Bandwidth and transmission zero control for compact dual-mode resonator filter by extraction of EM coupling

Abstract

The electric coupling and magnetic coupling are extracted for a dual-mode resonator filter. The resonator is a half-wave section with its center being shorted to ground. The extraction relies on an equivalent circuit model. With properly tuning of the coupled-line sections, the electric and magnetic coupling coefficients of the two quarter-wave resonators can be adjusted, and hence both the filter bandwidth and zero frequency can be controlled. Two experimental filters are fabricated and measured for validation. Good agreement between measurement and simulation is obtained.

A Compact Wide Bandpass Filter With Good Selectively

“…Compared to cross-coupling and source-load coupling, mixed EM coupling structures are simpler, and the induced TZs are controllable, thus they are now being studied extensively. In [9][10][11], a dual-mode resonator and mixed electric and magnetic coupling structure are used together to design filters with small size and good selectivity, but their operation passbands are in the radio frequency. In addition, the composite right/left-handed transmission lines are also used to design wideband or harmonic suppressed devices [12][13][14][15], but the circuits are complicated, and most of them have large size.…”