Application of frequency-domain polyphase filtering to quadrature sampling

摘要

Abstract: A new method for developing in-phase and quandraturesamples of a band limited real signal is presented andcompared with other methods. The proposed methodimproves the computational efficiency of afrequency-domain implementation of the requiredfiltering by taking advantage of mirror-image symmetrybetween the filters on the in-phase and quandraturechannels. This technique makes it possible to filteerboth the in-phase and quadrature channels at once usingone standard FFT for complex-valued input and onestandard IFFT for complex-valued output without addingcomputational overhead. The proposed method is morecomputationally efficient than techniques usingcommonly available FFT routines for real-valued input.Specialized FFT routines derived specifically for real-valued input can achieve greater computationalefficiency than the proposed method, but these routinesare not as commonly available as the standard FFTroutines used in the proposed method. For systems wherethe effective channel filter is short in length or hasspecial structure, there are other implementations ofthe channel filters which are more efficient than theproposed method. !12