RC Polyphase Filter as Complex Analog Hilbert Filter

This paper presents that the RC polyphase filer has characteristics as a complex analog Hilbert filter. Phase characteristics of the RC polyphase filter have the same as the Hilbert filter. Also its gain characteristics can be approximated as the Hilbert filter; as its order becomes higher, its gain characteristics become closer to the Hilbert filter. We have proved these for 1st to 4th RC polyphase filters, as well as in general n-th order case, and also confirmed with numerical simulations.

An Efficient Quadratic Conversion Architecture for Real-Time Wideband DDC

This paper presents an efficient quadratic conversion architecture for real-time wideband DDC, it can move IF signal to baseband in two steps. Firstly, IF signal is moved to baseband nearby with the help of an structure based on polyphase filter, which places mixers after polyphase filters. Then, the signal is moved to baseband through conventional orthogonal frequency mixing. This presented architecture can reduce filter resources and effectively reduce the sample rate and process cost. Finally, simulation results are presented to illustrate the validity of the new structure.