Adaptive-filter single-bit digital encoder and decoder and adaptation control circuit responsive to bitstream loading.

摘要

An adaptive single-bit encoder and decoder has its adaptive function determined by dynamically dividing the message frequency band into delta-sigma and delta modulation regimes of operation. In a practical embodiment this is accomplished by varying the corner frequency of a variable-frequency low-pass filter (14, 14 min ) in a leaky integrator so that below the corner frequency the operation is that of delta-sigma modulation and above the corner frequency the operation is that of delta modulation. An adaptation control circuit (18, 18 min ) removes the clock signal component from the encoded bit stream to provide an analog signal representative of bit stream information or loading for use in generating the control signal. The analog signal is peak rectified (22, 22 min ), smoothed (24, 24 min ), and (optionally) non-linearly processed (26, 26 min ) to provide the control signal.