A compact integrated combline band pass filter using LTCC technology for C-band wireless applications

An integrated tapped combline filter for C-band wireless applications was designed and fabricated by loading interdigital type capacitive loads using low temperature co-fired ceramic (LTCC) technology. In-situ measurement using T-pattern microstrip resonator was performed to acquire exact knowledge of electrical properties of the LTCC substrate. The presented filter can be built with relatively small size, 2.7 mm×2.03 mm, due to capacitive loads, therefore reducing the physical length and extending the electrical length of the microstrip line resonator. Also, it shows 1.8 dB insertion loss, 37.6 dB return loss, and 280 MHz bandwidth at the center frequency of 5.09 GHz. Its small size and relatively simple structure make it a good candidate as an integrated filter for various LTCC substrates.