Analysis of Second-Order LTCC Bandpass Filter with Two Finite Transmission Zeros

The paper proposes a new Low-temperature co-fired ceramic (LTCC) bandpass filter, which can be used to provide two finite transmission zeros in the lower stopband. The coupled electromagnet of the two stepped-impedance resonators (SIRs) is improved by adding a coupling pad. A feedback capacitor between input and output is also used to realize transmission zero. An equivalent lumped circuit is derived to explain the behaviors of the two finite transmission zeros .This filter operates at 2.45 GHz and has a compact size of 2.5 mm times 2.0 mm times 0.9 mm,which is widely used in Bluetooth wireless LAN transceiver system.