Noise suppression apparatus for FM receiver

• US 5,036,543 A
• Filed: 06/26/1990
• Issued: 07/30/1991
• Est. Priority Date: 06/30/1989
• Status: Expired due to Fees

• Current Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Original Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Inventors: Ueno, Eiji
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Chiang, Jack
• Application Number:
  US07/543,305
• Time in Patent Office: 399 Days
• Field of Search: 381/93, 381/94, 381/13, 381/10, 381/11, 455/222, 455/223
• US Class Current: 381/13
• CPC Class Codes: H03G 3/344 Muting responsive to the amount of noise (noise squelch) H03G3/345 takes precedence
• CPC Class Codes: H03G 3/345 Muting during a short period of time when noise pulses are detected, i.e. blanking H03G3/348 takes precedence

Abstract

A noise component is extracted either from FM-detected output or from the so-called signal meter in the intermediate frequency amplifier. The noise component is amplified and rectified to provide a d-c signal indicative of the noise level. The rectified noise is then shaped to produce a control signal having a predetermined level and a width. The control signal is supplied to the gate circuit to control the opening and closing of the gate through which the FM detected output passes. The gate is closed during a period when the pulse noise is superimposed on the FM detected output, and is opened during a period when the pulse noise is not superimposed to the FM detected output. In the mean time, the rectified d-c signal is smoothed out to be used as a control signal for controlling the stereo separation, the attenuation of high frequency component of the MPX-demodulated audio outputs, and the overall signal level of the audio outputs.

Claims

1. A noise suppression apparatus for an FM receiver comprising:

amplifying means (6,7) for extracting a noise component from an FM detected signal;

noise detecting means (8,9) for outputting a control signal when a level of said noise component exceeds a predetermined level;

gate means (3) through which said FM-detected signal passes, said gate means being closed by said control signal to inhibit the passage of said FM-detected signal;

d-c signal producing means for producing a d-c signal in accordance with an output level of said amplifying means (6,7) to control a gain of said amplifying means (6,7);

stereo separation control means (22) for continuously varying a stereo separation between a left channel and a right channel of a speaker output of the FM receiver in accordance with said level of the noise component when said noise component decreases below a predetermined level; and

high frequency response control means (23) for continuously varying frequency responses of said left and right channels in accordance with said level of the noise component when said noise component decreases below a predetermined level.

2. A noise suppression apparatus for an FM receiver comprising:

amplifying means (25) for extracting noise component in an intermediate frequency signal;

noise detecting means (26,27) for outputting a control signal when said noise component exceeds a predetermined level;

gate means (3) through which an FM detected signal passes, said gate means being closed by said control signal to inhibit the passage of said FM-detected signal;

d-c signal producing means (28) for producing a d-c signal in accordance with an output level of said amplifying means (25) to control a gain of said amplifying means (25);

stereo separation control means (22) for continuously varying a stereo separation between a left channel and a right channel of a speaker output in accordance with said d-c signal when said d-c signal decreases below a predetermined level; and

high frequency response control means (23) for continuously varying frequency responses of said left and right channels in accordance with said d-c signal when said d-c signal decreases below a predetermined level.

3. A noise suppression apparatus for an FM receiver comprising:

first amplifying means (6,7) for extracting a noise component from an FM detected signal;

first noise detecting means (8,9) for outputting a first control signal when an output of said first amplifying means (6,7) exceeds a predetermined level;

first d-c signal producing means for producing a first d-c signal in accordance with an output level of said first amplifying means (6,7) to control a gain of said first amplifying means (6,7);

a second amplifying means (25) for extracting a high frequency component of noise in an intermediate frequency signal;

second noise detecting means (26,27) for outputting a second control signal when an output of said second amplifying means (25) exceeds a predetermined level;

second d-c signal producing means (28) for producing a second d-c signal in accordance with an output level of said second amplifying means (25) to control a gain of said second amplifying means;

gate means (3) through which said FM detected signal passes, said gate means being closed by said first and second control signals to inhibit the passage of said FM-detected signal;

stereo separation control means (22) for continuously varying a stereo separation between a left channel and a right channel of a speaker output of the FM receiver in accordance with said first d-c signal when said first d-c signal decreases below a predetermined level; and

high frequency response control means (23) for continuously varying frequency responses of said left and right channels in accordance with said first d-c signal when said first d-c signal decreases below a predetermined level.

4. A noise suppression apparatus for an FM receiver comprising:

first amplifying means (6,7) for extracting a noise component from an FM detected signal;

first noise detecting means (8,9) for outputting a first control signal when an output of said first amplifying (6,7) exceeds a predetermined level;

first d-c signal producing means (11) for producing a first d-c signal in accordance with an output level of said first amplifying means (6,7) to control a gain of said first amplifying means (6,7);

a second amplifying (25) for extracting a high frequency component of noise of in intermediate frequency signal;

second noise detecting means (26,27) for outputting a second control signal when an output of said second amplifying means (25) exceeds a predetermined level;

second d-c signal producing means (28) for producing a second d-c signal in accordance with an output level of said second amplifying means (25) to control a gain of said second amplifying means;

gate means (3) through which said FM detected signal passes, said gate means being closed by said first and second control signals to inhibit the passage of said FM-detected signal;

stereo separation control means (22) for continuously varying a stereo separation between a left channel and a right channel of a speaker output of the FM receiver in accordance with said second d-c signal when said second d-c signal decreases below a predetermined level; and

high frequency response control means (23) for continuously varying frequency responses of said left and right channels in accordance with said second d-c signal when said second d-c signal decreases below a predetermined level.