JPS58129851A - Fm receiver - Google Patents

Abstract

PURPOSE:To perform sterephonic reproduction with relatively high quality, by detecting an interferenece signal to disturbing a received signal demodulated by an FM demodulating means and putting the interference signal eliminating means in operation. CONSTITUTION:When an interference signal is outputted from the FM demodulating circuit 2 together with the received signal, a interference signal detecting circuit 6 and a circuit connection control circuit 7 operate to obtain a left and a right signal having relatively high quality of reproduction in terms of a sense of hearing which are passed through an antibuddy filter 4, multiplex stereophonic circuit 3, and a high blending circuit 5. When only the received signal is outputted from the FM demodulating circuit 2, said circuits 6 and 7 operates to obtain a left and a right signal of high reproduction quality passed through the multiplex stereophonic circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM receiver that demodulates received stereo broadcast waves and reproduces them in stereo.

FIG. 1 shows a partial configuration of a conventional general FM receiver, in which 1 is an intermediate frequency amplification circuit, 2 is an FM demodulation circuit, and 3 is a multiplex stereo circuit.

In the conventional example configured in this way, when a desired stereo broadcast radio wave is received, the received signal is once amplified by the intermediate frequency amplification circuit l, demodulated by the FM demodulation circuit 2, and then demodulated by the multiplex stereo circuit 3. The signal is separated into a left signal and a right signal, resulting in high reproduction quality. However, along with the stereo broadcast radio waves of the desired station, so-called interference radio waves such as broadcast radio waves of other stations, other radio radio waves, or harmonics and subharmonics of these radio waves are received, and moreover, the FM demodulation circuit 2 receives The interference signal is demodulated together with the received signal, and for example, as shown in FIG. 2, when the demodulated interference signal B is superimposed on the stereo sub-channel signal A of the demodulated received signal, the multiplex stereo circuit 3 Also, since the received signal containing the interference signal is separated into the left signal No. 1 and the right signal, there is a drawback that the playback quality deteriorates.In particular, as the number of FM radio stations increases, this drawback becomes more frequent. If the output frequency difference between other stations is within 150kHz, this drawback will definitely occur.

In order to eliminate the drawbacks of the conventional example, the present invention provides an FM receiver in which interfering signal eliminating means is inserted after the FM demodulation circuit. Examples of the present invention will be described in detail below.

FIG. 3 shows the configuration of one embodiment of the present invention.
The same reference numerals as those in the figure indicate the same parts, and 4 is an antiverb filter inserted between the FM demodulation circuit 2 and the multi-branch stereo circuit 3, and this antiverb filter 4 is as follows: As shown in FIG. 4, it has an amplitude characteristic that allows the stereo main channel signal C and the stereo sub-channel signal A to pass, but the delay time is small in the region of the stereo main channel signal C, and
However, in the region of the stereo sub-channel signal A, the delay time has a phase delay characteristic that changes sharply, so a difference occurs in the phase between the pilot signal for stereo demodulation and the stereo sub-channel signal A. Although the separation characteristics between the left signal and the right signal deteriorate, the interference signal can be reduced.

5 is a high blend circuit that prevents a decrease in the S/N ratio of the stereo sub-channel signal; 6 is an interference signal detection circuit that detects whether or not an interference signal is included in the signal output from the FM demodulation circuit 2; 7 is configured such that when the interference signal detection circuit 6 detects an interference signal, the signal output from the FM demodulation circuit 2 passes through the anti-noise filter 4, the multiplex stereo circuit 3, and the high blend circuit 5 in sequence. Switch the circuit connection and also install the interference signal detection circuit 6
The circuit connection control circuit switches the circuit connection so that the signal output from the FM demodulation circuit 2 passes only through the multiplex stereo circuit 3 when the FM demodulation circuit 2 does not detect an interfering signal.

In this embodiment configured as described above, when the FM demodulation circuit 2 outputs the interference signal together with the received signal, the interference signal detection circuit 6 and the circuit connection control circuit 7 switch to the antiverb filter 4 and the multi-channel Although the degree of separation between the left signal and the right signal is reduced after passing through the flex stereo circuit 3 and the high blend circuit 5, the left signal and the left signal have a comparatively high playback quality in terms of audibility and have reduced interfering signals. If the right signal cannot be obtained and only the received signal is output from the FM demodulation circuit 2, the interference signal detection circuit 6 and the circuit connection control circuit 7 operate, and the reproduction signal that has passed through the multiplex stereo circuit 3 is activated. High quality left and right signals can be obtained.

As explained above, according to the present invention, in an area where there are a large number of FM broadcast stations or radio stations, the FM of a desired station can be
Even if interference radio waves are received along with the FM broadcast radio waves, relatively high-quality stereo playback can be performed in terms of audibility, and when only the FM broadcast radio waves of the desired station are received, high-quality stereo playback can be performed. be.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional FM receiver, Figure 2 is a block diagram of a conventional FM receiver.
FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. 4 is an amplitude characteristic and phase delay characteristic of an antiverb filter according to an embodiment of the present invention. 1...Intermediate frequency amplification circuit, 2...
...FM demodulation circuit, 3...Multiplex stereo circuit, 4...
・Antiverb filter, 5... High blend circuit, 6... Interfering signal detection circuit,
7......Circuit connection control circuit. Patent applicant: Matsushita Electric Industrial Co., Ltd. Agent: Koji Hoshino

Claims (2)

[Claims] (1) In an FM receiver that demodulates received stereo broadcast radio waves and reproduces them in stereo, when the interfering signal detecting means detects that there is an interfering signal within a range that interferes with the received signal demodulated by the FM demodulating means, the FM The interference signal eliminating means connected to the output end of the demodulating means operates,
outputting the received signal in which the interfering signal is reduced, and when the interfering signal detection means detects that there is no interfering signal;
An FM receiver characterized in that the interference signal eliminating means stops operating and outputs the received signal as it is. (2) The interfering signal eliminating means comprises an antiverb filter connected between the FM demodulating means and the multiplex stereo means, and a high blend circuit connected to the output end of the multiplex stereo means. The FM according to claim No. ( ]) characterized by
Receiving machine.