Method of producing a microwave filter comprising a body of gyromagnetic material and a source of a prepolarizing magnetic field whose resonant frequency is a predetermined function of the temperature

DETAILED DESCRIPTION What is claimed is: 1.
A method of fabricating a microwave filter with a resonant frequency which is a predetermined function of temperature, said filter having a gyromagnetic element and a source of a pre-polarizing magnetic field, said method comprising the steps of inserting into the filter structure a reference gyromagnetic element with a predetermined orientation relative to said magnetic field, adjusting the resonant frequency of the filter to a predetermined value by changing the magnetic field, removing said reference element from the filter structure, inserting into the filter structure a second gyromagnetic element of the same dimensions and composition as said reference element, adjusting the orientation of said second element until the resonant frequency of the filter is equal to said predetermined resonant frequency and locking said second element in that position.




Description:
BACKGROUND OF THE INVENTION (1) Field of the Invention The invention relates to a method of producing a microwave filter which comprises a body of gyromagnetic material and a source of a pre-polarizing magnetic field whose resonant frequency is a predetermined function of the temperature.
Such filters provided with one or more spheres of a gyromagnetic material such as yttrium iron garnet (YIG) are used in the microwave devices for realizing bandpass and bandstop filters having a high Q-factor.
(2) Description of the Prior Art U.
S.
Pat.
No.
3,713,210 issued on January 30th, 1973 to James M.
Schellenberg discloses a method of stabilizing the resonant frequency of a YIG filter having a permanent magnet which acts as a source of the pre-polarizing magnetic field.
In accordance with this method, a YIG sphere is disposed in the field of a permanent magnet and the change in the resonant frequency across a given temperature range is measured.
With this data and the knowledge of the variation of the anisotropic field with temperature a correctional resonant frequency f.
sub.
b is calculated such that the change of the prepolarizing magnetic field with temperature is eliminated by the change with temperature of the anisotropic field