Abstract: Broadband omnidirectional, vertically polarized communications antenna systems are disclosed. The antenna systems comprises a plurality of center-fed stacked dipole radiating elements disposed along a central axis, a coaxial feed line coupled between each of the stacked radiating elements. In certain embodiments, a two-wire balun is coupled to a feed point of each radiating element and a shunt inductor and capacitor are coupled to each radiating element. Other embodiments do not require the use of the balun. Certain embodiments use a printed-circuit dipole having a flat shape. Other embodiments use a metal dipole having a cylindrical shape. The array antenna systems may be stacked vertically in separate bays each with its independent RF port.

Abstract: A quadrifilar helix antenna system that is wound with a helical structure that changes pitch towards top of the antenna. An exemplary antenna system has first and second bifilar helical loops that each comprise a pair of orthogonal windings disposed around a common central axis. Each loop has a winding pitch that varies along the axis to achieve backlobe radiation suppression from the antenna system. First and second terminals are coupled to respective top ends of the bifilar helical loops. The terminals may be fed in phase quadrature by a quadrature hybrid. The antenna system may also include short circuit coupled to respective bottom ends the first and second bifilar helical loops. The antenna system is preferably used in vehicle-to-satellite mobile communication applications.

Abstract: An improved very small antenna terminal (VSAT) dual-beam antenna system for use with user subscriber terminals that communicate with low-earth orbiting and other satellites. In one embodiment, the dual-beam antenna system has two offset Gregorian dual-reflector antennas that each has an ellipsoidal subreflector and a rotatable paraboloidal reflector having a focus in common with a focus of the ellipsoidal subreflector. The rotatable paraboloidal reflector couples energy to and from the ellipsoidal subreflector. An RF feed system couples RF energy to and from the ellipsoidal subreflector. Rotating apparatus rotates the paraboloidal reflector and ellipsoidal subreflector together around an azimuth axis of the antenna. The rotating apparatus independently and simultaneously rotates the paraboloidal reflector about an axis between the paraboloidal reflector and ellipsoidal subreflector which points the antenna at an orbiting satellite.

Abstract: An inverted boxhorn antenna array comprising a power divider that is constructed from a single metal piece and a flat metal sheet that is fastened to a rear surface of the power divider. The power divider is fabricated using a variety of waveguide junctions coupled between substantially identical inverted boxhorn subarrays. The junctions includes a central magic tee junction for coupling energy from an input port into the power divider. Alternating folded shunt and folded series tee junctions are used to transfer power coupled by way of the central series junction to the inverted boxhorn subarrays. Specially dimensioned folded shunt and series tee junctions are used in the inverted boxhorn subarrays. Waveguide matched loads are bonded in waveguides between each of the inverted boxhorn radiators of the subarrays. A fully functional antenna assembly includes a radome cover, a quadrature correction plate 18a, and a twist polarizer disposed in front of radiating elements of the inverted boxhorn antenna array.

Abstract: A multi-band low-profile antenna includes a conductive ground-plane element; a first radiator element mounted on the ground-plane element to define a first vertical loop; a second radiator element mounted on the ground-plane element to define a second vertical loop; and a coupling element mounted on the ground-plane element to define a vertical coupling loop, with one end portion of the coupling element being connected to a feed terminal. In at least one embodiment, the first radiator element and the second radiator element are of such dimensions and are so disposed as to be parasitically coupled to each other, to cause the first radiator element to resonate at a first predetermined VHF frequency and to cause the second radiator element to resonate at a second predetermined VHF frequency.

Abstract: The methods and systems for reducing multipath fading and outage from blockage in a radio broadcasting system that is adapted to simultaneously broadcast signals having frequencies in the range of about 300 MHz to about 3,000 MHz from two or more satellite sources traveling on a substantially geosynchronous orbit with the satellite sources separated from one another by a sufficient distance to minimize outage from physical blockages and multipath fading of signals from these satellites and received by a plurality of fixed and mobile platforms using substantially flat, hemispherical coverage antennas, each antenna having an outer diameter no greater than about 10 inches and each adapted to receive frequencies in the range of about 300 MHz to about 3,000 MHz.

Abstract: A microstrip antenna includes an annular conducting element spaced by a dielectric element from a conducting ground plane and radiating circular polarization in a conical elevation pattern. A central whip antenna may be located on the axis of the annular-shaped element. Another microstrip antenna having an annular conducting element may be dielectrically spaced from the first-mentioned annular conducting element that comprises the ground plane for the second annular-conducting element.

Abstract: A dual frequency antenna feed includes colinear axially spaced coaxial and circular waveguide cavities separated by a conducting portion having a high frequency rectangular waveguide therein extending radially outward. The coaxial cavity includes a tubular inner conductor having a polarization rotator connected to the rectangular waveguide for propagating high frequency energy. Four small coaxial transmission lines equiangularly disposed about the cavity axes and terminating in probes about a quarter wavelength from the end of each cavity intercouples the circular and coaxial cavities. The end of the coaxial waveguide cavity forms an aperture for high frequency energy from the conducting inner tube and for the low frequency energy from the region between the conducting inner tube and the cylinder surrounding the outside of the cavity. The radiating aperture is surrounded by a set of concentric conducting rings.

Abstract: A microwave lens broadens the radiation pattern of an antenna feedhorn so as to result in improved illumination of the reflector surface. The lens, constructed of dielectric material in the shape of a half-torus, provides feed radiation patterns suitable for use with deep paraboloidal reflectors, typically ones having focal-length-to-diameter ratios between 0.25 and 0.35.

Abstract: A flat face annular grooved metal surface surrounds a circular waveguide opening coupled to a small dipole radiator which excites the circular waveguide in its fundamental propagating mode (TE.sub.11). The dipole is arranged to rotate about its axis by means of an extension of its inner conductor, which forms a simple probe in a section of rectangular waveguide situated behind the circular waveguide. A dielectric shaft is fastened to the inner conductor and is brought to the outside of the rectangular waveguide where it is connected to a small motor. The motor is arranged so that it may be actuated remotely by any of several circuits. The dipole may be before the corrugated plate with bent arms. A pair of dipoles may be arranged perpendicular to each other with two separate coaxial connector antenna feed outputs for direct attachment to coaxial-type low-noise amplifiers.

Abstract: A horn for radiating circularly polarized energy includes a rear launcher section commencing with a double-ridged cross section and ending at the horn flare with a square cross section with the plane of polarization so that the wave excited in the square cross section is along a diagonal of the square. The horn flare section opens up to a dimension of approximately 70% larger than the square throat dimension to narrow the elevation beam. A dielectric slab oriented in the horizontal plane is seated in the flare section for introducing a frequency-varying differential phase shift between orthogonal modes for effectively compensating for the inherent phase shift in the flare. Refracting lenses that are half-cylinders having a diameter of about 25% of the horizontal aperture dimension with their axes aligned vertically are located close to the vertical aperture edges for refracting the energy at the horn edges into the region between 30.degree. and 60.degree. from the horn axis.