Temperature-compensated bandpass filters in low temperature co-fired ceramic

Abstract

For low temperature co-fired ceramic (LTCC) modules targeting radio frequency applications, a near 0 ppm/C temperature coefficient of resonant frequency (τf) ensures temperature stability of embedded filters. The base dielectrics of most commercial LTCC systems have a τf in the range -50 to -80 ppm/C. By integrating co-fireable compensating dielectrics with an opposite τf to that of the host dielectric, we demonstrated multilayer stripline (SL) bandpass filters with a τf approaching 0 ppm/C using DuPont 951 LTCC. The effective dielectric constant of the SL in multilayer LTCC with dissimilar layered dielectrics was calculated using a variational method with transmission-line technique. © 2013 The American Ceramic Society.