Gm Global Technolgoy Operations, Inc.

Wayne A Smith

Burtron D Schertz

Lester Wilkinson

William F Gilbert

James E Mathews

Arthur R Hammond

A radio receiver is effective to receive a radio frequency signal and derive therefrom a standard stereo composite signal comprising a sum of channels signal having components within a first band of frequencies in the audio range and a difference of channels signal having components within a second band of frequencies above the first band of frequencies. The radio receiver is provided with a low pass filter having a high frequency roll-off characteristic within the first frequency band and a substantially flat attenuated amplitude characteristic across the second frequency band. Linear mixer apparatus mixes filtered and unfiltered stereo composite signals in controlled relative proportion responsive to a control signal to produce a modified stereo composite signal for application to stereo decoder apparatus in order to simultaneously roll-off the high frequencies in each derived channel and to attenuate the difference of channels signal in degree controlled by the control signal. Control signal generating apparatus provides said control signal in response to a parameter indicative of noise in the stereo composite signal.

Stereo composite processor for stereo radio receiver

An audio processor is disclosed which includes circuitry for modifying pure left and right audio signals by blending the left audio signal with the right audio signal as a function of frequency and for rolling off the higher frequencies of the blended signal. The processor further includes circuitry for selecting complementary portions of a blended, rolled-off audio signal and a pure audio signal as a function of the RF carrier strength to improve the overall listenability of the audio.

Audio processor circuit for an FM-stereo radio receiver

An automatic gain control system in which a DC voltage proportional to an on-channel signal is used to control the gain of the RF stage but is keyed from the wide band output of the mixer stage to reduce the possibility of mixer overload.

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Russiaville, IN, United States of America

Wayne A Smith