JP2010078375A - Radio active sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio active sensor in which a radio wave is not remarkably attenuated, and deterioration in sensor performance does not occur even when the thickness of an outer case and an installation distance are of low accuracy. <P>SOLUTION: The active sensor reads one frequency out of a plurality of prestored test frequencies (S1), transmits a radio wave from a transmitting antenna with the frequency and receives a reception radio wave (S2), reads the reception level of the reception radio wave only in a period of time during which an object is not detected (S3), stores the average value of the read reception levels (S4), repeats the processes S1 to S4 for all the test frequencies (YES in S5), and selects a test frequency when the average value of the reception levels reaches a maximum as an operating frequency (S6). A detection operation is thereafter performed with the selected frequency. Thereby, a radio wave is not remarkably attenuated due to the thickness of an outer case, and deterioration in sensor performance does not occur even when the thickness of the outer case and the installation distance are of low accuracy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio wave type active sensor.

2. Description of the Related Art Conventionally, an active sensor that detects a person entering or exiting a building or room using a radio wave Doppler effect is known (for example, see Patent Document 1). In this type of active sensor, the entire electric circuit portion including the antenna is housed in an outer case in order to protect the electric circuit portion from dust, impact, and the like and to adjust the appearance.
JP 2006-244777 A

  However, when the antenna itself is housed in the outer case as described above, the outer case itself becomes an obstacle to radio waves, so that the power level of the transmitted and received radio waves is attenuated when passing through the outer case. When the power level of the radio wave is attenuated, the sensor performance is lowered such that the detection distance is shortened.

  On the other hand, the attenuation of the power level when the radio wave passes through the obstacle is such that the distance from the antenna to the obstacle and the thickness of the obstacle are integral multiples of λ / 4 (the wavelength It is known that it becomes particularly large when it becomes an abdomen. This is because in the above case, the reflected wave at the boundary surface of the medium becomes a standing wave and easily interferes with radio waves.

  Therefore, in order to suppress the influence of attenuation due to the above-described outer case as much as possible, it is considered that the distance from the antenna to the outer case and the thickness of the outer case are assembled so as to deviate from an integral multiple of λ / 4 when manufacturing the active sensor. It is done.

  FIG. 5A shows a case where the installation distance d1 of the outer case 101 from the antenna 102 and the thickness t1 of the outer case 101 are an integral multiple of λ / 4 of the radio wave w. FIG. The case where the installation distance d2 from the antenna 102 of the case 101 and the thickness t2 of the exterior case 101 are out of an integral multiple of λ / 4 is shown. In the state shown in FIG. 5A, since the node of the radio wave w emitted from the antenna 102 is located at the boundary surface 103 between the outer case 101 and the air, the reflected wave from the boundary surface 103 becomes a standing wave and the radio wave w , And the antinode of the radio wave w that has entered the outer case 101 is located on the other boundary surface 104, so that the reflected wave from the boundary surface 104 becomes a standing wave in the outer case 101, and Interfering with the radio wave w traveling through On the other hand, in the state shown in FIG. 5B, since there is no antinode or node of the radio wave w at the position of the boundary surface 103, standing waves are generated in the space between the antenna 102 and the case 101 and in the case 101. It does not occur and radio waves do not attenuate significantly.

  However, in the active sensor for human detection, since the radio wave used is mainly in the millimeter wave band, for example, when using a radio wave with a wavelength λ of 12.5 mm, λ / 4≈3.1 mm, In order to prevent large attenuation, the thickness of the outer case must be formed with an accuracy of about 1 mm, and the installation distance must be adjusted with an accuracy of about 1 mm. As described above, complicated adjustment is required to form and assemble the outer case with high accuracy, resulting in high cost.

  Therefore, the present invention solves the above-described problems, and does not require complicated adjustments during manufacturing, and the power level of radio waves transmitted and received is greatly attenuated even when the thickness of the outer case and the installation distance are low. It is an object of the present invention to provide a radio wave type active sensor that does not cause deterioration in sensor performance such as a detection distance being shortened.

  In order to achieve the above object, the invention of claim 1 includes a transmission circuit unit that generates a transmission radio wave and a reception circuit unit that receives a radio wave reflected by the object to be detected. In a radio wave type active sensor that detects an object based on a frequency difference, a plurality of radio wave frequencies generated by the transmission circuit unit are set, and radio waves of a plurality of frequencies are sequentially transmitted. Checking the intensity of the radio wave received by the receiving circuit unit, comprising a selection means for selecting the highest frequency as the operating frequency, and performing the detection operation of the detection object at the operating frequency selected by the selection means. It is characterized by.

  According to a second aspect of the present invention, in the radio wave type active sensor according to the first aspect, the selection means examines the radio wave intensity when the fluctuation of the frequency of the received radio wave is small.

  According to the first aspect of the present invention, radio waves having a plurality of frequencies are sequentially transmitted, and the frequency with the highest received radio wave intensity is set as the operating frequency. During operation, the radio wave is not greatly attenuated, and the sensor performance is not deteriorated such that the detection distance is shortened.

  According to the invention of claim 2, since the radio wave intensity is checked when the state of the received radio wave is stable, the highest-intensity frequency can be determined more correctly, and thus the attenuation of the radio wave is suppressed. Frequency can be selected more appropriately.

  Hereinafter, a radio wave type active sensor (hereinafter referred to as a sensor) according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the sensor 1 of the present embodiment is used as a human sensor of a lighting control system 4 that automatically turns on a lighting fixture 3 when the presence of a person (detection target) 2 in a room is detected. .

  For example, the sensor 1 is integrated with a ceiling surface of a room or a housing of the lighting fixture 3 and outputs a detection signal 5 to the lighting fixture 3 when the presence of the person 2 is detected. The lighting fixture 3 turns on the light source 7 when the lighting control unit 6 receives the detection signal 5. When the sensor 1 no longer detects the presence of the person 2, the output of the detection signal 5 stops and the light source 7 is turned off.

  In the sensor 1, the entire electric circuit 10 including the transmission antenna 8 and the reception antenna 9 is accommodated in a resin outer case 11. The electrical circuit 10 outputs a frequency setting signal 16 to the transmission circuit unit 13 that generates the transmission radio wave 12, the reception circuit unit 15 that receives the radio wave (received radio wave) 14 reflected by the person 2, and the transmission circuit unit 13. And a microprocessor (selection means) 17 for setting the frequency of the transmission radio wave generated by the transmission circuit unit 13. In addition, a reception power detection unit 22 that converts the reception radio wave 14 itself distributed from the reception circuit unit 15 by the distributor 21 into a reception level signal 23 corresponding to the intensity thereof is provided. The reception level signal 23 from the reception power detection unit 22 is input to the microprocessor 17. The microprocessor 17 is responsible for the overall operation of the sensor 1, and executes an operation for selecting an operating frequency and an object detection operation in accordance with a program stored in the memory 17a. The above operation will be described later.

  The transmission circuit unit 13 includes an oscillator 132 that outputs a reference frequency signal 131 and a high-frequency signal 18 that is output from a voltage-controlled oscillator (VCO) 133 based on the frequency signal 131 from the oscillator 132. And a PLL (Phase Locked Loop) IC 134 that locks to a frequency corresponding to the frequency setting signal 16 from. A high frequency signal 18 is emitted from the transmission antenna 8 into the air and becomes a transmission radio wave 12.

  The reception circuit unit 15 multiplies the high-frequency signal 18 distributed by the distributor 19 from the transmission circuit unit 13 and the reception radio wave 14 received by the reception antenna 9, and generates a voltage 151 (hereinafter referred to as Doppler frequency) corresponding to the difference frequency. And a signal processing unit 154 that determines whether or not the person 2 exists based on the waveform of the Doppler frequency 151 amplified by the amplifier 153. The detection signal 5 from the signal processing unit 154 is output to the lighting fixture 3 and also to the microprocessor 17.

  Next, the frequency selection procedure executed by the microprocessor 17 when the power to the sensor 1 is turned on will be described with reference to the flowchart of FIG. The microprocessor 17 first reads out the lowest one of the plurality of test frequencies stored in advance in the memory 17a, outputs the frequency to the transmission circuit unit 13 as the frequency setting signal 16, and outputs the high frequency signal 18 of that frequency. Is generated (S1). Note that the frequency read first by the microprocessor 17 is not limited to the lowest frequency, and may be the highest frequency or an intermediate frequency. Further, the plurality of test frequencies may have a constant interval, or may have discrete values at different intervals.

  Then, the high-frequency signal 18 generated by the transmission circuit unit 13 is transmitted as a radio wave from the transmission antenna 8, and the reception antenna 9 receives the radio wave 14 reflected from the surroundings and returning (S2). Here, when the person 2 is present in the room, the frequency of the received radio wave 14 is changed by the movement of the person 2, so the Doppler frequency 151 changes greatly at short intervals. Specifically, as shown in the upper part of FIG. 3, in the time zones A and C, the Doppler frequency 151 changes greatly and there is a person 2. In the time zones B and D, the change in the frequency of the received radio wave 14 is small, the change in the Doppler frequency 151 is also small, and the person 2 does not exist.

  Since the Doppler frequency 151 changes as described above depending on the presence or absence of the person 2, the signal processing unit 154 outputs the detection signal 5 in the time zones A and C in which the waveform of the Doppler frequency changes greatly, and the time zone No output at B and D (see the middle of FIG. 3). On the other hand, the power level of the reception radio wave 14 is larger in the time zones A and C in which the person 2 exists than in the time zones B and D in which the person 2 does not exist. It changes as follows.

  As described above, the microprocessor 17 recognizes the presence / absence of the person 2 by receiving / not receiving the detection signal 5, and in this embodiment, the reception level only in the time zones B and D in which the detection signal 5 is not received. The signal 23 is read (S3). Time zones B and D are time zones in which the reception level signal 23 is relatively stable, and the microprocessor 17 can check the power of the reception radio wave 14 more accurately.

  The microprocessor 17 calculates and stores the average value of the reception levels read as described above (S4). Then, it is determined whether or not the steps S1 to S4 have been repeated for all of the plurality of test frequencies (S5). If NO, the process returns to S1 and the next test frequency is selected from the plurality of test frequencies. Reading and generating a high-frequency signal 18 of that frequency. In this way, the frequency of the transmission radio wave 12 is sequentially changed.

  If the result of determination in S5 is YES, the average values of the received levels for all test frequencies are compared, and the test frequency with the highest received level average value (the highest received radio wave intensity) is selected as the operating frequency. (S6).

  Next, the object detection procedure executed by the microprocessor 17 at the operating frequency selected as described above will be described with reference to the flowchart of FIG. The microprocessor 17 outputs the frequency setting signal 16 corresponding to the selected frequency to the transmission circuit unit 13, and generates the high frequency signal 18 of the frequency (S11). This frequency does not change during the detection operation and is fixed to a constant value. Then, the transmission antenna 8 transmits the transmission radio wave 12 of the frequency, the reception antenna 9 receives the reception radio wave 14 (S12), and the signal processing unit 154 determines the presence or absence of the person 2 based on the Doppler frequency 151 (S13). ). As a result of the determination, when the person 2 is detected (YES in S14), the detection signal 5 is output and the lighting fixture 3 is turned on (S15).

  Since the frequency selected by the frequency selection procedure is the frequency at which the intensity of the received radio wave 14 is highest, the detection distance of the active sensor 1 is shortened even if the thickness of the exterior case 11 and the accuracy of the installation distance are low. The sensor performance is not deteriorated, and as a result, the lighting fixture 3 can be correctly controlled to be lit.

  In S3 of the flowchart of FIG. 2, the radio wave intensity is checked when the reception radio wave intensity is stable by reading the reception level signal 23 only when the detection signal 5 is not received. Can be performed more accurately, and a more appropriate frequency for suppressing the attenuation of radio waves can be selected.

  As described above, in the sensor 1 of the present embodiment, radio waves having a plurality of test frequencies are sequentially transmitted, and the test frequency with the highest intensity of the received radio wave 14 is used as the operating frequency. Even with low accuracy, radio waves are not greatly attenuated during the detection operation, and the sensor performance is not deteriorated such that the detection distance is shortened.

  In this embodiment, the microprocessor 17 that gives the frequency setting signal 16 to the transmission circuit unit 13 controls the operation of the entire sensor and executes the frequency selection procedure. However, a circuit provided separately from the microprocessor 17 selects the frequency. You may make it perform a procedure.

  Further, in the present embodiment, the frequency selection procedure is executed when the power to the sensor 1 is turned on. However, the frequency selection procedure is appropriately performed according to a trigger signal input by the user. May be.

The block diagram of the illumination control system which uses the radio wave type active sensor which concerns on one Embodiment of this invention as a human sensitive sensor. The flowchart which shows the frequency selection procedure in the same radio wave type active sensor. The figure which shows the Doppler frequency at the time of the frequency selection in the same radio wave type active sensor, the detection signal of a target object, and a reception level signal. The flowchart which shows the target object detection procedure in the same radio wave type active sensor. (A) is a figure which shows the aspect in case the thickness and installation distance of an exterior case are both integral multiples of (lambda) / 4 of an electromagnetic wave, (b) is the integer of (lambda) / 4 of both the thickness and installation distance of an exterior case. The figure which shows the aspect in the case of deviating from double.

Explanation of symbols

1 Radio wave type active sensor 2 people (detection target)
12 Transmission radio wave 13 Transmission circuit unit 14 Reception radio wave 15 Reception circuit unit 17 Microprocessor (selection means)

Claims (2)

In a radio wave type active sensor that includes a transmission circuit unit that generates a transmission radio wave and a reception circuit unit that receives a radio wave reflected by a detection target, and detects an object based on a frequency difference between the transmission radio wave and the reception radio wave ,
The frequency of radio waves generated by the transmission circuit unit is set to a plurality, and radio waves of a plurality of frequencies are sequentially transmitted, and the strength of the received radio wave by the reception circuit unit at each frequency is examined, and the highest intensity Comprising a selection means for selecting the frequency as the operating frequency;
A radio wave type active sensor characterized in that a detection object is detected at an operation frequency selected by the selection means.   The radio wave type active sensor according to claim 1, wherein the selection unit checks the radio wave intensity when the frequency fluctuation of the received radio wave is small.

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