Tunable microwave magnetic devices

#This invention relates generally to devices which operate in the microwave and millimeter wave frequency ranges and more particularly to devices whose operation depends upon a gyromagnetic effect.

#In communications and radar systems applications, it is often desirable to control radio frequency (RF) signals with a variety of RF devices. Tunability of RF devices at microwave and millimeter wave frequencies is desirable for a variety of civilian and military applications. It has been recognized that the integration of ferrimagnetic, ferromagnetic and superconductor materials in microstrip configurations could improve tunable devices by providing the device with new capabilities such as lower loss and simpler geometries that reduce size and cost.

#A ferromagnetic material (also referred to as a “ferromagnet”) is a substance (e.g. iron, nickel cobalt, other metals and various alloys) that exhibits extremely high magnetic permeability, the ability to acquire high magnetization in relatively weak magnetic fields, a characteristic saturation point, and a magnetic hysteresis. A ferrimagnetic material (also referred to as a “ferrite”) is a substance (e.g. iron oxides) that possesses magnetic properties comparable in some respects to the magnetic properties of ferromagnetic substances. Although the magnetic strength of ferrites tends to be weaker than that of the ferromagnetic metals, an important and distinguishing feature of ferrites is that they exhibit a dielectric or electrical insulating property. For this reason, ferrites are particularly well suited for applications where electrical conduction is to be avoided.

#The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which:

#FIG. 1 is a is a perspective view of a prior art magnetically tunable ferrite resonator;

#FIG. 2 is a perspective view of a tunable planar circuit resonator including a magnetic structure and a transducer according to the invention;

#Before providing a detailed description of the invention, it may be helpful to define some of the terms used in the description.

#As used herein, the term “magnetic structure” refers to a spontaneous magnetic material, for example, a ferrimagnetic material or ferromagnetic material which interacts gyromagnetically with an electromagnetic signal as described below. A magnetostrictive material has the property of changing dimensions in the form of strains in response to a change in its state of magnetization. Magnetostrictive materials generally have an inverse magnetostrictive property wherein the directions of the magnetic moment vectors in magnetic structures comprising magnetostrictive material can be altered when a force applied to the structure causes strains in the material.

#A “domain pattern” is a pattern of the magnetic domains in a magnetic structure. A “180-degree domain pattern” is a pattern in which an approximately first half of a plurality of the magnetic domains in a magnetic structure are aligned collinear with and opposed 180 degrees to an approximately second half of the plurality of domain fields. A “stripe domain pattern” is a 180-domain degree pattern which occurs in a planar magnetic structure. The magnetic domains can be thought of as being included in a volume having walls and in a 180-degree pattern the walls are parallel.