A distributed antenna system is provided which is formed from a series of modular stages (104) interconnected by cables (106). Each stage may include an antenna (134), a filter (135), a compensating amplifier (138) and preferably elements for impedance matching to connecting cables (110, 112). Connecting stages also include a coupler (136) for combining the output from the stage antenna with the output from the preceding stage and passing the combined signal to the stage output (110). Where the stages are part of a transmitting system, the coupler is replaced by or functions as a splitter, an input thereto from, for example, a preceding stage, being applied to the stage antenna and to the stage output.

Modular distributed antenna system

A method and device for removing undesired jammer signals from desired signals which comprises forming a beam on the desired signal in an adaptive antenna array characterized by an orthogonalizer array (12) to receive digitised signals from the antennas, and pass signals to a beamforming array (14) and including a late jammer canceller array (16) and an intelligent controller (24) arranged to control weights (W) and select a row having the desired beamformed signal.

Adaptive antenna array

In a digital signal processor (DSP), input data is configured as a data matrix comprising data samples collected from an input signal. A weight vector is applied to the data matrix, where the weight vector comprises three parts including (a) a rank reduction transformation produced by decomposition of the data samples in a multistage Wiener filter having a plurality of stages, each stage comprising projection onto two subspaces. Each subsequent stage comprises projecting data transformed by the preceding second subspace onto each of a first subspace comprising a normalized cross-correlation vector at the previous stage and a second subspace comprising the null space of the normalized cross-correlation vector of the current stage, to form a reduced rank data matrix. Part (b) of the weight vector comprises minimizing the mean squared error in the reduced rank data space. The output is a linear estimate of the input data. In one embodiment, further processing produces an estimate of the power spectral density of the input signal.

System and method for linear prediction

An antenna subject to standoff sidelobe barrage jamming exhibits a null in its sidelobe structure at a selectable elevation angle for all azimuth angles of interest. The null can be set to the elevation angles corresponding to the angle of the standoff jammers. The null is generated with the aid of an interferometer associated with each column of the antenna array. The interferometer produces a pattern having a plurality of lobes. The interferometer pattern is phased and amplitude adjusted relative to the antenna pattern of its associated column line array so that subtraction of the patterns causes one or more sidelobe of the antenna pattern to be at least partially canceled. An azimuth beamformer combines the elevation patterns of a plurality of column arrays, each connected to its own interferometer, to produce a pencil beam with a sidelobe structure exhibiting a null at the particular elevation angle.

Phased array antenna with wide null

A sound receiving system has an array of microphone elements for producing output signals in response to incident sound, and signal processing means for processing the output signals to provide the array with pre-selected directional acceptance and rejection characteristics. Such processing includes integrating the difference between the output signals of a pair of elements to produce an integrated signal, summing the outputs of the same or different pair of elements to obtain a sum signal, and combining the integrated signal with the sum signal. The spatial position of pairs of elements and their orientation permit closely spaced pairs of elements to exhibit a single highly directional characteristic, or two angularly related highly directional characteristics. Thus, an array of microphone elements clustered at essentially a point location can exhibit either monaural or stereophonic characteristics, depending upon the type of signal processing applied to their outputs. To minimize wind noise pickup, low frequency components of the integrated signal are suppressed to produce a filtered integrated signal, and high frequency components in the output signal of at least one of the elements are suppressed for producing a filtered output signal. The two filtered signals are added together to produce a resultant signal wherein only the higher frequency information signals will be directionally picked up and amplified.

Receiving system having pre-selected directional response

Self-adapting anti-jamming device having (n + 1) sensors and enabling the restituting of the signal emitted by a source in the presence of n punctiform noise sources, comprising a combination assembly having an adder and n subtractors, an orthonormalization assembly comprising n AGC circuits, n (n - 1)/2! subtractors each combined with a correlation module, an intercorrelation set comprising n correlation modules, an adder and a subtractor.

Giraudon Claude

Papers

Adaptive antenna processing