Tunable capacitor arrays of coalesced resonators for dispersion control

Abstract

In this work, the coupling and dispersion characteristics of coalesced resonators as a function of their capacitance is investigated, with the goal of developing novel ways of dispersion control. When planar resonators are coalesced and their shared side is capacitively loaded, the total coupling coefficient is positive, allowing for the propagation of forward magnetoinductive waves. By varying the capacitive load on their shared side, the sign and size of the total coupling can be controlled. This is demonstrated in an 11-element array, where the magnetoinductive wave can switch between forward and backward propagation depending on the capacitive load of the shared side. Furthermore, there is a critical value of the ratio between the capacitive loads on shared and non-shared sides, at which the coupling becomes zero, effectively cutting of wave propagation on the structure. It is shown that the structure can be tuned in two ways: maintain a constant operating frequency while tuning the coupling, or tune the operating frequency while keeping the coupling constant. At the same time, an optimisation procedure for setting up numerical simulations to match the experimental data is proposed. The simulations provided significant insight on the electric coupling's behaviour. Experimental, numerical and analytical data verify this behaviour.