questions on complex bandpass CTSDM?

soupdawn

1) First, start with the design of the noise transfer
4 a* a( a: ^: `. P1 jfunction (NTF) for a lowpass (LP) discrete-time sigma delta
modulator, and mapped it to a CT modulator.
2 a$ R/ @$ e2 s% u/ R2) Secondly, replicate exactly the prototype LP
modulator in order to realize the signal path for the
imaginary signal components.
  l, @, }& B* U# m5 k6 k5 A3) Finally, add cross-coupled coefficient to perform
frequency-shifting from DC to the desired
intermediate frequency.
/ d0 O9 x; B0 s7 C3 H+ s9 @$ Abut it doesn't work,my question is how to determine the feedford coefficients?
the method is cited from "Continuous-Time Complex Bandpass sigma delta Modulator: Key Component for Highly Digitized Receiver