JP2014095657A - Microwave Doppler detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave Doppler detection device which is less affected by rain, water drops, and water film and enables even inexpensive microcomputers or the like to successfully detect moving objects.SOLUTION: A flat cover is installed in parallel with an antenna surface in front of a microwave Doppler sensor. In a sensor circuit section 14, a quadrature detection circuit generates two Doppler signals with a 90-degree phase difference, an I signal and Q signal, which are fed to high-pass filters 15a, 15b to attenuate low frequency components corresponding to movement of rain, water drops, and water film. I-Q signal multiplication/moving average processing is performed on the I and Q signals sampled at a predetermined interval, in which a product of one of the signals, shifted by approximately a quarter of a period of a center frequency of the Doppler signal, and the other signal is obtained and a moving average of the product is computed. The flat cover described above may be replaced by a spherical cover or a cylindrical cover.

Description

  The present invention relates to a microwave Doppler detection device, and more particularly to a configuration of a detection device that is installed outdoors and is directly incorporated into a device / apparatus that may be rained, and detects the approach of a moving body such as a person using a Doppler signal.

  Conventionally, devices that use microwaves to detect moving objects using the Doppler effect have been used. With this type of detection device, the effects of rain, such as reducing false detection due to rainfall, and environmental noise levels are reduced. Regarding the mitigation of the influence of fluctuations, the techniques of the following patent documents have been proposed.

In the security device of Patent Document 1 (Japanese Patent No. 4799173), the Doppler sensor is installed at an angle of 45 degrees with respect to the plastic window so that rain always moves away from the Doppler sensor. By using the mixer output, the approach and separation are determined, the direction in which the rain flows is ignored as the separation direction from the sensor, and only the approaching person is detected.
In the sensing means and approach warning system disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2006-71499), raindrops traveling downward by gravity are caused by directing the Doppler detector (radio wave transmitter and radio wave receiver) obliquely downward. And by moving all the snow particles away from the detection unit and excluding them from the detection target, the frequency of occurrence of false detection caused by raindrops or snow particles is reduced.

  Moreover, in the obstacle detection sensor of patent document 3 (Unexamined-Japanese-Patent No. 2006-275858), a Doppler signal is transmitted with a different amplification factor for every output frequency, and an obstacle is adjusted appropriately adjusting a sensitivity according to the situation. The presence or absence of is detected.

Japanese Patent No. 4799173 JP 2006-71499 A JP 2006-275895 A

  However, the conventional Doppler detection device has a problem in that if a raindrop or the like causes water droplets to collect and flow in the window (protective cover), a good moving body cannot be detected due to the flow of the raindrops or water film. It was. For example, when a person (purchaser) or the like is detected by a microwave Doppler sensor using a device such as a vending machine, the detection range is narrow and the radio wave reflected by the human body is relatively large. If the device is not directly exposed to rain, the effects of rain will not be a problem. However, when rain is directly applied to the device and water droplets or water films are formed on the plastic window (protective cover) or case for radiating microwaves, the radio wave reflected by the water becomes very large. When the amplifier that amplifies the sensor output is saturated, a problem that the detection state is sustained occurs.

  Further, in Patent Documents 1 and 2 described above, sensors are arranged obliquely at an angle to try to distinguish people approaching with rain as a separation, but the noise level due to drought and water film is large, and plastic is also used. By arranging the sensors diagonally in the window, most of the microwaves are reflected, and there is a problem that it is difficult to detect people and the like.

  The present invention has been made in view of the above problems, and its purpose is to reduce the influence of rain, hail and water film, and to detect a moving object satisfactorily even with an inexpensive microcomputer or the like. It is to provide a detection device.

In order to achieve the above object, a microwave Doppler detection device according to the invention of claim 1 has an antenna surface and is disposed in front of the microwave Doppler sensor for detecting a moving object, A protective cover (detection window) having a substantially flat surface parallel to the antenna surface or a curved surface formed at substantially the same distance from the antenna surface in at least a vertical direction, and orthogonal to output two Doppler signals having a phase difference of 90 degrees A detection circuit; a high-pass filter that inputs an output of the quadrature detection circuit and attenuates a low frequency corresponding to the movement of rain, hail, and water film; and an amplifier that amplifies the output of the high-pass filter. It is characterized by that.
According to a second aspect of the present invention, two I and Q signals having a phase difference of 90 degrees are sampled at a predetermined interval based on the output of the high-pass filter, and either the I signal or the Q signal is sampled at the center frequency of the Doppler signal. An IQ signal product / moving average process for obtaining a product of a signal shifted by approximately ¼ period and the other signal and calculating a moving average of the product is executed, and the IQ signal product / moving average process is performed by the IQ signal product / moving average process. It is characterized by detecting.
According to a third aspect of the present invention, the filter characteristic of the high-pass filter is variable, and when the detection state continues for a predetermined time (period) or more based on the output of the Doppler sensor, the low-pass cutoff frequency of the high-pass filter is set high. It controls to do.

According to a fourth aspect of the present invention, when the detection state continues for a predetermined time or more based on the output of the Doppler sensor, the IQ signal product / moving average process is controlled to be executed.
The invention according to claim 5 is characterized in that the protective cover has a spherical or cylindrical shape.
The invention of claim 6 is characterized in that a water eaves (roof) is provided above the protective cover.

  According to the above configuration, the protective cover (detection window) is a plane parallel to the antenna surface of the Doppler sensor or a curved surface (for example, a spherical surface or a cylindrical surface) formed at substantially the same distance from the sensor in at least the vertical direction. In the soot (water droplets) and water film formed by rain or the like, the component that flows in the direction perpendicular to the microwave propagation direction with respect to the sensor is mainly used. As a result, the sensor output due to the flow of water is detected as random noise having no directivity because the frequency is biased near 0 Hz and proximity and separation exist simultaneously. This sensor output is amplified after passing through a high-pass filter that sharply attenuates on the low frequency side, so that most of the noise components due to rain, hail, and water film are removed. Is prevented.

  According to the configuration of the second aspect, the IQ signal product / moving average processing at the center frequency of the Doppler signal is executed on the I and Q signals obtained from the quadrature detection circuit, so that the movement of the moving body can be detected well. can do. That is, in the case of the configuration of the sensor and the protective cover as in claim 1, the I and Q signals due to the flow of water are detected as random noise having no correlation between the signals, but the Doppler signal ( I, Q signals) are observed as correlated signals having phases different by 90 degrees. The product of the signal obtained by shifting either the I or Q signal by approximately ¼ period at the center frequency of the Doppler signal and the other signal has a correlation between the I and Q signals, and there is a phase difference of about 90 degrees. In the case of a certain signal, as shown in FIGS. 4B and 4C, only a positive or negative value is obtained depending on the direction of shifting the phase. Therefore, a positive or negative value can be obtained by obtaining a moving average. When there is no correlation due to random noise, even if the product is shifted by shifting one of the results, plus and minus are included at random, and the moving average becomes a value close to zero. By such processing, noise due to rain, hail, water film, etc. is reduced, and human movement is detected with good sensitivity.

  When the sampling is performed at a time interval of 1/8 period or less at the center frequency of the Doppler signal, one of the I and Q signals is moved approximately 1/4 period before the operation for shifting the 1/4 period. Since it can be performed by using the sampled data and taking the product with the other data, it can be easily realized even with a microcomputer having a small memory.

  According to the configuration of claims 3 and 4, when the detection is in a continuous state (when a rainy state or the like is determined), the low-pass cutoff frequency of the high-pass filter is increased, or IQ signal product / moving average processing is performed. By performing the above, it is possible to reduce noise and perform stable detection.

  In particular, when the protective cover has a hemispherical shape or a semicylindrical shape and is disposed at substantially the same distance from the sensor at least in the vertical direction, the water flowing on the surface of the protective cover does not always change the distance from the sensor. Compared with a flat protective cover, signal components due to the flow of water are concentrated on the low frequency side. Therefore, the effect of removing soot and water film components (noise components) by the high-pass filter is enhanced.

  According to the microwave Doppler detection device of the present invention, the influence of raindrops and water films can be reduced, and the reflection of microwaves can be reduced compared to the case where the sensor is arranged obliquely with respect to the protective cover. Detection can be performed satisfactorily. Therefore, in various devices such as vending machines, it is possible to save energy by performing necessary operations such as turning on the indicator lamp and electric light when the purchaser, user, etc. approach. An inexpensive microcomputer or the like can be used for the detection calculation, and the cost can be reduced.

It is a block diagram which shows the signal processing circuit of the microwave Doppler detection apparatus which concerns on the Example of this invention. It is a side view (section hatch abbreviation) showing the example of installation (the vending machine etc.) of the Doppler detection device of an example. It is a figure for demonstrating the relationship between the incident angle of the mobile body in an Example, and a Doppler frequency. It is a wave form diagram for demonstrating the product of the signal which shifted one quarter of IQ signal in an Example by 1/4 period, and the other signal with a correlated signal and a random signal. The Doppler signal obtained in the sensor circuit unit of the embodiment is shown. FIG. (A) is a configuration diagram of the embodiment, FIG. (B) is a waveform diagram of an output (IQ signal) from the quadrature detection circuit, and FIG. FIG. The Doppler signal obtained when the sensor is arranged at an angle of 45 degrees is shown. FIG. (A) is a configuration diagram thereof, FIG. (B) is a waveform diagram of an output (IQ signal) from the quadrature detection circuit, and FIG. Is a diagram of frequency components. FIG. 3 is an output (IQ signal) waveform diagram [FIG. (A)] when passing through the high-pass filter of the embodiment, and a diagram (FIG. (B)) showing frequency components thereof. The output (IQ signal) from the quadrature detection circuit of the embodiment is shown, FIG. (A) is a Doppler waveform diagram due to human movement, and FIG. (B) is a waveform diagram due to rain, hail and water film. In the embodiment, an output (IQ signal) waveform diagram [FIG. (A)] from the case where a human movement is detected simultaneously with rain, hail and water film noise, It is a wave form diagram [figure (B)] after performing signal processing. The structure when a protective cover is made into spherical shape by the microwave Doppler detection apparatus of an Example is shown, A figure (A) is a side view (a cross-sectional hatch is abbreviate | omitted), and a figure (B) is a front view. The structure when a protective cover is made into a cylindrical surface shape by the microwave Doppler detection apparatus of an Example is shown, A figure (A) is a side view (a cross-sectional hatch is abbreviate | omitted), and a figure (B) is a front view. It is a graph which shows the frequency component of the noise produced by rain, hail, and a water film in the case where the protective cover of the embodiment is flat and in the case of a spherical / cylindrical shape. The structure when an eaves is provided in the microwave Doppler detection apparatus of an Example is shown, A figure (A) is a side view (a cross-sectional hatch is abbreviate | omitted), and a figure (B) is a front view.

  1 and 2 show a configuration of a microwave Doppler detection device according to an embodiment of the present invention, and FIG. 2 shows an example attached to a vending machine or the like. As shown in FIG. 2, a flat cover (protective cover, flat plate) 11 made of plastic or the like that transmits radio waves is provided on the front surface of the vending machine 10, and a Doppler sensor 12 is provided inside the flat cover 11. The antenna surface (detection surface) 12 </ b> A on the front surface of the Doppler sensor 12 is disposed so as to be parallel to the flat cover 11.

  FIG. 1 shows a signal processing circuit of the embodiment. The sensor circuit unit 14 of FIG. 1 includes the Doppler sensor 12 and includes a quadrature detection (mixer) circuit and the like, so that the sensor 12 receives the signal. The I signal and the Q signal having a phase difference of 90 degrees are output from the obtained signal. High-pass filters (HPF) 15a and 15b for attenuating low frequencies corresponding to the movement of rain, hail, and water film are provided at the subsequent stage of the sensor circuit unit 14 in response to two IQ signal outputs. In the example high-pass filters 15a and 15b, the low-frequency cut-off frequency is set to about 50 Hz, for example. The high-pass filters 15a and 15b are connected to amplifiers (amplifiers) 16a and 16b, AD (analog / digital) converters 17a and 17b, and a microcomputer 18 having a memory.

  That is, the amplifiers 16a and 16b amplify the IQ signal from which the low-frequency region corresponding to the movement of the ridge or water film is removed, and the AD converters 17a and 17b convert the amplified IQ signal to, for example, the center of the Doppler signal. Sampling is performed at a sampling time of 1/8 cycle or less of the frequency, and the microcomputer 18 obtains a plurality of (time series) data for each time corresponding to approximately 1/4 cycle of the Doppler signal center frequency for each sampled IQ signal. The data is stored in the memory as a data string for a predetermined time, and the IQ signal product / moving average process is executed based on each data string of the IQ signal.

  The embodiment is configured as described above, and the antenna surface (detection surface) 12A of the Doppler sensor 12 is arranged in parallel to the flat cover 11, so that rain, hail and water film flowing on the surface of the cover 11 are the sensor antenna surface 12A. Therefore, the rain, hail, and water film flow in a direction closer to the sensor 12 (to the sensor 12) and a direction away from the sensor 12.

FIG. 3 shows the relationship between the sensor and the movement of the moving body. As shown, the Doppler output frequency fd of the sensor 12 is the speed v of the moving body 50 and the angle α of the moving body with respect to the sensor 12. From the above, it is expressed by the following formula 1.
[Equation 1]
fd = 2 · f ₀ (v / C ₀ ) · cos α
Here, C ₀ is the speed of light, and f ₀ is the transmission frequency of the Doppler sensor 12.
As described above, when water flows parallel to the antenna surface 12A, the frequency component of the Doppler output is concentrated on the lower frequency side because the angle α is close to 90 degrees.

  FIG. 5 shows the Doppler signal output waveform [figure (B)] and its frequency component [figure (C)] of [figure (A)] when the antenna surface 12A and the flat cover 11 (flow of water) are parallel. FIG. 6 shows the Doppler signal output waveform [FIG. (B)] and its frequency component [FIG. (C)] when the angle between the antenna surface 12A and the flat cover 11 is 45 degrees [FIG. (A)]. 5C and FIG. 6C, when the antenna surface 12A and the flat cover 11 are parallel, that is, when the water flow is parallel, the frequency components are concentrated at a lower frequency. I understand that

Therefore, in the embodiment, high-pass filters 15a and 15b are provided to remove the low-frequency components of the Doppler signal, whereby noise components due to rain, hail and water film are greatly attenuated, and the amplifiers 16a, 16a, Saturation of 16b can also be prevented.
FIG. 7 shows a signal waveform [FIG. (A)] obtained by passing the signal [signal of FIG. 5 (B)] output from the sensor circuit section 14 through high-pass filters 15a and 15b (for example, a cut-off frequency of 80 Hz) and its The frequency component [FIG. (B)] is shown. By passing through the high-pass filters 15a and 15b, the low frequency region side is attenuated as shown in FIG. 7 (B).

  Next, in the embodiment, IQ signal product / moving average processing is performed on the IQ signals output from the amplifiers 16a and 16b via the high-pass filters 15a and 15b. That is, by using the high-pass filters 15a and 15b, the noise can be attenuated to some extent by the flow of water. For example, when the sensor 12 of 24 GHz is used, the Doppler frequency due to the movement of the person approaching at 2 km / h is Since the frequency is about 80 Hz, noise due to rain, hail and water film cannot be completely eliminated by a filter. Also, since microwaves are attenuated by rain, hail and water film, the human motion Doppler signal has a low detection level, and when rain is strong, the human motion signal is buried in the noise caused by rain. As a result, the threshold for detection cannot be set. Therefore, in the embodiment, IQ signal product / moving average processing is executed to favorably reduce the influence of heavy rain, hail and water film, and to easily detect by human movement.

  FIG. 8 shows a comparison between a Doppler signal (IQ signal) waveform [Figure (A)] due to human movement and an IQ signal waveform [Figure (B)] due to rain, hail or water film, As is apparent from this waveform diagram, the Doppler signal waveform with respect to the movement of the person shows a phase lag of 90 degrees with respect to the I signal, but the I and Q signals have similar shapes. On the other hand, the output by rain, hail or water film has a random waveform with no correlation between the I and Q signals. Utilizing this fact, processing that reduces the effects of rain and makes it easier to detect human movements is performed.

  In the embodiment, paying attention to the fact that the phase difference between the I signal and the Q signal is 90 degrees and the speed range of human movement is not so wide, the high-pass filters 15a and 15b are used to convert the low frequency side signal. The IQ signal product / moving average processing is efficiently performed after attenuation and limiting the range of the Doppler frequency.

First, each of the I and Q signal outputs from the amplifiers 16a and 16b is input to the AD converters 17a and 17b, and is sampled with a sampling time of, for example, 1/8 period or less of the Doppler center frequency (f _d0 ). Since the Doppler frequency of human movement can be limited to a certain range, the sampling time is preferably the center frequency of the Doppler frequency to be acquired, and an interval shorter than 1/8 period.

Next, the AD-converted digital data is stored in the memory of the microcomputer 18 for a predetermined time, and the time corresponding to ¼ period of the Doppler center frequency (f _d0 ) from the current time of one of the IQ signals. Are obtained in time series, and stored in a memory as a data string (a plurality of product data). Then, an average value (moving average value) of data from the current time to a certain time before in the data string is calculated and used as detection data. As a result, noise components of rain, hail, and water film that are not correlated with the IQ signal are reduced, and a Doppler signal of a correlated person (moving body) is extracted.

  FIG. 4A shows the waveform of the product of the waveforms of the I signal and the Q signal having a phase difference of 90 degrees and their current values. The product values are alternately positive and negative. Therefore, if the moving average is taken as it is, the value becomes close to zero. 4B and 4C show the waveform of the product of the signal corresponding to the time approximately ¼ period before either the I signal or the Q signal and the signal at the other current time. It is. Which of the I signal and the Q signal is used as a signal corresponding to the time before ¼ period, the product value is either the positive side or the negative side as shown in FIGS. Only the value. Therefore, the moving average of this value is a positive or negative value.

  On the other hand, in the case of random noise as shown in FIG. 4D, even if the product of the I signal or the Q signal and the other current time is obtained by using the time before ¼ period, the correlation is obtained. Because there is no sex, positive and negative values appear randomly in the product result. When this result is a moving average, it becomes a value close to 0. Therefore, the random noise component of rain, hail, and water film is attenuated by the processing of this embodiment, and the correlation between the I signal and the Q signal such as human movement is obtained. Only certain signals are extracted. Since the phases of the I signal and the Q signal differ by 180 degrees when a person approaches and moves away, the positive and negative results of the product are inverted in this process. This makes it possible to determine whether a person is approaching or moving away.

  FIG. 9 shows the output waveforms of the high-pass filters 15a and 15b when the movement of a person who moves away from the plane cover 11 in the state where rain, raindrops, and a water film are flowing is measured. )] And the output [Fig. (B)] when the IQ signal product / moving average signal processing is performed. As shown in FIG. It is possible to clearly identify the movement (approach and separation) of a person buried in the noise.

  Further, the frequency removed by the high-pass filters 15a and 15b and the IQ signal product / moving average process may be changed depending on the rainfall state and the detection state. That is, the filter characteristics of the high-pass filters 15a and 15b are variable, and the filter control signal for changing the low-frequency cutoff frequency of the high-pass filters 15a and 15b is output from the microcomputer 18 as shown in FIG. When the rain condition is determined, the low-pass cut-off frequency of the high-pass filter is set higher.

  For example, when the cut-off frequency of the high-pass filters 15a and 15b is set to a relatively low frequency fa, if the detection state continues for a predetermined time or longer, it is determined that the rain state is present, and the cut-off frequency of the high-pass filters 15a and 15b. By using an algorithm that sets the frequency fb to be higher than fa, detection is performed in the rainy state to remove the influence of rain, hail and water film, and when it is not raining, Can be detected with good sensitivity.

  In addition, the IQ signal product / moving average processing described above can be executed by a low-cost microcomputer or the like with a small amount of calculation. However, by performing this calculation, the current consumption of the microcomputer increases and the reaction time for detection of a person or the like also increases. Longer due to moving average processing. In order to avoid such inconvenience, an algorithm may be used in which the signal processing is not performed in the initial state, and IQ signal product / moving average processing is performed when the detection state continues for a certain time or more. Even if the above measures are applied, the occurrence of false detections in the case of torrential rains cannot be completely avoided. The output may be stopped.

  FIG. 10 shows a configuration of an example in which the shape of the protective cover in front of the sensor is spherical. In the example of FIG. 10, the protective cover is formed on a hemispherical surface that is concentric with the center of the antenna surface 12A of the Doppler sensor 12. A spherical cover 20 is provided. In the case of the flat cover 11, the Doppler frequency becomes slightly higher by moving up and down from the front of the sensor. However, according to the spherical cover 20, rain, hail, water film and antenna surface 12 </ b> A flowing on the surface due to rainfall. Therefore, the Doppler component is more concentrated on the low frequency side than the flat cover 11. Accordingly, the effect of removing noise signals such as soot and water films by the high-pass filters 15a and 15b is enhanced. Moreover, even when the rain is blown obliquely or when the rain flows sideways by wind or the like, they move at an equal distance from the sensor, so that stable characteristics can be obtained.

  FIG. 11 shows a configuration of an example in which the shape of the protective cover in front of the sensor is a cylindrical surface. In the example of FIG. 11, a concentric circle with respect to the center of the antenna surface 12A in a direction perpendicular to the ground. A cylindrical surface cover 21 formed on the semi-cylindrical surface is provided. Also with this cylindrical surface cover 21, rain, hail and water film flowing in the direction perpendicular to the surface are always at the same distance from the antenna surface 12 A, and the Doppler component is concentrated on the low frequency side compared to the flat cover 11. To do.

  FIG. 12 shows a comparison of a change in Doppler frequency components for rain, hail and water film between a flat protective cover and a spherical and cylindrical protective cover, which can also be seen from FIG. As described above, the Doppler frequency component due to the movement of rain, hail and water film shifts to a lower frequency in the spherical and cylindrical covers (20, 21). Therefore, when the spherical cover 20 and the cylindrical cover 21 are applied, the effect of removing noise components from rain, hail and water film by the high-pass filters 15a and 15b can be enhanced.

  The noise removal effect of the spherical cover 20 and the cylindrical surface cover 21 is the same in the vertical direction. In particular, the spherical cover 20 has rain, hail, and water film that flows on the cover surface even when it is raining obliquely. Since the relative distance between the sensor 12 and the sensor 12 does not always change, it is more effective.

  FIG. 13 shows a configuration of an example in which a rain eave is provided above the protective cover. In this example, as shown in FIG. (Roof) 23 is arranged. For example, in a device with a high height such as a vending machine, rain hitting the cover surface flows downward from the surface, so that a hail or a water film is always formed. The amount of soot and water film that flows into the spherical cover 20 is reduced, and noise is reduced. In other words, a wide eaves can be provided to prevent most of the rain or rain that is blown at an angle from the wind from hitting the protective cover. A long eaves is not preferable.

  Therefore, in this embodiment, a short eave with a narrow width inclined from the center to the left and right is formed so that the raindrops hitting the upper side of the spherical cover 20 and the flow of the water film do not flow into the spherical cover 20 portion. Thus, the state in which water flows from above is eliminated, and the noise can be significantly reduced by preventing the soot and water film from flowing into the spherical cover 20. Even if it is raining obliquely, it is only due to raindrops that hit the spherical cover 20 directly, so the amount of flowing water is less than that of raindrops that gather and flow from the upper surface, and noise is also generated. Since it can be kept low, the influence of drought and water film can be reduced as much as possible. In particular, in the case of the spherical cover 20, in the case of rain sprayed obliquely, the water film flows not only downward but also on the spherical surface to the left and right, so that the thickness of the water film is reduced and attenuation due to reflection of microwaves is reduced.

  In the above embodiment, a (semi) spherical surface and a (semi) cylindrical surface are used as the curved surface of the protective cover (20, 21) formed at substantially the same distance from the antenna surface 12A of the sensor 12, but the antenna surface 12A is used. A central region having substantially the same area as the antenna surface 12A of the front protective cover (20, 21) may be a flat surface, and the other surface may be a spherical surface or a cylindrical surface.

10 ... Vending machine, 11 ... Flat cover,
12 ... Doppler sensor, 12A ... antenna surface (detection surface),
14 ... sensor circuit part,
15a, 15b ... high pass filter (HPF),
16a, 16b ... amplifier, 17a, 17b ... AD converter,
18 ... Microcomputer, 20 ... Spherical cover,
21 ... Cylindrical cover, 23 ... Eaves.

Claims (6)

A microwave Doppler sensor for detecting a moving object having an antenna surface;
A protective cover disposed in front of the Doppler sensor and having a substantially flat surface parallel to the antenna surface or a curved surface formed at least approximately the same distance from the antenna surface in the vertical direction;
A quadrature detection circuit for outputting two Doppler signals having different phases by 90 degrees;
A high-pass filter that inputs the output of this quadrature detection circuit and attenuates the low frequency corresponding to the movement of the water film,
A microwave Doppler detection device comprising: an amplifier that amplifies the output of the high-pass filter.   Based on the output of the high-pass filter, two I and Q signals having a phase difference of 90 degrees are sampled at a predetermined interval, and either the I signal or the Q signal is shifted by approximately ¼ period at the center frequency of the Doppler signal. An IQ signal product / moving average process for obtaining a product of the signal and the other signal and calculating a moving average of the product is executed, and a moving object is detected by the IQ signal product / moving average process. The microwave Doppler detection device according to claim 1.   The filter characteristic of the high-pass filter is variable, and when the detection state continues for a predetermined time or more based on the output of the Doppler sensor, control is performed to set the low-pass cutoff frequency of the high-pass filter high. The microwave Doppler detection apparatus according to claim 1 or 2.   4. The microwave Doppler detection device according to claim 2, wherein the IQ signal product / moving average process is controlled to be executed when a detection state continues for a predetermined time or more based on an output of the Doppler sensor. .   The microwave Doppler detection device according to any one of claims 1 to 4, wherein the protective cover has a spherical shape or a cylindrical shape.   6. The microwave Doppler detection device according to claim 1, further comprising a water eaves provided above the protective cover.

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