Rotational resonance of magnetoinductive waves: Basic concept and application to nuclear magnetic resonance

Abstract

Magnetoinductive waves propagating along a set of resonant metamaterial elements are studied under the condition when the wave travels round a closed circular path and the total phase shift is an integral multiple of 2 . The resonant frequency of the circulating wave is shown to be related to the resonant frequency of the element via the known dispersion relationship. The currents in the elements are determined with the aid of the impedance matrix when the excitation is by a rotating magnetic dipole located at the center of the structure. It is shown that the power taken out from one element in the loop may approach N times that from a single element, where N is the number of elements, provided the quality factor of the individual elements is sufficiently high and suitable modifications are made to nearby elements. Potential applications to magnetic resonance spectroscopy are discussed.

Radiation Properties and Coupling Analysis of a Metamaterial Based, Dual Polarization, Dual Band, Multiple Split Ring Resonator Antenna

“…The simulations were performed by using CSTMicrowave Studio: a full-wave solver based on finite integration method [27]. Among the earlier results, one should mention those obtained by Shamonina and co-workers, who were focused on coupling of metamaterial elements and developed theoretical models that explain effects, which eventually lead to magneto-inductive waves [28][29][30][31][32][33][34][35]. Here, we do not get into theoretical details and just briefly discuss the coupling effects.…”

Surgical wound monitoring by MRI with a metamaterial-based implanted local coil

“…In this case, backward waves propagate in both rings. For ring resonance, the propagation constant must satisfy ka = 2pm/N where m = 0, 1 … is the mode number [19]. For N = 8 (for example) there are ten modes overall, five symmetric and five anti-symmetric, at ka = 0, p/4, p/2, 3p/4 and p. If the system is tuned to place the lowest-order (m = 1, arrowed) anti-symmetric resonance at the Larmor frequency v L , this mode will not be excited by uniform B 1 fields and will remain decoupled during the excitation phase of MRI.…”

“…The coil design is based on magneto-inductive (MI) waveguides [16,17], exploiting their lack of connection between the resonant elements to allow fragmentability. A coupled pair of waveguides [18] and a ring resonant geometry [19,20] are used to obtain decoupling and a FOV matched to annular wounds. The resulting sensor has the potential for eventual implantation in a two-part biofragmentable anastomosis ring (BAR) [21,22].…”

Mapping inter-element coupling in metamaterials: Scaling down to infrared

“…22,23 Depending on the sign of the coupling coefficient, these waves can have positive or negative group velocity. 24 Coupling effects have potential in applications such as magnetoinductive lens, [25][26][27][28] amplifiers for MRI, 29 polarizers, 30 etc. Obviously, to be able to effectively employ metamaterials for the manipulation of the electromagnetic fields, it is crucial to understand their "microscopic" properties, i.e., the way how the electric and magnetic fields are created and the details of the coupling mechanism between the elements.…”