JP2007043641A - Disaster preventive wireless broadcast receiver and disaster preventive administrative wireless system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disaster preventive wireless broadcast receiver and disaster preventive administrative wireless system with which the influence of a local oscillation signal of an ordinary broadcast receiving circuit can be suppressed and reception capability of the disaster preventive wireless receiver can be prevented from being reduced. <P>SOLUTION: A disaster preventive wireless broadcast receiver includes: a disaster preventive receiving circuit 12 for receiving a disaster preventive radio signal; an AM/FM receiving circuit 13 for receiving an ordinary broadcasting signal and obtaining an intermediate frequency signal on the basis of a local oscillation signal; an audio amplifier 14 that can be shared between the disaster preventive wireless receiving circuit 12 and the AM/FM receiving circuit; a changeover switch 16 for selectively inputting, to the audio amplifier 14, outputs of the disaster preventive wireless receiving circuit 12 and the AM/FM receiving circuit 13; and a squelch circuit 122 which instructs the changeover switch 16 to select the output of the AM/FM receiving circuit 13 when no disaster preventive radio signal is received, and to select the output of the disaster preventive wireless receiving circuit 12 when the disaster preventive radio signal is received, wherein the local oscillation frequency of an FM broadcast receiver circuit is set to be added to the frequency of an FM broadcasting signal just for an intermediate frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a disaster prevention radio system and a disaster prevention radio broadcast receiver capable of receiving a disaster prevention radio system used in administrative agencies such as municipalities.

Government agencies such as municipalities have adopted disaster prevention radio systems that notify residents residing in municipalities of emergency reports, evacuation information, and information related to general administrative work in the event of a disaster such as an earthquake, fire, or flood.
The above-mentioned disaster prevention administrative radio system is installed, for example, in a master station installed at a municipal office, an outdoor loudspeaker receiving device equipped with a receiving device, a speaker, etc. in each district of the municipality, and in each resident's home It consists of a system having a separate door-to-door receiver.
In an emergency, various types of information are transmitted from the master station, and the outdoor loudspeaker receiving apparatus amplifies the received information through a speaker and notifies the residents in the area where the outdoor loudspeaker receiving apparatus is installed.
Various information transmitted from the master station is also received by the door-to-door receiver, and the emergency information is notified to the residents of each household through the door-to-door receiver.
As mentioned above, the disaster prevention administrative radio system is mainly used to notify the residents of emergency information promptly, and is also used to notify general administrative work information at regular time intervals, as well as on the hour, etc. Is done.

  In the disaster prevention administrative radio system described above, the door-to-door receiver installed in each home has an automatic incoming call function that receives a radio signal transmitted from the master station and automatically outputs it from a speaker, etc. Can always receive radio signals.

In addition to the disaster prevention radio receiver, the door-to-door receiver is also equipped with an AM radio / FM radio receiving circuit, and is configured to be able to listen to AM radio or FM radio.
And in the door-to-door receiver, even if the disaster prevention radio is receiving a normal radio broadcast, a method is adopted in which the disaster prevention broadcast is detected and automatically switched to the reception of the disaster prevention broadcast.

The local oscillation frequency of FM broadcasting is generally set to a frequency obtained by subtracting an intermediate frequency from the broadcasting frequency.
In conventional door-to-door receivers, it is common to switch between FM radio reception and disaster prevention radio reception by switching an existing FM radio reception circuit and disaster prevention radio receiver with a switch.

  By the way, in a door-to-door receiver that combines FM radio and disaster prevention radio receiver, if the local oscillation frequency of FM radio approaches the frequency of disaster prevention radio broadcasting, or in the worst case, the local oscillation signal is close If the received disaster prevention radio receiver is in a so-called interference state or the local oscillation signal level is high, the local oscillation signal is received instead of the disaster prevention reception signal, and the reception capability of the disaster prevention radio receiver is There is a disadvantage that it falls extremely.

  An object of the present invention is to provide a disaster prevention radio broadcast receiver capable of suppressing the influence of a local oscillation signal of a normal broadcast receiving circuit and preventing a reduction in reception capability of the disaster prevention radio receiver, and a disaster prevention administrative radio using the disaster prevention radio broadcast receiver. The purpose is to provide a system.

  In order to achieve the above object, a disaster prevention radio broadcast receiver according to a first aspect of the present invention receives a disaster prevention radio reception circuit that receives a disaster prevention radio signal, a normal broadcast signal, and at least an intermediate frequency based on a local oscillation signal. A broadcast receiving circuit having a function of obtaining a signal, an output amplifier that can be shared by the disaster prevention radio receiving circuit and the broadcast receiving circuit, and outputs of the disaster prevention radio receiving circuit and the broadcast receiving circuit are selectively used as the output amplifier. If the disaster prevention radio signal is not received, the output of the broadcast receiving circuit is selected, and if the disaster prevention radio signal is received, the output of the disaster prevention radio receiving circuit is selected. And a circuit for instructing the changeover switch, and the local oscillation frequency of the broadcast receiving circuit is set to be added to the frequency of the broadcast signal by an intermediate frequency.

  Preferably, the disaster prevention radio reception circuit includes detection means for detecting that the disaster prevention radio signal has been received even when the normal broadcast signal is being received, and the disaster prevention radio signal is received by the detection means. If not detected, the changeover switch selects the output of the broadcast receiving circuit, and if the disaster prevention radio signal is detected by the detection means, the changeover switch outputs the output of the disaster prevention radio reception circuit. Select.

  Preferably, the detection means compares whether the magnitude of the noise included in the output signal of the disaster prevention radio reception circuit is larger or smaller than a preset value, and if the noise is larger, the disaster prevention radio is It recognizes that it has not been detected, and recognizes that a disaster prevention radio signal has been detected if the noise is smaller.

  Preferably, the broadcast signal is an FM broadcast signal, and the frequency band of the disaster prevention radio signal is set to a frequency band obtained by subtracting the intermediate frequency from the frequency of the FM broadcast signal or in the vicinity of the frequency band.

  A disaster prevention administrative radio system according to a second aspect of the present invention includes a master station that transmits a disaster prevention radio signal, and a disaster prevention radio broadcast receiver that can receive a disaster prevention radio signal from the master station, and the disaster prevention radio The broadcast receiver includes a disaster prevention radio reception circuit that receives a disaster prevention radio signal, a broadcast reception circuit that has a function of receiving a normal broadcast signal and obtaining an intermediate frequency signal based on at least a local oscillation signal, and the disaster prevention radio reception circuit. An output amplifier that can be shared with the broadcast receiving circuit, a changeover switch that selectively inputs the output of the disaster prevention radio reception circuit and the broadcast reception circuit to the output amplifier, and a case where the disaster prevention radio signal is not received A circuit for selecting the output of the broadcast receiving circuit and instructing the changeover switch to select the output of the disaster prevention radio receiving circuit when the disaster prevention radio signal is received. Local oscillation frequency of the broadcast receiving circuit is set to sum the frequency of the intermediate frequency component only the broadcasting signal.

  According to the present invention, there is an advantage that it is possible to suppress the influence of the local oscillation signal of the normal broadcast receiving circuit and to prevent the reception capability of the disaster prevention radio receiver from being lowered.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of a disaster prevention administrative radio system according to the present invention.

A disaster prevention administrative radio system 100 shown in FIG. 1 includes a master station 101, a disaster prevention radio broadcast receiver 1 that is a door-to-door receiver provided in each home 301, and an outdoor loudspeaker reception device 201 that is installed for each area of a municipality, for example. And have.
For example, the master station 101 is installed in a municipal office, and outputs an emergency broadcast as a radio signal in an emergency such as a disaster.
The master station 101 outputs information related to administrative work as a radio signal at predetermined time intervals, for example, at predetermined times in the morning and evening.
The disaster prevention radio signal output from the master station 101 is transmitted by, for example, FM waves in a very narrow frequency band. The frequency band is 68 MHz to 70 MHz, which is a frequency band near a part of the FM broadcast frequency band.

FIG. 2 is a block diagram showing an embodiment of the disaster prevention radio broadcast receiver provided in each home 301 described above.
As shown in FIG. 2, the disaster prevention radio broadcast receiver 1 includes a reception antenna 11, a disaster prevention radio reception circuit 12, a radio broadcast (AM / FM) reception circuit 13, an audio amplifier (output amplifier) 14, a speaker 15, and a changeover switch. 16 as a main component.

  The receiving antenna 11 is an antenna that receives a disaster prevention radio signal from the master station 101 and receives a generally broadcast AM / FM broadcast. The disaster prevention radio receiving circuit 12 and the AM / FM receiving circuit 13 Shared with.

  The disaster prevention radio reception circuit 12 includes a disaster prevention radio circuit 121 that receives the disaster prevention radio and performs predetermined processing such as predetermined detection, and a squelch circuit 122.

The disaster prevention radio circuit 121 receives the disaster prevention radio, performs predetermined processing such as detection, and outputs a disaster prevention signal, which is an electrical signal obtained, to the changeover switch 16.
More specifically, the disaster prevention radio circuit 121 is set to be able to receive only FM waves in the frequency band of the radio signal from the master station 101, for example, and the radio signal from the master station 101 via the reception antenna 11. And outputs the disaster prevention signal S121 to the changeover switch 16.

  The squelch circuit 122 receives FM waves, determines whether or not a disaster prevention radio (disaster prevention radio wave) is received, and selects and receives the output signal S121 of the disaster prevention radio circuit 121 when it is determined that it has been received. If it is determined that it is not, the output signal S13 of the AM / FM receiving circuit 13 is selected and the squelch signal S122 instructing to output to the audio amplifier 14 is output to the changeover switch 16.

  That is, the squelch circuit 122 functions as a detection unit that detects that a disaster prevention radio signal has been received even when a normal broadcast signal is being received. When the disaster prevention radio signal is not detected by the squelch circuit 122, the changeover switch 16 selects the output signal S13 of the AM / FM receiving circuit 13 and outputs it to the audio amplifier 14. When the disaster prevention radio signal is detected by the squelch circuit 122, the output signal S121 of the changeover switch 16 and the disaster prevention radio circuit 121 is selected and output to the audio amplifier 14.

  The squelch circuit 122 of this embodiment compares whether the magnitude of noise included in the output signal of the disaster prevention radio circuit (disaster prevention radio reception circuit) 121 is larger or smaller than a preset value, and the noise is larger Recognizes that the disaster prevention radio is not detected, and recognizes that the disaster prevention radio signal is detected when the noise is smaller.

Here, squelch means that in an FM receiver, in order to reduce or reduce noise generated between stations at the time of tuning, a difference in SN ratio between tuning and non-tuning is detected, and the SN ratio is a specified value. When the value is smaller, the output is turned off because there is a lot of noise, and when the S / N ratio is larger than a specified value, it means a function that turns on the output with little noise.
In the disaster prevention radio reception circuit 12 of the present embodiment, this squelch function is used to turn off the reception circuit output when there is no broadcast and to turn on the reception circuit output when the broadcast is received. The switching signal at this time controls band switching and on / off of the audio amplifier and radio receiving circuit.

FIG. 3 is a diagram illustrating a control state of the changeover switch by the squelch output.
As shown in FIG. 3, in this embodiment, when the squelch is on, the disaster prevention output is off, the AM / FM output is on, and when the squelch is off, the disaster prevention output is on and the AM / FM output is off. To be controlled.

The AM / FM receiver circuit 13 includes an AM radio circuit 131 and an FM radio circuit 132. The AM / FM receiver circuit 13 tunes the radio signal of AM / FM broadcast received by the receiving antenna 11, performs detection to an intermediate frequency, and the like to perform an electrical signal. Is output to the changeover switch 16.
By turning on an AM / FM switch (not shown), the AM / FM receiving circuit 13 is set in a receivable state.

  FIG. 4 is a circuit diagram showing a configuration example of the FM radio circuit according to the present embodiment.

  4 includes a high-frequency amplifier circuit 1321 that amplifies a high-frequency signal received by the antenna 11, a high-frequency tuning circuit 1322 that performs a tuning operation by receiving the amplified high-frequency signal, and a local frequency having a frequency corresponding to the tuning result. A local oscillation circuit 1323 that outputs an oscillation signal, a mixed intermediate frequency circuit 1324 that converts an output signal of the high-frequency tuning circuit 1322 into an intermediate frequency signal based on the local oscillation signal, a detection circuit 1325 that detects the intermediate frequency signal, and a detection signal A low-frequency output circuit 1326 that outputs the low-frequency output signal S132 is provided.

In the FM radio circuit 132 having such a configuration, when the oscillation frequency of the local oscillation circuit 1323 is the same as or near the frequency of the disaster prevention radio (68 MHz to 70 MHz), the disaster prevention radio reception signal receives interference.
Therefore, in this embodiment, the oscillation frequency of the local oscillation signal is set to the plus side by 10.7 MHz. With this setting, the oscillation frequency becomes (76 to 90 MHz) +10.7 MHz = 86.7 to 100.7 MHz, and there is no case of overlapping with the disaster prevention radio frequency, and interference with the disaster prevention radio signal can be greatly reduced.

The audio amplifier 14 is basically a dedicated amplifier for the FM / AM receiver circuit 13, but is shared with the disaster prevention radio receiver circuit 12, and is a radio broadcast selectively input by the changeover switch 16. An audio signal or a disaster broadcast audio signal is amplified and output to the speaker 15.
The speaker 15 outputs the audio signal amplified by the audio amplifier 14.

  As described above, the changeover switch 16 selects either the output S121 of the disaster prevention radio circuit 121 or the output signal S13 of the AM / FM reception circuit 13 in accordance with the squelch signal of the disaster prevention radio reception circuit 12, and supplies it to the audio amplifier 14. Output.

  Next, the operation of the disaster prevention radio broadcast receiver 1 having the above configuration will be described with reference to FIG.

When the user of the disaster prevention radio broadcast receiver 1 turns on a power supply (not shown) and listens to FM radio broadcast, for example, the FM wave is received by the AM / FM receiver circuit 13 and subjected to a predetermined process to generate a low frequency signal. The output is output to the changeover switch 16.
At this time, the narrowband FM wave is also received in the disaster prevention radio reception circuit 12. In the squelch circuit 122, it is determined whether or not the disaster prevention radio wave is received. In this case, since the squelchon is not received, the changeover switch 16 is notified of the squelchon.
As a result, broadcast audio is output from the speaker 15 via the audio amplifier 14.

For example, when the disaster prevention radio signal is received from the master station 101 side by the disaster prevention radio receiver 12 while receiving this AM / FM broadcast, the changeover switch 16 is notified of the squelch-off.
As a result, the disaster prevention broadcast from the master station 101 can be heard through the speaker 15 via the audio amplifier 14.

As described above, according to the present embodiment, the AM / FM has a function of receiving the disaster prevention radio signal 12 and the function of receiving the normal broadcast signal and obtaining the intermediate frequency signal based on at least the local oscillation signal. The output amplifier 14 that can be shared by the reception circuit 13, the disaster prevention radio reception circuit 12, and the AM / FM reception circuit 13, and the outputs of the disaster prevention radio reception circuit 12 and the AM / FM reception circuit 13 are selectively sent to the audio amplifier 14. When the changeover switch 16 to be input and the disaster prevention radio signal are not received, the output of the AM / FM reception circuit 13 is selected, and when the disaster prevention radio signal is received, the output of the disaster prevention radio reception circuit 12 is selected. And a circuit 122 for instructing the changeover switch 16 so that the local oscillation frequency of the FM broadcast receiving circuit is added to the frequency of the FM broadcast signal by an intermediate frequency. From being an advantage of the influence of the interference of the local oscillation signal of an ordinary AM / FM receiver circuit 13 can suppress, it is possible to prevent deterioration of receiving capability of disaster prevention radio receiver.
That is, interference can be reduced, and the reception sensitivity can be greatly improved by setting the local oscillation frequency of the FM radio circuit 132 to be added to the FM broadcast frequency by the intermediate frequency.

It is a figure which shows the structural example of the disaster prevention administrative radio system which concerns on this invention. It is a block diagram which shows one Embodiment of the disaster prevention radio broadcast receiver provided in each household. It is a figure which shows the control state of a changeover switch by a squelch output. It is a circuit diagram which shows the structural example of the FM radio circuit which concerns on this embodiment. It is a figure for demonstrating the operation | movement of this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Disaster prevention radio broadcast receiver, 11 ... Reception antenna, 12 ... Disaster prevention radio reception circuit, 121 ... Disaster prevention radio circuit, 122 ... Squelch circuit, 13 ... Radio broadcast (AM / FM) receiving circuit 131... AM radio circuit 132 132 FM radio circuit 1321 high frequency amplifier circuit 1322 high frequency tuning circuit 1323 local oscillation circuit 1324 mixed Intermediate frequency conversion circuit, 1325... Detection circuit, 14... Audio amplifier, 15.

Claims (8)

A disaster prevention radio receiving circuit for receiving a disaster prevention radio signal;
A broadcast receiving circuit having a function of receiving a normal broadcast signal and obtaining an intermediate frequency signal based on at least a local oscillation signal;
An output amplifier that can be shared by the disaster prevention radio reception circuit and the broadcast reception circuit;
A changeover switch for selectively inputting the output of the disaster prevention radio reception circuit and the broadcast reception circuit to the output amplifier;
When the disaster prevention radio signal is not received, the output of the broadcast receiving circuit is selected. When the disaster prevention radio signal is received, the changeover switch is selected to select the output of the disaster prevention radio receiving circuit. A circuit for indicating,
A disaster prevention radio broadcast receiver set so that the local oscillation frequency of the broadcast receiving circuit is added to the frequency of the broadcast signal by an intermediate frequency. The disaster prevention radio reception circuit includes a detecting means for detecting that the disaster prevention radio signal is received even when the normal broadcast signal is received.
When the disaster prevention radio signal is not detected by the detection means, the changeover switch selects the output of the broadcast receiving circuit,
The disaster prevention radio broadcast receiver according to claim 1, wherein when the disaster prevention radio signal is detected by the detection means, the changeover switch selects an output of the disaster prevention radio reception circuit. The detection means compares whether the magnitude of noise included in the output signal of the disaster prevention radio reception circuit is larger or smaller than a preset value, and if the noise is larger, the disaster prevention radio is not detected The disaster prevention radio broadcast receiver according to claim 2, recognizing that the disaster prevention radio signal is detected when the noise is smaller. The broadcast signal is an FM broadcast signal, and the frequency band of the disaster prevention radio signal is set to a frequency band obtained by subtracting the intermediate frequency from the frequency of the FM broadcast signal or in the vicinity of the frequency band. The disaster prevention radio broadcast receiver according to any one of the above. With the master station that transmits the disaster prevention radio signal,
A disaster prevention radio broadcast receiver capable of receiving a disaster prevention radio signal from the master station,
The above disaster prevention radio broadcast receiver
A disaster prevention radio receiving circuit for receiving a disaster prevention radio signal;
A broadcast receiving circuit having a function of receiving a normal broadcast signal and obtaining an intermediate frequency signal based on at least a local oscillation signal;
An output amplifier that can be shared by the disaster prevention radio reception circuit and the broadcast reception circuit;
A changeover switch for selectively inputting the output of the disaster prevention radio reception circuit and the broadcast reception circuit to the output amplifier;
When the disaster prevention radio signal is not received, the output of the broadcast receiving circuit is selected. When the disaster prevention radio signal is received, the changeover switch is selected to select the output of the disaster prevention radio receiving circuit. A circuit for indicating,
A disaster prevention administrative radio system in which the local oscillation frequency of the broadcast receiving circuit is set to be added to the frequency of the broadcast signal by an intermediate frequency. The disaster prevention radio reception circuit includes a detecting means for detecting that the disaster prevention radio signal is received even when the normal broadcast signal is received.
When the disaster prevention radio signal is not detected by the detection means, the changeover switch selects the output of the broadcast receiving circuit,
The disaster prevention radio system according to claim 5, wherein when the disaster prevention radio signal is detected by the detection means, the changeover switch selects an output of the disaster prevention radio reception circuit. The detection means compares whether the magnitude of noise included in the output signal of the disaster prevention radio reception circuit is larger or smaller than a preset value, and if the noise is larger, the disaster prevention radio is not detected The disaster prevention radio system according to claim 6, wherein if the noise is smaller, the disaster prevention radio signal is recognized. The broadcast signal is an FM broadcast signal, and the frequency band of the disaster prevention radio signal is set to a frequency band obtained by subtracting the intermediate frequency from the frequency of the FM broadcast signal or in the vicinity of the frequency band. The disaster prevention administrative radio system according to any one of the above.

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