Low complexity flexible filter banks for uniform and non-uniform channelisation in software radios using coefficient decimation

Abstract

A new approach to implement computationally efficient reconfigurable filter banks (FBs) is presented. If the coefficients of a finite impulse response filter are decimated by M, that is, if every Mth coefficient of the filter is kept unchanged and remaining coefficients are replaced by zeros, a multi-band frequency response will be obtained. The frequency response of the decimated filter will have bands with centre frequencies at 2πk/M, where k is an integer ranging from 0 to M−1. If these multi-band frequency responses are subtracted from each other or selectively masked using inherently low complex wide transition-band masking filters, different low-pass, high-pass, band-pass and band-stop frequency bands are obtained. The resulting FB, whose bands’ centre frequencies are located at integer multiples of 2π/M, is a low complexity alternative to the well-known uniform discrete Fourier transform FBs (DFTFBs). It is shown that the channeliser based on the proposed FB does not require any DFT for its implementation unlike a DFTFB. It is also shown that the proposed FB is more flexible and easily reconfigurable than the DFTFB. Furthermore, the proposed FB is able to receive channels of multiple standards simultaneously, whereas separate FBs would be required for simultaneous reception of multi-standard channels in a DFTFB-based receiver. This is achieved through a second stage of coefficient decimation. Implementation result shows that the proposed FB offers an area reduction of 41% and improvement in the speed of 50.8% over DFTFBs.