Compact dual-mode dual-band balun filter using double-sided parallel-strip line

摘要

Proposed is a compact dual-band balun filter adopting a double-sided parallel-strip line (DSPSL). The middle conductor plane can be treated as a virtual ground. Then, two sets of short-stub loaded dualmode resonators on the top and the bottom layer act as two dualband filters. They are fed by the DSPSL at the input port, and the filters can be excited simultaneously. Meanwhile, an out-of-phase feature is obtained between the two output ports. In addition, the proposed dual-band balun filter has good frequency selectivity which is due to multiple transmission zeros. Finally, a dual-band balun filter sample was designed and fabricated with good agreement obtained between its measured and simulated S-parameters.