Abstract: Compact bidirectional repeaters are provided for wireless communication systems. Their compact size is realized with repeater structures that include different-polarization antennas, back lobe suppressing structures, circuit feedback paths, antenna-feedback detectors, and automatic gain control.

Abstract: Compact bidirectional repeaters are provided for wireless communication systems. Their compact size is realized with repeater structures that include different-polarization antennas, back lobe suppressing structures, circuit feedback paths, antenna-feedback detectors, and automatic gain control.

Abstract: Antenna systems for use within wireless communication devices such as radiotelephones are provided and include an internal multi-frequency band antenna and an elongated antenna member that is retractable. The elongated antenna member is extendible from the housing of a communications device so as to have an extended position and a retracted position. The elongated antenna member includes an elongated conductive element that is capacitively coupled with the multi-frequency band antenna when the elongated antenna member is in the extended position. The multi-frequency band antenna is electrically isolated from the elongated conductive element when the elongated antenna member is in the retracted position. When the elongated antenna member is in an extended position, the elongated conductive element is configured to resonate as a half-wave monopole antenna when the internal antenna resonates within a first frequency band.

Abstract: A feed circuit connects an antenna to a communications circuit to achieve an increased operating bandwidth. The feed circuit includes a folded balun having a balanced port configured to connect the antenna and an unbalanced port configured to connect to the communications circuit. In addition, a resonating capacitance is connected across the balanced port of the folded balun. The resonating capacitance has a value that provides resonance with an inductance of the balun in such a way that the operating bandwidth of the combined feed circuit and antenna is increased.

Abstract: A raised patch antenna is disclosed which includes a base having a ground plane, a plurality of leg supports interconnected to and extending upwardly to the base, a raised patch antenna element supportedly interconnected to the leg supports and positioned over the ground plane and an RF feed comprising a feed-leg portion provided on the leg supports and a feed base portion provided as a part of the base. The RF feed includes impedance matching components for matching the impedance of the feed base portion with the impedance with the raised patch antenna element in series with the feed-leg portion. The feed-leg portion comprises at least a first pair of balanced feed-leg lines interconnected to opposing sides of the raised patch antenna element. Baluns can be provided in said feed base portion for balancing.

Abstract: An electronically reconfigurable antenna includes individual antenna elements which can be reconfigured as active or parasitic elements in the process of variable mode operation. In the antenna, an active subset of antenna elements excites a wave on a parasitic subset of antenna elements, which are controlled by a plurality of electronically variable reactances.The plurality of electronically variable reactances is used to provide the reconfigurable array, which may operate in a plurality of modes of wave propagation. Furthermore, the plurality of variable reactances allow compensation for the inherently narrow operating bandwidth of the high-gain surface wave antennas.

Abstract: A directional scanning antenna includes a circular array of a plurality of antenna elements extending several wavelengths in diameter. The number of antenna elements are sufficient to form a plurality of directionally-oriented subsets of active antenna elements and associated subsets of parasitic antenna elements. An antenna feed system provides connections to each one of the plurality of antenna elements that include connections to electronically variable reactances and connections to a source or receiver of electromagnetic energy. The antenna feed system is controllable to provide connections between the subsets of active antenna elements providing wave propagation and reception in one or more directions and to provide connections between a plurality of the remainder of antenna elements in associated subsets of parasitic antenna elements to assist the directionality of the antennas.

Abstract: A microstrip annular antenna structure is formed by four quarter-wavelength microstrip radiator patches arranged in a quadrant formation and having outwardly directed adjacent radiating apertures which together provide a composite annular radiating slot extending about 360.degree. of azimuth. All such radiators are fed in-phase by a single centrally located feedpoint and equal length microstrip transmission lines extending diagonally therefrom to a respective matched impedance feedpoint associated with each radiator patch structure. An extremely low profile rf antenna system results with a monopole or annular slot vertically polarized radiation pattern.

Abstract: A resonant cavity having at least one radiating antenna slot formed in a wall of the cavity includes an electrically conducting plate disposed within the cavity and substantially spaced from all internal cavity walls so as to effectively lengthen the electrical resonant dimensions of the cavity for a given physical size. This slotted cavity antenna permits the use of simplified feeding structures, provides a more efficient antenna structure and reduces the necessary physical dimensions of the structure for operation at a given frequency.

Abstract: Method and apparatus for improving the r.f. isolation between a transmitting and receiving antenna disposed at respectively corresponding spaced apart but relatively adjacent locations. A special compensation radiator is provided at the transmitting and/or receiving antenna site and fed from the same r.f. input/output which feeds the main antenna. The direction, magnitude and phase of r.f. energy radiated and/or received from the compensating radiator are chosen so as to substantially cancel the undesirable r.f. energy otherwise directly received by the receiving antenna from the transmitting antenna.

Abstract: A collinear series-fed antenna array formed from two spaced-apart electrical conductors extending parallel to one another in a longitudinal direction and having regularly spaced complementary changes in transverse dimensions along the longitudinal direction. These two shaped conductors are connected at one end to an RF transmitter or receiver and are substantially isolated from electromagnetic interaction with other unconnected electrical conductors in the immediate vicinity. The array is preferably fabricated by etching a copper laminate adhered to one side of a dielectric sheet which serves solely to support the shaped conductors etched thereon. There is no ground plane associated with these conductors and the dielectric merely serves to support the antenna elements. The whole assembly can therefore be made very thin and flexible and formed into a compact unit for storage when not in use.

Abstract: Radio frequency antenna arrays of radiating slot apertures serially connected along a predetermined path transverse to the radiating slot apertures. In the exemplary embodiments, the radiating slot apertures are formed by parallel edges of conductive radiator surfaces where the edges are spaced apart by substantially one-half wavelength at the anticipated antenna operating frequency. Such radiator surfaces are, in some embodiments, dimensioned in a direction parallel to the apertures in relation to the relative proportion of radio frequency energy which is to be radiated to/from the slot apertures associated therewith to thus determine the total array aperture amplitude taper while the spacing between the radiator surfaces determines the phase taper across the total array aperture. Other exemplary embodiments utilize internal reflections in an array to determine the array amplitude taper and still other exemplary embodiments combine a plurality of such arrays to form two-dimensional special purpose arrays.

Abstract: A resonant circularly or elliptically polarized microstrip radiator wherein the size of the radiator is reduced in the resonant or non-resonant dimensions, or both, without reducing the effective resonant dimension or substantially lowering the efficiency of the radiator. Reduction of the resonant dimension is provided by folding the resonant cavity, while reduction of the non-resonant dimension is facilitated by utilization of a low density, low loss dielectric, such that the loss resistance of the element is appreciable with respect to the radiation resistance of the element. The preferred embodiment comprises interdigitated antenna structures.

Abstract: A resonant microstrip radiator wherein the size of the radiator is reduced in the resonant or non-resonant dimensions, or both, without reducing the effective resonant dimension or substantially lowering the efficiency of the radiator. Reduction of the resonant dimension is provided by folding the resonant cavity, while reduction of the non-resonant dimension is facilitated by utilization of a low density, low loss dielectric, such that the loss resistance of the element is appreciable with respect to the radiation resistance of the element. Also disclosed are interdigitated antenna structures and provisions for circularly or elliptically polarized radiation.

Abstract: A multiple resonance microstrip antenna radiator which includes a plurality of stacked electrically conductive element surfaces disposed above an electrically conductive reference surface with each element surface dimensioned so as to resonate at a different radio frequency. The various element surfaces are spaced one from another and from the reference surface with a dielectric material and an rf feed is attached to at least one of the element surfaces. Non-resonant element surfaces provide inductive capacitive coupling of rf energy to/from a resonant element surface.

Abstract: A radio frequency antenna structure is disclosed wherein a raised pedestal portion of the ground plane surface is provided and above which pedestal portion a microstrip radiator is disposed. The microstrip radiator is thus disposed on a pedestal at a predetermined distance above the base ground plane to produce mirror image or apparent radiating aperture(s) therebelow. The combined radiation pattern from the real radiating aperture(s) and the mirrored image(s) thereof produces an increase in radiation power at low pointing angles located near the ground plane, thus producing a wider radiation beam without sacrificing radiation efficiency. This form of raised pedestal microstrip radiator is especially useful in phased arrays where it is desired to steer the beam of the array to angles near the ground plane itself.

Abstract: A microstrip antenna structure is provided wherein a plurality of relatively narrow elements, resonant in their longer dimensions, are organized into two staggered or offset sets of interleaved elements with each set being fed from opposite sides of the structure through a corporate microstrip feed line from a common feed point. The aligned radiating ends of the two offset sets of elements simulate four line sources of radiation. The preferred embodiment produces an efficient end-fire radiation pattern from this relatively compact structure which may, in turn, constitute an individual end-fire radiator in a larger array structure.