Abstract:

Based on a new open-stub loaded dual-mode open-loop resonator, a dual-band microstrip filter is designed for applications of wireless local area networks (WLAN) IEEE 802.11b/a (2.4/5.2 GHz). The odd-mode and evenmode resonant frequencies of the dual-mode open-loop resonator are created by structures of open-loop and loaded open-stub separately. A dual-band filter is realized by two electrically and magnetically mixed coupling resonators with four transmission zeros. Two passbands of the filter are produced by the basic resonant frequency and the one-order spurious frequency. In order to match the input and output impedances and to improve performance of two passbands, a taper-line is used to feed the coupling resonator in terms of 0°. Electromagnetic simulation frequency responses S₁₁ and S₂₁ of the dual-mode filter show agreements with experimental results, indicating good passband characteristics and isolation between two passbands. 

Key words: dual-mode; open-loop resonator; dual-band; band pass filter (BPF); taper-line feed