Abstract: The usable range of incidence angles for electromagnetic wave polarizers using arrays of polarizer elements is increased by introduction of a dielectric medium having a dielectric constant large enough to reduce the angle of wave incidence upon the polarizer elements. For example, arrays of 45 degree inclined meander-line polarizer elements are encased in a dielectric medium having a dielectric constant of about 3. The polarizer includes impedance matching layers at the surfaces of the dielectric medium to reduce reflections at those surfaces. The resulting polarizer is indicated to be usable to reciprocally convert an incident polarization to a desired polarization (e.g., from linear to circular polarization) for waves with incidence angles from zero to 70 degrees in any plane.

Abstract: A field monitor in the near field receives an antenna signal which approximates that which would be received by the monitor if located in the far field. In one aspect of the invention, the antenna signal is produced by an array of spaced apart receiving elements. In another aspect of the invention, the signal received from a near field sampling antenna is passed through a signal processor having the necessary characteristics to construct from the sample a signal corresponding to that which would have been received in the far field. Antenna element arrays are also used as plane wave sources permitting antenna testing with a radiating path length of one-eighth or one-quarter of the far field distance. Compact indoor antenna test ranges are also provided.

Abstract: Synthesizer radiating systems providing efficient wideband operation incorporate a radiating element (20a), such as a loop, dipole or whip, which has dimensions which are small relative to wavelength in the radiated frequency band. Energy dissipation is substantially reduced by cycling stored energy back and forth between a radiating element (20a) having a first reactance and a storage element (22a) having the same or opposite reactance, in order to achieve energy efficiency along the lines of a narrowband tuned-circuit antenna. Wideband operation is achieved by synthesizing a representation of an input waveform (at 28) by actively controlling (30) solid-state switching devices (24), responsive to rate control and direction control parameters, which are interactive with the energy transferred between the opposite reactances. Higher efficiencies are achieved by bipolar circuits providing separate positive and negative energy transfer paths between a radiating element and a storage element.

Abstract: Linear array antenna systems are used in X-scan aircraft location systems and methods able to avoid disabling azimuth error conditions caused by multipath reflections under roll and pitch conditions during aircraft carrier landing operations. Aircraft azimuth and elevation data is derived based upon time of incidence at an aircraft location of two transverse, diagonally oriented, scanned antenna beams. The aircraft location data is derived by comparing time of incidence data with data on known timing of scanning of the beams, which have diagonally-oriented fan beam patterns. A plurality of vertically oriented radiating elements are typically positioned along a line diagonal to the vertical to produce a diagonally oriented fan beam pattern. Beam scanning results from relative adjustment of signal portions supplied to the radiating elements.

Abstract: A portable test receiver for field maintenance of a remote sensor monitoring system for underground transformers. The apparatus uses a phase locked loop method to demodulate the DPSK modulation of the remote monitor transmitter. The apparatus is battery operated and easily moved to permit monitoring of spot networks and critical locations for maintenance work. The apparatus features a single software driven display offering good visibility with low current drain. Decoding the transmitter signal is accomplished by using the crystal oscillator circuit of the transmitter is used to generate a reference which is compared to the transmitter signal to detect phase flips. Since the apparatus is battery-powered, there is no AC power to provide "zero" crossing points of the monitored transmitter. Bit timing is provided by taking advantage of the nulls at the 60 cycle "zero" crossings found in the transmitter signal.

Abstract: A compact wide-band panel antenna is modified to provide a dual-mode antenna system with improved operation, particularly in the presence of interfering signals and varying reception conditions in mobile communications applications. A hybrid junction arrangement is used to combine received signals in sum and difference modes suitable for adaptive processing. Signal transmission is provided by reciprocal operation, with a circulator incorporated for signal isolation. The dual mode capability provides previously unavailable performance in a small, economical broad-band antenna.

Abstract: A field monitor in the near field receives an antenna signal which approximates that which would be received by the monitor if located in the far field. In one aspect of the invention, the antenna signal is produced by an array of spaced apart receiving elements. In another aspect of the invention, the signal received from a near field sampling antenna is passed through a signal processor having the necessary characteristics to construct from the sample a signal corresponding to that which would have been received in the far field. Antenna element arrays are also used as plane wave sources permitting antenna testing with a radiating path length of one-eighth or one-quarter of the far field distance. Compact indoor antenna test ranges are also provided.

Abstract: Airborne navigation receivers are designed to derive navigation information with accuracy immune to beam asymmetry errors. Scanned navigation beams of the Microwave Landing System are subject to asymmetry causing beam center measurement errors at power levels other than a standard level 3dB down from peak. Dwell gate and split gate type receivers achieve error immunity through offsetting of errors at power levels above and below a standard power level.

Abstract: An antenna comprising a linear array of active elements positioned in one or more rows. The back portion of the array is partially enveloped by a reflector. The reflector includes a backwall and at least one sidewall perpendicular to the backwall and extending forward of the backwall. In one embodiment of the invention, a single row of dipole radiators form the linear array. In a second embodiment of the invention, a row of folded monopoles mounted on an imaging ground plane form the linear array. The radiation pattern is directed forward of the reflector, the back radiation in the E-plane being suppressed by the sidewall of the reflector.

Abstract: First and second aluminum members are joined by the steps of(a) dissolving and removing completely the aluminum oxide layer from the surface of each of said first and second members to be joined and replacing each of the aluminum oxide layers with a layer consisting essentially of zinc;(b) plating at least one of the zinc layers with a non-alloy cadmium;(c) assembling and retaining together said first and second aluminum members so that the surfaces to be joined are held in contact with one another and placing said aluminum members in a vacuum; and(d) heating the members while in the vacuum thereby forming a bond between said first and second aluminum members.

Abstract: An antenna comprising a linear array of active elements positioned in one or more rows. The back portion of the array is partially enveloped by a reflector. The reflector includes a backwall and at least one sidewall perpendicular to the backwall and extending forward of the backwall. In one embodiment of the invention, a single row of dipole radiators form the linear array. In a second embodiment of the invention, a row of folded monopoles mounted on an imaging ground plane form the linear array. The radiation pattern is directed forward of the reflector, the back radiation in the E-plane being suppressed by the sidewall of the reflector.

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 reference signal is obtained by adding samples of signals in other ones of the channels. The phase shift is introduced by phase-shift apparatus responsive to a command signal directing a continuous monotonic increment of phase. The phase incrementing introduces a frequency shift (a serrodyne), which produces a beat-frequency signal for mixing a channel signal with the reference signal. The beat-frequency signal is phase locked to a modulation patern of a 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: A flat panel display system is provided in which the pixels thereof are illuminated by optical fibers. Economy and compactness are achieved by using micromechanical light modulators to demultiplex light from a limited number of LED's to a large number of pixels. By using micromechanical light modulators incorporated in an integrated circuit, the flat panel display system is relatively economical, has low power consumption, and produces a display of very high resolution. The display also may be provided in full color.

Abstract: A sonobuoy system and method for deploying an array of transducers in a substantially horizontal line at a desired depth below the surface of a body of water. The trailing end of the array is deployed first, allowed to descend, and suspended at the desired operating depth. The leading end of the array is then released, allowed to descend slowly, and suspended at the desired operating depth. A drag device attached to the trailing end of the array causes the trailing end of the array to be stretched out away from the leading end, thereby maintaining the array in a substantially horizontal line at the desired depth. The system and method make it possible to deploy horizontal line arrays in a minimum of time and at shallow depths.

Abstract: First and second aluminum members are joined by the steps of(a) dissolving and removing completely the aluminum oxide layer from the surface of each of the first and second members to be joined and replacing each of the aluminum oxide layers with a layer consisting essentially of zinc;(b) plating at least one of the zinc layers with a non-alloy cadmium;(c) assembling and retaining together the first and second aluminum members so that the surfaces to be joined are held in contact with one another and placing the aluminum members in a vacuum; and(d) heating the members while in the vacuum thereby forming a bond between the first and second aluminum members.

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 amplitude control system particularly suitable for an active antenna array includes a power detector for generating a power level signal representative of a level of radio frequency (RF) energy radiated by an antenna element, or groups of elements, in a phased antenna array. A reference signal corresponding to a desired value for the radiated level of RF energy is set by a control device, and the power level signal and the reference signal are compared with one another. Depending on the comparison result, an attenuator associated with an RF amplifier than drives the antenna elements, is adjusted to maintain the radiated RF energy at the desired value set at the control device.

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 method and apparatus for enhancing the resolution of an analog-to-digital converter. The method uses the addition of a second analog waveform to a first analog signal which is to be converted. When the composite signal is converted to digital form, this enhances the effective resolution of the A/D converter with respect to the first signal. Integration of the composite digital signal causes the effects of the second waveform to average to zero. The result is an enhanced resolution signal without undesired effects of the added second signal.

Abstract: A process for joining first and second aluminum sheets in which the bonding surfaces of the aluminum sheets have their aluminum oxide layer replaced by a zinc layer and the zinc layers are plated with a non-alloy metal bonding material such as cadmium. The first and second aluminum sheets are then assembled and fastened together with an engaging means for holding the sheets together, and then the assembled sheets are placed in a vacuum. The sheets are subsequently heated in the vacuum thereby creating a bond of cadmium between them, removed from the vacuum, and then passivated.