Ladder decompositions for wideband SI filter applications

Methods for designing switched-current ladder filters for wideband applications are presented. By performing UL-LU and LU-UL decompositions on the z-domain matrix description of a bilinear transformed passive ladder, filter structures are derived which preserve low passband sensitivity even for large relative bandwidths. Derivation procedures are outlined and illustrated by the example of a 5th order lowpass UL-LU filter and a 10th order LU-UL bandpass. The switched-current filters are realised using Euler-type integrators based on S³I cells. A comparison of the properties of different structures demonstrate the advantages of the UL-LU and LU-UL methods