JPH0633708Y2 - FM receiver - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention relates to a tuning detection circuit of an FM receiver, and in particular, an FM reception suitable for determining a tuning center frequency by detecting a busy signal during reception. Regarding the machine.

(B) Prior Art Conventionally, the FM receiver having the block diagram of FIG. 3 has been provided.

In the figure, 1 is a receiving antenna, 2 is an RF amplifier circuit for amplifying the RF signal received by the antenna 1, and 3 is the RF signal and PL.
Mixing circuit in which the local oscillation signals from the L circuit are mixed, 4 is an intermediate frequency amplifier circuit, 5 is an FM detection circuit having a discriminator, 6 is a squelch circuit that operates on the output signal of the FM detection circuit 5, and 7 is an audio system. A signal power amplifier circuit, and 8 is a speaker.

Reference numeral 9 denotes a PLL circuit controlled by a microcomputer (hereinafter referred to as a microcomputer). The VCO output signal of the PLL circuit 9 is supplied to the mixing circuit 3 as a local oscillation signal. 10 is a microcomputer for controlling each part, which is a microprocessor (CP
U) is built in, and is formed by a ROM that is programmed in advance, a RAM that stores and stores necessary data, and an input / output port. Reference numeral 13 is a display for displaying the status such as frequency under the control of the microcomputer 10, and 20 is a window comparator for judging the output signal of the FM detection circuit 5 when the FM receiver receives a signal.

The FM receiver receives the reception signal, the IF signal is amplified by the IF amplification circuit 4, and the IF signal is supplied to the FM detection circuit 5. The modulated signal of the FM reception signal is demodulated by the FM detection circuit 5, and the squelch circuit 6 releases the squelch by the output signal of this FM detection circuit 5,
The FM detection signal becomes an audio signal and is amplified and output from the speaker 8.

On the other hand, the output signal of the FM detection circuit 5 is supplied to the window comparator 20, and it is determined whether or not it matches the center frequency of the discriminant characteristic of the FM detection circuit 5.

The squelch circuit 6 is released, and the deviation signal from the window comparator 20 is supplied to the microcomputer 10 as a busy stop signal through the AND circuit 21.

When the receiver is scanning, the received signal is received as a busy signal, and when this received signal is recognized as the center frequency by the window comparator 20, the busy stop signal causes the scan to be suspended and the reception Receive the signal.

This temporary stop is canceled after a reception signal disappears or after a hold time of a fixed time, and scanning is restarted.

In this way, the window comparator 20 determines whether it is at the tuning center frequency (set to a frequency within a certain range) and supplies it to the microcomputer 10.

(C) Problems to be solved by the invention However, in the above-mentioned conventional FM receiver, in order to detect the tuning center frequency of FM reception, the output signal of the FM detection circuit is supplied to the window comparator. Since it is judged by the comparison deviation signal of
There is a drawback that the circuit configuration becomes complicated.

The present invention has been made in view of the above points, and an object thereof is to solve the drawbacks of the conventional example and to provide an FM receiver that does not use a window comparator or the like.

(D) Means for solving the problem The FM receiver of the present invention has a scan function capable of sweeping the local oscillation frequency of the receiver and continuously receiving the reception signal, and the output signal of the FM detection circuit In an FM receiver that controls and detects the center frequency, a busy circuit that obtains a busy signal from the output signal of the FM detection circuit, and an A / D that converts the discriminator output signal of the FM detection circuit into a digital signal
When the FM receiver is in a busy state with a conversion circuit, the above FM
It is provided with detection means for detecting whether or not the center frequency is within a set range by a digital signal of the detection circuit, and busy stop means for temporarily stopping the scan sweep by detecting the center frequency.

(E) Action When the FM receiver receives the received signal and the squelch circuit releases the squelch with the output signal of the FM detection circuit, the busy signal is supplied to the microcomputer and the FM receiver becomes busy. At the same time, the discriminator output deviation signal of the FM detection circuit is converted into a digital signal by the A / D conversion circuit and supplied to the microcomputer.

The microcomputer compares and determines the deviation signal with the preset upper and lower limits of the tuning center frequency, and detects whether the deviation signal is within the set range.

This detection center frequency sets a certain range of upper and lower limits,
When the deviation signal falls within the upper and lower limits, a busy stop signal is generated to indicate that the reception condition is valid.

(F) Embodiment An embodiment of the FM receiver according to the present invention will be described with reference to FIGS. 1 and 2.

The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In the figure, 11 is a busy signal circuit that operates the squelch circuit 6 that operates with the discriminator output signal of the FM detection circuit 5, and generates a busy signal when the squelch is released, and 12 is
It is an A / D conversion circuit that converts the discriminator output signal of the FM detection circuit 5 into a digital signal.

The squelch of the squelch circuit 6 operates when the FM receiver does not receive the received signal and is in the non-received state, so that unnecessary signals such as noise are cut and unnecessary sound is not generated from the speaker.

When the FM receiver receives a certain reception signal by the program scan method, the VFO scan method, or the like, the FM detection circuit 5 outputs a detection output signal obtained by detecting the reception signal.

The detected output signal releases the squelch of the squelch circuit 6, and the audio signal obtained by detecting the received signal is output to the speaker 8 to generate sound.

When the squelch circuit 6 operates to release the squelch, the squelch release signal is supplied to the busy signal circuit 11, and a busy signal is generated and supplied to the microcomputer 10.

On the other hand, the detection output signal of the FM detection circuit 5 is supplied to the A / D conversion circuit 12 as a deviation signal from the tuning center frequency and converted into a digital signal. This digital signal is supplied to the microcomputer 10 for signal processing.

FIG. 2 is a flowchart showing a part of the signal processing of the microcomputer 10, and description will be given based on this flowchart.

When the squelch circuit 6 operates as described above upon receiving the reception signal and the busy signal circuit 11 supplies the busy signal to the microcomputer 10, the microcomputer 10 confirms the busy signal (step S1).

If the busy signal is YES in step S1, the microcomputer 10
Receives the frequency deviation signal converted into the digital signal from the FM detection circuit 5 (step S2).

The microcomputer 10 judges the frequency deviation signal by a preset program, and judges whether the frequency deviation signal is within the set upper limit value or lower limit value (steps S3, S4).

When it is not within the upper limit value or the lower limit value, since it is not a valid reception signal, busy stop is not performed and data is given to the PLL circuit 9 so as to receive the next channel or the next reception frequency (steps S3, S4).

When a deviation signal enters the set upper and lower limits, the squelch circuit 6 cancels the squelch, and the microcomputer 10 generates a busy stop signal to display that the reception state is valid and stop scanning temporarily. (Step S5).

Although the A / D conversion circuit 12 is used in FIG. 1, many recent microcomputers 10 have a built-in multi-channel A / D conversion circuit. By using this built-in A / D conversion circuit, the external A / D conversion circuit 12 can be omitted.

Further, the output deviation signal of the FM detection circuit 5 can also be used as a deviation signal for controlling the frequency of the AFC circuit used in a general FM receiver.

(G) Effect of the Invention According to the FM receiver according to the present invention, when the received signal is received, the busy signal is generated, the busy state is generated, the tuning center frequency is detected, and the tuning frequency is set to a certain value. If a valid reception state is reached, a busy stop signal is generated, so it is possible to receive near the center frequency of the received signal in the program scan method or VFO scan method reception. The effect is that you can receive in a comfortable state without distortion.

Moreover, unlike the conventional example, since a complicated circuit such as an analog signal window comparator is not used, it has an excellent feature that it can be implemented with a simple circuit configuration with a small number of parts and cost can be reduced. There is.

[Brief description of drawings]

1 and 2 show an embodiment of an FM receiver according to the present invention, FIG. 1 is a block diagram, and FIG. 2 is a flow chart showing the operation of a microcomputer. FIG. 3 is a block diagram of a conventional example. Explanation of main numbers 3 …… Mixing circuit 4 …… Intermediate frequency amplifier 5 …… FM detection circuit 6 …… Squelch circuit 9 …… PLL circuit 10 …… Microcomputer 11 …… Busy signal circuit 12 …… A / D conversion Circuit 20 ... Window comparator

Claims (1)

[Scope of utility model registration request] 1. An FM receiver having a scan function capable of sweeping a local oscillation frequency of the receiver to continuously receive a received signal and detecting a center frequency by controlling with an output signal of an FM detection circuit. , A busy circuit for obtaining a busy signal from the output signal of the FM detection circuit, and an A / D conversion circuit for converting the discriminator output signal of the FM detection circuit into a digital signal are provided, and when the FM receiver is in a busy state, An FM receiver comprising: detection means for detecting a center frequency by a digital signal of the FM detection circuit; and busy stop means for temporarily stopping scan sweep by detecting the center frequency.