A bandpass filter using dielectric coaxial resonators with a temperature-stable stepped-impedance structure

In this paper, a bandpass filter using stepped-impedance coaxial resonators is presented. Each stepped-impedance resonator (SIR) is composed of ceramic/material to ensure temperature stability of the resonant frequency; one has a positive temperature coefficient of resonant frequency (tau(f)), and the other has a negative tau(f). A capacitively coupled three-pole bandpass filter is designed and fabricated to have a center frequency of 915 MHz and a passband bandwidth of 20 MHz. The improved temperature stability of this filter is demonstrated by experimental results. (C) 2002 Wiley Periodicals, Inc.