JPS6013149B2 - Compact radar sensor with malfunction prevention function - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a small radar sensor with a malfunction prevention function, and in particular, to prevent malfunction due to radio wave interference that performs frequency sweep, and to protect the normal function of the small radar sensor from radio wave interference. This invention relates to a small radar sensor with a function to prevent malfunction.

The small radar sensor is composed of a CW Doppler radar, and detects the presence of a target approaching at a relative speed around the speed of sound, and outputs a predetermined detection signal.

FIG. 1 shows a secondary Nozu type radar sensor that does not have a malfunction prevention function.

In this figure, an antenna 2 is connected to a self-excited oscillator 1, and this antenna 2 emits a high-frequency signal from the self-excited oscillator 1 into space. Receive reflected waves. The self-excited oscillator 1 receives the reflected wave via the antenna 2, and as a result, fluctuations (autodyne detection output) occur in its current consumption. This fluctuation is amplified by a low frequency amplifier 3 connected to the self-excited oscillator 1 and then applied to the trigger circuit 4.
When the fluctuation waveform amplified by the low frequency amplifier 3 reaches a predetermined frequency and amplitude, the trigger circuit 4 outputs a trigger signal to the output terminal 5 indicating that the target has approached. By the way, in the above configuration, if there is radio wave interference that causes frequency distortion, the self-excited oscillator 1 will be affected by this external radio wave and its current consumption will fluctuate.

Therefore, when the false fluctuation waveform amplified by the low frequency amplifier 3 reaches an appropriate frequency and amplitude, the trigger circuit 4 generates an erroneous trigger signal. That is, since the conventional small radar sensor does not take any measures against radio wave interference, it has the disadvantage of causing an erroneous trigger operation due to radio wave interference. The present invention aims to eliminate the drawbacks of the above-mentioned prior art and provide a small radar sensor with a malfunction prevention function that prevents malfunctions due to radio wave interference and improves reliability.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a small radar sensor with a malfunction prevention function according to the present invention will be described with reference to the drawings. FIG. 2 shows a first embodiment of the invention. In FIG. 2, an antenna 2 is connected to an oscillator 1 via a coupler 8, and a high frequency signal from the oscillator 1 is radiated into space from the antenna 2 via a coupler IQ. At the same time, the self-excited oscillator 1
The antenna 2 receives reflected waves from the target when the target approaches the antenna 2 via the coupler 10. Furthermore, a low frequency amplifier 3 is connected to the self-excited oscillator 1 in order to amplify fluctuations in its current consumption caused by reflected wave signals, etc.
The fluctuation waveform amplified here is applied to the gate circuit 11 as an input signal. On the other hand, a mixer 2 is connected to the coupler 0' so that a part of the radio signal received by the antenna 2 is branched by the coupler 10 and added.

The mixer 2 further connects the self-excited oscillator 1 via the supply path 13.
The radio wave signal is mixed with the high frequency signal to generate a beat signal that vibrates based on the frequency difference between the two signals. This beat signal is amplified only in a predetermined frequency range by the Obishiro amplifier 14, and the gate circuit 11
is added as an open/close signal to open/close it. and,
The output of the gate circuit 11 drives the trigger circuit. In this case, the pass frequency band of the low frequency amplifier 3 is set to fL, ~f2, as shown in Fig. 4, and the pass frequency band of the band amplifier 14 is similarly set to fH, ~f.
fL2, and fL. <fL2<fH. <fH2. In the above configuration, when a target approaches when there is no radio wave interference, the current consumption of the signal excitation oscillator 1' fluctuates due to the reflected wave signal from the target, and the output of the low frequency amplifier 3 changes as shown in Figure 5. A low-frequency Doppler beat signal as shown in a appears, and this is the gate circuit turtle 11.
This can be added.

At the same time, a similar Doppler beat signal is generated at the output of the mixer 12, but "the Obishiro passing characteristic of the Obishiro amplifier 14 is such that the above-mentioned Doppler beat signal generated by the original target does not pass through. are set in advance, so no significant signal appears in the output.As a result, the gate circuit remains open and the Doppler beat signal, which is the output signal of the low frequency amplifier 3, is As a result, a trigger signal indicating that the target has approached is outputted to the output terminal 5, similar to the conventional small radar sensor.On the other hand, if there is an interfering radio wave that causes L frequency fringing, The self-excited oscillator is affected by the interference radio waves, causing fluctuations in its current consumption.

As a result, the output of the low frequency amplifier 3 has a signal similar to that generated when the target approaches the original target (Fig. 5b)! A false signal like this appears. At the same time, the interference radio wave is branched by the coupler 10 and added to the mixer 12, where it is mixed with the output of the self-excited oscillator 1. As a result, a high frequency beat signal as shown in waveform A in FIG. 5c is generated at the output of mixer i2. This beat signal continues until the frequency of the interfering radio wave approaches the frequency of the self-excited oscillator 1 and a pull-in phenomenon occurs, at which point the frequency of the self-exciting oscillator 1 matches the frequency of the interfering radio wave, and for now The beat signal will no longer appear because it will be dragged along by the interfering radio waves for a while. Even while this pull-in occurs, the self-excited oscillator tortoise fluctuates in its current consumption as described above, so a false signal as shown in FIG. 5b appears at the output of the low-frequency amplifier 3. Eventually, the pull-in limit is reached, and when the pull-in is removed, the frequency of the self-excited oscillator 1 returns to the original self-excited oscillation frequency.The fluctuation in the current consumption of the self-excited oscillator 1 subsides, and the false signal as shown in Figure 5b disappears. However, a high-frequency beat signal as shown in waveform B in FIG. Since this is the period during which the false signal is generated, the beat signals appearing at the output of the mixer 12 are always generated in a time relationship that sandwich the false signal from both sides.In other words, two beat signals are generated immediately before and after the false signal. The beat signal is amplified by the Obishiro amplifier 14 and applied to the gate circuit 11. When the two lotus beat signals come together, the gate circuit 11 closes only for the period sandwiched between the two beats. The false signal output from the low frequency amplifier 3 is blocked, and the trigger circuit 4 is not activated.Furthermore, if a nearby target appears in the presence of interference radio waves that sweep the frequency, the output of the low frequency amplifier 3 does not contain the target signal. A mixture of Doppler repeat signals indicating the proximity of the radio waves and false signals caused by interfering radio waves appear.

On the other hand, the output of the band amplifier 14 has two signals indicating the presence of false signals.
A lotus beat signal is generated. As a result, gate circuit 1
1 prevents the activation of the trigger circuit 4 when a false signal arrives, but since the proximity signal continues to appear even after the false signal disappears, the proximity signal activates the trigger circuit 4 and sends a trigger signal to the output terminal 5. Output. As explained above, according to the above embodiment, it is possible to reliably eliminate malfunctions caused by interference radio waves that perform frequency sweeping.

Note that the decrease in sensitivity of the self-excited oscillation circuit 1 due to the addition of the coupler 10 and the supply path 13 can be compensated for by increasing the oscillation voltage within the circuit, so that changes in characteristics due to the addition of the malfunction prevention function can be virtually ignored. FIG. 3 shows another embodiment of the invention.

In FIG. 3, an antenna 2 is connected to the self-excited oscillator 1, and a broadband amplifier 20 is connected to the output side of the self-excited oscillator 1. This broadband amplifier 20' also handles the Doppler beat signal generated by the approach of the target and the necessary part of the beat signal (usually 100 KHz to IMH) generated due to interference radio waves.
Z) has the bandwidth to pass both. and,
The output of the wideband amplifier 20 is passed through a low frequency filter 21 whose cutoff frequency is set so as not to pass the latter beat signal.
The signal is applied as an input signal to the gate circuit 11 via.
That is, a Doppler beat signal indicating the approach of a target and a low-frequency false signal generated by interference radio waves are input as input signals to the gate circuit 11. On the other hand, the output of wideband amplifier 20 is also applied to bandpass amplifier 14 . This band amplifier 14 extracts only the beat signal caused by the interference radio wave, amplifies it, and supplies it to the gate circuit 11 as an opening/closing signal. The frequency band of the low frequency filter 21 corresponds to fL, ~fL2 in FIG. 4, and the frequency band of the band amplifier 14 corresponds to fH, ~fL2 in the same figure.
Corresponds to fH2. Further, the frequency band of the wideband amplifier 20 should be wider than h, to fH2. In addition, gate circuit 1
1 drives the trigger circuit 4. In the above configuration, when a target approaches without radio wave interference, no beat signal is generated due to radio wave interference and the output of the band amplifier 14 is zero, so the gate circuit 11 triggers the Doppler beat signal in an open state. It is connected to a circuit 4, thereby outputting a trigger signal to an output terminal 5 indicating that the target has approached.

When radio wave interference exists, this generates a beat signal, which is selectively amplified by the Obishiro amplifier 14 and applied as an opening/closing signal to the gate circuit 11, so that the gate circuit 11 operates as in the case of FIG. actuated to prevent false signals from being supplied to the trigger circuit 4.

That is, it can be considered that the self-excited oscillator 1 also functions as the mixer 12. As described above, in any of the embodiments, malfunctions caused by interference radio waves that perform frequency sweeping can be reliably eliminated. In particular, the first embodiment is characterized by a configuration suitable for modifying a currently used small radar sensor, and other embodiments can be applied to the circuit without changing the principles and functions of the first embodiment. Since the configuration is simplified, it has advantages such as being small, lightweight, and inexpensive. Thus,
To obtain a small radar sensor with a malfunction prevention function, which has improved reliability as a function to prevent malfunctions caused by radio wave interference.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional small radar sensor, FIG. 2 is a block diagram showing an embodiment of a small radar sensor with a malfunction prevention function according to the present invention, and FIG. 3 is a block diagram showing another embodiment of the present invention. FIG. 4 is a block diagram showing an example, FIG. 4 is a characteristic diagram showing the frequency pass band strength of the amplifier, and FIG. 5 is a characteristic diagram showing the output signal waveform of the amplifier. 1... Eye excitation oscillator, 2... Antenna, 3...
...Low frequency amplifier, 4...Trigger circuit,
5...Output terminal, 10...Coupler, 11...
...Gate circuit, 12.... ...Mixer, 14...Obijo amplifier, 20...Broadband amplifier, 21...
Low frequency filter evening. Figure 1 Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] 1. A self-excited oscillator that generates a high frequency wave, an antenna that radiates this high frequency wave into space and receives reflected waves, and extracts an autodyne detection signal of the self-excited oscillator output generated by the reflected wave. a first circuit; a second circuit that extracts a beat signal generated between the high frequency wave and an interfering radio wave that has a frequency passing characteristic in a frequency region higher than that of the first circuit and performs a frequency sweep; A small radar sensor with a malfunction prevention function, comprising a gate circuit that is opened and closed by the output of the second circuit and blocks the output of the first circuit when interference radio waves are present. 2. The first circuit includes a low frequency amplifier that selectively amplifies the autodyne detection signal, and the second circuit includes a mixer that receives the high frequency signal and the received signal from the antenna, and selects the beat signal from the output of the mixer. A small radar sensor with a malfunction prevention function according to claim 1, characterized in that the small radar sensor is comprised of a band amplifier that amplifies the noise. 3. The first circuit is a low frequency filter that passes only the autodyne detection signal from the self-excited oscillator output that has been amplified to a predetermined size, and the second circuit selectively passes the beat signal. The compact radar sensor with malfunction prevention function according to claim 1, characterized in that it is a band amplifier for amplification.