JPS5839313B2 - dotsupra radar - Google Patents

Description

[Detailed description of the invention] The present invention relates to a Doppler radar.

As a direction-discriminative CW Doppler radar, two mixers are provided, and the local signal is supplied with a phase difference of π/2 and the received signal is supplied in the same phase, or the local signal is supplied with the same phase and the received signal is supplied with a phase difference of π/2. A device that discriminates the direction of movement of a target (whether it is approaching or receding from the radar) from the phase relationship of the two Doppler signals obtained from these two mixers. It is publicly known.

The present invention provides a CW Doppler radar configured as described above so that the velocity of a moving target can be accurately determined in a desired direction of movement from the two Doppler signals of the CW Doppler radar.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, 1 is a microwave oscillator, 2 and 3 each supply a part of the output of the microwave oscillator 1 as a local signal to mixer 6 and mixer 7 with a phase difference of π/2, and the remaining A directional coupler 4 supplies most of the microwave oscillator 1 to the antenna 5 and sends the power received by the antenna 5 to the directional couplers 6 and 7. 5 is a transmitting/receiving antenna that irradiates the circulator output to a moving target and receives the reflected wave; 6; 7 is a mixer that mixes the local signal and the received signal and outputs a Doppler signal; 8 is a mixer that amplifies only the frequency range of the Doppler signal output from the mixer 6 that corresponds to the moving speed range of the target to be detected; (Fig. 2, 31, 3)
9 is a band amplification device that amplifies only the frequency range of the Doppler signal output from the mixer 7 that corresponds to the range O of the moving speed of the target to be detected (see Figure 2). Figure 3b
@ Teru), 10 is the instantaneous level of the output of the band amplifier 8 when the switch 18 (to be described later) is turned on to the T1 side, and the instantaneous level of the output of the band amplifier 9 when it is turned on to the T2 side to a constant value ■' (Output converted to mixer 6 vA) When the output is above ゛°1'', when it is below, the output is
A level comparator that outputs 0'' (see Figure 2 a, c, Figure 3 a, c, when the switch 18 is on the T1 side), 11 is a band increaser when the switch 18 is on the T1 side. T2 side of the output of the band amplifier 9 (if this is ON, output when the instantaneous level of the output of the band amplifier 8 is above a certain value VB' (converted output VB of mixer 7)! 111 When it is below T, output II O
A level comparator that outputs IT, provided that ■A'σB'(VA<
VB).

Naori 8' is unaffected by the noise level.
A level close to C is selected, and B' is selected so that velocity calculation is performed when a Doppler signal higher than that level is obtained.

(See Figures 2b and d and Figures 3 and d, but when the switch 18 is turned on to the T1 side) 12 is the level comparator 10
A delay circuit that delays the output of the circuit by a fixed time TdA (see Fig. 2 C2e1 Fig. 3 c, e), 13 inputs the output of the level comparator 11 to the D terminal, and inputs the output of the delay circuit 12 to the clock (CL) terminal. A D-type flip-flop (hereinafter referred to as D-FF) whose Q output is a signal corresponding to the D terminal input at the rising edge of the clock input (see Figure 2).
+fz See d, e, f in Figure 3. However, f indicates the Q output.

)14 uses the Q output of D-FF13 as the reset terminal input, counts the clock (CLI) while the Q output is IT Oll, and outputs the output 11.11 when the number of clocks σ corresponding to the fixed time TM is reached. Time TM counting circuit, (second
(see Figures f, q, Figure 3 f, q), 15 is D-FF13
A wave number counting circuit that uses the Q output of the reset terminal manually and counts the number of pulses of the level comparator input and output while the Q output is 011;
16 is a memory circuit that stores the count of the wave number counting circuit 15 when the output of the counting circuit 14 becomes 1'' for a certain time; 17 is a memory circuit that delays the output of the counting circuit 14 for a certain period of time by TDB and transmits this output to the D-FF 13; A delay circuit 18 inputs the output of the band amplifier 8 to the level comparator 10 and the output of the band amplifier 9 to the level comparator 11 when measuring the speed of an approaching target. When measuring the speed of a moving target, the output of the band amplifier 8 is supplied to the level comparator 11, and the output of the band amplifier 9 is supplied to the level comparator 10. Switching of the moving direction of the target to be measured switch”.

Next, the operation will be explained using FIG.

First, consider a case where a target to be detected approaches.

However, it is assumed that the changeover switch 18 is connected to the T1 side.

In this case, the Doppler signal output from the mixer 6 is delayed in phase by π/2 compared to the Doppler signal output from the mixer 7.

After both signals are band-amplified by band-amplifier 8 and band-amplifier 9, both outputs are input to level comparators 10 and 11, respectively, and the outputs become as shown in FIG. 2c and d.

After the output of the level comparator 10 passes through the delay circuit 12, the output of the level comparator 11 is directly input to the clock terminal and D terminal of the D-FF13, respectively.If the D input is 1'' at the rising edge of the clock input, the D-FF13 The Q output of 1' is +1011 when the D input is 0.

That is, a state in which the Q output of the D-FF 13 is '1' is a state in which the Doppler signal level is above a certain value and the target is approaching.

If the Doppler signal wave number is counted for a certain period of time while this state continues, the speed of the approaching target can be accurately measured with a sufficient Doppler signal level.

Also, when the Doppler signal level does not exceed a certain level for one cycle during wave number counting, the D-FF13
When the D terminal is turned on, the clock terminal input signal rises and the Q output of D-FF13 is "1" (the Q output is "0").
”), and the count values of the fixed time counting circuit 14 and the wave number counting circuit 15 are reset.

Therefore, the fact that the output of the counting circuit 14 becomes "1" for a certain period of time means that the Doppler signal level continues to be above a certain level within the wave number counting time TM and the phase of the output of the mixer 6 is equal to that of the mixer 7. It can be said that the phase was behind the output phase by π/2.

Next, consider the case where the target is moving away.

(See FIG. 3) In this case, the phase relationship between the output of the mixer 6 and the output of the mixer 7 is such that the former leads the latter by π/2.

Therefore, even if the Doppler signal level is above a certain value, the output of the level comparator 11 is O'' when the output of the delay circuit 12 rises, and therefore the Q output of the D-FF 13 is 1'' and speed counting is not performed. .

The above is an explanation regarding the detection of a target that is approaching, but for detection when the target is moving away, the output of the band amplifier 8 is sent to the level comparator 11, and the output of the band amplifier 9 is sent to the level comparator 10. This is possible by turning on the changeover switch to the T2 side to connect.

Also, instead of the CW Doppler radar having two mixers as shown in Figure 1, the mixer uses a Doppler signal obtained as a sideband of an odd-order harmonic of the modulation signal frequency and an even-order harmonic in one FM Doppler radar. Needless to say, it is impossible to employ a method in which direction discrimination is performed based on the phase relationship of Doppler signals obtained as sideband waves of harmonics (including zeroth order).

In the embodiment of the present invention, velocity was measured by counting Doppler wave numbers within a certain period of time, but it goes without saying that velocity can be measured by, for example, measuring the period of the Doppler signal.

As described above, by counting Doppler wave numbers during the period determined by the Doppler radar of the present invention, accurate speed counting can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating a Doppler radar according to an embodiment of the present invention, and FIGS. 2 and 3 are waveform diagrams illustrating its operation. 1...Microwave oscillator, 2,3...
Directional coupler, 4...Circulator, 5...
...Antenna, 6.7...Mixer, 8,9
... Bandwidth amplifier, 10°11 ... Level comparator, 12 ... Delay circuit, 13 ...
・D type flop flop, 14.15...
Counting circuit, 16... Memory circuit, 17...
・Delay circuit.

Claims (1)

[Claims] 1. A first, which is supplied with a part of the transmitted wave with a phase difference of π/2 and a received wave with the same phase, or with a received wave with a phase difference of π/2 and a part of the transmitted wave with the same phase, respectively. a second mixer; and a first level comparator that outputs an output u111 when the instantaneous level of the output of the first mixer is above a certain level (VA), and outputs an output '011' during other times; a second level comparator that outputs an output 'D' when the instantaneous level of the output of the second mixer is above a certain level (VB%, however, VB>VA), and outputs an output '0' during other times; a flip-flop means that outputs an output corresponding to the output of the second level comparator when the output of the first level comparator rises; and a fixed time counting circuit that counts a fixed time from when the flip-flop means is inverted. , a wave number counting circuit that counts the output wave number of the first level comparator for a certain period of time counted by the certain time counting circuit from the time when the flip-flop means is inverted; A Doppler radar that is characterized by determining the velocity of an object in a more specific direction. 2 A part of the transmitted wave is supplied with a phase difference of π/2 and a part of the transmitted wave is supplied with the same phase, or a part of the transmitted wave is supplied with a phase difference of π/2 and a part of the transmitted wave is supplied with the same phase. , the instantaneous level of the output of the first or second mixer is a constant level (VA)
Outputs ``1'' during the above period and outputs ``1'' during other periods.
The instantaneous levels of the outputs of the first level comparator that outputs 1 and the second or first mixer are at a constant level (vB, VB>V
A) A second level comparator which outputs an output e+ I I+ during the above period and outputs an output "091" during other times;
switching means for switching the connection between the second mixer and the first and second level comparators; and an output corresponding to the output of the second level comparator when the output of the first level comparator rises. a fixed time counting circuit for counting a fixed time from the time of inversion of the flip-flop means; and a fixed time counting circuit for counting a fixed time from the time of inversion of the flip-flop means; A Doppler radar comprising a wave number counting circuit that counts output wave numbers of a level comparator, and determining an object speed in a specific direction from the counted value of the wave number counting circuit.