A Miniature Lumped- element LTCC Bandpass Filter with Finite Transmission Zeros for Bluetooth Applications

摘要

A compact, lumped-element bandpass filter with two finite transmission zeros, using a LTCC technique, is proposed for Bluetooth applications. Based on the traditional second-order bandpass filter, a feedback capacitor is added in the middle of the coupled line to obtain two transmission zeros. After describing its working mechanism both graphically and mathematically, commercial software tools were used to accurately model and simulate the filter. To validate the design scheme, the proposed filter was realized using the LTCC technique with the compact size of 3.0 × 1.5 × 0.5 mm. To the best of the authors' knowledge, this is the smallest size for a bandpass filter operating at the center frequency of 2.45 GHz.