Abstract: An antenna radome, suitable for use with high precision, environmentally sensitive array antennas, includes a dielectric sheet formed to protect the antenna from environmental conditions and a series of conductors fixed on the sheet in a certain pattern so that the sheet with the conductors provides a lower reflection coefficient to electromagnetic waves at the antenna's operating wavelength than in the absence of the conductors. Current is caused to flow through the conductors, thus generating heat in areas of the dielectric sheet where the conductors are fixed. Accordingly, ice formation on the protective dielectric sheet can be prevented while the antenna array is operational, and accurate antenna performance is ensured. Further, the dielectric sheet presents a significantly lower reflection coefficient at the operating wavelength than radomes in which a conventional grid of heater wires is provided for melting ice.

Abstract: An MLS system having redundant subsystems. Dual signal sources feed dual power dividers. A first switch array selects the power divider to be used and provides the selected signals to an array of phase shifters. A second switch array provides the phase shifted signal, which may be amplified, to either a primary array having elements for radiating a scanning beam or a recombining network having outputs connected to auxiliary antennas. A third switch array provides control signals to the array of phase shifters from either a main beam steering unit or a standby beam steering unit. Alternatively, the dual signal sources feed a single power divider through a circulator. Duplicate auxiliary antennas may be used with antenna switches located before the power dividers or circulator for selectively providing the signals to the auxiliary antennas instead of the primary array.

Abstract: A waveguide manifold for monitoring the operation of an array antenna. The waveguide is centerfed and has reflecting terminations at either end. The waveguide output is matched to the waveguide as if non-reflecting terminations were at either end of the waveguide. The waveguide input is a plurality of groups of slots wherein adjacent groups have alternating phase. Adjacent slots in each group have alternating polarity. A standing wave created in the waveguide has a plurality of cells of alternating phase. Each slot is located within one of the resonating standing wave cells. The resulting manifold beam forming characteristic will be temperature and frequency independent over a practical range.

Abstract: A external feedback network for decreasing variations in a beam pointing angle of a scanning antenna array. A dedicated aperture manifold is intergral with the aperture of the scanning antenna and provides a signal which represents the beam pointing angle. The signal is detected, decoded, and converted into digital data for averaging and processing by a CPU. The processed data is then compared with a value stored in memory and any difference forms the basis of a correction signal. For application to a microwave landing system, the correction signal is used to adjust the start/stop time of the scanning commands of the antenna to remove the error without modifying the beam steering algorithm. A space-coupled monitor may also be used independent of the feedback network to provide an alarm in response to any failure of the dedicated aperture manifold, the automatic stabilization circuitry or the array system.

Abstract: In a system having plural signal-carrying channels, a phase shift is introduced between a signal in one of the channels and a reference signal for calibrating the individual channels. The phase shift is introduced by phase-shift apparatus responsive to a command signal directing the continuous monotonic increment of phase. The apparatus may be contained within each channel for use in the signal-carrying process, or may be placed in the reference channel for use solely in the calibration process. The phase incrementing introduces a frequency shift (a serrodyning) which produces a beat-frequency signal upon mixing a channel signal with a reference signal. The beat-frequency signal is phase locked to a modulation pattern of the command signal whereby a measurement of phase (or delay) can be made between the two signals for calibration of each channel within the system.

Abstract: In a phased array antenna wherein signals are supplied to a plurality of antenna elements by a coupling network which includes digital phase shifters for varying the phase of wave energy signals supplied to the elements, there is provided apparatus for discontinuing the supply of wave energy signals to the elements through any malfunctioning phase shifter.

Abstract: A phased array antenna includes a coupling network which is arranged to supply signals to pairs of elements located on opposite sides of the array center with a phase difference which is an odd-integral multiple of one-half the smallest phase step of the array phase shifters. This coupling network arrangement reduces antenna beam pointing errors which arise from a phase quantization of the array phase shifters.

Abstract: In an array antenna system having a coupling network interconnecting a plurality of element groups, the coupling network is provided with phase adjustments to shift the angular location of the effective element radiation pattern. An effective technique for this phase adjustment in a microstrip coupling network makes use of a field altering structure positioned adjacent the microstrip.

Abstract: In any array antenna system having a coupling network interconnecting a plurality of element groups, the coupling network is provided with phase adjustments to shift the angular location of the effective element radiation pattern. An effective technique for this phase adjustment in a microstrip coupling network makes use of a field altering structure positioned adjacent the microstrip.

Abstract: In a doppler radionavigation system wherein a transmitted signal has opposite frequency coding during alternating time intervals, a reference antenna is provided which has different radiation modes during the alternating time intervals. In a preferred embodiment, the two reference antenna modes have substantially the same amplitude radiation pattern, but different phase radiation characteristics. The phase between the radiation in a selected direction and the radiation in the remaining directions is different for the two antenna modes. This phase change substantially reduces the position determination error resulting from multipath signals.

Abstract: Disclosed are array antenna systems wherein the effective element pattern is modified by means of coupling circuits to closely conform to the ideal element pattern required for radiating the antenna beam within a selected angular region of space. Use of the coupling circuits in the embodiment of a scanning beam antenna significantly reduces the number of phase shifters required as compared to prior art array antennas.