Unaliased quadrature audio synthesizer

摘要

The apparatus described unaliases a Doppler signal which is related to the velocity of blood flowing in a sample volume. It then generates an audio output corresponding to the unaliased Doppler signal. The device generates an unaliased, instantaneous signal which corresponds to the Doppler frequency associated with the blood velocity in the sample volume. That unaliased instantaneous frequency is fed into programmable read only memories (PROMs) which provide digitized values for the sine and cosine functions. Those values are fed into digital-to-analog converters, and they are scaled to provide audio outputs.