Abstract: Method for coherently combining signals received from two widely separated antenna apertures (204, 206). The method includes positioning a first antenna aperture (204) at a first location spaced apart a distance with respect to a second location of a second antenna aperture (206). A distance between the first antenna aperture and the second antenna aperture is selected to be at least a plurality of wavelengths at a predetermined operating frequency of the first antenna aperture and the second antenna aperture. An antenna beam or pattern (208, 210) from each antenna aperture (204, 206) is directed toward a target (212) positioned at a location remote from the first antenna aperture and the second antenna aperture. Adaptive digital processing (416) is then used to coherently combine the signals independently received by each aperture from the common source.

Abstract: RF amplifier system (200) incorporating feedforward linearization. The system includes a digital waveform source (202) generating digital data s(t) representative of at least one analog signal. The system also includes a feedforward linearization circuit for reducing a distortion of an RF power amplifier (212). The feedforward linearization circuit includes a differential amplifier (230) arranged for generating an error signal. The error signal is determined based on a difference between the distorted RF output signal and an analog RF reference signal (229) generated from the digital data.

Abstract: RF amplifier system (200) incorporating feedforward linearization. The system includes a digital waveform source (202) generating digital data s(t) representative of at least one analog signal. The system also includes a feedforward linearization circuit for reducing a distortion of an RF power amplifier (212). The feedforward linearization circuit includes a differential amplifier (230) arranged for generating an error signal. The error signal is determined based on a difference between the distorted RF output signal and an analog RF reference signal (229) generated from the digital data.

Abstract: Method for accurately measuring hearing loss includes the steps of selecting a series of audio tones within the normal range of hearing (502) and then measuring a relative sensitivity of a test subject with respect to the ability to hear each of the audio tones, exclusive of the effects of tinnitus. (504, 506, 508, 510, 512) The relative sensitivity of the test subject to hear the tones can be measured by determining (510) for each tone an intensity necessary for the test subject to hear the tones at a subjectively equal loudness level which is selected to exceed a perceived level of noise attributable to tinnitus for the test subject.

Abstract: Predistorting an input signal prior to amplification in an RF power amplifier (206) includes isolating a plurality sub-band signals, each representing a portion of the input signal s(t). The method includes independently modifying an amplitude and a phase of each of the plurality of sub-band signals. The modification of the amplitude and/or phase is performed using a set of signal weighting parameters (weights) w and W, controlling linear and nonlinear modifications respectively, which are determined in an adaptive process by an adaptive controller (224). After modification, each of the sub-bands are summed together to obtain a predistorted input signal for an RF power amplifier (206).

Abstract: The invention concerns a method and apparatus for cascaded processing of signals in a phased array antenna system in which a plurality of antenna elements are configured as a plurality of sub-arrays. A weighting factor is applied to each of the antenna elements to form a plurality of sub-array beams, each pointed in a selected direction. For each sub-array, an output from each the antenna elements in the sub-array can be combined to produce a sub-array output signal. The sub-array output signals are selectively weighted and combined in a fully adaptive process. Subsequently, the system can estimate an angle-of-arrival direction for a signal-of-interest (“SOI”) and at least one signal-not-of-interest (“SNOI”). Based on this estimating step, the system calculates a new set of weighting factors for controlling one or more of the sub-array beams to improve the signal-to-noise plus interference ratio obtained for the SOI in the array output signal.

Abstract: Blind source separation (BSS) of statistically independent signals with low signal-to-noise plus interference ratios under a narrowband assumption utilizes cumulants in conjunction with spectral estimation of the signal subspace to perform the blind separation. The BSS technique utilizes a higher-order statistical method, specifically fourth-order cumulants, with the generalized eigen analysis of a matrix-pencil to blindly separate a linear mixture of unknown, statistically independent, stationary narrowband signals at a low signal-to-noise plus interference ratio having the capability to separate signals in spatially and/or temporally correlated Gaussian noise. This BSS provides the ability to blindly separate signals in situations where no second-order technique has been found to perform the blind separation satisfactorily, for example, at a low signal-to-noise ratio when the number of sources equals the number of sensors or when the noise is spatially and temporally colored.

Abstract: The invention concerns a method and apparatus for cascaded processing of signals in a phased array antenna system in which a plurality of antenna elements are configured as a plurality of sub-arrays. A weighting factor is applied to each of the antenna elements to form a plurality of sub-array beams, each pointed in a selected direction. For each sub-array, an output from each the antenna elements in the sub-array can be combined to produce a sub-array output signal. The sub-array output signals are selectively weighted and combined in a fully adaptive process. Subsequently, the system can estimate an angle-of-arrival direction for a signal-of-interest (“SOI”) and at least one signal-not-of-interest (“SNOI”). Based on this estimating step, the system calculates a new set of weighting factors for controlling one or more of the sub-array beams to improve the signal-to-noise plus interference ratio obtained for the SOI in the array output signal.

Abstract: Blind source separation (BSS) of statistically independent signals with low signal-to-noise plus interference ratios under a narrowband assumption utilizes cumulants in conjunction with spectral estimation of the signal subspace to perform the blind separation. The BSS technique utilizes a higher-order statistical method, specifically fourth-order cumulants, with the generalized eigen analysis of a matrix-pencil to blindly separate a linear mixture of unknown, statistically independent, stationary narrowband signals at a low signal-to-noise plus interference ratio having the capability to separate signals in spatially and/or temporally correlated Gaussian noise. This BSS provides the ability to blindly separate signals in situations where no second-order technique has been found to perform the blind separation satisfactorily, for example, at a low signal-to-noise ratio when the number of sources equals the number of sensors or when the noise is spatially and temporally colored.