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Title: Audio processor circuit for an FM-stereo radio receiver
Claims: Having thus described our invention what we claim is: 1. An audio processor for processing left and right stereophonically related input signals, said processor including left and right signal processing channels, each of said signal processing channels including first and second subchannels, means coupling said left audio input signal to said first and second subchannels of said left signal processing channel and means coupling said right audio input signal to said first and second subchannels of said right signal processing channel, means coupling the first subchannel of said left processing channel with the first subchannel of said right processing channel for producing a blended signal in each of said first subchannels, said second subchannel of said left and right processing channels maintaining the original separation between said left and right audio signals and passing said left and right input signal substantially unaltered, means providing a control voltage related to a characteristic of the carrier signal from which said input signals are obtained, and means responsive to said control voltage for summing a portion of the signal at the output of each of said first subchannels with a complementary portion of the signal at the output of its associated second subchannel to produce a composite left and a composite right audio signal. 2. A radio frequency receiver including means providing left and right stereophonically related audio signals, means providing a DC voltage indicative of the strength of a received carrier signal, an audio processor including left and right signal processing channels responsive to said left and right audio signals respectively, each of said signal processing channels including first and second subchannels which are electrically isolated one from the other, means including a capacitor coupling the first subchannel of said left processing channel with the first subchannel of said right processing channel for producing in each of said first subchannels a frequency dependent blended signal, said second subchannel of said left and right processing channel passing said left and right audio signal substantially unaltered, and means responsive to said DC voltage for summing a portion of the signal at the output of each of said first subchannels with a portion of the signal at the output of each of said second subchannels to produce a composite left and a composite right audio signal. 3. A radio frequency receiver including means providing left and right stereophonically related audio signals, means providing a DC voltage indicative of the strength of a received carrier signal, an audio processor including left and right signal processing channels responsive to said left and right audio signals respectively, each of said signal processing channels including first and second subchannels which are electrically isolated one from the other, means including a capacitor coupling the first subchannel of said left processing channel with the first subchannel of said right processing channel for producing in each of said first subchannels a frequency dependent blended signal, means for attenuating the blended signal in each of said first subchannels as a function of frequency above a predetermined break frequency, said second subchannel of said left and right processing channel passing said left and right audio signal substantially unaltered, and means responsive to said DC voltage for summing a portion of the signal at the output of each of said first subchannels with a portion of the signal at the output of each of said second subchannels to produce a composite left and a composite right audio signal. 4. A radio frequency receiver including means providing pure left and right stereophonically related audio signals, means providing a DC voltage indicative of the strength of a received carrier signal, an audio processor including means for reducing the separation between said left and right audio signals as a function of signal frequency to provide processed left and processed right audio signals, and means responsive to said DC signal for combining complementary portions of said pure left signal and said processed left signal and for combining complementary portions of said pure right signal and said processed right signals to produce a composite left audio signal and a composite right audio signal. 5. In an FM stereo radio receiver which develops pure L and R stereophonic signals and which develops a control signal indicative of the strength of a received carrier signal, the combination comprising: means including active and inactive L channels through which the L input signal is passed to obtain processed and unprocessed L signals respectively, and including active and inactive R channels in which the R input signal is passed to obtain processed and unprocessed R signals respectively, where the signal transfer characteristics of the active and inactive L channel and of the active and inactive R channel are identical except as hereinafter indicated, means including a capacitor connected between the active L channel and the active R channel for cross-coupling the signals in the active L channel and the active R channel as a function of signal frequency, means including a resistor/capacitor filter stage connected in each of the active L channel and the active R channel for attenuating the signal in the active L and active R channels as a function of signal frequency above a predetermined breakpoint frequency, and means for combining complementary portions of the processed and unprocessed L signals and of the processed and unprocessed R signals to form composite L and R output signals respectively where the portion of processed L signals and the portion of processed R signals increases as the strength of the carrier signal decreases. 6. An FM receiver comprising means providing left and right audio signals, means providing a DC voltage indicative of the strength of a received carrier signal, left and right audio amplifier means, an audio processor including left and right signal processing channels, each of said channels including first and second subchannels, means coupling the left and right audio signals to said first and second subchannels of said left and right channels respectively, each of said first subchannels including first and second unity gain voltage followers, an active filter, and a voltage-to-current converter, a capacitor interconnecting said first subchannels at a junction between said first and second voltage followers, each of said second subchannels including first, second, and third unity gain voltage followers and a voltage-to-current converter, first and second current steering multipliers, means connecting the outputs of the voltage-to-current converters of said left channel to first and second inputs respectively, of said first current multiplier, means connecting the outputs of the voltage-to-current converter of said right channel to first and second inputs respectively of said second multiplier, voltage translator means responsive to said DC voltage for producing a voltage differential related to the difference between said DC voltage and a reference voltage and for applying said differential voltage to said current multipliers to steer complementary portions of the input currents to said first multiplier and produce a first composite current signal at the output of said first multiplier and for steering complementary portions of the input currents to said second multiplier to produce a second composite current signal at the output of said second multiplier, means for converting said first and second composite current signals to first and second composite voltage signals, respective unity gain voltage followers responsive to said first and second composite voltage signals, means for coupling the output of said unity gain voltage followers to said left and right audio amplifiers, respectively. Other info: Inventors: Gilbert, William F. (Kokomo, IN, US) Schertz, Burtron D. (Kokomo, IN, US) Smith, Wayne A. (Russiaville, IN, US) Wilkinson, Lester (Kokomo, IN, US) Application Number: 516797 Filing Date: 1974-10-21 Publication_date: 1976-04-20 Assignee: General Motors Corporation (Detroit, MI) Primary Class(es): 381/10 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Claffy, Kathleen H. Assistant Examiner: Stellar, George G. Attorney: Duke; Albert F. |
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