LTCC highly loaded cavities for the design of single- and dual-band low-loss miniature filters

The use of capacitively loaded cavities implemented in low temperature co-fired ceramics (LTCC) technology allows designing low-loss and small-size microwave filters for low-frequency applications. The designs of highly loaded LTCC cavities as well as single- and dual-bandpass filters based on these resonators are presented. It is demonstrated by the results of electromagnetic simulations and experimental investigations that the size of a highly loaded LTCC cavity can be as low as one eighth of the guided wavelength and even smaller while its Q-factor still remains much higher compared to a quasi-lumped-element LTCC resonator. A novel very compact dual-mode resonator consisting of two capacitively loaded LTCC cavities nested one into another is proposed and shown to be well suited for the dual-band filter design.