Efficient design of switched-current lowpass elliptic wave filters using Bruton transformation

摘要

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 frequency dependent negative resistance (FDNR) component, capacitive source and capacitive load are presented. The proposed design technique 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 technique. This is achieved by having a filter structure with a number of resistors and simplified series adapters. Simulated results based on a typical CMOS process for a lowpass elliptic filter with a cutoff frequency of 100 kHz and a sampling frequency of 1 MHz are included.