Massachusetts Institute of Technology

Jerald A Weiss

Gerald Francis Dionne

Donald H Temme

In a magnetically-tunable resonator, a wave-guiding structure comprising an electromagnetic frequency filter, or component of such a filter, is placed in sufficient proximity with a magnetic structure so as to be gyromagnetically coupled therewith. The resonator is supportable of two fundamental normal modes of propagation which, in the absence of magnetic interaction are even and odd with respect to the resonator center plane of symmetry. Each normal mode possesses a spectrum of resonance frequencies. When the magnetic structure is magnetized, the formerly even and odd modes become mixed due to gyromagnetic interaction, and the resulting wave fields become elliptically polarized. With appropriate design such that the identities of the modes are preserved under conditions of resonance, this in turn results in a nonreciprocal reinforcement action in the resonator, which leads to the desired shift in resonance frequency in at least one of the two normal modes. The device is especially attractive to application in miniaturized planar microwave devices, for example MMICs, in conferring small size and weight, simplicity of structure, low power required for tuning, capability of fixed, continuous or digitally-stepped frequencies, and low-loss high-Q performance; applicable with superconducting or conventional metallic conductors.

Tunable resonators

In a planar gyrator, parallel transmission lines are positioned proximal to a magnetized gyrotropic substrate. Input and output transducers couple the ends of the transmission lines to corresponding input and output ports. The input and output transducers are configured to excite first and second partial wave fields on the transmission lines of similar or different phases respectively. The wave fields, in turn, interact gyromagnetically with the substrate, such that the resultant difference in phase change for a first wave propagating from the first to the second port and a second wave propagating from the second to the first port is an odd-integer multiple of 180 degrees. Alternatively, if the magnetization of the substrate is reversed, the phase of a wave propagating from the first to the second port is changed by 180 degrees. The planar gyrator is amenable to application in miniaturized planar microwave devices, for example as a magnetically-controlled phaser or switch, or as a component in a circulator or isolator implemented in planar microwave technology.

Planar gyrator

In an apparatus and method for forming an advanced ring-network circulator, a plurality of junctions are interconnected by a plurality of non-reciprocal phase shifters. Each junction has a predetermined inductive reactance and capacitive susceptance which renders each junction partially reflective of an incident signal in a predetermined frequency-dependent manner. The junctions are selected such that a predetermined combination of average phase shift and differential phase shift provided between junctions produces substantially ideal circulation about a designated band center, the band center being determined by the selected reactance and susceptance of the junctions. The phase shifters are selected to provide an ideal combination of average phase shift and differential phase shift for providing substantially ideal circulation within a frequency band about the band center in a predetermined frequency dependent manner. The invention is amenable to miniaturization, operation with self-biased and reversible magnetic structures, and operation with superconducting components.

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Wayland, MA, United States of America

Jerald A Weiss