Litton Systems, Inc.

Litton Industries, Inc.

Christopher F Schiebold

William J Keane

Dirk M Hoekstra

A frequency synthesizer using a fixed oscillator driving a comb line generator to generate a spectrum of comb lines, one of which is selected by a switched array of fixed-tuned, YIG passband filters. The selected comb line is combined in a mixer with a signal from a local oscillator, which, preferably, is a direct digital synthesizer. The output of the mixer is fed to another switched array of fixed-tuned YIG passband filters where only the desired sideband is selected and the comb line and the other sideband is filtered out. In various alternative embodiments, tunable YIG filters are substituted for each array. Some embodiments also use a reverse slope equalizer to break up the coherent energy in the comb line spectrum at the output of the comb line generator to allow RF amplification to be applied without saturating the amplifier.

Fast tuning YIG frequency synthesizer

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. Both the input and output spheres are coupled to full RF coupling loops coupling an RF input and an RF output, respectively, to the ferrimagnetic spheres and to ground. The effective electrical length between the RF input or RF output and ground through the respective RF coupling loops is 1/4 wavelength. Coupling is set tight to achieve wide bandwidth. The ferrimagnetic spheres are offset from the plane of the loop to achieve nonreciprocal coupling thereby allowing the (2,2,0) Walker mode spurious responses to be eliminated from the tunable passband.

Growing community of inventors

Palo Alto, CA, United States of America

Christopher F Schiebold