Abstract: A compact aircraft antenna for reception of GPS signals includes eight elements to provide eight antenna patterns usable for anti-jam signal processing. Four bent monopole elements are configured with vertical portions and horizontal inward-extending portions. The bent monopole elements are arranged for multimode excitation to provide a primary progressive phase omnidirectional right-hand circularly-polarized antenna pattern for basic signal GPS signal reception. Multimode excitation of the bent monopoles also provides omnidirectional left-hand circularly-polarized, uniform phase omnidirectional, and clover leaf auxiliary antenna patterns. Four individual slot element figure-eight type auxiliary antenna patterns are also provided. With availability of these primary and auxiliary patterns, adaptive type anti-jam processing can be employed to actively provide reduced-gain antenna pattern notches or nulls at incident angles of interference or jamming signals.

Abstract: Collision avoidance systems are provided for groups of aircraft operating in close proximity, as during formation flights or cooperative missions. Fixed and rotary airfoil aircraft with separations of 30 feet to 5 miles, for example, participate in a local radio sub-net. An aircraft receiving CAS sub-net signals derives signal transit time values representing differences between send and receive times and which are used to derive data on inter-aircraft range and closing rate. With synchronized clocks, highly-accurate one-way ranging uses assigned time slots with predetermined sub-net time-of-day timing of transmissions. Round-trip ranging operates with less accurate time synchronization, and systems may operatively select between one-way and round-trip ranging. By exchange of range and closing rate data among aircraft, 3-D data for current three-dimensional location of aircraft enables evasive action determination.

Abstract: A source of interference signals may be present at a fixed incident angle relative to a stationary antenna. Horizontal array antennas are provided with radiation pattern notches or nulls at selected fixed angles to suppress reception of interference signals. By excitation of elements on the left side of an array in opposite phase relative to elements on the right side and provision of an appropriate line-length differential between left and right radiation element feed lines, a radiation pattern notch is positioned at a selectable angle relative to boresight. Notch width optimization is provided by use of relative excitation levels of radiating elements as disclosed. Other configurations are disclosed.

Abstract: A space diversity antenna system provided with dither circuitry in the signal path to one of the antennas to switch a circuit element in and out of the signal path at a high rate. The circuit element can be an amplitude attenuator or a phase changer. This switching results in the substantial elimination of nulling between the two antennas.

Abstract: A microstrip antenna radiates and receives six beams in sequence out of a common aperture and processes return signals with common electronics in order to measure the velocity components relating to a backscattering surface. Sequentially, the first four beams are processed by measuring Doppler shift in a return signal while the last two beams are processed for time correlation. The result of the present invention is a combined time correlation and Doppler measurement velocity sensor available for operation over virtually all terrains and the vehicle speed range.

Abstract: Modified configurations for electrical connectors to ceramic transducers are designed to reduce failure rates due to fatigue during transducer operation. These modifications eliminate or reduce one or both of the problems causing the fatigue, tensile forces acting on electrical wires connected to ceramic electrodes and unreliable solder joints. Star and pin configurations of wire soldered to ceramic transducers control the position of the wires, thus reducing the tensile forces on the wire. Plug connectors use pressure contacts between the ceramics, eliminating the need for solder joints.

Abstract: For broadcast transmission of Differential GPS data signals, a vertical array antenna provides broad band omnidirective phase-progressive radiation with elliptical polarization. Four-dipole sub-arrays use diagonally aligned two-piece cut and bend dipoles with isolated conductive frontal strip. With these vertically arrayed sub-arrays, lower and upper sub-arrays are excited at 70 percent amplitude and respective plus and minus 90 degree phase rotation relative to middle sub-array, for optimized performance with low elevation lobing. Divided transmission line operation provided by the frontal strip of appropriate length achieves double-tuned dipole performance with very low VSWR over the operating band.

Abstract: A multi node network communications protocol which provides high information throughput at high efficiency, while also maximizing low probability of detection and interception characteristics by optimizing use of transmitting power and other characteristics including but not limited to modulation method, FEC rate and spread spectrum processing gain. The network is optimized by dividing into sub-networks and optimizing the sub-networks to consider local conditions, thus optimizing the overall network to a level of efficiency not possible from a central control point. A protocol which periodically adapts to changing conditions and allows silent entry and exit of nodes as well as providing locations of all nodes within the network.

Abstract: Low impedance loop antennas utilize a loop separated into a plurality of radiating segments fed in parallel. A four point feed loop antenna, including radiating segments 12, 13, 14, 15 had a measured input impedance varying from 1.8 to 5.8 Ohms over a range of 5 to 15 MHz, without excessive radiation Q degradation. An incorporated feed network includes transmission line segments, with conductors on opposite surfaces of a thin substrate, connecting the radiating segments to a centrally mounted coaxial connector for parallel excitation. Operating bandwidth of the loop antenna is determined by the characteristic impedance of the transmission line feed segments. Low impedance loop antennas which are small relative to operating wavelength can be fabricated on a thin flexible substrate for field transport and use. Incorporation of the antenna into a jacket or other clothing enables field use while minimizing restriction of activity of the user.