Abstract: Apparatus and method for analyzing data collected from a physical structure for purposes of damage detection or structural health monitoring. The invention attempts to detect signs of nonlinear distortion, which is known to result from most forms of structural damage. The invention uses generic models that can be adjusted to fit arbitrary data to explore the relationship between data sets collected from different locations on or near the physical structure and to capture and detect nonlinearity with those models when it exists in the structural dynamics.

Abstract: In a transmission line, nonlinear impairments resulting from imperfect splices are mitigated by providing a bias current that shifts the operating points of these impairments resulting in improved stability, conductivity and linearity.

Abstract: A series of time domain reflectometry (tdr) measurements are made on a channel having nonlinear impairments as well as linear impairments. In a given measurement, the reflected signals from the impairments are digitized and sequentially stored in memory. The parameters characterizing the channel are then changed, preferably by biasing the line by means of a dc current. The changed bias condition modifies the impedance of nonlinear impairments in a nonlinear manner, while the impedance of linear impairments are unchanged by the bias. A second tdr measurement is initiated, and the reflected signals digitized and sequentially stored. The two sets of stored reflected signals are then sequentially compared, and corresponding signals having either the same amplitudes or linearly proportional amplitudes are identified as reflected from linear impairments, while those not the same, nor proportional, are identified as from nonlinear impairments.

Abstract: In a digital communication system where digitally modulated signals are transmitted in a signal path including a bi-directional channel, a multistage echo-canceller has two or more stages connected in a sequence to remove the linear and nonlinear echo of the outgoing signal from the incoming signal. Results are of importance both to systems with overlapping outgoing and incoming frequency bands and to those with separated bands (for which only the nonlinear echo is of concern). The two or more stages are each characterized by a respective function, and the sequence is characterized by alternation of the functions of the two or more stages between linear and nonlinear.

Abstract: In a digital communication system, the peak-to-average power ratio (PAR) is reduced by means of a compressor characterized by a nonlinear function that operates on a digitally-modulated signal prior to its conversion to analog form. The compressed, converted signal is transmitted through a dispersive channel, received, and converted back into digital form. The received signal is decompressed by a nonlinear equalizing element characterized by decompression function. The decompression function may be a one-dimensional power series with settable parameters, it may be the inverse of the compression function; and it may be a generalized expansion other than a power series. Decompression may be preceded by correction of the received signal for the effects of linear distortion.

Abstract: In a digital communication system or a digital storage system where digitally-modulated signals are transmitted in a signal path including a dispersive channel, a multistage equalizer has two or more stages connected in a sequence to correct for the effects of linear distortion and nonlinear distortion encountered during transmission through the signal path. The two or more stages are each characterized by a respective function, and the sequence is characterized by alternation of the functions of the two or more stages between linear and nonlinear.