Design of compact tri-band bandpass filter using multilayer substrate technique

In this paper, the compact tri-band bandpass filter (BPF) using multilayer substrate technique is presented. The filter is designed at 2.4 GHz, 3.5 GHz and 5.2 GHz. The multilayered filter consists of the cross-shaped stepped-impedance resonator (CS-SIR) on the top layer for generating the 1st passband and two T-shaped stepped-impedance resonators (TS-SIR) on the bottom layer for generating the 2nd and 3rd passband, respectively. The transmission zeros at each passband skirts can be controlled by tuning the proposed resonators. The measured results are in good agreement with the full-wave electromagnetic (EM) simulation results.