Hughes Aircraft Company

Krishnan K Raghavan

Mon N Wong

Paramjit S Bains

Harold A Rosen

Rolf Kich

Paul J Tatomir

Louis W Hendrick

Gregory D Kroupa

Robert J Patin

Craig N Schwartz

Dean N Paul

Brennan J Trese

Gary J Gawlas

A bandpass microwave filter (32) is constructed by use of a right cylindrical cavity resonator (10) wherein end regions (22, 24) of the resonator are tapered. The tapering is accomplished by replacing end portions of a right cylindrical sidewall with frusto-conic sections (22, 24) of side wall. Each frusto-conic section joins a central cylindrical section (26) of the sidewall with a planar end wall (14, 16). Each of the end walls is provided with a coupling slot (28, 30) having dimensions substantially smaller than a half wavelength of the center resonant frequency of the resonator so as to be a nonresonant slot. The slots in the end walls may be coupled to rectangular waveguides (34, 36) which form input and output ports by which electromagnetic signals are applied to and extracted from the resonator.

Biconical multimode resonator

A right angle waveguide junction for a microwave multiplexer is provided including a step in one of the waveguides for improved electrical response. A rectangular waveguide manifold (10) is coupled to a filter (12) which includes a coupling iris (14) and a circular cavity resonator (16). The circular cavity resonator is a circular waveguide with two ends closed by a metal wall. The structure of the waveguide multiplexer includes a step change (18) in the rectangular waveguide (10) height which controls the electrical response properties of the junction.

Microwave waveguide multiplexer

A bicone microwave antenna having an orthomode tee as an input/output terminal, an internal dielectric polarizer, a circular waveguide with eight longitudinal radiating slots, two 30 degree conical reflectors, an external meanderline polarizer, and a partial circular waveguide short. An RF signal from the input/output terminal is converted into a rotating TE.sub.11 mode by the internal dielectric polarizer. The radiating slots in combination with the conical reflectors radiate the RF signal as a horizontally polarized field in a doughnut-shaped pattern. The meanderline polarizer converts the horizontally polarized field into a circularly polarized field. The partial circular waveguide short leaks a predetermined amount of radiation out the end of the waveguide to fill the center hole of the doughnut-shaped radiation pattern, thus producing a hemispherical RF beam having an elevation angle from 110 to -110 degrees. The use of impedance-matching circular rings in the waveguide further enhances the ability of the antenna to operate in three frequency bands.

Bicone antenna with hemispherical beam

A patch antenna is formed of one or more flat disc-shaped radiators disposed parallel to and spaced apart from a common ground-plane element. At each radiator, there is a feed assembly of two feeds positioned to one side of a center of the radiator in space quadrature and excited in phase quadrature for generating circularly polarized radiation from the radiator. Each of the feeds, in a preferred embodiment of the invention, is formed as a post extending through an aperture in the ground-plane element partway to the radiator for capacitive coupling with the radiator. At each radiator, a reactance element on the form of a capacitive block extends from the ground-plane element partway to the radiator at a location diametrically opposite the feed assembly. Capacitive reactance of the reactance element is approximately one order of magnitude less than the sum of the capacitive reactance of the two feeds at each radiator to reduce mutual coupling between the feeds of each radiator to counteract any elliptical polarization to produce accurately a circular polarization.

Patch antenna with polarization uniformity control

A horn radiator assembly includes two horn radiators each of which is formed as a conical horn and a waveguide of constant cross section connected to the small end of the horn as a feed and providing a signal port. The first of the horn radiators is of relatively large cross section and serves to radiate electromagnetic waves at a relatively low frequency. The second of the horn radiators is of relatively small cross section and serves to radiate electromagnetic waves at a relatively high frequency. The second radiator is nested within the first radiator, and is positioned with its radiating aperture coplanar with the radiating aperture of the first radiator. In the second radiator, the waveguide feed is provided with a bend allowing the waveguide feed to pass through a wall of the first radiator. A strut may be affixed to the bend to provide a symmetrical transverse support within the first radiator for the second radiator. A doubly-tapered electrically conductive sheet extends from an apex within the throat of the first radiator horn to the transverse support, and from there tapers back to contact the horn of the second radiator. The tapered sheet guides low-frequency radiation past the strut and the bend to minimize standing wave ratio.

Nested horn radiator assembly

An antenna is constructed of an array of contiguous circular cylindrical radiators each of which extends forwardly of a radiator assembly producing two circularly polarized waves of opposite direction of rotation of their respective electric fields. The radiators measure one wavelength at the transmit frequency band, and approximately 1.5 wavelengths in diameter at the receive frequency band. A section of cylindrical waveguide in the back of each radiator assembly encloses a microwave structure for generating the circularly polarized waves, the microwave structure including an orthomode transducer at the back of the assembly and an electric field rotator disposed forward of the orthomode transducer. In each radiator assembly, there is disposed between the rotator and the radiator a transition between smaller diameter waveguide to larger diameter waveguide. The transition may have the form of a step or a flare for a more gradual transition. The transducer produces a higher order TM.sub.11 mode which is evanescent within the radiator 24. By attenuating the transverse magnetic mode, a match is made between electric field components thereof and those of curved electric fields of the dominant propagating modes to cancel curvature and reduce cross polarization between the two circularly polarized waves in each radiator.

Growing community of inventors

Redondo Beach, CA, United States of America

Krishnan K Raghavan