Abstract: An interference cancellation system for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath. This interference cancellation system includes a frequency hopped radio adapted to operate in a dispersion environment. This frequency hopped radio has an instantaneously limited bandwidth communication channel operating over a substantially larger bandwidth. Transmission of a signal from the frequency hopped radio is via a directly coupled reference path and a received coupled path. A delay means is used for variably adjusting the phase slope delay of the signal in one path relative to the other path. The system employs an amplitude slope means for variably adjusting the amplitude slope of the signal in one path relative to the other path.

Abstract: Without use of separate auxiliary antennas, adaptive nulling automatically reduces jamming or other interference affecting a radar or IFF system. A primary beam forming network utilizes four-port directional coupler devices, each having an ancillary port which would have been resistively terminated in the absence of the invention. Signals from ancillary ports are coupled to an auxiliary beam forming network to form auxiliary beam patterns which are orthogonal to and track steered main beam patterns. Auxiliary signals are received via the auxiliary beam patterns. Least mean square (LMS) control loops operate on a feedback basis to derive weighted auxiliary signals responsive to jamming signals. The weighted auxiliary signals are combined with the primary received signals (which may be sum and difference signals) in reverse polarity, so as to be additively destructive of the jamming signals. Multiple LMS control loops enable nulling of jamming signals simultaneously in sum and difference channels.

Abstract: An LMS adaptive control loop module for reducing the effects of received interference includes a single antenna coupled to a first hybrid for generating a reference channel and an auxiliary channel. The auxiliary channel provides I/Q signals from a second hybrid and I/Q drive signals from I/Q correlation multipliers which are used to weight the I/Q signals from said second hybrid. The weighted signals and the reference channel signals are combined and provide an output.

Abstract: An apparatus for cancelling undesired signals affecting an antenna system. The apparatus includes a plurality of adaptive modules. Each module provides sum and difference signals from a pair of antennas in the system. Each difference signal is weighted by an adaptive controller coupled to the difference signal and the apparatus output signal. All sum signals from the modules are sum and all weighted difference signals from modules are summed and the total weighted difference signal is subtracted from the total sum signal to provide an apparatus output. The adaptive controller is a multiplexer associated with each of the difference signals of the modules, a reference receiver receiving a multiplexed information and a correlator coupled to the received information and the apparatus output. The correlator controls the weights affecting each of the difference signals of each module. The output of the subtractor is decoded by a main receiver.

Abstract: Multiple interference signals in an electromagnetic wave communication system are individually discriminated against by a beamport sidelobe canceller comprising a multichannel auxiliary system in which spatial filtering of the angular sectors of interest is performed prior to sidelobe cancellation. Each spatial filter of the auxiliary system has its own adaptive control and only those interfering signals appearing in its assigned sector are operated on by that loop. The output of the main communication system receiver is summed with the outputs of the auxiliary system channels to produce a system output and an adaptive control loop feedback signal. The feedback signal initiates the generation of a cancellation signal in any adaptive control loop in which correlation of interference signals occur in both the main communication system received signal and the signal received by the auxiliary system channel to which that loop is connected.