Bandwidth Enhancement and Further Size Reduction of a Class of Elliptic-Function Low-Pass Filter Using Modified Hairpin Resonators

A compact elliptic-function low pass filter using microstrip stepped-impedance modified-hairpin resonators is developed and a multiple cascaded filter using semi-hairpin resonators is designed, analyzed and tested. Sharpness of cut off frequency, low insertion-loss, enhancement of bandwidth and very compact size are features of the proposed low-pass filter. Size reduction of this filter is reported about 62% with 13% enhancement of bandwidth respects to the conventional filter with comparable performance. The measurement results are in good agreement with the theoretical ones.