questions on complex bandpass CTSDM?

soupdawn

1) First, start with the design of the noise transfer
% X' ?# z5 W* {$ y, hfunction (NTF) for a lowpass (LP) discrete-time sigma delta
- j* ~1 B7 `* I/ e0 D- Q, A0 }modulator, and mapped it to a CT modulator.
2) Secondly, replicate exactly the prototype LP
modulator in order to realize the signal path for the
6 ^) Q  x- K! z1 X& timaginary signal components.
. U6 J. M* G' |3) Finally, add cross-coupled coefficient to perform
6 e  t2 L8 f7 F* Q; q( G! qfrequency-shifting from DC to the desired
intermediate frequency.
but it doesn't work,my question is how to determine the feedford coefficients?
' I( i7 M7 x0 K/ r6 d) x+ kthe method is cited from "Continuous-Time Complex Bandpass sigma delta Modulator: Key Component for Highly Digitized Receiver