BTSC TV multichannel sound decoder including digital expander

A description is given of a system consisting of 2 ICs which digitally process most of the functions carried out by the main FM demodulator in a Broadcasting Television System Committee (BTSC) standard TV transmission. Emphasis is on the digital implementation of the expander circuit using a single instruction computer (SIC) digital signal processor (DSP) IC. The systems are essentially the same as in an analog expander, except for an equalizing bandpass and a gain alignment stage at the inputs of both the sum and the difference channel.<
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