JP5222190B2 - Doppler sensor - Google Patents

Description

  The present invention relates to a Doppler sensor.

  Conventionally, for example, a radio wave (transmission wave) such as a millimeter wave is irradiated on a detection range, a radio wave reflected by the detection range (reflection wave) is received, and a Doppler signal obtained from the transmission wave and the reflection wave is used. A Doppler sensor for detecting a moving body such as a human body is provided. This type of Doppler sensor is used for detecting a human body in, for example, an illumination system that switches on / off a light source in accordance with detection of a human body (see, for example, Patent Document 1).

  Other sensors that detect the human body include, for example, a heat ray sensor that detects a heat ray emitted from the human body, but a Doppler sensor has an advantage that it can detect a human body at a longer distance than a heat ray sensor. It is suitable for use in such a way that it is attached to the ceiling in a building with a high ceiling.

JP 2001-238272 A

  However, when the Doppler sensor itself vibrates, a relative velocity is generated between the stationary object and the Doppler sensor, so that the Doppler shift also occurs in the reflected wave reflected by the stationary object, and there is actually no human body. Nevertheless, a false detection that a human body is detected may occur.

  Further, when the Doppler sensor is used by being attached to the ceiling as described above, and the duct is exposed and arranged below the ceiling, the Doppler is avoided in order to avoid a blind spot caused by the duct. The sensor may be supported by being suspended from the ceiling surface. In such a case, the above-described erroneous detection is particularly likely to occur.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a Doppler sensor capable of suppressing erroneous detection.

  The invention according to claim 1 transmits an electric wave to a predetermined detection range, receives an electric wave from the detection range, and generates an output including a Doppler signal having a frequency corresponding to a changing speed of a distance from a moving object existing in the detection range. And a signal processing circuit that analyzes the output of the transmission / reception circuit and determines the presence or absence of a moving object in the detection range. The transmission / reception circuit converts the transmission signal into an oscillator that generates a transmission signal of a predetermined frequency. Transmitting antenna that transmits a transmitted wave that is a transmitted radio wave to a detection range, and a receiving antenna that receives a reflected wave that is a radio wave reflected from the detection range by the transmission antenna and converts it to a received signal And a Doppler signal having a difference between the frequency of the transmission signal and the frequency of the reception signal by mixing the transmission signal output from the oscillator and the reception signal output from the reception antenna And a mixer that outputs to the signal processing circuit. The signal processing circuit includes an FFT unit that performs a fast Fourier transform on the Doppler signal output from the transmission / reception circuit, and a predetermined noise level at the output of the FFT unit over a predetermined noise determination time. When there is a noise frequency that is a frequency that continues to be equal to or greater than the determination amplitude, a Doppler is obtained so as to obtain a removal target frequency that is the lowest of the noise frequencies and at least attenuate a component of the removal target frequency in the Doppler signal. Generate and output a shaped signal that is shaped signal, and when there is no noise frequency, the signal shaping unit that outputs the Doppler signal as it is as a shaped signal, and the detection range based on the shaped signal output by the signal shaping unit And a determination unit that determines whether or not a moving object exists.

  According to the present invention, when a noise frequency is present, the presence or absence of a moving object is determined based on the shaped signal obtained by shaping the Doppler signal so that the component of the removal target frequency that is the lowest frequency among the noise frequencies is attenuated. Since the determination is made, erroneous detection due to vibration of the Doppler sensor itself can be suppressed as compared with the case where the Doppler signal is always used for determination.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the noise frequency exists, the signal shaping unit uses a noise period that is the reciprocal of the frequency to be removed, and the intensity of the shaped signal is transmitted to The intensity obtained by subtracting the difference (Vpc−Vav) between the intensity Vpc of the Doppler signal output before the period and the average value Vav for the noise period of the intensity of the Doppler signal output from the transmission / reception circuit from the intensity Vor of the latest Doppler signal. (Vor−Vpc + Vav).

  According to the first aspect of the present invention, when there is a noise frequency, the moving object is based on the shaped signal obtained by shaping the Doppler signal so that the component of the removal target frequency, which is the lowest frequency among the noise frequencies, is attenuated. Therefore, erroneous detection due to vibration of the Doppler sensor itself can be suppressed as compared with the case where the Doppler signal is always used for the determination as it is.

It is a block diagram which shows embodiment of this invention. It is explanatory drawing which shows an example of the output of an FFT part. It is explanatory drawing which shows an example of the waveform of a shaping signal.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the present embodiment, as shown in FIG. 1, a distance between a radio wave transmitted to a predetermined detection range (not shown), a radio wave from the detection range, and a moving object (not shown) existing in the detection range. A transmission / reception circuit 1 that generates an output including a Doppler signal having a frequency corresponding to a change rate of the signal, and a signal processing circuit 2 that analyzes the output of the transmission / reception circuit 1 and determines the presence or absence of a moving object in the detection range.

  More specifically, the transmission / reception circuit 1 includes an oscillator 11 that generates a transmission signal having a predetermined frequency, a transmission antenna 12 that transmits a transmission wave, which is a radio wave converted from the transmission signal, to a detection range, and a transmission antenna. A receiving antenna 13 that receives a reflected wave, which is a radio wave reflected from the detection range in the detection range, and converts it into a received signal; a transmission signal output from the oscillator 11; and a received signal output from the receiving antenna 13. And a mixer 14 that extracts a Doppler signal having a frequency difference between the frequency of the transmission signal and the frequency of the reception signal and outputs the signal to the signal processing circuit 2. That is, the mixer 14 includes a low-pass filter that extracts and outputs a Doppler signal by selectively attenuating the frequency component of the sum of the frequency of the transmission signal and the frequency of the reception signal in the mixed signal. The frequency of the transmission signal is 24 GHz, for example.

  The signal processing circuit 2 includes an amplifying unit 21 that amplifies and outputs the Doppler signal output from the mixer 14 of the transmission / reception circuit 1. The amplifying unit 21 has a characteristic that the amplification factor is high at a relatively low frequency corresponding to the frequency of the difference between the frequency of the transmission signal and the frequency of the reception signal, thereby improving the S / N ratio. Is done. The signal processing circuit 2 also includes an FFT unit 22 that performs fast Fourier transform on the Doppler signal output from the amplification unit 21, and a signal shaping unit 23 that outputs a shaping signal corresponding to the output of the amplification unit 21 and the output of the FFT unit 22. And a determination unit 24 that determines whether there is a moving object in the detection range based on the shaping signal output from the signal shaping unit 23.

  Specifically, the signal shaping unit 23 has an A / D conversion circuit (not shown) at the input stage, and the intensity (voltage value) of the Doppler signal A / D converted by the A / D conversion circuit. ) Is stored for a predetermined storage time and updated as needed. Further, the signal shaping unit 23 refers to the output of the FFT unit 22 as needed, compares the amplitude | V | of each frequency with the predetermined noise determination amplitude Vth in the output of the FFT unit 22, and the amplitude | V | If there is a frequency that is equal to or greater than the amplitude Vth, the number of times that the amplitude | V | If there is at least one frequency (hereinafter referred to as “noise frequency”) whose amplitude continues to be equal to or greater than the noise determination amplitude over a predetermined number of noise determination times, the lowest noise frequency is selected. The frequency to be removed is set, and the reciprocal (that is, the cycle) of the frequency to be removed is set to a noise cycle Ta (see FIG. 3). That is, the noise determination time in the claims is obtained by multiplying the cycle in which the signal shaping unit 23 refers to the output of the FFT unit, in other words, the cycle of the output of the FFT unit 22 (the width of the window function) by the number of times of noise determination. This noise determination time is, for example, 10 seconds. For example, as shown in FIG. 2, when the amplitude | V | exceeds the noise determination amplitude Vth over the number of times of noise determination at the two frequencies fa and fb, the reciprocal 1 / fa of the lower frequency fa is the noise cycle Ta. Is done.

  In the period when the noise frequency does not exist and the noise period Ta cannot be obtained, the signal shaping unit 23 is the intensity (voltage value) of the Doppler signal output by the amplification unit 21 before the timing t1 in FIG. ) Output Vor as the intensity V of the shaped signal as it is. On the other hand, during the period in which the noise frequency is present and the noise period Ta is obtained, the signal shaping unit 23 is the intensity of the Doppler signal output by the amplifying unit 21 before the noise period Ta, as after the timing t1 in FIG. The average value of Vpc and the noise period Ta of the intensity of the Doppler signal output from the amplifying unit 21 (that is, the average value within the latest period of the noise period Ta and the so-called simple moving average) The intensity (Vor−Vpc + Vav) obtained by subtracting the difference (Vpc−Vav) from Vav from the intensity Vor of the latest Doppler signal is calculated as the intensity V of the shaped signal. That is, in the Doppler signal, the component that is periodically repeated over the noise determination time (for example, 10 seconds) is regarded as noise caused by vibration of the transmission / reception circuit 1 itself, and is removed from the Doppler signal by the above calculation. To do.

  The determination unit 24 stores the history of the strength of the shaped signal output from the signal shaping unit 23 (hereinafter referred to as “shaping strength”) V for a predetermined monitoring period (for example, 5 seconds) from the newest time, and from time to time. It has been updated. Furthermore, the determination unit 24 determines the average value of the shaping intensity for the monitoring period (so-called simple moving average; hereinafter referred to as “monitoring average intensity”) Vm and the upper peak value of the shaping intensity V (that is, from increasing to decreasing). The average value Vu within the monitoring period of the shaping intensity V immediately before turning) and the average value within the monitoring period of the lower peak value of the shaping intensity V (that is, the value of the shaping intensity V immediately before changing from increasing to decreasing). Half of the difference from the value Vl (hereinafter referred to as “monitoring average amplitude”) Vp = (Vu−Vl) / 2, the presence of 1.5 times the monitoring average amplitude Vp and the monitoring average intensity Vm The determination threshold Vb = Vm + 1.5Vp is calculated as needed, and the obtained presence determination threshold Vb is compared with the latest shaping strength V as needed. If the latest shaping strength V is equal to or greater than the presence determination threshold Vb, the moving object It is determined that it exists, and the latest shaping strength V exists. It is determined that the moving object does not exist is less than the determination threshold value Vb, and outputs a determination signal of the voltage value corresponding to the determination result.

  The determination result indicated by the determination signal output from the determination unit 24 is, for example, that there is a moving object (mainly a human body) with the light source turned off in an illumination control system (not shown) that turns on and off the electrical light source. Then, the light source is turned on when it is determined, and the light source is turned off when a state where it is not determined that a moving object is present continues for a predetermined lighting holding time. The amplifying unit 21 is designed to selectively amplify a frequency component corresponding to a normal moving speed of a moving object (for example, a human body) to be detected, depending on the application.

  Each configuration of the transmission / reception circuit 1 and the signal processing circuit 2 as described above can be realized by a well-known technique using an electronic circuit as appropriate, and thus detailed illustration and description thereof are omitted.

  According to the above configuration, when there is a noise frequency that maintains an amplitude equal to or greater than the predetermined noise determination amplitude in the Doppler signal over the predetermined noise determination time, the removal target frequency that is the lowest frequency among the noise frequencies Since the presence / absence of the moving object is determined based on the shaping signal from which the component is removed from the Doppler signal, the Doppler sensor (transmission / reception circuit 1) is used as compared with the case where the Doppler signal is always input to the determination unit 24 and used for the determination. ) False detection due to its own vibration is suppressed. Therefore, it is suitable for a usage pattern in which the transmission / reception circuit 1 is supported by being suspended from the ceiling.

  Instead of the operation of the signal shaping unit 23 in the period in which the noise frequency is present as described above, in the period in which the frequency characteristic is variable and the noise frequency is present, mainly the removal target frequency in the Doppler signal. A variable filter (not shown) that generates a shaped signal by attenuating the component may be provided in the signal shaping unit 23. Since the variable filter as described above can be realized by a well-known technique, illustration and detailed description thereof are omitted.

DESCRIPTION OF SYMBOLS 1 Transmission / reception circuit 2 Signal processing circuit 11 Oscillator 12 Transmission antenna 13 Reception antenna 14 Mixer 21 Amplification part 22 FFT part 23 Signal shaping part 24 Determination part

Claims (2)

A transmission / reception circuit that transmits a radio wave to a predetermined detection range, receives a radio wave from the detection range, and generates an output including a Doppler signal having a frequency according to a change speed of a distance from a moving object existing in the detection range;
A signal processing circuit that analyzes the output of the transmission / reception circuit and determines the presence or absence of a moving object in the detection range;
The transmission / reception circuit includes an oscillator that generates a transmission signal having a predetermined frequency, a transmission antenna that transmits a transmission wave, which is a radio wave converted from the transmission signal, to the detection range, and a transmission wave transmitted from the transmission antenna. The frequency of the transmission signal and the frequency of the reception signal by mixing the reception antenna that receives the reflected wave, which is the reflected radio wave, and converting it to the reception signal, and the transmission signal output by the oscillator and the reception signal output by the reception antenna And a mixer that outputs a Doppler signal having a difference frequency to the signal processing circuit,
The signal processing circuit includes an FFT unit that performs a fast Fourier transform on the Doppler signal output from the transmission / reception circuit, and noise having a frequency at which the amplitude continues to be equal to or greater than a predetermined noise determination amplitude over the predetermined noise determination time in the output of the FFT unit. If there is a frequency, it obtains the removal target frequency that is the lowest of the noise frequencies, and generates and outputs a shaped signal that shapes the Doppler signal so that the Doppler signal attenuates at least the component of the removal target frequency. When there is no noise frequency, a signal shaping unit that outputs the Doppler signal as it is as a shaping signal, and a determination for determining whether or not there is a moving object in the detection range based on the shaping signal output by the signal shaping unit And a Doppler sensor.   When there is a noise frequency, the signal shaping unit uses a noise period that is the reciprocal of the removal target frequency, the intensity of the shaped signal, the intensity Vpc of the Doppler signal output by the transmission / reception circuit before the noise period, and the transmission / reception circuit The difference (Vpc−Vav) from the average value Vav for the noise period of the Doppler signal intensity outputted from is set to the intensity (Vor−Vpc + Vav) obtained by subtracting from the latest Doppler signal intensity Vor. The Doppler sensor according to 1.

Images