设计一种新颖的双频带带通滤波器(bandpass filter,BPF),可应用于无线局域网（wireless local area network，WLAN） IEEE 802.11 b/a (2.4/5.2 GHz).该滤波器是由折叠的阶跃阻抗谐振器(stepped impedance resonator，SIR)外加2个枝节构成，并具有一个传输零点.该滤波器的2个通带分别由折叠型SIR的基频和一次杂散频率产生.为了满足输入和输出阻抗匹配的要求，改善双频段的通带性能，采用零度馈电方式.仿真结果显示，2个频带在2.4/5.2 GHz时的3 dB相对带宽分别为6.3%和3.4%.测量结果和仿真结果基本吻合.

A novel compact dualband bandpass filter (BPF) is designed for applications of wireless local area network (WLAN) IEEE 802.11 b/a (2.4/5.2 GHz). The filter is composed of folded stepped impedance resonators (SIRs) and two stubs with one transmission zero. The two passbands are centered at the basic resonant frequency and the firstorder spurious frequency. To match the input and output impedances and improve performance of the two passbands, a tapline is used to feed the coupling resonator at zero degree. Simulation results show that the two center frequencies are located at the desired 2.4 and 5.2 GHz with 3 dB fractional bandwidths of  6.3% and 3.4%, respectively. The measured results are in general agreement with the simulation results.