Magneto-inductive waveguide devices

TLDR

Magneto‑inductive waveguides built from coupled loop resonators are studied analytically under lossless, nearest‑neighbour coupling assumptions, with two‑port devices such as mirrors, Fabry–Perot resonators, Bragg gratings, tapers, and N‑port devices like power splitters and directional couplers considered. The authors analyze conditions for multiple‑beam resonance and Bragg reflection in two‑port devices, demonstrating that simple layout variations can produce quasi‑optical filters, and identify design rules for low‑reflection splitters and matched three‑port splitters with arbitrary power division ratios for a specific input port. They find that matched three‑port splitters cannot be achieved for all ports simultaneously, directional couplers perform optimally only at mid‑band with weak coupling, and that high‑Q resonators mitigate loss to approach idealised performance.

Abstract

Devices formed from magneto-inductive waveguides based on coupled loop resonators are considered using simple analytic theory, initially assuming lossless propagation and nearest-neighbour coupling. Two-port devices that were considered include mirrors, Fabry–Perot resonators, Bragg gratings and tapers, while more general N-port devices include power splitters and directional couplers. Conditions for multiple-beam resonance and Bragg reflection in two-port devices are identified, and it is shown that quasi-optical filters may be constructed by simple layout variations. Conditions for low reflection are identified in splitters, and it is shown that matched three-port splitters with arbitrary power division ratios may be achieved for a particular input port. However, matching is not possible for all ports simultaneously. Directional couplers are shown to operate well only at mid-band and with weak coupling. The effect of loss is then examined and it is shown that idealised performance is obtained using resonators with sufficiently high Q-factors.