JP2834233B2 - Radio alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a radio wave transmitting unit and a radio wave receiving unit in a predetermined area facing each other, and uses a radio wave radiated in the same area to cover a security area. An on-off type radio alarm device that detects an intruder or an intruding object such as an intruder, and issues an alarm when detected.
In particular, the present invention relates to an improved radio alarm device that compensates for a decrease in the level of a received radio wave caused by a phase change of a reflected wave included in a received radio wave in a receiving unit.

(Prior art)

2. Description of the Related Art Conventionally, various intruder detection methods using radiated radio waves have been proposed and realized as radio wave alarm devices. Conventional radio warning devices generally take measures to generate a warning when the level of a received radio wave at a receiving unit falls below a predetermined value for radio waves transmitted within a security area. Generally, when radio waves are used, the radio waves have a property of being radiated with a spread. Therefore, when the radio waves hit the ground surface or the surface of another object, they are reflected waves, are combined into a direct wave, and are received by the receiving unit.

[Problems to be solved by the invention]

In this case, the reflection coefficient and the phase of the reflected wave change according to the surface state of the object surface or the like at the reflection point. In other words, if the phase of the reflected wave is delayed by 180 ° from that of the direct wave, they are combined so as to cancel each other out, the intensity of the received radio wave is greatly attenuated, and it is as if the intruder cut off the radio wave and malfunctions. Occur. A main object of the present invention is to solve the above-mentioned problems in the radio alarm device.

Another object of the present invention is to solve the above-mentioned conventional problems by detecting a change in the phase caused by a change in the reflection state of the reflected wave, thereby reducing the received radio wave intensity caused by the change in the phase. As a result, and as a result, it is intended to provide a highly reliable radio alarm apparatus which is not affected by the reflected wave from the object surface.

[Means for solving the problem]

That is, according to the present invention, a transmission unit that radiates radio waves in a security area and a reception unit that is provided in an arrangement facing the transmission unit and receives radio waves radiated from the transmission unit into the security area are provided. In the radio wave alarm device of the opposing cutoff type, which monitors the state of attenuation of radio waves in the security area to determine the presence or absence of an intruder and issues an alarm indicating the presence of the intruder, the radio wave is directly transmitted to the receiver. First filter means for extracting a DC component from a composite radio wave of the received radio wave and the received radio wave propagated through the reflection path; second filter means for extracting a modulated AC component having a predetermined frequency from the composite radio wave component; Phase detecting means for comparing the modulated AC component taken out by the second filter means with a reference wave having a constant frequency to detect a phase difference, and detecting a phase difference by the phase detector. And compensating circuit means for providing a compensation component to the DC component extracted from the first filter means only when an output value is input, wherein the output level from the compensation circuit means is set to a constant attenuation setting. A radio alarm device is provided that issues an alarm when the value is attenuated below a value.

Hereinafter, the radio wave alarm device of the present invention will be described through embodiments with reference to the accompanying drawings.

〔Example〕

FIG. 1 is a block diagram of a radio alarm device according to an embodiment of the present invention. FIG. 2 is a diagram showing a transmission path of a microwave in a radio wave alarm device of an opposing cutoff system using a microwave according to the present invention. FIG. 3 is a waveform diagram for explaining the operation of the radio wave alarm device.

First, referring to FIG. 2, a microwave transmitting unit 1 and a microwave receiving unit 2 are provided in a predetermined security area R in an opposed arrangement. Here, D is a direct wave radiated from the transmission unit 1, and R is a point a on the surface in the security area.
Is a reflected wave reflected at. For example, if the reflection condition changes temporarily due to accumulation of rainwater at the point a, the phase of the reflected wave may change and the direct wave D may be canceled. As a result, since there is no intruding object such as an intruder or an intruding vehicle, the received radio wave is attenuated. Therefore, the receiving unit 2 determines that an intruding object has occurred, and as a result, malfunction may occur. possible. Therefore, the present invention is intended to prevent such a malfunction.

Referring to FIG. 1, the transmission unit 1 includes a stabilized power supply circuit 1.
1, a gun oscillator 12, a modulator 13, and a transmitting antenna 14. When a predetermined voltage is applied by the stabilized power supply circuit 11, a predetermined microwave is generated from the gun oscillator 12. The microwave is, for example, is amplitude modulated by a modulator 13 which outputs a pulse signal of a frequency f _1, is radiated from the transmitting antenna 14 to space security area.

On the other hand, the receiving unit 2 is provided with a receiving antenna 21, and the receiving antenna 21 is provided at a predetermined interval from the transmitting antenna 14 of the transmitting unit 1 in the security area. The micro radio wave received by the receiving antenna 21 is detected by a detection circuit 22.
The output of the detection circuit 22 includes a DC component, a modulated AC component, and a carrier component of the received radio wave corresponding to the combined wave of the direct wave and the reflected wave. The radio wave component other than the DC component has a reflection coefficient r at the reflection point and a phase delay Φ
And function. Therefore, for example, when rainwater accumulates at the reflection point, the condition of the reflection point changes, that is, the reflection coefficient r and the phase delay Φ change. The DC component of the radio wave input detected by the detection circuit 22 is extracted by the low-pass filter 23, amplified by the DC amplifier 25 at the next stage, and output.

On the other hand, the modulated AC component is extracted by the band-pass filter 24, and then the modulated AC component is converted into a rectangular wave by the level converter 26.

The radio wave component converted into a rectangular wave by the level converter 26 is sent to the phase detector 28. At this time, the reference pulse
f ₂ the reference local oscillator 27 which outputs a rectangular wave is in phase detector
Connected to 28. A reference pulse f ₂ of the reference local oscillator 27 emits a phase detector 28 and a radio wave components from the level converter 26 detects the phase difference. That is, when a phase change occurs at the reflection point a, the phase detector 28 detects a phase difference. The phase detector 28 is connected to a next-stage level compensation signal generator 29. The level compensation signal generator 29 is activated when a phase change signal from the phase detector 28 is input, and the level compensation signal generator 29 is activated. It is provided so as to generate an output signal for a radio wave corresponding to the minute. A compensation circuit 30 is provided as electric circuit means for receiving the output signal of the level compensation signal generator 29 and performing a compensation operation for the level decrease. A judging circuit 31 is provided in connection with the compensating circuit 30. The judging circuit 31 judges whether or not the degree of attenuation of the received radio wave is greater than a predetermined value (criterion for judging the presence of an intruder). Then, when it is determined that the radio wave is interrupted and the degree of attenuation is larger than a certain value, it is determined that the intruding object has interrupted the radio wave in the security area, and a warning circuit is output. The operation of the receiving section 2 having the above-described configuration will be described in more detail with reference to waveform diagrams shown in FIGS.

First, assuming a normal time when there is no intruding object in the alarm area, at this time, the intensity (level) of the received radio wave should be maintained at a constant level. In this state, since there is no cause of radio wave interruption in the security area, the output level of the phase detector 28 in FIG. 1 is adjusted in advance to be zero. The output of the compensation circuit 31 is also set to a constant level.

When the combined wave of the direct wave and the reflected wave is adjusted to be the maximum under the above-described setting conditions, the combined wave on the input side of the detection circuit 22 is directly changed as shown in the waveform diagram of FIG. The radio wave intensity of the combined wave of the reflected wave and the reflected wave is added, and the output side of the detection circuit 22 outputs a high DC component as shown in the waveform diagram of FIG. I have.

In such a state, when the reflected wave is reflected by a pool of rainwater, for example, a phase shift occurs in the reflected wave, and the detection circuit 22
As shown in the waveform diagram of FIG. 3 (b), the reflected wave whose phase is shifted acts to cancel the direct wave and the synthesized wave is attenuated, and the output side of the detection circuit 22 receives the third wave. As shown in the waveform diagram of FIG. 3D, the phase of the modulation component of a predetermined frequency is delayed, the DC component is reduced, and an erroneous alarm is generated when the modulation component falls below a predetermined reference value.

However, in the radio alarm device having the receiving unit 2 according to the present embodiment, the malfunction is not caused by performing the compensation action identified as the radio wave interruption by the intruder even in this case, and FIG.
A description will be given based on (i).

First, the receiving unit 2 of the radio wave alarm device, during the action of the apparatus, reference local oscillator 27 outputs the reference pulse f ₂ as shown in FIG. 4 (A) to the phase detector 28. Further, the output of the level converter 26 as shown in FIG. 4 (b) in which the frequency of the modulated AC component is a rectangular wave is also output to the phase detector 28. Then detected as a waveform signal as shown the phase difference between the output from the phase detector 28 in the reference pulse f ₂ and level converter 26 in FIG. 4 (c), also shown in FIG. 4 (e) As described above, when the output of the DC amplifier 25 is attenuated, the phase detector 28 performs detection based on the phase shift as shown in FIG. 4 (c) and performs the waveform output in FIG. 4 (d). (Same as (f))) is output. Further, the level compensation signal generator 29 is triggered by the output of the phase detector 28 and corresponds to the level decrease to be compensated, FIG.
The compensation circuit 30 outputs a waveform as shown in FIG. Accordingly, the output of the compensating circuit 30 becomes constant, and the determination circuit 31 does not attenuate to a predetermined constant value, so that no alarm signal is transmitted.

〔The invention's effect〕

According to the present invention, in the security operation process in which the radio wave alarm device detects the presence or absence of an intruder in the security area and generates an alarm,
When a radio wave radiated from a transmitter is received by a receiver via a space in a security area or a reflecting surface, a radio wave attenuation based on a phase change of a reflected radio wave generated in the received radio wave is detected and the attenuation is detected. Since the phase of the reflected radio wave changes and cancels the directly propagated radio wave, the radio wave intensity is attenuated and a malfunction such as determining that there is an intruder is prevented. There is an effect that reliability in operation is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a radio alarm device according to an embodiment of the present invention. FIG. 2 is a diagram showing a transmission path of a microwave in a radio wave alarm device of an opposing cutoff system using a microwave according to the present invention. FIG. 3 and FIG. 4 are waveform diagrams for explaining the operation of the radio wave alarm device. 1 ... transmitting unit, 2 ... receiving unit, 21 ... receiving antenna, 22
...... Detector circuit, 23 ... Low pass filter, 24 ... Band pass filter, 26 ... Level converter, 28 ... Phase detector, 29 ... Level compensation signal generator, 30 ... Compensation circuit, 31
... Judgment circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G08B 13/00-15/02

Claims (2)

(57) [Claims] A transmitting unit that radiates radio waves into the security area; and a receiving unit that is provided to face the transmitting unit and receives radio waves radiated from the transmitting unit into the security area. In a radio alarm device of the opposing cutoff type that monitors presence or absence of an intruder by monitoring the attenuation state of the radio wave in the security area and issues an alarm indicating the presence of the intruder, the received radio wave transmitted directly to the receiving unit A first filter for extracting a DC component from a composite radio wave of the received radio wave and the received radio wave propagated through the reflection path; a second filter for extracting a modulated AC component having a predetermined frequency from the composite radio wave component; Phase detecting means for comparing the modulated AC component taken out by the second filter means with a reference wave having a constant frequency to detect a phase difference, and detecting the phase difference by the phase detecting means And a compensation circuit means for providing a compensation component to the DC component extracted from the first filter means only when a value is input, wherein the output level from the compensation circuit means is a constant attenuation set value. An electric wave alarm device, wherein an alarm can be issued when the electric power is attenuated. 2. The apparatus according to claim 1, wherein said first filter means is formed of a low-pass filter for extracting only a DC component, and said second filter means is constituted of a band-pass filter for extracting only an AC component of a predetermined frequency in a received radio wave. Item 7. The radio wave alarm device according to Item 1.