ANALYSIS AND DESIGN OF STUB BANDPASS FILTERS USING TAPPED-LINE GEOMETRY
Tae-Soon Yun, Yong-Kyu Yoon, Byungje Lee, Jin-Joo Choi, Jin-Young Kim and Jong-Chul Lee
A simplified mathematical design method for tapped-line geometry is presented and the stub bandpass filters (BPFs) of λg/4 and λg/2 stubs with a center frequency of 5.8 GHz and a bandwidth of 5% are successfully designed, fabricated, and characterized using this approach. Design parameters for the tapped-line geometry of the filter prototypes are obtained using input (output) admittance toward source (load), where the open-stub and the additional transmission-line with a negative electrical length are taken into account for filter implementation. The electrical lengths of the stubs and lines are functions of the line admittance and J-inverter. The filters are implemented on a RT-duroid substrate and the results from modeling and measurement show good agreement with each other. ? 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2338?2341, 2009; Published online in Wiley InterScience (www.interscience.wiley.com).
Keywords: tapped-line, stub bandpass filter, J-inverter, equivalent circuit and bandwidth