Single circulation frequency operation (SCFO) Y-ring circulators have been explored in earlier papers, where their inner circumference has been assumed to exhibit a magnetic wall (MW). In this paper, a new design is given using air in the center of the ring and treating the ring circulator as a composite dielectric-ferrite (DF) circulator. This DF circulator offers a wider bandwidth than the MW ring component. >

On planar Y-ring circulators

A novel low-profile leaky-wave electric monopole loop antenna in the regime of a composite right/left-handed (CRLH) ferrite-loaded open waveguide is presented. Despite its closed configuration, this structure supports a traveling-wave mode due to its non-reciprocity. Moreover, this mode exhibits an infinite wavelength in the regime, achieved at the transition frequency between the backward and forward CRLH bands, which leads to an electric monopole antenna field distribution when the loop is electrically small. The structure is analyzed theoretically and shown to admit, for a given loop width, different groups of discrete modes. The modes within each group converge to the unique mode of the straight waveguide when the radius of the loop becomes very large, as a consequence of the decreased curvature of the structure. A complete antenna, with a wire feed and a stub matching section, is demonstrated by both full-wave and experimental results. The omnidirectional azimuthal gain of the antenna is of -5 dBi with a co-to-cross polarization discrimination in excess of 20 dB. Removal of the ground plane would lead to a unique electric dipole loop antenna.

Low-Profile Leaky Wave Electric Monopole Loop Antenna Using the $\beta=0$ Regime of a Ferrite-Loaded Open Waveguide

Novel nonreciprocal components based on hollow ferrite discs, i.e. ferrite ring resonators, are discussed. Some three-port and four-port components are analyzed, and some design guidelines are presented. It is shown that a ring structure requires a smaller diameter and ferrite thickness than a disc structure for the same frequency. A ring also provides another variable in design and permits ports to be connected to the inside as well as the outside. Novel components and increased component density may therefore be possible at the expense of bandwidth. >

Nonreciprocal devices using ferrite ring resonators

The analysis of two novel types of three-port junction circulator is discussed in detail, and, neglecting losses, graphs of the predicted performance of specific theoretical designs are shown. The first type of circulator is based on a ferrite ring, and it is shown that by appropriately selecting the ratio of the inner/outer radius of the ring the need for transformers can be eliminated. The second type is based on a three-port ferrite disk with two ports positioned 60 away from a middle port. This provides a more compact layout and a design for 94 GHz is presented. >

More compact ferrite circulator junctions with predicted performance

Planar junction circulators using weakly magnetised disc, wye, triangular and hexagonal resonators have by now been described in the literature. Another resonator that has the symmetry of the 3-port junction circulator is the ring resonator. Since the degenerate and split frequencies in this type of gyromagnetic resonator have already been established in the literature, an understanding of its complex gyrator circuit requires only a definition of its susceptance slope parameter. The purpose of this effort is to tackle this problem.

Complex gyrator circuit of junction circulators using weakly magnetised ring resonators

The modes and frequencies of demagnetised and magnetised planar disc, triangular, wye and hexagonal resonators have already been described in the literature. Another resonator which has the required symmetry is the ring resonator. Here we give the resonant frequencies of this type of gyromagnetic resonator.

W.T. Nisbet

Papers

Mode charts of gyromagnetic planar ring resonators