Broadcom Corporation

Russ Lambert

David Chaohua Wu

Alexander Garland MacInnis

Hoang Nhu

Ronald Crochiere

A system and method are disclosed for performing digital multi-channel decoding of a BTSC composite audio signal. Each subsequent stage of the digital multi-channel decoding process is performed at the lowest sampling rate that yields acceptable performance for that stage. Analog-to-digital conversion of the composite audio signal is performed first to generate a composite digital audio signal. After analog-to-digital conversion, all signal processing may be performed in the digital domain. The composite digital audio signal is digitally filtered to frequency compensate for variations caused by previous stages of processing, including IF demodulation. Digital channel demodulation and filtering are performed to isolate single channels of the composite digital audio signal such as SAP, L&#x2212;R, and L+R channels. SAP and L&#x2212;R channels are DBX decoded resulting in corresponding decoded signals using a unique combination of digital filters that are an efficient translation of a corresponding combination of analog filters.

System and method of performing digital multi-channel audio signal decoding

Certain embodiments of the present invention provides a system and method for SAP FM demodulation. The system includes a bandpass filter for isolating the SAP signal, a Hilbert filter to produce a copy of the SAP signal phase shifted by 90 degrees, an FM demodulator for demodulating the SAP signal using the phase shifted SAP signal and a delayed SAP signal, and a lowpass filter to eliminate noise from the FM demodulated SAP signal. The system may also include an automatic gain control for normalizing amplitude of FM demodulator input signals. The digital FM demodulator uses a simplified approximation using non-unity delay for simplified demodulation of frequency modulated signals.

System and method for SAP FM demodulation

A system and method are disclosed for performing digital multi-channel decoding of a BTSC composite audio signal. Analog-to-digital conversion is performed on a composite analog audio signal at a fast clock rate to generate a composite digital audio signal at a first sample rate. Digital frequency compensation is performed on the composite digital audio signal at the first sample rate to generate a compensated composite audio signal. Digital channel demodulation and filtering are performed on the compensated composite audio signal at the first sample rate to generate a first single channel audio signal at a second sample rate.

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Fountain Valley, CA, United States of America

Russ Lambert