DELTA SIGMA MODULATOR AND WIRELESS COMMUNICATION APPARATUS

摘要

A delta sigma modulator has a loop along which an output signal from a quantizer is digital processed and then fed back to an analog filter via a DAC. In the delta sigma modulator, the quantizer (110) quantizes an analog signal from the analog filter part (100) to a digital signal. The digital signal from the quantizer (110) is digital processed by a first-order recursive filter circuit (125) comprising a variable gain (123) and a delay element (124). An LUT (121) receives as inputs the digital signal from the quantizer (110) and a table control signal (S1200), which is an output signal from the recursive filter circuit (125), to store a compensation value in accordance with these two signals in advance. The compensation value from the LUT (121) is a digital output signal in which the delay has been corrected, while this digital output signal is converted by the DAC (130) to an analog signal, which is then used to perform a subtraction from an analog input signal in the analog filter part (100). Thus, the influence of delay is reduced for high-speed wideband signals, whereby the precision of output signals can be improved.