Tunable active filters having multilayer structure using LTCC

Two types of tunable filters have been developed at 400- and 800-MHz frequency bands, respectively. These filters have been fabricated with low-temperature co-fired-ceramics multilayer technologies assisted by varactor diodes. The filter size is 5.6 x 5.6 x 3.0 mm. Each filter has approximately 11% and 13% tuning range of frequency with a controlling voltage of 1-4 V, IL < 2.0 dB, and has an attenuation over 40 dB at fo [+ or -] 30%, respectively. Temperature stability data is also discussed. Index Terms--Ceramics, multilayers, tunable filters, varactors.