This paper proposes a simple approach for realizing a dualband response bandpass filter (BPF) comprising two strip feed lines on the upper layer and a twin-spiral etched ground structure (EGS) on the lower layer. It is shown that by moving the two strip feed lines from the center of the EGS toward the upper-left and lower-right corners of the EGS unit, respectively, a 5.2-GHz passband can be excited in addition to the original 2.4-GHz passband. Moreover, by carefully controlling a dimension of the EGS, the second passband can be tuned in such a way as to realize a 2.4/5.7 GHz BPF. The experimental results show that the dual-band 2.4/5.2 GHz BPF has a good passband selectivity and an excellent out-of-band noise suppression capability. Consequently, the device provides an ideal solution for both Industrial-Scientific-Medical (ISM) and Wireless Local Area Network (WLAN) applications.

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