JPH06284479A - Radio monitoring system - Google Patents

Abstract

PURPOSE:To prevent a malfunction and to extend communication distance by transmitting and receiving a burst wave by spread spectrum communication by a signal generation part, a spread spectrum modulation part and a spread spectrum demodulation part. CONSTITUTION:A burst signal (c) generated in the signal generation part of a deciding device 10 is modulated in a spread spectrum modulator 15 and the burst signal is transmitted from an antenna 16. The antenna 21 of a response device 20 receives the signal and generates a reception signal. At this time, when a door to be an object to be monitored is closed, a switch 22 transmits the reception signal to a solid resonance element 23, the resonance element 23 resonates by the reception signal and the antenna 21 transmits it as an echo wave. Where the antenna 16 of the device 10 receives the echo wave, the reception signal is transmitted to a spread spectrum demodulator 17 and it is demodulated. A decision part decides the state as the opening and closing state of the switch 22 of the device 20 based on the demodulation signal from the demodulation part. Thus, by transmitting and receiving the burst wave by spread spectrum communication, a malfunction can be prevented and communication distance can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless monitoring system used for monitoring a change in the status of monitored objects such as doors, windows and keys.

[0002]

2. Description of the Related Art In this wireless monitoring system, a response device attached to an object to be monitored and wirelessly communicates with the response device,
Some include a determination device that monitors a change in the state of the monitored object. Further, in some wireless monitoring methods, the response device operates without a power source.

In the wireless monitoring system which operates without a power source, the response device resonates with the frequency of the received signal generated by receiving the radio wave of the determination device. Then, the response device uses this resonance to send an echo wave (reflected wave) to the determination device. At this time, whether to send an echo wave is controlled depending on the state of the monitored object.

An example of this wireless monitoring system is Japanese Patent Laid-Open No. 3-11.
It is shown in Japanese Patent No. 8691.

With such a wireless monitoring system, the open / closed state of, for example, a door or a window can be checked by a determination device installed at a remote place. Moreover, since the response device attached to the door or the window operates without a power source, the wiring for the power source is not required in the door or the window.

[0006]

By the way, in the above-mentioned wireless monitoring system, the response device generates an echo wave by resonance and sends it to the determination device, so that there is a similar device in the same communication area. , They interfere with each other and cannot communicate. In addition, the above-described wireless monitoring method is weak against external noise, and if the distance between the determination device and the response device is long, the wireless monitoring system is easily affected by noise and a malfunction is likely to occur.

An object of the present invention is to eliminate the above drawbacks and to provide a radio monitoring system capable of preventing malfunction and extending the communication distance.

[0008]

In order to achieve the object of the present invention, a determination device is provided with a first signal generating section for generating a burst signal and a first antenna section for radiating the burst signal as a burst wave. A second antenna unit that receives a burst wave and generates a reception signal, and a signal that resonates with the reception signal of the second antenna unit
The response device includes a resonance unit that emits an echo wave from the antenna unit, and a switch unit that is inserted between the second antenna unit and the resonance unit and that opens and closes according to a change in the state of the monitored object.
In the wireless monitoring method in which the determination device includes a determination unit that determines the open / closed state of the switch unit based on the reception signal generated by the first antenna unit that receives the echo wave, the determination device is
A second signal generating unit that generates a predetermined code sequence signal, and is inserted between the first signal generating unit and the first antenna unit, modulates the burst signal with the code sequence signal,
A spectrum that is inserted between a spread spectrum modulation unit that spreads a burst signal in a wide band and a first antenna unit and a determination unit, and demodulates a reception signal of the first antenna unit with a code sequence signal from the second signal generation unit. And a spread demodulation unit.

[0009]

With this configuration, the spread spectrum modulator of the determination device modulates the burst signal from the first signal generator with the code sequence signal from the second signal generator. The modulated burst signal is radiated as a burst wave from the first antenna unit.

The second antenna section of the transponder generates a reception signal when receiving the burst wave. At this time, if the switch unit is in the closed state in the state of the monitored object, the resonance unit resonates with the received signal of the second antenna unit and causes the second antenna unit to radiate the echo wave. Further, when the switch section is in the open state, the received signal of the second antenna section is not sent to the resonance section, so that no echo wave is generated.

The first antenna section of the determination device generates a reception signal when receiving the echo wave. The spread spectrum demodulation unit demodulates the received signal from the first antenna unit with the code sequence signal from the second signal generation unit. The determination unit determines the open / closed state of the switch unit of the response device based on the demodulated signal from the spread spectrum demodulation unit.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
It is a block diagram showing. This wireless monitoring system is
A determination device 10 that determines the open / closed state of a monitored object such as a window, a key, and a crescent, and a response device 2 that is attached to the monitored object and communicates with the determination device 10 by magnetic field coupled communication.
It has 0 and.

The determination device 10 includes an original oscillator 11 and
A burst signal generator 12, a burst generator 13,
A spread code generator 14 as a second signal generator, a spread spectrum modulator 15 as a spread spectrum modulator,
An antenna 16 as a first antenna unit, a spread spectrum demodulator 17 as a spread spectrum demodulation unit, and a processing / display unit 18 as a determination unit are provided.

In the first embodiment, the first signal generator is
An original oscillator 11, a burst signal generator 12, and a burst generator 13 are provided.

The response device 20 further includes an antenna 21 as a second antenna section, a switch 22 as a switch section, and an individual resonator 23 as a resonance section.

The original oscillator 11 of the judging device 10 generates a pulse-shaped original oscillation signal a as shown in FIG. Then, the original oscillation signal a is sent to the burst generator 13.

The burst signal generator 12 generates a burst signal b as shown in FIG. The burst signal b is, for example, a pulse-shaped signal having a cycle eight times that of the original oscillation signal a.

The burst generator 13 generates a burst signal c based on the original oscillation signal a from the original oscillator 11 and the burst signal b from the burst signal generator 12. In order to generate the burst signal c, the burst generator 13 calculates the logical product of the original oscillation signal a and the burst signal b, for example.

The spread code generator 14 generates a signal of a predetermined code sequence necessary for spread spectrum modulation and spread spectrum demodulation. The signal of this code sequence has a wider band than the burst signal from the burst generator 13.

The spread spectrum modulator 15 is a signal of the code sequence from the spread code generator 14, and is a burst generator 13.
The burst signal from is spread-spectrum-modulated into a broadband signal.

The antenna 16 transmits and receives the magnetic field component of electromagnetic waves. That is, the antenna 16 is a burst signal which is spread spectrum modulated by the spread spectrum modulator 15,
Emit a burst wave. Further, the echo signal sent from the response device 20 is received to generate a reception signal. That is, the antenna 16 generates an induced voltage by electromagnetic induction of an echo wave.

The spread spectrum demodulator 17 includes the antenna 1
The received signal from 6 is subjected to spread spectrum demodulation. That is, the spread spectrum demodulator 17 uses a correlator (not shown) to obtain the correlation value between the signal of the code sequence from the spread code generator 14 and the received signal. Then, a comparator (not shown) is used to compare the preset threshold value with the correlation value to demodulate the received signal.

The processing / display unit 18 determines the open / closed state of the monitored object based on the demodulated received signal from the spread spectrum demodulator 17. That is, the processing / display 1
8 makes this determination based on the presence or absence of an echo wave from the response device 20. Then, the processing / display unit 18
For example, a light emitting diode is turned on or off, or a liquid crystal display is used to notify the outside.

The antenna 21 of the response device 20 transmits and receives the magnetic field component of the radio wave in the same manner as the antenna 16.

The switch 22 is attached to an object to be monitored and opens / closes according to the change of the state. For example, switch 2
When attached to a door, 2 is open when the door is open and closed when the door is closed. And
In the closed state, the switch 22 directly connects the antenna 21 and the solid resonator 23.

The solid resonator 23 is composed of a crystal resonator, a ceramic resonator, or the like, resonates with a signal received from the antenna 21, and stores energy due to resonance. Then, the solid resonator 23 causes the antenna 21 to radiate an echo wave with this energy.

Next, the operation of this embodiment will be described.

The spread spectrum modulator 15 spread spectrum modulates the burst signal c generated by the original oscillator 11, the burst signal generator 12 and the burst generator 13 of the judging device 10 to convert it into a wide band signal. Antenna 16
Transmits the magnetic field component of this broadband burst signal into the air.

Upon receiving the magnetic field from the antenna 16, the antenna 21 of the response device 20 generates an induced voltage as a reception signal. At this time, if the door to be monitored is closed, the switch 22 sends the reception signal from the antenna 21 to the solid resonator 23. The solid resonator 23 resonates with this received signal, and the antenna 21 transmits a magnetic field component as an echo wave by this resonance. That is, the echo wave is transmitted during the time T (FIG. 2) between the pulses of the burst signal b.

Upon receiving the echo wave, the antenna 16 of the determination device 10 sends the induced voltage as a received signal to the spread spectrum demodulator 17. The spread spectrum demodulator 17 spread spectrum demodulates the received signal and processes / displays it 18.
Send to. The processing / indicator 18 displays during the time T (FIG. 2),
Since the echo signal from the determination device 10 exists, it is determined that the switch 22 of the response device 20 is in the closed state.

On the other hand, when the door to be monitored is opened, the received signal from the antenna 21 is not added to the solid resonator 23, so that no echo wave is generated. At this time, the processing / display unit 18 of the determination device 10 determines that the switch 22 of the response device 20 is in the open state because there is no echo signal during the time T (FIG. 2).

In this way, the judgment device 10 and the response device 20 communicate with each other. At this time, since the burst signal c is transmitted by spread spectrum, it is less likely to be affected by noise from the outside. As a result, the communication distance between the determination device 10 and the response device 20 can be extended.

Even if a plurality of similar devices exist in the communication area, they can interfere with each other if the code sequence signals generated by the spread code generator 14 of the determination device 10 are different. Absent.

Furthermore, since the determination device 10 performs modulation and demodulation of spread spectrum communication, one spreading code generator 14 can be shared for modulation and demodulation, and synchronization of the spreading code generator 14 is unnecessary. Therefore, the circuit configuration can be simplified.

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention.
It is a block diagram showing. The second embodiment uses a burst signal generator 19 instead of the burst signal generator 12 of the first embodiment. The burst signal generator 19 divides the original oscillation signal a from the original oscillator 11 to generate a burst signal b.

According to the second embodiment, the burst signal generator 1
Since 9 uses the original oscillation signal a from the original oscillator 11, the burst signal generator 19 does not need an oscillation circuit, and the circuit configuration can be simplified. As a result, the second embodiment enables cost reduction as compared with the first embodiment.

The first and second embodiments have been described above. The spread spectrum modulation used in these embodiments may be any method, for example, direct spread (DD) method, frequency hopping (FH) method, time hopping (TH) method, hybrid method and the like. further,
The code modulation includes AM (amplitude) modulation, FM (frequency) modulation, PSK (pulse phase) modulation and the like.

[0039]

As described above, according to the present invention, since the burst signal is transmitted / received by the spread spectrum communication by the second signal generating section, the spread spectrum modulating section and the spread spectrum demodulating section, it is resistant to noise. The malfunction can be prevented and the communication distance can be extended. As a result, the reliability of the device can be improved.

At this time, since the second signal generator is used for modulation and demodulation of spread spectrum communication, synchronization between modulation and demodulation is unnecessary. As a result, control related to synchronization is not required, and the circuit configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform diagram of the embodiment of FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 10 Judgment device 13 Burst generator 14 Spread code generator 15 Spread spectrum modulator 16 Antenna 17 Spread spectrum demodulator 18 Processing / display

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G08B 13/22 4234-5G 25/10 9377-5G

Claims (1)

[Claims] 1. A first signal generator that generates a burst signal, and a first signal generator that radiates the burst signal as a burst wave.
A determination device includes an antenna unit, a second antenna unit that receives the burst wave and generates a reception signal, and a signal that resonates with the reception signal of the second antenna unit and the resonance generates the second antenna. The response device includes a resonance unit for radiating an echo wave from the unit, and a switch unit that is inserted between the second antenna unit and the resonance unit and opens / closes according to a change in the state of the monitored object. In the wireless monitoring system in which the determination device includes a determination unit that determines the open / closed state of the switch unit based on the received signal generated by the first antenna unit, the determination device is a predetermined code sequence. A second signal generating section for generating a signal, inserted between the first signal generating section and the first antenna section, modulating the burst signal with the signal of the code sequence, A spread spectrum modulation unit that spreads a burst signal in a wide band, and a received signal of the first antenna unit that is inserted between the first antenna unit and the determination unit and is a code sequence signal from the second signal generation unit. And a spread spectrum demodulation unit that demodulates the wireless monitoring system.