A miniaturized LTCC Lowpass filter with two transmission zeros

A integrated quasi-lumped LOW pass filter (LPF) for Wireless application was designed and fabricated by low temperature co-fired ceramic (LTCC) technology. The circuit is based on the quasi-lumped filter topology, and two transmission zeros were introduced to achieve sharp suppression rate. Three dimensional inductances and capacitances have been investigated and used to design the LPF. The proposed filter was designed with a cut-off frequency of 1 GHz and the measured insertion loss is less than 0.7 dB. The attenuation is less than -52 dB at 2.4 GHz and two transmission zeros are located at 2.5 GHz and 3.1 GHz respectively. The total size including the test pad is 5.6 × 3.6 × 0.9 mm³. The low temperature cofired ceramic (LTCC) materials have a dielectric constant of 5.9, a loss tangent of 0.0015, and a metallization of gold The LPF was simulated and optimized by Finite Element Method (FEM). Its good performance, small size and relatively simple structure make it a good candidate as an integrated filter to be embedded in wireless application system.