Dual-Mode Tunable Loop Resonator with Stub

The analysis results of a dual-mode loop resonator with a stub tunable by two variable capacitors are presented. It was established for the first time that, contrary to the existing idea, such resonators have not only dual-mode oscillations, but also single-mode oscillations, and these oscillations alternate with each other. The resonant frequencies of these resonators are described not by two but by three resonance equations: one equation for single-mode oscillations and two equations for even and odd modes of dual-mode oscillations. The single-mode oscillations are fixed and do not depend on variable capacitances. The range of even and odd modes of dual-mode oscillations is different. The even mode has a wider resonant region and is characterized by a higher range. It is proved that an increase in the characteristic impedance of the stub leads to an expansion of the range of the odd mode, and, consequently, of the dual-mode oscillation. The results of experimental measurements and simulation are presented.