Design of an active 2nd-order polyphase filter for image rejection in subsampling receivers

Receivers that work with real subsampling, have the disadvantage that they can not transform a bandpass signal directly to baseband. By using complex subsampling, direct conversion into the baseband is made possible. For this purpose, the bandpass signal must first be converted into a complex or analytic signal. This signal, consisting of real and imaginary parts, is filtered by a polyphase filter. This type of filter allows the transition of positive frequencies and filtering the corresponding negative frequencies. In order to ensure the requirements of the receiver, a high image rejection between negative and positive frequencies must be achieved. This can be done by cascading several first-order filters. To obtain a cheap cost alternative, a novel second-order polyphase filter is described, employing only half the number of OpAmps compared to known cascaded first-order filters. For this reason, this paper focuses specifically on the design and verification of a second-order polyphase filter on a printed-circuit-board (PCB).

[1]  F. Henkel,et al.  A 1 MHz-bandwidth second-order continuous-time quadrature bandpass sigma-delta modulator for low-IF radio receivers , 2002, 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315).

[2]  M. Steyaert,et al.  An analog integrated polyphase filter for a high performance low-IF receiver , 1995, Digest of Technical Papers., Symposium on VLSI Circuits..

[3]  Mikko Valkama,et al.  Advanced I/Q Signal Processing for Wideband Receivers: Models and Algorithms , 2001 .

[4]  Rodney G. Vaughan,et al.  Frequency-shifting using bandpass sampling , 1994, IEEE Trans. Signal Process..

[5]  Michiel Steyaert,et al.  Low-IF topologies for high-performance analog front ends of fully integrated receivers , 1998 .

[6]  Michiel Steyaert,et al.  A single-chip 900 MHz CMOS receiver front-end with a high performance low-IF topology , 1995, IEEE J. Solid State Circuits.

[7]  Yeo Kiat Seng,et al.  A new active polyphase filter for wideband image reject downconverter , 2002, ICONIP '02. Proceedings of the 9th International Conference on Neural Information Processing. Computational Intelligence for the E-Age (IEEE Cat. No.02EX575).