Dirk Macy Hoekstra

US Patent:

52219127, Jun 22, 1993

Filed:

Oct 24, 1991

Appl. No.:

7/783455

Inventors:

William J. Keane - San Jose CA
Cristopher F. Schiebold - Palo Alto CA
Dirk M. Hoekstra - Los Altos CA

International Classification:

H01P 1218

US Classification:

333202

Abstract:

A YIG notch filter using full RF coupling loops and having a notch filter center frequency tunable as high as 18 GHz comprising a plurality of undoped YIG spheres of much smaller volume than used in the prior art and linearly arranged in a air gap. The spheres are suspended in cavities in a nonmagnetic block which are spaced much more closely than in the prior art. The 50 ohm stripline impedance inverters formed on a substrate and connecting the RF coupling loops of the spheres used in the prior art are eliminated. The quarter-wavelength impedance inverter function necessary to fabricate a notch filter is implemented by using the RF coupling loops themselves and measuring the distance from centerline to centerline of adjacent RF coupling loops. Twin insulated wires with up to one diameter separation for the RF coupling loops are preferred with the wires soldered together between the spheres.

US Patent:

54185076, May 23, 1995

Filed:

Oct 8, 1992

Appl. No.:

7/958265

Inventors:

William J. Keane - San Jose CA
Christopher F. Schiebold - Palo Alto CA
Dirk M. Hoekstra - Los Altos CA

Assignee:

Litton Systems, Inc.

International Classification:

H01P 1218

US Classification:

333202

Abstract:

A nonreciprocally coupled ferrimagnetic band reject and bandpass filter having passbands from 2-18 GHz and 6-18 GHz respectively. The band reject filter comprises one or more ferrimagnetic spheres shielded from each other by placement in nonmagnetic, electrically conductive cavities in a block placed in the flux gap of a tuning magnet. Nonreciprocal coupling is achieved by using full RF coupling loops and establishing all factors that affect the transmission line delay for travel of signals from one point in the filter to another such as loop length and size, cavity size, sphere size and spacing, dielectric constant, RF coupling loop wire size and spacing etc. such that the effective electrical length from the center of one full RF coupling loop to the centerline of the neighboring RF coupling loop is 1/4 wavelength, i. e. , an electrical phase change of 90 degrees occurs, and by placing the ferrimagnetic spheres outside the planes of their respective RF coupling loops to minimize the effect of (2,2,0) Walker modes. A ferrimagnetic passband filter comprises at least an input ferrimagnetic sphere in a cavity and an output ferrimagnetic sphere in a cavity in a nonmagnetic, conductive block located in the flux gap of a tuning magnet.