Electromagnet for programmable microwave circulator
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorsWalter E. Milberger, Joel R. Cohen, Leonard Dubrowsky
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Abstract
A "Spacercore" design is used to provide the cores of the electromagnets which are used to bias ferrite slabs in phase shifters of a high power RF attenuator. The phase shifters require a given flux to provide a phase shift from zero to 90.degree.. With laminations of high permeability silicon steel, the core weight may be substantially reduced by including a filler comprising spacers of non-magnetic material (such as lightweight transformer pressboard. With 14-mil silicon steel laminations and 64-mil spacers, this construction provides a core which weighs 25 percent of a full ferrite core for the same flux density.
Claims4
An electromagnet structure for a high-power variable attenuator using a programmable microwave circulator, wherein the circulator comprises input power divider means which divides input RF power to two phase shifters, and an output hybrid coupler between the two phase shifters and an output RF port to recombine the power, the power form the input power divider means to the two phase shifters having the same relative phase and the same amplitude, the two phase shifters being controlled to introduce a relative phase shift, the two phase shifters being designed to operate from zero to 90.degree. phase shift to achieve minimum to maximum attenuation characteristics;
- wherein each of said phase shifters comprises a waveguide section having ferrite slabs mounted on interior walls, and the electromagnet structure forms a yoke for each phase shifter, comprising core means for each phase shifer with winding means on part of the core means, the core means having pole faces adjacent opposite outer surfaces of the waveguide means, so that there is an air gap between the pole faces, the ferrite slabs being located in the air gap to be biased by the magnetic flux;
- wherein the core means includes laminations of magnetic material having a high permeability, with a magnetic path having a first portion through the magnetic material and a second portion through the air gap, so that the effective length of the magnetic path is equal to the sum of first and second terms, the first term being the length of the first portion and the second term being equal to said permeability multiplied by the length of the second portion, the second term being very large such that the first term is insignificant and therefore the flux density is substantially equal to ampere turns supplied by said winding means divided by the length of the air gap, and the permeability required is much smaller than the permeability of the magnetic material;
- wherein said core means further includes a non-magnetic filler forming spacers between said laminations, the laminations being relatively thin and the spacers comparatively thick so that the resulting average permeability is sufficient to provide said required phase shift.
An electromagnet structure for supplying magnetic flux to bias an element of a high-power microwave device
- wherein the electromagnet structure forms a yoke for said element, comprising core means, with winding means on part of the core means, the core means having pole faces with a gap between them, said element being located in the gap;
- wherein the core means includes laminations of magnetic material having a high permeability, with a magnetic path having a first portion through the magnetic material and a second portion through the gap, so that the effective length of the magnetic path is equal to the sum of first and second terms, the first term being the length of the first portion and the second term being equal to said permeability multiplied by the length of the second portion, the second term being very large such that the first term is insignificant and therefore the flux density is substantially equal to ampere turns supplied by said winding means divided by the length of the gap, and the permeability required is much smaller than the permeability of the magnetic material;
- wherein said core means further includes a non-magnetic filler forming spacers between said laminations, the laminations being relatively thin and the spacers comparatively thick so that the resulting average permeability is sufficient to provide a maximum value of flux for providing a specified operation of the device.
Dependencies are inferred from the claim text.