• ETRI Journal
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• v.32 no.1
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• pp.148-150
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• 2010

This letter presents the design of a compact bandstop filter (BSF) operating at two frequencies. The proposed BSF consists of open-ended stepped impedance resonators (OSIR) and an end-shorted parallel-coupled microstrip line (E-PCML). The OSIRs are used to achieve the impedance-controlled stopband positions. The wide BSF bandwidths are achieved through enhanced coupling of the E-PCML. Explicit design guidelines are derived using a lossless transmission line model. To validate theoretical predictions, a prototype dual-band BSF operating at 900 MHz and 2,100 MHz with fractional bandwidths of 72% and 36%, respectively, is implemented in microstrip.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.150-154
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• 2003

In this letter, a novel compact duplexer which consists of Tx and Rx Filter using microstrip line ${\lambda}/4$ resonators with a pair of tap-connected open-ended stepped impedance stubs is designed. The tapped open stubs not only work as K-inverters but also introduce attenuation poles, attenuation poles are located at upper and lower side of the passband by adjusting the open stub length and width. The result of measurement duplexer has been yielded better isolation and sharper skirt behavior than that with a conventional bandpass filter and similar to those of simulation results.