High-selectivity Dual-band Bandpass Filter By Utilizing Asymmetrical Stepped-impedance Resonator

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Natchayathorn Wattikornsirikul
Jessada Konpang
Suttee Tubtongdee
Adisorn Sirikham


This paper proposed a high cutoff rejection of dual-band bandpass filter by utilizing an asymmetrical stepped-impedance resonator. The dual-band bandpass filter with high‐selectivity is introduced the controllable transmission zeros (TZs) with good cutoff signal rejection to improve the signal responses. The transmission zeros are present between the first resonant filter and the second passband filter to combine a good cutoff signal rejection. The TZs are located at both side passbands of both filters to suppress harmonic signals and achieve a reasonable cutoff rate in the out-off band. The first filter is operated at the operational resonance of 1.8 GHz, and another one is designed at 2.45 GHz. The coupled feed lines filters can combine two passband filters that enable an easy dual-band structure. Both minimum passband’s insertion losses are 1.35 dB, and the harmonic signal suppression between the first and the second passband is less than 20 dB of the frequency range 1.9 to 2.3 GHz. A high‐selectivity performance with an asymmetrical stepped-impedance resonator can be applied in many wireless communications.

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