JP2002311154A - Microwave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave(MW) sensor that can be improved in operational reliability by suppressing the interference between radio waves transmitted from a plurality of MW sensors although the radio waves are made to have the same frequency when the sensors are arranged in the same space or respectively arranged in adjacent spaces. SOLUTION: Anticrime sensor units 1A and 1B respectively installed to facing wall surfaces of a room are respectively provided with MW sensors. The extending directions of the antennas 31 of the sensors are inclined by 45 deg. from the vertical direction. In the state where the sensor units 1A and 1B are respectively installed to the wall surfaces, the antennas 31 of the sensors are twisted from each other by 90 deg. and the microwave polarizing planes of the antennas 31 are formed in orthogonal planes. Consequently, the interference between the microwaves is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave sensor (hereinafter, referred to as "MW sensor") which is an active sensor using electromagnetic waves having a frequency lower than that of visible light.
In particular, the present invention relates to a measure for suppressing interference between radio waves when a plurality of MW sensors are arranged.

[0002]

2. Description of the Related Art Conventionally, as one of security devices, a microwave is transmitted toward a detection area, and when a human body exists in the detection area, a reflected wave from the human body (modulated by the Doppler effect). A MW sensor that receives a microwave and detects a human body (intruder) is known.

The MW sensor has an antenna for transmitting and receiving microwaves. The microwave transmitted from the antenna toward the detection area is subjected to a Doppler effect when a human body exists in the detection area. The frequency of the reflected wave from the human body is modulated and received by the antenna. That is, in this case, since the microwave received by the antenna is modulated with respect to the frequency of the microwave transmitted from the antenna, a change occurs in the output signal waveform of the MW sensor, whereby the human body detection signal is output from the MW sensor. It is being transmitted.

[0004] Generally, this type of MW sensor is used in combination with a PIR sensor that receives an infrared ray from a human body in a detection area and detects an intruder based on a temperature difference between the human body and its surroundings (for example, special features). See JP-A-11-39574). In other words, the detection area of the MW sensor and the detection area of the PIR sensor are overlapped, and the weak outputs of the two sensors are complemented by taking the AND of the detection outputs of both, thereby enhancing the reliability of human body detection.

[0005]

When a plurality of the MW sensors are arranged in the same space or when they are arranged in adjacent spaces, there is a concern that radio waves emitted from the MW sensors may interfere with each other. Hereinafter, a specific description will be given.

[0006] Generally, the antenna of the MW sensor is arranged in a direction extending in the vertical direction when the sensor is installed.
As shown in FIG. 10A, when the pair of sensors configured as described above are arranged on mutually facing wall surfaces b and b in the same room a, the antenna polarization planes of the MW sensors c and c have the same plane. This causes the radio waves to interfere with each other. For this reason, noise is mixed in the output signal waveform of the MW sensor c, which may cause a malfunction. Also, as shown in FIG. 10 (b), even when the MW sensors c, c are respectively arranged in the indoor rooms a1, a2 adjacent to each other, the arranged wall surfaces b, b are not mutually opposed wall surfaces. If
Since the microwave passes through the wall surface d, the radio waves interfere with each other in the same manner as described above, which may cause a malfunction.

[0007] As one means for preventing such interference between radio waves, the frequencies of microwaves emitted by the respective MW sensors c, c are made different. However, in this case, it is necessary to prepare a plurality of types of MW sensors having different oscillation frequencies and to install the MW sensors in combination with those having different oscillation frequencies, which complicates the work of manufacturing and installing the MW sensor. Is not preferred.

[0008] The present invention has been made in view of the above points, and an object thereof is to provide a case where a plurality of MW sensors are arranged in the same space or a case where MW sensors are arranged in adjacent spaces. It is an object of the present invention to provide a configuration in which microwaves transmitted by the respective MW sensors can have the same frequency as each other while suppressing interference of radio waves, thereby improving operation reliability.

[0009]

Means for Solving the Problems-Summary of the Invention-In order to achieve the above object, the present invention provides a method of setting a plurality of MWs by appropriately setting the extending directions of antennas for transmitting and receiving microwaves. Even when the sensors are arranged to face each other, the configuration is such that the antenna polarization planes do not overlap on the same plane.

-Solution Means- Specifically, an antenna is provided for transmitting microwaves toward a detection area and receiving microwaves reflected from the detection area, and detecting based on the microwaves received by the antenna. A microwave sensor for detecting a human body in the area is assumed. For this microwave sensor, the antenna is disposed so as to extend in an oblique direction excluding the vertical direction and the horizontal direction when the sensor is installed.

According to this specific matter, when a pair of microwave sensors having the same configuration are arranged on wall surfaces facing each other, the respective antennas are not on the same plane, that is, the torsion having a predetermined torsion angle. Will be present at the position. For this reason, the antenna polarization planes of the microwaves transmitted from the microwave sensor do not overlap on the same plane, whereby interference between radio waves can be suppressed.

The optimum value of the inclination angle of the antenna is 45 ° with respect to the vertical direction when the sensor is installed.
The direction is set to be inclined. According to this, each antenna polarization plane of the microwave transmitted from the microwave sensor is formed on the plane orthogonal to each other,
Interference between radio waves can be greatly reduced, malfunction of the sensor can be avoided, and its reliability can be improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a case will be described in which the MW sensor according to the present invention is applied to a security system configured to be used in combination with a PIR sensor.

-Description of Overall Configuration of Security System- FIG. 1 shows the M used in the security system according to the present embodiment.
1 shows a security sensor unit 1 provided with a V sensor 3. FIG.
FIG. 1A is a front view of the security sensor unit 1, and FIG. 1B is a cross-sectional view taken along line BB in FIG. 1A. In the security sensor unit 1, a MW sensor 3 and a PIR sensor 4 are accommodated in a case 2, and a front surface of the case 2 is covered with a cover 5 that transmits microwaves.
A Fresnel lens 6 is formed on the front surface of the sensor 4.

FIG. 2 shows a unit arrangement position in a room (for example, a warehouse or the like) in which the security sensor unit 1 is arranged.
FIGS. 2A and 2B are diagrams showing a relationship between a W sensor 3 and a detection area of a PIR sensor 4, wherein FIG. 2A is a side view and FIG. 2B is a plan view. In FIG. 2, the security sensor unit 1
Is the wall surface 7 facing the mutually among the wall surfaces forming the room 7
a, 7a. Here, the one installed on the left side in the figure is called a first security sensor unit 1A, and the one installed on the right side in the figure is called a second security sensor unit 1B. A detection area 3A indicated by a dashed line in the drawing is a detection area by the MW sensor 3 of the first security sensor unit 1A. The detection area 3B indicated by a dashed line in the figure is the MW of the second security sensor unit 1B.
This is a detection area of the sensor 3. Further, the detection areas 4A, 4A,...
.. Are detection areas of the security sensor unit 1A by the PIR sensor 4, and the detection areas 4B, 4B,.
This is a detection area of the IR sensor 4. These detection areas 4A and 4B are set so that the interior 7 is covered with a plurality of beams by the Fresnel lens 6. Thereby, the detection area 3A of the first security sensor unit 1A by the MW sensor 3 and the detection area 4 by the PIR sensor 4
A overlap with each other, and the detection area 3B of the second security sensor unit 1B by the MW sensor 3 and the PIR
The sensor 4 overlaps with the detection area 4B.

FIG. 3 is a block diagram showing the configuration of the first security sensor unit 1A. As shown in FIG. 3, in the first security sensor unit 1A, the human body detection signal m detected by the MW sensor 3 is input to the first detection circuit 82. On the other hand, the human body detection signal p detected by the PIR sensor 4
Is input to the second detection circuit 84.

When the human body detection signals m and p exceed predetermined threshold values, the detection signals d1 and d2 are individually output from the detection circuits 82 and 84 to the discrimination circuit 85. I have. That is, the first detection circuit 82 is a circuit that detects the presence or absence of an intruder from the human body detection signal m.
The first detection circuit 82 determines the detection signal d1 when the level of the human body detection signal m exceeds a predetermined threshold value.
5 is output. On the other hand, the second detection circuit 84 is a circuit that detects the presence or absence of an intruder from the human body detection signal p. This second
The detection circuit 84 outputs a detection signal d2 to the determination circuit 85 when the level of the human body detection signal p exceeds a predetermined threshold.

The discriminating circuit 85 calculates each of the detection signals d1 and d2 input within a predetermined time,
When the calculation result is within a predetermined numerical value determined based on the actually measured data, it is determined that there is an intruder, and an alarm signal a is output. As a result, a report is sent to the security company via the central management device of the present system.

The configuration of the second security sensor unit 1B is the same as the configuration of the first security sensor unit 1A described above. If it is determined that an intruder is present, the security company passes through the centralized management device of the present system. Is to be reported to.

-Detailed Description of MW Sensor 3- Next, a detailed configuration of the MW sensor 3 will be described.

FIG. 4 shows a circuit configuration of the MW sensor 3. As shown in this figure, the MW sensor 3 includes an antenna 31 for transmitting and receiving microwaves. When a human body is present in the detection area, the microwave transmitted from the antenna 31 toward the detection area is received by the antenna 31 after the frequency of the reflected wave from the human body is modulated by the Doppler effect. The received reflected wave is mixed with the voltage waveform of the oscillation power supply 33 by the mixer 32 and then amplified by the IF amplifier 34, and the output from the IF amplifier 34 is obtained as the output signal of the MW sensor 3. ing.

When no human body is present in the detection area, the frequency of the microwave transmitted and received by the antenna 31 is equal, so that the IF frequency in the output signal from the IF amplifier 34 is "0" and the MW Sensor 3
Does not output a signal. On the other hand, when a human body exists in the detection area, the microwave received by the antenna 31 is modulated with respect to the frequency of the microwave transmitted from the antenna 31, so that the output signal waveform of the MW sensor 3 is changed. , A human body detection signal m is transmitted from the MW sensor 3.

The feature of the present MW sensor 3 lies in the installation state of the antenna 31. FIG. 5 shows this antenna 31.
FIG. 3 is a front view of the inside of the MW sensor 3 showing an installation state of the MW sensor. As shown in this figure, the antenna 31 is arranged to be inclined in a direction having a 45 ° inclination angle in the counterclockwise direction in the figure with respect to the vertical direction of the MW sensor 3 when viewed from the front of the MW sensor 3. I have. As a result, the antenna polarization plane of the microwave transmitted from the antenna 31 is formed as a plane inclined at an inclination angle of 45 °.
In this manner, the antenna 31 is arranged to be inclined by the same angle in the same direction when viewed from the front in both the first and second security sensors 1A and 1B.

Since the pair of security sensor units 1A and 1B provided with the MW sensor 3 configured as described above are arranged to face each other, as shown in FIG. 6, the MW sensors of the security sensor units 1A and 1B are provided. 3,3 antennas 31,3
No. 1 does not exist on the same plane, that is, exists at a twist position having a twist angle of 90 °. As a result, the MW sensor 3 of each security sensor unit 1A, 1B
The antenna polarization planes of the microwaves transmitted from are formed on planes orthogonal to each other. That is, the polarization planes of the antennas do not overlap on the same plane, so that interference between radio waves can be suppressed. As a result, it is possible to suppress a situation in which the MW sensor 3 is influenced by the microwave from the MW sensor 3 on the partner side and noise is mixed in the output signal waveform, thereby avoiding a malfunction of the MW sensor 3. And its reliability can be improved.

-Experimental Example- Next, an experimental example performed to confirm the effect of the present invention will be described. In this experiment, as shown in FIG.
And a dipole antenna 92 rotatable around a horizontal axis while receiving the oscillation signal from the MW sensor 3.
The security sensor unit 1 provided with was installed. The distance between the dipole antenna 92 and the security sensor unit 1 is set to, for example, 500 mm. Then, a predetermined microwave was transmitted toward the MW sensor 3 while rotating the dipole antenna 92, the electric field intensity ratio received by the MW sensor 3 was measured, and the sensor detection level waveform was detected by the oscilloscope 93.

FIG. 8 shows the angle between the extension direction of the dipole antenna 92 and the extension direction of the antenna 31 of the MW sensor 3 (the dipole antenna 9 with respect to the extension direction of the MW sensor 3).
2 is a graph showing the relationship between the angle in the extension direction of 2 (hereinafter, simply referred to as a relative angle) and the electric field intensity ratio. The smaller the value of the electric field intensity ratio is, the smaller the influence of the microwave from the dipole antenna 92 on the MW sensor 3 is, that is, the smaller the interference of the radio wave is. FIG. 9A shows a detection level waveform on the oscilloscope 93 when the relative angle between the dipole antenna 92 and the antenna 31 of the MW sensor 3 is 0 °, and FIG.
Is the dipole antenna 92 and the antenna 3 of the MW sensor 3
Oscilloscope 9 when relative angle to 1 is 90 °
3 is a diagram showing a detection level waveform on No. 3; The smaller the amplitude of the detection level waveform on the oscilloscope 93, the smaller the influence of the microwave from the dipole antenna 92 on the MW sensor 3, that is, the less the interference of the radio wave.

As can be seen from these results, as the relative angle between the dipole antenna 92 and the antenna 31 of the MW sensor 3 gradually increases from 0 °, the electric field intensity ratio gradually decreases, and the relative angle is 90 °. At times, the electric field intensity ratio is -20 dB as a minimum value.

When the relative angle between the dipole antenna 92 and the antenna 31 of the MW sensor 3 is 0 °, the sensor detection level is 739 mV. The sensor detection level when the relative angle is 90 ° is 68.
It was 5 mV. That is, when the relative angle is 90 °, it is understood that there is almost no interference of radio waves.

As described above, the dipole antenna 92 and the M
It can be seen that when the relative angle between the W sensor 3 and the antenna 31 is 90 °, the interference of radio waves can be minimized. For this reason, as shown in FIG. 6, when a pair of security sensor units 1A and 1B are arranged to face each other, the inclination angle of the antenna 31 is set to 45 ° to set the relative angle between the antennas 31 and 31 to each other. Can be set to 90 °, and the security sensor units 1A and 1B can be installed in a state where interference of radio waves is the least. As an example of this effect, it is possible to suppress radio wave interference even when the distance between the sensors is set to 1/10 as compared with the conventional MW sensor.

-Other Embodiments- In the above embodiment, the case where the MW sensor 3 is applied to the security system 1 configured by using the PIR sensor 4 together is described. The present invention is not limited to this.
The present invention is also applicable to a case where the W sensor 3 is used alone.

Further, the inclination angle of the antenna 31 is not limited to 45 °, and the effect of reducing the interference of radio waves can be obtained regardless of the inclination angle except vertical and horizontal directions. . As described above, the effect is greatest when the tilt angle of the antenna 31 is set to 45 °, but by setting the tilt angle of the antenna 31 so that the relative angle falls within the range of 45 to 135 °. That is, the inclination angle of the antenna 31 is set to 45 ° ± 22.
By setting the angle to 5 °, a practically effective effect of reducing the electric field intensity ratio to −3 dB or less can be obtained.

As shown in FIG. 6, the security sensor unit 1 is mounted on opposing wall surfaces 7a, 7a of the same room 7.
The present invention is not limited to the case where the A and 1B are arranged, and is also applicable to the case where the security sensor units are arranged in the rooms a1 and a2 adjacent to each other as shown in FIG.

[0033]

As described above, in the present invention, a plurality of MW sensors are arranged to face each other by setting the extension direction of the antenna for transmitting and receiving microwaves to the MW sensor in an oblique direction. Even in such a case, the polarization planes of the antennas are prevented from overlapping on the same plane. Therefore, the antenna polarization planes of the microwaves transmitted from the MW sensor do not overlap on the same plane, whereby interference between radio waves can be suppressed,
A malfunction of the sensor can be avoided and its reliability can be improved. Conventionally, the oscillation frequencies of the MW sensors have been different from each other in order to prevent interference between radio waves. According to the present invention, interference between radio waves can be suppressed even when MW sensors having the same configuration are combined, so that the work of manufacturing and installing the MW sensor can be simplified.

[Brief description of the drawings]

1A and 1B are diagrams showing a security sensor unit according to an embodiment, wherein FIG. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line BB in FIG.

FIGS. 2A and 2B are diagrams for explaining a detection area of each security sensor unit, wherein FIG. 2A is a side view of a room and FIG. 2B is a plan view of the room.

FIG. 3 is a block diagram showing a system configuration of the security system.

FIG. 4 is a diagram showing a circuit configuration of the MW sensor.

FIG. 5 is a front view of the inside of the MW sensor showing an installation state of the antenna.

FIG. 6 is a diagram showing a state where each security sensor unit is installed on a wall surface.

FIG. 7 is a diagram showing an experimental device used in an experimental example.

FIG. 8 is a diagram illustrating a relationship between a relative angle between a dipole antenna and an antenna of a MW sensor and an electric field intensity ratio.

FIG. 9 is a diagram showing a detection level waveform on an oscilloscope in an experimental example, where (a) shows a dipole antenna and M
FIG. 7B is a diagram illustrating a waveform when the relative angle between the W sensor and the antenna is 90 °, and FIG. 7B is a diagram illustrating a waveform when the relative angle between the dipole antenna and the MW sensor antenna is 0 °.

FIG. 10 (a) shows M on the wall facing each other in the same room.
It is a figure which shows the state which arranged the W sensor, and (b) which shows the state which arranged the MW sensor in the mutually adjacent room.

[Explanation of symbols]

 3 Microwave sensor 3A, 4A Detection area 31 Antenna

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Claims (2)

[Claims] 1. An antenna for transmitting microwaves to a detection area and receiving microwaves reflected from the detection area, and detects a human body in the detection area based on the microwaves received by the antenna. In the microwave sensor, the antenna is provided so as to extend in a diagonal direction except a vertical direction and a horizontal direction in a sensor installation state. 2. The microwave sensor according to claim 1, wherein an extension direction of the antenna is set to a direction inclined by 45 ° with respect to a vertical direction in a state where the sensor is installed.