標題: questions on complex bandpass CTSDM? [打印本頁] 作者: soupdawn 時間: 2009-4-10 01:06 PM 標題: questions on complex bandpass CTSDM? 1) First, start with the design of the noise transfer . n* b( Z: t! B3 P; g
function (NTF) for a lowpass (LP) discrete-time sigma delta 7 e, h4 p3 l! A# h8 umodulator, and mapped it to a CT modulator. z, T# W) P2 [: d6 X5 p6 b' H5 z7 B2 c
2) Secondly, replicate exactly the prototype LP ) C: a& M1 }" T: kmodulator in order to realize the signal path for the , C$ N: X4 t5 y5 Simaginary signal components. / {) `5 W$ v8 {" X, m, N
3) Finally, add cross-coupled coefficient to perform . t$ B- {- X% o, _( U0 D3 p4 ]frequency-shifting from DC to the desired * R. h/ v& N2 c# s0 W
intermediate frequency. " k' ^/ X' ~4 h( P0 r" s
but it doesn't work,my question is how to determine the feedford coefficients? ' r% u& o4 F* ^: v8 P
the method is cited from "Continuous-Time Complex Bandpass sigma delta Modulator: Key Component for Highly Digitized Receiver