A dual-mode bandpass filter with tuning transmission-zero and harmonic suppression for RFID and WiMax applications

摘要

A dual-mode T-shape stub loaded bandpass filter (BPF) with wide stopband is proposed. To design a narrow BPF for suitable use in 5.8 GHz radio frequency identification (RFID) and worldwide interoperability for microwave access (WiMax) applications, a dual-mode T-shape stub-loaded resonator (TSSLR) is introduced and studied. Due to the symmetrical plane, odd-even mode theory can be adopted to characterize it. One transmission zero is located near the passband, which leads to a high selectivity. An extra transmission zero can be tuned at the second harmonic frequency to realize a wide stopband. The center frequency of the proposed BPF is 5.8 GHz, and the 3 dB fraction bandwidth is 8.9%. The super response is below 20 dB from 7.1–15.0 GHz.