (7)
is the second directional coupler, (8) is the circulator, (9
) is a shared transmitting and receiving antenna, (+01 is a mixer, (2
1) l yo high frequency amplification M. (12) is a detector, and (13) is a second high-speed high-frequency switch. (14) is a directional coupler. Note that the same line numbers in the two figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A transmission circuit consisting of an oscillator, an isolator for stabilizing the frequency and output of the oscillator, and a first high-speed high-frequency switch that pulse-modulates the output of the oscillator, and a transmitting/receiving antenna that radiates into space and receives a reflected wave from the target; a mixer that extracts Doppler frequency shift due to the target using a beat signal of the transmitted pulse and the reflected wave from the target;
a first whose input terminal is connected to the output terminal of the transmitting circuit and whose coupling terminal is connected to the local signal input terminal of the mixer;
a directional coupler, a terminal circulator whose input terminal is connected to the output terminal of the first directional coupler and whose output terminal is connected to the input terminal of the transmitting/receiving antenna; a second directional coupler whose input terminal is connected to the output terminal of the second directional coupler and whose coupling terminal is connected to the input terminal of the mixer; A microwave circuit device comprising: a high-frequency amplifier that amplifies the signal to a level of (2) Between the output end of the second directional coupler and the input end of the high frequency amplifier in order to prevent the receiving circuit after the high frequency amplifier or the detector from becoming saturated due to leakage waves during transmission. Alternatively, the microwave circuit device according to claim 1, further comprising a second high-speed high-frequency switch connected between the output end of the high-frequency amplifier and the input end of the detector.