CIRCUITRY FOR MULTIPLYING A SIGNAL BY A PERIODIC WAVEFORM

摘要

Apparatus for multiplying a sampled data signal by a sinusoid having a period which is a multiple of the sample rate includes a plurality of sample scaling means (116) to scale the sampled data signal by factors corresponding to the sine of angle theta over an angular range of 90 degrees in angular increments of 2 pi divided by said multiple. A multiplexer (118,120) multiplexes the scaled samples at the sample rate to produce a signal corresponding to the sampled data signal multiplied by the sinusoid. The data sample rate is phase-locked to the sinusoid. An embodiment is described for demodulating the stereo difference signal of a BTSC sound signal with serial-bit digital processing circuitry.