JPH0629876A - Receiver of area disaster prevention radio equipment - Google Patents

Abstract

PURPOSE:To make it possible to select and receive the both of local government disaster prevention administration radio waves and area disaster prevention radio waves by the device of a low cost. CONSTITUTION:Local government disaster prevention administration radio waves of 400MHz band pass a filter 2 from an antenna terminal 1, are injected to a mixing circuit 3 along with the output of a local oscillation circuit 4 and the frequency conversion of 800MHz band which is the same as area disaster prevention radio waves is performed. Therefore, by selecting either of the output and the area disaster prevention radio waves from the antenna terminal 1 by a switch 6, an expensive filter for intermediate frequency 9 can be shared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for a local disaster prevention radio for receiving a local disaster prevention radio wave and a local government administration radio wave.

[0002]

2. Description of the Related Art FIG. 2 shows the structure of a conventional receiver for a local disaster prevention radio. In FIG. 2, reference numeral 21 denotes an antenna terminal to which radio waves are input, which is connected to the switch 22 on the input side. One terminal of the switch 22 on the input side is 8
It is connected to the 00 MHz band reception filter 23, and its output is connected to the amplifier circuit 24. The output of the amplifier circuit 24 is connected to the intermediate frequency filter 25, and its output is the first
It is connected to the first mixing circuit 26 together with the output of the local oscillation circuit 27. The output of the first mixing circuit 26 is connected to the output side switch 28, and the output thereof is connected to the first intermediate frequency output terminal 29. On the other hand, the other terminal of the input side switch 22 is connected to the 400 MHz band reception filter 30, and thereafter, the amplification circuit 31 and the intermediate frequency filter 3 are sequentially arranged.
2, the first mixing circuit 33, the first local oscillation circuit 34, the switch 28 on the output side, and the first intermediate frequency output terminal 29. After that, it is connected to the second intermediate frequency circuit, the detection circuit, the low frequency amplifier circuit, and the receiver.

Next, the operation of the above conventional example will be described.
In FIG. 2, the 800 MHz band local disaster prevention radio wave passes from the antenna terminal 21 through the input-side switch 22, passes through the reception filter 23, is amplified by the amplification circuit 24, passes through the intermediate frequency filter 25, and It is injected into the first mixing circuit 26 together with the output of the 1-local oscillation circuit 27,
The output passes through the switch 28 on the output side and is output to the first intermediate frequency output terminal 29.

On the other hand, 400 MHz band local government disaster prevention administrative radio waves are transmitted from the antenna terminal 21 to the switch 2 on the input side.
2 through the reception filter 30, and the amplification circuit 31
Is amplified by and passes through the intermediate frequency filter 32,
With the output of the first local oscillator circuit 34, the first mixing circuit 3
3 and the output passes through the switch 28 on the output side and is output to the first intermediate frequency output terminal 29.

As described above, even in the conventional receiver for the local disaster prevention radio, by switching the input side switch and the output side switch, the local government disaster prevention administrative radio wave is received in addition to the local disaster prevention radio wave. be able to.

[0006]

However, in the conventional receiver for the local disaster prevention radio, the circuit for receiving the local government disaster prevention radio wave is equivalent to the circuit for receiving the local disaster prevention radio wave. Since an expensive intermediate frequency filter having a high selectivity characteristic is required, there is a problem that the cost of the device increases.

The present invention solves such a conventional problem. Even if a simple filter is used in the circuit for receiving the local government disaster prevention administrative radio wave, the high selection equivalent to the conventional one can be achieved. It is an object of the present invention to provide an excellent receiving device for a local disaster prevention wireless device that can obtain a degree characteristic.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an input unit of a circuit for receiving an 800 MHz band local disaster prevention radio wave and outputting a first intermediate frequency, in which 400 M is provided.
A frequency conversion circuit for converting a local government disaster prevention administration radio wave in the Hz band into a local disaster prevention radio wave in the 800 MHz band is connected via a switch.

[0009]

Therefore, according to the present invention, by converting the local government disaster prevention administration radio wave to the band of the regional disaster prevention radio wave by the frequency conversion circuit, the filter for the intermediate frequency of the regional disaster prevention radio wave can be shared. , By using a simple filter that can remove spurious generated by the frequency conversion circuit in the previous stage, it is possible to receive local government disaster prevention administrative radio waves with high selectivity characteristics equivalent to those when receiving local disaster prevention radio waves. You can

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an antenna terminal to which a radio wave is input, which is connected to the 400 MHz band reception filter 2 and the switch 6. The 400 MHz band reception filter 2 is connected to the mixing circuit 3 together with the local oscillation circuit 4,
The output of the mixing circuit 3 is connected to the switch 6. The mixing circuit 3 and the local oscillation circuit 4 constitute a frequency conversion circuit 5. The output of the switch 6 is connected to the 800 MHz band reception filter 7, and the output thereof is connected to the amplifier circuit 8. The output of the amplifier circuit 8 is connected to the intermediate frequency filter 9, and its output and the output of the first local oscillation circuit 11 are both connected to the first mixing circuit 10. The intermediate frequency filter 12, the first mixing circuit 10, and the first local oscillation circuit 11 constitute an intermediate frequency circuit 12. The output of the intermediate frequency circuit 12 is connected to the first intermediate frequency output terminal 13.

Next, the operation of the above embodiment will be described.
When it is desired to receive the 400 MHz band local government disaster prevention administration radio wave, the switch 6 is first connected to the frequency conversion circuit 5 side. In FIG. 1, when a 400 MHz band local government disaster prevention administration radio wave is input to the antenna terminal 1, 400 M
The signal passes through the Hz band receiving filter 2, is injected into the mixing circuit 3 together with the output signal of the local oscillation circuit 4, and is frequency-converted into an 800 MHz band signal. The output of the frequency conversion circuit 5 passes from the switch 6 through the 800 MHz band reception filter 7, is amplified by the amplification circuit 8, passes through the intermediate frequency filter 9, and is output together with the output of the first local oscillation circuit 11 to the first mixing circuit. 10 is injected, frequency-converted to the first intermediate frequency, and output to the output terminal 13.

Next, when it is desired to receive the 800 MHz band local disaster prevention radio wave, the switch 6 is connected to the antenna terminal 1 side. The 800 MHz band radio wave input to the antenna terminal 1 passes through the switch 6, is selected by the 800 MHz band reception filter 7, is amplified by the amplifier circuit 8, and is transmitted to the intermediate frequency circuit 1
At 2, the signal is converted to the first intermediate frequency and output to the output terminal 13.

As described above, according to the above-described embodiment, the simple 400 MHz band receiving filter 2 capable of removing spurious generated by the mixing circuit 3 and the local oscillation circuit 4 is used just before the frequency conversion circuit 5. , It is possible to receive the local government disaster prevention administration radio wave with the same high selectivity characteristic as the case of receiving the regional disaster prevention radio wave.

[0014]

As is apparent from the above embodiment, the present invention is for receiving the local disaster prevention radio wave by converting the local government disaster prevention radio wave into the band of the regional disaster prevention radio wave by the frequency conversion circuit. Since the expensive intermediate frequency filter in the circuit can be shared and only the inexpensive filter needs to be used in the circuit for receiving the local government disaster prevention administration radio wave, the local government disaster prevention administration radio wave can be used. It has the effect that it can be received by a low-cost device with high selectivity characteristics equivalent to waves.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a part of the configuration of a receiving device of a local disaster prevention radio in one embodiment of the present invention.

FIG. 2 is a schematic block diagram showing a part of the configuration of a receiving device of a conventional regional disaster prevention radio.

[Explanation of symbols]

 1 Antenna Terminal 2 400MHz Band Reception Filter 3 Mixing Circuit 4 Local Oscillation Circuit 5 Frequency Conversion Circuit 6 Switch 7 800MHz Band Reception Filter 8 Amplifier Circuit 9 Intermediate Frequency Filter 10 1st Mixing Circuit 11 1st Local Oscillation Circuit 12 Intermediate Frequency Circuit 13 First intermediate frequency output terminal

Claims (1)

[Claims] 1. A frequency conversion circuit comprising a mixing circuit and a local oscillator circuit for converting a 400 MHz local disaster prevention administrative radio wave received by an antenna into an 800 MHz band local disaster prevention radio wave, and the frequency conversion circuit. A switch for selecting one of the output of the circuit and the 400 MHz band local disaster prevention radio wave received by the antenna, a filter for receiving the output of the switch for 400 MHz band, and amplifying the output of the filter An amplifier circuit that
A receiver for a local disaster prevention radio, comprising: a filter for converting the output of the amplifier circuit into a first intermediate frequency; an intermediate frequency circuit including a mixing circuit and a local oscillation circuit.