Design of an Economical Compact Coaxial Cavity Combline Filter for 3G TD Base Station

Abstract

The cross coupled microwave filter is widely used in the communication sub system .The synthesis of the cross coupled filter is from prescribed transmission zeros and return loss till the attainment of the coupling matrix of each cavity. A compact narrowband combline high rejection filter with cross coupled is presented. A configureiton using identical resonator post with capacitance-loading is introduced. Tested results show that with order-8 filter center frequency at 2017.5MHz, return loss lower than-25dB can be achieved over a relative bandwidth of 1.29%. A sample filter has been fabricated and tested result confirmed the theory result.