NEW COMPACT TRIPLE-MODE RESONATOR FILTER WITH EMBEDDED INDUCTIVE AND CAPACITIVE CROSS COUPLING

Abstract

Two new compact planar triple-mode resonators embed- ded with inductive or capacitive cross coupling are proposed for band- pass fllter design. Both resonators consist of a shorted half-wave ring. In the flrst resonator, two shorted half-wave sections with inductive coupling are connected to the shorted via of the ring. In the second, two quarter-wave sections with capacitive coupling are connected. The inductive coupling is realized by a short grounded high-impedance seg- ment, and the capacitive coupling is implemented by an interdigital ca- pacitor. When both the inductive and capacitive coupling coe-cients are properly realized, a transmission zero can be created at designated position in either upper or lower stopband. The shorted ring is accom- modated inside the area of the other two resonance sections so that a compact area can be achieved. As compared with a conventional dual- mode ring resonator fllter, the proposed resonators use only 46.7% and 22.5% in area. Two triple-mode resonator bandpass fllters are fabri- cated and measured to validate the ideas. Measurement results have good agreement with the simulation responses.