Efficient design of switched current lowpass elliptic filters using Bruton transformations

This paper describes how the Bruton transformation facilitates the development of an efficient design methodology for switched current elliptic lowpass wave filters. Wave models for the design methodology including FDNR, capacitive source and load are presented. The proposed design method offers a significant reduction in the filter transistor count. For example, a 7th-order lowpass elliptic filter utilises 20% less delay elements and 16% less current mirrors when compared with a recently reported design method. This is achieved by having a filter with a large number of resistors and simplified series adapters. Simulated results based on a typical CMOS process for a lowpass elliptic filter with Fc=100KHz and Fs=1MHz are included