Abstract: Disclosed is an array antenna (10) that may be reconfigured to point in multiple directions. The array antenna includes a driven element (12) coupled to a transmission line (14) and a pair of passive elements (22) and (24). The passive elements (22) and (24) each include three antenna segments that are coupled together by a pair of optoelectronic switches (26) and (28), respectively. When the optoelectronic switches coupled to a particular passive element are closed the element functions as a reflector; when the switches are open, the element functions as a director. Other reconfigurable antennas are also disclosed, including antennas with reconfigurable gain and field pattern characteristics.

Abstract: A phased array antenna structure has a distribution network, and a composite of feed, module, and antenna honeycomb structures. The distribution network distributes or collects electromagnetic (EM) energy. The feed honeycomb structure is positioned adjacent the distribution network and connected to receive the EM energy from the distribution network or to distribute EM energy to the distribution network. The module honeycomb structure is positioned adjacent the feed honeycomb structure so as to receive EM energy from the feed honeycomb structure or to transmit EM energy to the feed honeycomb structure. The antenna honeycomb structure is positioned adjacent the module honeycomb structure on a side opposite the feed honeycomb structure so as to receive EM energy from the module honeycomb structure or to transmit EM energy to the module honeycomb structure. Each of the feed, module and antenna honeycomb structures have a plurality of aligned waveguides for transmitting EM energy therealong.

Abstract: One or more decoys (22) are towed by an aircraft (18) to confuse hostile radar. The tow lines (20) to the decoys (22) include fiber optic components which optically transmit to the decoys (22) both radio frequency signals for retransmission to hostile radar (24), and direct current power. The fiber optic components absorb strain forces imposed by towing the decoys (22). Multiple decoys (22) are deployed at varying distances from the aircraft (18) to increase the overall range of frequencies covered by the system, simulate a plurality of false targets, or accomplish angle gate deception. The deception may be accomplished by transmitting signals from the decoys in sequence and can be enhanced by dynamically varying the power levels of the decoy transmitting antennas. The fiber optic components may be separate optical fibers deployed separately or joined together for simultaneous deployment. The preferred configuration is a single optical fiber with coaxial inner and outer cores.

Abstract: One or more decoys (22) are towed by an aircraft (18) to confuse hostile radar. The tow lines (20) to the decoys (22) include fiber optic components which optically transmit to the decoys (22) both radio frequency signals for retransmission to hostile radar (24), and direct current power. The fiber optic components absorb strain forces imposed by towing the decoys (22). Multiple decoys (22) are deployed at varying distances from the aircraft (18) to increase the overall range of frequencies covered by the system, simulate a plurality of false targets, or accomplish angle gate deception. The deception may be accomplished by transmitting signals from the decoys in sequence and can be enhanced by dynamically varying the power levels of the decoy transmitting antennas. The fiber optic components may be separate optical fibers deployed separately or joined together for simultaneous deployment. The preferred configuration is a single optical fiber with coaxial inner and outer cores.

Abstract: A polarization diversity system (10) including an adaptive polarization combiner (14) is disclosed. The combiner receives input signals V.sub.i1 and V.sub.i2 of arbitrary relative phase and amplitude, produced in response to orthogonally polarized components of an incident electromagnetic field. The combiner includes a hybrid network (18) that performs the combination of the input V.sub.i1 and V.sub.i2 based on phase adjustments initiated by a feedback circuit (20). The feedback circuit includes a limit set and sensing circuit (26) that allows feedback signals V.sub.c1, V.sub.c2, V.sub.c3, and V.sub.c4 to be swept through a range suitable to phase shifters (28, 32, 36, and 38) included in the hybrid network, thus allowing different components to be more easily used in the hybrid network. Further, the combiner is constructed to function properly in the absence of one of the signals input to the combiner.

Abstract: In a preferred embodiment, the disclosed system is part of a communication system (10) formed by a satellite (12) and aircraft (14). The system includes a controllable antenna network (16) and polarization tracking network (18). The controllable antenna network includes an array (28) of orthogonal antenna pairs (34) whose beams are steerable by phase shifters (46) to correct for changes in the aircraft's attitude. Similarly, amplifier circuits (44) compensate for changes that would otherwise occur in the signal-to-noise ratio of the antenna's output. The polarization tracking network includes a forward section (62), defined by quadrature hybrids (66) and (70) and an adjustable phase shifter (68), and a feedback section (64) that monitors each polarity for the presence of a single select channel. The phase shifter responds to the comparison made by a phase detector (86) in the feedback section to maintain the desired polarization of all channels.

Abstract: A distribution network for a modified space-fed phased array antenna consists of a planar array of radiating slots distributed along a coplanar wall in each of an ensemble of parallel waveguides. This waveguide ensemble is fed or excited by an orthogonal waveguide or waveguides, through a row of slots in a wall common to the excitation waveguides and the parallel waveguide ensemble, one slot per waveguide. A predetermined amplitude distribution is achieved in the plane parallel to the axis of the exciting waveguide by adjusting the coupling value of each exciting slot, and in the orthogonal plane by adjusting the displacement of the radiating slots from the center line of the waveguides, and by adjusting slot width, length, and geometry. Such an array of slots is used to feed the inside face of a quasi-space-fed antenna array having identical, individual electronics modules.

Abstract: A ferrite device has a closed superconductor which encircles a ferrite element. The closed superconductor continuously circulates a current to produce a magnetic field for biasing the ferrite element.

Abstract: A nearly square waveguide below cutoff has a microstrip substrate disposed diagonally therein. A first shunt capacitance is provided by either a conductor formed on the microstrip substrate or a conductor disposed in the waveguide perpendicular to the microstrip substrate. A dielectric window is disposed in the end to provide a shunt capacitance at the opposite end of the waveguide.

Abstract: A radar antenna element comprises a lower band waveguide and an array of parallel, dual-polarized, higher band waveguides and dipoles mounted within or directly adjacent an aperture of the lower band waveguide. The lower band waveguide and each higher band waveguide have one cross-sectional dimension less than 0.5 wavelength. A choke section, tuned dielectric or absorber isolates signals of the higher band waveguides from signals of the lower band waveguide. An array of such radar antenna elements locates a radar target with lower band signals and tracks that target with higher band signals, for instance.

Abstract: Disclosed is a variable angle conical scanning antenna that employs an offset paraboloidal reflector which is rotated about an axis that extends through the focus of the paraboloid of revolution that defines the reflector. Electromagnetic energy is supplied to the reflector by an antenna feed that is mounted at the focus of the paraboloid of revolution and directed along the axis of rotation. In this arrangement the electromagnetic energy that is reflected from the offset paraboloidal reflector forms an angle between the axis of rotation and the beam of reflected electromagnetic energy that is equal to the angle between the axis of rotation and the focal axis of the paraboloid of revolution that defines the reflector. Thus, conical scanning at a cone angle that is equal to twice the angle between the axis of rotation and the reflected beam of electromagnetic energy is achieved as the offset paraboloidal reflector is rotated. Variable angle scanning (i.e.

Abstract: The multiple feed antenna comprises a primary focussing element and at least two feeds. The feeds are spaced from each other and have different characteristics such as different frequency bands. The focussing element is moved such that its focal point coincides individually with the feeds. The focussing element may be designed to be offset with respect to its focal axis. In this manner, the antenna may have a common aperture and common boresight for each of the feeds.

Abstract: A monopulse spiral antenna system of the type having a minimum of three, interwound spiral arms for multimode, direction of arrival sensing, is disclosed in which the antenna arms are shaped and arranged in an overlapping configuration that allows the interarm impedance of the antenna to be adjusted, substantially independently of other electrical properties of the antenna, for matching of the antenna impedance of a mode forming network while preserving the broadband, directional capabilities of the antenna. Several different embodiments of the impedance adaptive antenna are disclosed including a preferred, eight-arm exponential spiral in which the arms are conductive strips transversely inclined relative to a plane formed by the spiral so that opposed and parallel surfaces of adjacent arm strips create a dominant interarm capacitance that in turn determines the overall input impedance of the antenna.

Abstract: To optimize antenna bandwidth and efficiency in broad-band antenna elements of the planar, multiarm spiral and log periodic types, a conically shaped ground plane characterized by progressively sized circumferential chokes, is arranged on a common axis with the axial center of the spiral or log periodic elements so that the electrical spacing between the excited regions of the log periodic of spiral elements and the ground plane maintains a constant one-quarter wavelength relationship. The progressively sized circumferential chokes on the ground plane cut off the flow of excessive radial currents along the ground plane surface to achieve an improved mix of excitation and reexcitation modes. In one embodiment, the circumferential chokes on the conical ground plane are partially shunted by shunting strips that electrically or capacitively bridge the choke walls to reestablish limited radial currents along the ground plane for sustaining certain desirable antenna modes.

Abstract: Spiral antennas are disclosed wherein each antenna arm includes one or more choke elements that resonate at predetermined operating frequencies to eliminate or minimize undesired radiation and reception characteristics. Multi-arm arrangements for broadband applications requiring sum and difference mode operation with both right-hand and left-hand circularly polarized radiation characteristics are attained by including a plurality of selectively positioned and dimensioned choke elements in each antenna arm. A variety of transmission line sections, suitable for use as choke elements in several types of spiral antennas, is described.