Compact dual-band bandpass filter using stepped impedance resonators

摘要

A modified λ /4 stepped impedance resonator (SIR) is proposed, in which a shunt open stub is loaded between the low impedance line and high impedance line of a conventional λ /4 SIR. Based on this modified λ/4 SIR a compact dual-band bandpass filter (BPF) with high selectivity is presented. Two transmission zeros (TZs) are generated near each passband for high selectivity. To demonstrate this method, a 2.4/5.2 GHz dual-band BPF for WLAN application has been designed, fabricated and measured. The measurement result shows four finite TZs in the stopband, located at 1.82, 3.14, 5.35, and 7.63GHz, respectively. The circuit only occupies 0.06 λg×0.09 λg.