Patent TW-275168-B (TW)
Title: Analog to digital converter
Inventor: HORNG HAW-CHYAU
IPC: H03M1/12
Filed: 1995-10-09
Granted: 1996-05-01
Abstract: A high order sigma-delta modulator for converting analog signal to digital signal comprises: one sigma-delta modulator network of analog signal including four or more cross cascaded first order sigma-delta modulators, each first order sigma-delta modulator comprises: one sampling quantum signal input, one recover signal input, one sampling quantum signal output, one recover signal output and one digital signal output; one amplifier amplifying the above recover signal input with one specific gain to form one amplified signal output; one adder with three input ends, in which the first input end is connected to the above sampling quantum signal input, the second input end is connected to the above amplified signal output, the adder subtracts the signal sum of the second input end and the third input end from the first input end to form adder output; one loop filter with one input end connected to the above adder output which is the above sampling quantum signal output, and the system transform function could be represented by one numerator polynomial and denominator polynomial defined in z domain, in which the coefficient of numerator polynomial is real number and transform function of bypass or bandpass filter in baseband range, and the coefficient of dominator polynomial is real number and transform function of highness filter in baseband range; one analog signal to digital signal converter whose input end is connected to the above filter output, and converting it to digital output with at least one bit to form one of the above signal signal output; one digital signal to analog signal converter whose input end is connected to the output of the above analog signal to digital signal converter, both have same bit number, and converting it to analog feedback signal output; one signal polynomial defined as the above numerator polynomial; one noise polynomial defined as the above denominator polynomial; one output polynomial defined as the sum of the above numerator polynomial and denominator polynomial; one digital output signal mixed network consisting of multiple filter mixer, in which the count of filter mixer in the mixed network is same as the count of sigma-delta modulator in analog signal sigma-delta modulator, every filter mixer has one corresponding sigma-delta modulator, in which every filter mixer comprises: one digital input, one middle input and one middle output, in which digital input is connected to digital signal output of sigma-delta modulator corresponding to the filter mixer; the first adder to calibrate the above digital input to one calibrated input with one offset base; one time correction filter for receiving the above calibrated input, filtering it to generate one output, whose system transform function could be defined as the multiplication of the first polynomial and the second polynomial; the second adder for adding the above time correction filter output and the above middle input; one middle filter for filtering the above second adder output to form middle output, whose transform function is noise polynomial of sigma-delta modulator one before sigma-delta modulator corresponding to the filter mixer.