Gm Global Technolgoy Operations, Inc.

Delco Electronics Corporation

Jeffrey M Stricker

Michael John Easterwood

Michael Allen Shoemaker

A method and apparatus for suppressing noise in a radio receiver or the like due to electromagnetic interference generated by the firing of a spark plug which coordinates the operation of a noise blanker with the EST signal generated by an electronic engine control module or similar spark timing signal. The apparatus of the present invention comprises a noise blanker disposed within a radio receiver for blanking the output of the radio receiver for a predetermined duration after a predetermined time delay has elapsed after each EST signal pulse. The noise blanker is activated for a time duration slightly longer than the duration of the impulse noise. The noise blanker may also be designed to be deactivated when the desired signal level reaches a predetermined level. The apparatus of the present invention may be used in conjunction with other noise suppression systems to eliminate noise due to sources other than the electronic ignition system.

Impulse noise blanking apparatus

A signal seeking radio receiver is disclosed in which the AGC voltage applied to the RF amplifier is automatically reduced only when a sweep tune signal is present with a signal generated by the detection of a parameter associated with low ambient light typical of nighttime operating. The night signal may be produced by an ambient light sensor or in response to the activation of a vehicle running light. Thus the stop sensitivity of the tuner in signal seeking mode is reduced at night to prevent stopping on undersirable skywave signals but is normal during daytime operation when the running light is not activated. The sweep tune signal may be the fast/slow AGC control signal or mute signal generated during signal seeking; and its removal when the sweep stops on a station provides normal AGC operation for listening, even at night. The AGC voltage is provided to the control electrode of a variable gain RF amplifier through a first impedance; and a second impedance connects the control electrode to the collector of a transistor having a base controlled by the ambient light signal and an emitter controlled by the sweep tune signal. Thus, when the night signal and sweep tune signal are simultaneously present, the transistor conducts to reduce the applied AGC voltage by the proportion of the first to the second impedance. Otherwise, full AGC voltage is applied to the control electrode of the RF amplifier.

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Kokomo, IN, United States of America

Jeffrey M Stricker