JPS62147382A - Displacing object detector - Google Patents

Abstract

PURPOSE:To definitely detect the displacing direction of an object and eliminate misinformation on a noise to improve a detecting ability by branching signals from a ultrasonic wave transmitter and receiver into two paths, detecting the signals after mixed with signals having different phases in a mixer in one path and conducting a detection without mixing in the other path to obtain a pair of Doppler signals. CONSTITUTION:Oscillated (1) wave transmitting signals are amplified (2) and applied to a ultrasonic wave transmitter and receiver 3. Ultrasonic waves transmitted from the transmitter and receiver 3 are reflected from an object to be detected and received by the transmitter and receiver 3 to be combined with the wave transmitting signals. The output signals of the transmitter and receiver 3 are divided to two groups and one group is inputted to a detecting circuit 9 directly, the other group, after mixed with signals from an oscillator 1 via a phase shifter 15 in a mixer 14, is inputted to a detecting circuit 8 to obtain a pair of Doppler signals. A phase difference of about 180 deg. from the output signals of the transmitter and receiver 3 is obtained by the phase shifter 15. After a pair of the Doppler signals obtained in the circuits 8 and 9 are amplified (10, 11), whether a displacing object or a noise is discriminated by a signal processing circuit 12 and, when it is judged that the displacing object is present, the object is displayed (13).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] Zero-shot 8A relates to a moving object detection device that detects an object moving within a monitoring space by using the Doppler effect of ultrasonic waves.

[Background technology]

A single ultrasonic transducer emits ultrasonic waves into the monitoring space and receives the reflected waves of the ultrasonic waves from an object to be detected within the monitoring space, resulting in a Doppler signal generated as the object to be detected moves. Various devices have been proposed and implemented in the past for detecting a moving object, especially a human body, in a monitoring space by detecting the object and operating a switch or outputting a detection signal. A conventional moving object detection device with integrated transmission and reception is shown in FIG. In FIG. 3, a transmission signal oscillated by an oscillator tl is amplified by a power amplifier (2) and applied to an ultrasonic transducer (3). The ultrasonic transducer (3) transmits ultrasonic waves corresponding to the applied signal toward the monitoring space, and the transmitted ultrasonic waves are reflected by the object to be detected in the monitoring space, and the ultrasonic wave is transmitted and received. The signal is received by the receiver (3), converted into an electrical signal, and combined with the transmitted signal. The output signal of the ultrasonic transducer (3), in which the transmitted signal and the received signal are combined, is divided into two parts and sent to a mixer +
41+5) respectively. These mixers (41 (
51 local oscillation signals are supplied from the oscillator (1),
The mixer (4) is supplied via a π/4 leading phase shifter (6), and the mixer (5) is supplied via a π/4 lag phase shifter (7). The outputs of both the above mixers +4++51 are detected by the detection circuits (8) and (91) to obtain only the Doppler shift frequency. In other words, when there is an object that continuously moves in a certain direction, such as when a person moves, the phase relationship between a pair of Doppler signals is constant, and the phase relationship is constant, causing jealous oscillations like random noise. When distributed over the upper and lower frequencies, the phase relationship between the pair of Doppler signals becomes random.Therefore, after amplifying the outputs of the detection circuit (8) +9+ with amplifiers (lo) and (o), the signal processing circuit α The above phenomena are distinguished by smell, and when it is determined that there is a moving object, the indicator (I3) is activated.

However, in the case of an integrated transmitter/receiver type, it is difficult to obtain a sufficient phase difference (900) between Doppler signals using the circuit shown in Figure 3.In other words, mixers f4 and f5) adjust the phase of the local oscillation signal. If the phase of the Doppler signal is shifted by φ, the phase of the Doppler signal will be shifted by +φ or −φ.If the received signal frequency is lower than the oscillation signal frequency, it will be +φ, and if it is higher than the oscillation signal frequency, it will be −φ. Since the input signal of +41(5) also includes a transmission component, even if the phase difference of the local oscillation signal is 9d), the phase difference of the Doppler signal is 90°.
I can't get it. FIG. 4 shows these phase relationships in a vector diagram. In FIG. 4, a and b are local oscillation signals, and A is the output of the ultrasonic transducer (3), which is a combination of the transmitted signal A+ and the received signal A2. Now A and a.

When A and b are mixed, since a, b and A1 have the same frequency, the actual mixture is the resultant vector B and A2 of AI and a.
and a mixture of the composite vectors C and A2 of and b. Therefore, the phase difference between the local oscillation signals is equivalent to being small, and the phase difference between the Doppler signals cannot be 90°. In order to increase the phase difference of the local oscillation frequency in this circuit, it is possible to increase the phase shift angle of the phase shifter (6) (7+), but it is difficult to control the phase shift angle, and the circuit The disadvantage is that it is complicated.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to clarify the detection of the moving direction of an object, eliminate false alarms due to noise, and improve reliability in a moving object detection device integrated with transmitter and receiver. The objective is to improve the sensitivity and detection ability and to simplify the device.

[Disclosure of the invention]

In the case of a moving object detection device with integrated transmitter and receiver, when a moving object exists in the monitoring space, the output signal of the ultrasonic transducer changes in amplitude at the Doppler frequency according to the object's moving speed, It is possible to obtain one Doppler signal by directly detecting the output signal of the transducer, or by mixing only one signal with a signal with a phase difference and detecting it, a pair of Doppler signals with a phase difference can be obtained. I can do it. The phase of the two signals to be mixed differs depending on the signal level, but as shown in the vector diagram in Figure 2, if the phase is approximately 180°, a sufficient phase difference can be obtained, and it is possible to obtain a phase difference of 180°. is easy, and the level can be easily set. Here, although the synthesized vector 1 becomes small due to this mixing, there is no problem at all as long as it is larger than the peak 15 of the order signal.

The moving object detection device according to the present invention will be explained below using an embodiment shown in FIG. In FIG. 1, a transmitted signal 8 oscillated by an oscillator t1+ is amplified by a power amplifier (2) and applied to an ultrasonic transducer (3). Ultrasonic transducer (3
) transmits ultrasonic waves corresponding to the applied signal toward the monitoring space, and the transmitted ultrasonic waves are reflected by the object to be detected in the monitoring space and are received by the ultrasonic receiver (3). The signal is converted into an electrical signal and combined with the transmitted signal. When a moving object exists in the monitoring space, the output signal of the ultrasonic transducer (3) changes in amplitude at the Doppler frequency corresponding to the moving speed of the object. Therefore, the output signal of the ultrasonic transducer (3) is divided into two parts, one of which is input to the detection circuit (9) as it is, and the other is sent to the mixer (14) from the oscillator (1) to the phase shifter (15). ) and then input to a detection circuit (8) to obtain a pair of Doppler signals. This phase shifter (15) obtains a phase difference of approximately 1800 with respect to the output signal of the ultrasonic transducer (3), which is inverted with the phase of the output signal of the oscillator (1) in the power amplifier (2). If this is done, the phase shifter α5) becomes unnecessary. Also,
The phase difference between the two signals entering the mixer θ4) is exactly 18
If it is 0°, the phase difference of the Doppler signal cannot be 900°, but since the ultrasonic transducer (3) includes a capacitive component, the phase difference will not be 180°. Next, the pair of Doppler signals obtained by the detection circuit t8) +9+ are amplified by the amplifier (10j (11)), and then the signal processing circuit (12) determines whether there is a moving object or not.
It is determined whether it is noise or not, and when it is determined that a moving object exists, the display device (I3) is driven.

〔Effect of the invention〕

As mentioned above, the present invention transmits signals from an ultrasonic transducer into two
The system is divided into two paths, one of which is detected after being mixed with signals of different phases in a mixer, and the other is detected without being mixed with other signals to obtain a pair of signals. The moving direction of the sensor can be clearly determined, there is no malfunction due to noise, and reliability and detection ability can be improved.
Since the phase difference between the two input signals to the mixer is about 1800, a complicated phase shifter is not required, and the device can be simplified and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a vector diagram of the same as above, and FIG. 3 is a block circuit diagram of a conventional example.
Figure 4 is a vector diagram similar to the above. (3) Ultrasonic transducer, (8)...detection circuit, (9)...detection circuit, θ
4)...mixer, (16)...phase shifter. Agent Patent Attorney Ishi 1) Chief Figure 1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A single ultrasonic transducer is used to transmit ultrasonic waves to the monitoring space and to receive reflected waves from objects to be detected within the monitoring space, and the reflected waves from moving objects to be detected are transmitted. In a moving object detection device with an integrated transmitter and receiver that detects the presence of a moving object by detecting a Doppler signal generated by waves using a detection circuit, the signal from the ultrasonic transducer is divided into signals of two paths. A moving object detection device characterized in that one of the signals is detected after being mixed with a signal having a different phase in a mixer, and the other is detected without being mixed with other signals to obtain a pair of Doppler signals. (2) The phase difference between the two input signals to the mixer is approximately 180°.
A moving object detection device according to claim 1, characterized in that the moving object detection device comprises: