JPH0131335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frequency demodulation device used in an FM receiver, and particularly to a frequency demodulation device for demodulating signals from various lines other than the main line (hereinafter referred to as auxiliary lines).

In a microwave FM heterodyne relay station that performs large-capacity transmission, it is necessary to frequency demodulate and extract necessary signals on several lines, such as meeting telephone signals and control signals other than the microwave on the large-capacity main line. . Conventionally, in this type of frequency demodulator,
A method was used to demodulate and amplify all input signals. Therefore, the saturation power of the amplifier circuit after frequency discrimination is required to be extremely large, since it is necessary to amplify the large-capacity main line signal, which is unnecessary in this case. The power consumption in the amplifier circuit was extremely large.

Therefore, an object of the present invention is to provide a frequency demodulation device for demodulating signals of ancillary lines as described above.
It is an object of the present invention to provide a frequency demodulation device which demodulates a signal on an auxiliary line without deteriorating frequency discrimination characteristics and reduces power consumption in a terminal amplifier circuit as much as possible.

In order to achieve the above object, the present invention amplifies only the necessary auxiliary circuit signals in the terminal amplifier circuit.

That is, according to the present invention, there is provided an amplitude limiting circuit which inputs an FM signal consisting of signals of a main line and an auxiliary line and outputs an FM output with the AM component removed;
A frequency discriminator circuit that discriminates the frequency of FM output and generates a demodulated signal, and divides the demodulated signal into a main line component and an auxiliary line component, and the demodulated signal of the separated main line component is terminated. A frequency demodulation device is obtained, which includes the constant resistance branching means and an amplifier circuit that amplifies the demodulated signal of the branched incidental line component to a required level.

Next, a detailed explanation will be given with reference to the drawings.

FIG. 1 is a block diagram showing an example of the circuit configuration of a conventional frequency demodulator for comparison. In the figure, reference numeral 1 is an amplitude limiting circuit, 2
3 and 4 are resonant circuits, 5 and 6 are detection diodes, 7 is a frequency discrimination circuit combining 2 to 6, and 8 is an amplifier circuit. For example, the FM signal S is a 10MHz main line signal.
It consists of a 1kHz to 10kHz ancillary line signal, and this signal is converted into an FM signal by the amplitude limiting circuit 1.
The AM component is removed and 2 electrons are generated by hybrid 2.
Resonant circuit 3, which is divided into equal parts and whose resonant circuit frequencies are adjusted above and below the FM signal carrier frequency, respectively.
After passing through 4, the detection diodes 5 whose directions are opposite to each other
and 6, respectively, and a demodulated signal D is obtained by combining the detected outputs in reverse phase. This demodulated signal D is amplified to a required level by an amplifier circuit 8,
It is output as an output signal P. However, even though this amplifier circuit 8 only needs meeting telephone signals and control signals, it must amplify all the signals to the required level, so it must have a large saturation power, and therefore the power consumption is low. The disadvantage was that it became larger.

FIG. 2 is a block diagram showing the circuit configuration of an embodiment of the frequency demodulating device according to the present invention. In FIG. 2, circuits having the same function as in FIG. 1 are shown with the reference numerals in FIG. 1 plus 10. And reference number 19 is constant resistance branching circuit, 20
is a terminator. The signal D demodulated by the frequency discrimination circuit 17 is demodulated without deteriorating the frequency discrimination characteristics because its load is the constant resistance branching circuit 19 of, for example, 50 ohm or 75 ohm. It is divided by a constant resistance branching circuit 19 and terminated by a terminator 20 . On the other hand, the necessary signal is applied from the constant resistance branching circuit 19 to the amplifier circuit 18, and is output as P after being amplified to a required level. Since only the necessary signals are amplified in the amplifier circuit 18 in this way, the saturation power of the amplifier circuit can also be small, and low power consumption can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the circuit configuration of a conventional frequency demodulation device, and FIG. 2 is a block diagram showing the circuit configuration of a frequency demodulation device which is an embodiment of the present invention. Explanation of symbols: 11 is amplitude limiting circuit, 12 is hybrid, 13 and 14 are resonant circuits, 15 and 16 are detection diodes, 17 is frequency discrimination circuit, 18 is amplifier circuit, 19 is constant resistance branching circuit, 20 is terminal Each represents a vessel.

Claims (1)

[Claims] 1: an amplitude limiting circuit that receives an FM signal consisting of main line and auxiliary line signals and generates an FM output with AM components removed; a frequency discrimination circuit that discriminates the frequency of the FM output and generates a demodulated signal; a constant resistance branching means configured to split the signal into a main line component and an incidental line component, and terminate the demodulated signal of the branched main line component; and a demodulated signal of the branched incidental line component. A frequency demodulator equipped with an amplifier circuit that amplifies and amplifies to a required level.