Design of an LTCC switchable filter for dual- band RF front-end applications

This work presents a frequency switchable filter used in a highly integrated dual-band RF frond end module. The proposed filter topology employs a PIN diode as the switching device, facilitating the use of two capacitors in a semi-lumped resonator with a specified ratio of capacitances, to realize various frequency switching ratios. A dual band external Q approach is introduced to improve the input/output matching in both bands. The presented topology enables the integration of the filter in a multi-layer circuit for miniaturized implementation. Finally, an example design, fabricated using low-temperature co-fired ceramic (LTCC) technology is presented to validate the filter configuration.