A compact bandpass filter using interdigital and step-impedance hairpin resonators

Abstract

A four-pole elliptic function bandpass filter is designed using miniaturized microstrip interdigital hairpin resonator and stepimpedance hairpin resonator. Miniaturization hairpin resonators are realized by using interdigital structure and step-impedance structure having parallel coupled lines. The full-wave simulator IE3D is used to design the compact hairpin resonator and to calculate the coupling coefficient of the basic coupling strictures. The response of the fabricated filters using Al 2 O 3 (e r ¼ 9.7, Q Â f ¼ 350000 GHz) and 0.6Sm(Co 1/2 Ti 1/2 )O 3 -0.4CaTiO 3 (e r ¼ 37, Q Â f ¼ 43000 GHz) dielectric substrates are designed at a center frequency of 2 GHz. The compact size and the performance of this class of filter have been demonstrated.