Abstract: A multiple-hypothesis, multipath-matched filter (10) is disclosed for use in combining multipath components of transmissions between, for example, an aircraft (12) and aircraft (14) through a multipath environment (16). Rather than sensing the characteristics of the environment and adjusting the multipath components accordingly, the disclosed filter is designed on the basis of several hypotheses concerning the differences in the path lengths traversed by the various multipath components, as well as the phase shift introduced into each. In a preferred arrangement, the path length differences .DELTA.R are assumed to be some integer multiple of the range gate setting .delta.R of a transmitter/receiver (28) included on the aircraft. The phase shifts .psi. are assumed to be either 0.degree. or 180.degree..

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: An over-the-horizon, synthetic aperture radar (OTHSAR) system (10) is disclosed. The OTHSAR system is used to locate moving objects (14) at long distances in response to modulated high-frequency radiation reflected by the objects and distinguishes the objects from stationary clutter (16) that also reflects the radiation. Specifically, a central processor (26) synthesizes information received from an antenna (18) and receiver (22) over an interval of time t.sub.s to enhance azimuth resolution. Although ambiguous Doppler information is likely to be received from the moving object and the stationary clutter, the antenna is selected to have a real antenna beam that resolves the ambiguous data, ensuring that conflicting clutter data is eliminated.

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 phased-array antenna (14) is disclosed including modules (12) that respond to optic signals provided by a central processor (16) vai an optic feed network (18). In a transmit mode of operation, the central processor provides optic transmit signals to the modules, controlling the phase and attenuation of the various signals to accomplish the desired steering of the antenna beam produced by the array. A mixer or avalanche photodiode (42) in each module provides suitable optical-to-RF power conversion for the input signal to allow antenna elements (44) in the module to radiate the desired electromagnetic beam. During a receive interval, a received electric signal produced by the antenna elements is combined by the mixer with a local oscillator frequency optic signal applied to the mixer by the central processor. As a result, the RF frequency of the received signal is reduced to an IF frequency for low-cost amplification by an amplifier (52).