Design of Cascaded Three- Conductor Coupled Line Filter

This article presents analysis approach and applications of symmetrical three-conductor coupled microstriplines with aperture in the ground plane for the design of microwave filters. Analysis is based on splitting the entire symmetrical three-conductor coupled line structure into simple two-conductor coupled lines. Various possible terminations have been shown in three-conductor coupled lines to derive a class of structures for the construction of filters. These coupled line structures are analyzed based on evenand odd-mode propagation characteristics to design filters in this article. An experimental cascaded threeconductor coupled line band stop filter with defected ground has been designed using the method of circuit model analysis. Defected ground has been used under the coupled lines to widen the filter’s bandwidth. Measured results of the designed band stop filter have been compared against the circuit model analysis for the purpose of validation. Results are in good agreement between them. VC 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2431–2436, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.28615