Design the Duplexer and Dual-band Filter with Multiple Capacitively Loaded Coupled Lines

C.-W. Tang and S.-F. You (Taiwan)


Duplexer, dual-band filter, multiple capacitively loadedcoupled lines.


This paper proposes a new method to design the microstrip duplexer and dual-band filter with multiple capacitively loaded coupled lines. The filter with multiple capacitively loaded coupled lines can produce a transmission zero located within the higher stopband. Tapping the input/output port to the filter can create other transmission zeros around the passband skirts. These features can be adopted to develop the microstrip duplexer. Moreover, these characteristics can be employed to the dual-band filter design as well in order to develop dual mode portable telephones. As for the fabrication, two separate passbands appear in a single circuit instead of stacking two individual bandpass circuits. Furthermore, the duplexer and dual-band filter with uniplanar structure are easily integrated with MIC or MMIC. The measured results of implemented circuits match well with the electromagnetic simulation, which can validate the proposed structure.

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