AN AUDIO A/D CONVERTER USING FREQUENCY MODULATION

摘要

PURPOSE: An audio analog/digital convertor using frequency modulation is provided to reduce noise generated by supplying a bias. CONSTITUTION: A frequency of a voltage or a current-control oscillator is controlled by a signal provided from a microphone. A frequency modulated signal is supplied to a digital discriminator displaying an instantaneous frequency at desired voice sampling rate. The digital discriminator formed by directly supplying a oscillation signal to a phase digitization circuit and computing a instantaneous phase sequence. The phase sequence is supplied to a digital phase locked loop to generate a sequence of binary word. A low-level voice wave is not inputted to an integrated circuit without a frequency-modulated carrier of high-level.