JPH034630A - Fm stereo receiver - Google Patents

Abstract

PURPOSE:To surely reduce multi-path noise without increasing considerably number of parts by generating a monaural output as to a band including a prescribed multi-path noise and generating a stereo output as to the band except the prescribed multi-path noise. CONSTITUTION:An L output signal and an R output signal from an FM stereo demodulation circuit 1 are fed in parallel with an L notch filter 2, an L band pass filter 3, an R notch filter 4 and an R band pass filter 5 acting like a band reject filter. Output signals from the filters 3, 5 are added by a 1st adder section 6 and a halved LR output signal is obtained from a succeeding attenuation section 9. Then the L output signal passing through the filter 2 is added to the LR output signal halved from the attenuation section 9 at the 2nd adder section 7 to obtain an L' output signal. On the other hand, the R output signal passing through the filter 4 is added to the LR output signal halved from the attenuation section 9 to obtain an R' output signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an FM stereo receiver,
In particular, we have focused on the multipath noise that occurs when receiving stereo broadcasts, which occurs in the reverse phase of R, and are equipped with a function that reliably reduces multipath noise without significantly increasing the number of parts. This relates to an FM stereo receiver.

[Prior Art] Generally, FM broadcast waves are greatly influenced by topography and the like, and the electric field strength changes significantly. Therefore, especially in vehicle-mounted FM receivers, skip noise may occur or be affected by multipath noise, resulting in a significant drop in S/N especially in environments with weak electric fields. 6 Therefore, various efforts have been made to overcome this type of drawback, but all of them basically have the disadvantageous side effects of deteriorating the sound quality and reducing the stereo effect. Ta.

In other words, the conventionally used multipath noise reduction circuit (so-called 5RC), when noise occurs,
Switching from stereo to monaural is performed over the entire band of the reproduced signal, and in some cases, a high frequency cut is also used.

For this reason, although the multipath noise reduction effect itself is remarkable, there is a problem in that the sound quality is significantly degraded and the sound is unnatural.

[Problems to be Solved by the Invention] As mentioned above, conventional FM stereo receivers have been devised in various ways to avoid the negative effects of multipath noise. This has had the problem of causing inconvenient side effects such as deterioration and a reduction in the stereo effect.

This invention was made to solve the problems described in E. Focusing on the multipath noise that occurs when receiving stereo broadcasts, which occurs in the reverse phase of R, the number of parts was significantly increased. An object of the present invention is to obtain an FM stereo receiver that can reliably reduce multipath noise without causing damage.

[Means for Solving the Problems] The FM stereo receiver according to the present invention provides demodulated FM
a pair of L notch filters and an L band pass filter provided corresponding to the front component of the stereo signal; a pair of R notch filters provided corresponding to the R component of the demodulated FM stereo signal; a filter and an R band pass filter; a first addition unit that adds the output of the band pass filter and the output of the R band pass filter; the first addition unit;
an attenuator that performs a predetermined attenuation on the output from the adder;
a second addition section that adds the output of the L-notch filter and the output of the attenuation section; and a third addition section that adds the output of the R-notch filter and the output of the attenuation section. It is something.

[Operation] In the present invention, a monaural output is generated for a band including a predetermined multipath noise, and a stereo output is generated for a band excluding the predetermined multipath noise.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a schematic configuration diagram showing the main parts of an FM stereo receiver that is an embodiment of the present invention. In this Figure 1, F
The output signal from the M stereo demodulation circuit (1) is passed through an L notch filter (2) and an L band pass filter (3), which are used as band reject filters in the next stage.
), and the R output signal from the FM stereo demodulation circuit (1) is applied to the R notch filter (4) which acts as a band reject filter in the next stage.
and R band pass filter (5) in parallel.

Here, the L notch filter (2) and the R notch filter (4) are each used to remove a harsh noise band of about several kHz. And L
Band pass filter (3) and R band pass filter (3)
The filter (5) is for adding the noise bands removed by the L notch filter (2) and the R notch filter (4), respectively, to obtain a monaural LR output signal.

The output signal from the L-band pass filter (3) and the output signal from the R-band pass filter (5) are added in the first adder (6) at the next stage, and the subsequent attenuator (
9), a halved LR output signal is obtained. and,
The output signal that has passed through the L notch filter (2) is summed with the halved LR output signal from the attenuator (9) in a second adder (7), and the resulting L° output signal is can get. On the other hand, the R output signal that has passed through the R notch filter (4) is added to the halved LR output signal from the attenuation section (9) in a third addition section (8), resulting in an R'' output. A signal will be obtained.

That is, according to the embodiment described above, the harsh noise band of about several KHz is output as a monaural signal, and the other bands are output as a normal stereo signal. , deterioration of sound quality and deterioration of stereo effect are reliably reduced.

[Effects of the Invention] As explained above, the FM stereo receiver according to the present invention includes a pair of L-notch filters and an L-band bus provided corresponding to the front component of the demodulated FM stereo signal. - Filter; a pair of R notch filters provided corresponding to the R component of the demodulated FM stereo signal;
band bass filter; a first addition section that adds the output of the L-band bass filter and the output of the R-band bass filter; an attenuation section that performs a predetermined attenuation on the output of the first addition section; a second addition unit that adds the output of the L-notch filter and the output of the attenuation unit; and
a third addition section that adds the output of the R-notch filter and the output of the attenuation section; and generates a monaural output for a band including a predetermined multipath noise. Since it functions to generate stereo output in the band excluding the predetermined multipath noise, multipath This brings about the effect that noise can be reliably reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an FM stereo receiver that is an embodiment of the present invention. (1) is an FM stereo demodulation circuit, (2) is an L-notch filter, (3 is an L-band bass filter, (4) is an R-notch filter, (5) is an R-band bass filter, (6 is the first Adding unit, (7) is the second adding unit, <8 is the third adding unit,

Claims (1)

[Claims] (1) A pair of L notch filter and L band pass filter provided corresponding to the L component of the demodulated FM stereo signal; provided corresponding to the R component of the demodulated FM stereo signal. a pair of R-notch filters and an R-band pass filter.
filter; a first addition section that adds the output of the L-band pass filter and the output of the R-band pass filter; an attenuation section that attenuates the output from the first addition section to a predetermined value; An FM stereo receiver comprising: a second addition section that adds the output of the filter and the output of the attenuation section; and a third addition section that adds the output of the R-notch filter and the output of the attenuation section. An FM stereo receiver characterized in that a monaural output is generated for a band including a predetermined multipath noise, and a stereo output is generated for a band excluding the predetermined multipath noise.