METHOD OF IMPROVING STABILITY OF SIGMA DELTA MODULATOR BY USING DITHER

摘要

PROBLEM TO BE SOLVED: To improve the stability of a sigma delta modulator by adjusting a dither signal according to a signal applied to a signal bus of the sigma delta modulator. SOLUTION: The circuit realizing the method is provided with a rough input power level rough calculation device 160 applying an analog input signal to a multiplier and a dither signal is adjusted and regulated by the multiplier 150. A digital output signal generated by the multiplier 150 is fed to a D/A converter and the modified dither signal therein is superimposed properly on a signal fed along with a feed forward signal bus of the sigma delta modulator via a filter 120. A digital output signal of a quantizer 140 is fed to the D/A converter and superimposed on the input signal at a node 110. Furthermore, dither processing is employed for the sigma delta modulator to reduce an action of the quantization error generated by the sigma delta modulator while keeping a sufficient dynamic range of the sigma delta modulator.