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: In the ground-based equipment of a microwave landing system (MLS), a linear array antenna is employed to generate both a scanning guidance beam, which provides azimuthal position data to an incoming aircraft, and a pair of out-of-coverage indication (OCI) beams, which are disposed outside of the sector covered by the scanning guidance beam. For sweeping the guide beam, phase shifts are updated in a linear phase gradient to scan the beam to the right and to the left of the centerline of the antenna. To form the pair of OCI beams, the main lobe of the antenna radiation pattern is directed to one side of the antenna's centerline, outside the normal scanning range, thereby producing a grating lobe on the opposite side of the centerline. Furthermore, a quadratic phase shift function is superimposed upon the linear phase gradient to defocus the OCI beams so as to fill a sufficient sector of space, on both sides of the scanned region, for OCI coverage.

Abstract: A lossless spatial filter having N input ports and N output ports and printed on a single substrate. The filer is used in combination with an antenna system which radiates wave energy signals into a selected angular region of space and into a desired radiation pattern. The aperture of the system includes a plurality of N antenna elements. The antenna elements are arranged along a predetermined path and each element is connected to only one output port of the spatial filter. A beam steering unit controls the direction of radiation. A signal generator supplies a power divider having N output signal ports each connected to a phase shifter controlled by the beam steering unit.

Abstract: The fault monitoring function of an executive monitor contained in a microwave landing system is verified by evaluating a history of the parametric information sampled by an executive monitor and storing in memory the number of out of tolerance parametric signals received from an antenna means over a predetermined time period, replacing the stored number of out-of-tolerance parametric signals with a predetermined number that will be beyond a second predetermined limit if another out-of-tolerance parametric signal is added to said number, adding one such internally generated out-of-tolerance parametric signal to said predetermined number, generating an alarm if said sum is beyond the second predetermined limit, and restoring the previously stored number of out-of-tolerance parametric signals received from the antenna means if the alarm was generated, and shutting the system down if an alarm was not generated.

Abstract: Proper operation of a beam steering unit for a phase array antenna, is verified by simulating the pattern of wave energy which would be radiated to an observation point in space when the beam steering unit is connected to phase shifters associated with elements of the antenna. The simulated pattern thus obtained may be compared with a preset pattern for the observation point during a scanning operation of the beam steering unit, and an alarm or other indication is obtained when the difference between the simulated and the preset pattern exceeds a certain limit. The simulated pattern is obtained by storing phase angle data from the beam steering unit in a memory at areas corresponding to phase shifters associated with elements of the phased array antenna.Observation angle data corresponding to the angle of the point in space relative to the antenna array is generated, the observation angle data being a function of observation angle, antenna element spacing and radiation wavelength.

Abstract: A scanning system for a phased array antenna for operation at a selected frequency between a first frequency and a second frequency includes the storage of phase shift command signals for each of the phase shifters coupled to radiating elements of the antenna. The memory which stores the phase shift commands is addressed sequentially to provide for a step-wise scanning of a beam of radiant energy at a first frequency of the antenna. The addressing is accomplished by incrementing a count resulting from a counting of clock pulses. Compensation for the stepped positions of the beam for the difference between the selected frequency and the first frequency is accomplished by altering the number of pulses which increment the count of the addressing. The altering is accomplished by the storing of sequences of clock pulses at varying temporal spacings which are used for gating out selected ones of the incrementing pulses.

Abstract: A waveguide manifold for monitoring the operation of an array antenna. The waveguide is centerfed and has reflecting termination 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 slots wherein adjacent slots have alternating polarity. A standing wave created in the waveguide have a plurality of cells of alternating phase. Each slot is located within one of the resonating standing wave cells. The resulting manifold beam forming characteristics will be temperature and frequency independent over a practical range.

Abstract: A conductive sheet having slots therein is located between dielectric sheets having microstrip feed networks printed thereon forming a multilayered structure which is spaced from a ground plane by a dielectric substrate and covered by another dielectric substrate having a dielectric skin thereon. The slots comprise an array of horizontal slots perpendicular to vertical slots. One of the dielectric sheets and the microstrip feed network printed thereon is associated with the horizontal slots and the other dielectric sheet and the microstrip feed network printed thereon is associated with the vertical slots.

Abstract: An array antenna for radiating wave energy signals into a selected region of space and suppressing radiation in other regions of space is formed with an aperture which is an array of N antenna element modules, each comprising two or more antenna element groups, and each group comprising one or more antenna elements. A plurality of 2N first transmission lines is provided, each for supplying wave energy signals to one of the element groups. The antenna also includes N second transmission lines. Each of the second transmission lines has an input terminal, intersects a selected number of first transmission lines, and is terminated at its other end. Directional couplers are provided for coupling the second transmission lines to the intersected first transmission lines.

Abstract: Phase quantization errors in a phased array antenna are reduced by providing phase control signals which approximate ideal phase functions for symmetrical pairs of elements having an average phase value which is displaced from a nominal phase quantization value by one-quarter the smallest phase step.

Abstract: A processing apparatus for determining the frequency of a supplied signal is usable in a Doppler microwave landing system. The apparatus derives scalar signals representative of signal frequency and amplitude and computes the average value of the scalar signals over a number of time intervals prior to dividing the signals to produce an output signal representative of average supplied signal frequency.

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.

Abstract: An apertured metallic ground plate antenna element having a high input impedance is driven from a lower impedance input transmission line by means of an exciter that provides broadband impedance transformation. The input transmission line is divided into two higher impedance feed lines that feed two parallel plate transmission lines. The parallel plate transmission lines are positioned in close proximity to the element aperture and are oriented to provide antenna excitation in series.