baohulu wrote on Mar 31st, 2008, 6:49pm:then how to implement it ? use input forward feedthrough to the input?
The followings are not best reference, but might be helpful for you.
In [2], 1st IIR is implemented as incomplete integral(leaky integral).
[1] AUTHORS: Stephen A. Jantzi, Kenneth W. Martin, and Adel S. Sedra
TITLE: Quadrature bandpass ΔΣ modulation for digital radio
ISSUE: IEEE Journal of Solid-State Circuits, vol. 32, pp. 1935 - 1950, December 1997
[2] TITLE: A discrete-time bluetooth receiver in a 0.13μm digital CMOS process
ISSUE: IEEE International Solid-State Circuits Conference, vol. XLVII, pp. 268 - 269, February 2004
baohulu wrote on Mar 31st, 2008, 6:49pm:however, in the SC bandpass sigma delta adc, the resonator is usually implemented use the a/(1-z^(-1)) or a*z^(-1)/(1-z^(-1)), rather than 1/(1-a*z^(-1)) , and why?
See above [1].