BANDSTOP FILTERS WITH VARIABLE UPPER PASSBANDS USING EMBEDDED LINE, SPURLINE, AND CONVENTIONAL MICROSTRIP

摘要

Three planar structures including embedded line, spurline, and conventional microstrip are used to implement bandstop filters and their performances of bandwidth, center frequency and higher-order stopbands are studied in the discrete-time domain. A two-section, equal-length stub is presented to change the ratio of the next higher-order harmonic frequency to the fundamental frequency. A filter having upper passband widths of up to nine times the fundamental stopband central frequency can be obtained by using conventional microstrip. A higher-order bandstop filter is implemented with hybrid embedded line, spurline, and conventional microstrip to show the validity of the design method.