Tunable active filters having multilayer structure using LTCC

Two types of tunable filter have been developed at 400 MHz and 800 MHz frequency band respectively. These filters have been fabricated with LTCC (low temperature cofired ceramics) multilayer technologies assisted by varactor diodes. Filter size is 5.6/spl times/5.6/spl times/3.0 mm. Each filter has about 11% and 13% tuning range of frequency with controlling voltage of 1-4 V, IL<2.0 dB, and has attenuation more than 40 dB at fo+-30% respectively. Temperature stability data is also discussed.