摘要:
A synthetic array comprising a moving magnetic sensor that provides a signal representative of an array of magnetic sensors is coupled to a digital signal processor is used to break a magnetic dipole field into its components, and a magnetic signature of the present magnetic field is created. Predicted dipole signatures are precomputed for multiple magnetic orientations of the dipole at each of a plurality of range locations, expressed in terms of Anderson functions, which are a set of equations that decompose the magnetic field in each of the magnetic response locations, and are stored in a lookup table for reference. Input data measured by the moving synthetic array are processed and each magnetic value is predicted to process against background noise. A long term time average consistent with the relative motion of the dipole is computed using bandpass filtering of the signals from the synthetic array. The bandpass filtered data is used to update the predicted data so that anomalies and other non-dipole data is removed from the signals that are processed. The data are then expressed in terms of Anderson functions. The data are matched faltered, wherein it is correlated with the stored precomputed predicted dipole signatures. The correlation yields a set of values that is then thresholded. If a dipole is present at any of the locations, then the correlated normalized value computed as stated above will be higher than the chosen threshold. The dipole locations that are above the threshold are then displayed on a monitor showing the relative location and dipole orientation.
摘要:
An alignment process is applied to each sensor of an array of three axis magnetic sensors to electronically align the three axes of each sensor after the array has been deployed. The alignment process compensates for each sensor not being aligned perfectly with the earth's N-S, E-W and vertical magnetic field components. A field registration process is applied to each sensor of the array that uses a dipole moment detection and localization process and the alignment process combined with a known calibrated dipole source to define the shape of the array. The present invention improves the performance of the array of sensors in detecting magnetic anomalies by digitally compensating for sensor-to-sensor nonalignment and magnetic interferers within interfering range. The alignment process electronically aligns the three axes of each of the sensors to gain maximum performance from the sensor array. Using digital signal processing techniques reduces the physical deployment requirements on the sensors and their relative positions. The alignment process allows the use of three axis vector magnetometers in a distributed field with out having to lay each sensor in perfect alignment with the earth's three magnetic axis. This simplifies the deployment requirements and allows for maximizing the system performance.
摘要:
An array of magnetic sensors and a digital signal processor are used to break a target magnetic dipole field into its components, and a magnetic signature of the present magnetic field is created. Predicted target signatures are precomputed for multiple magnetic orientations of the dipole at each of a plurality of range locations, expressed in terms of Anderson functions, which are a set of equations that decompose the magnetic field in each of the magnetic response locations, and are stored in a lookup table for reference. Input data measured by the sensors are processed and each sensor's magnetic value is predicted to process against background noise using the other sensors of the array. A long term time average consistent with the relative motion of the target is computed using bandpass filtering of the signals from the sensor array. The bandpass filtered data is used to update the predicted data so that anomalies and other non-target data is removed from the signals that are processed. The data are then expressed in terms of Anderson functions. The data are matched filtered, wherein it is correlated with the stored precomputed predicted target signatures. The correlation yields a set of values that is then thresholded. If a target is present at any of the locations, then the correlated normalized value computed as stated above will be higher than the chosen threshold. The target locations that are above the threshold are then displayed on a monitor showing the relative location and dipole of orientation.
摘要:
A system and method for automating signal tracking, estimation of signal parameters, and extraction of signals from sonar data to detect weaker signals. A maximum a posteriori (MAP) algorithm processing provides a track output of the signal which is used as a guide or template to provide optimal spectral integration on an unstable or frequency varying line. The present invention includes track integration, parameter estimation, signal track normalization, and sequential signal detection. The present invention partitions the input band into frequency subwindows. For each subwindow, the strongest signal is tracked, its parameters are estimated, and then the signal is normalized (removed) from the subwindow. This is repeated until the entire subwindow set is processed. Then the subwindows, now with their strongest signals removed, are recombined to form one input band. This aggregated procedure represents one processing pass. In the next pass, the entire above procedure is repeated with either the same or new subwindow boundaries. This continues until a predetermined number of passes is completed. Sequential signal detection is provided from one data frame to the next, a problem that is beyond the capability of conventional systems and methods for tracking frequency lines of unknown frequency modulation and amplitude.
摘要:
Methods for low-temperature fusion are disclosed. In one embodiment, a symmetrical crystal lattice including a plurality of deuterons either absorbed or embedded in a heavy-electron material is selected. The method provides alternatives for initiating a vibration mode involving the deuterons on the crystal lattice that induces them to converge. The oscillating convergence of the deuterons is enhanced by the charge screening effect of electrons. The electron screening effect is in turn enhanced by the high effective-mass associated with the selected materials. The vibration modes are excited, for example, by applying an electrical stress, a uniform magnetic field, mechanical stress, non-uniform stress, acoustic waves, the de Haas van Alphen effect, electrical resistivity, infrared optical radiation, Raman scattering, or any combination thereof to the crystal lattice.
摘要:
A multistatic passive sonar is disclosed having a time-aligned source combiner, that exploits the cross-correlation between a target beam and all other beams to detect and measure the range of a target. This combiner performs long-term cross-correlation between the target beam and each individual source beam, and then aggregates the individual correlation results, time aligned based on the scenario geometry, and averaged to enhance the composite signal-to-noise ratio of the range measurement. In doing so, innocuous acoustic sources may be opportunistically exploited as if the array were part of a multi-static, active (e.g., sonar) system.
摘要:
A method for compensating for lateral distortion in a moving linear array using a frequency domain beamformer, comprising the steps of measuring the instantaneous lateral distortion of the linear array at discrete points along the array, corresponding to array element locations, calculating a shading weight for each of the discrete points along the array, corresponding to array element locations based on the instantaneous lateral distortion at each said point and calculating the compensated beam magnitude by multiplying said shading weight into the frequency domain beamformer equation.
摘要:
An adaptive processor which uses the successive range and Doppler outputs of a conventional matched-filter to improve the signal-to-noise ratio for non white noise/clutter. The adaptive processor minimizes the output for a given range and Doppler cell with the constraint that the response to signals returning with specified range and Doppler offsets, with respect to the center of the range-Doppler cell, each have specified values. Weights are derived which can be applied to range-Doppler outputs in the neighborhood of the range-Doppler cell to minimize its output subject to the constraints. The weights depend on an estimate of the cross-covariance matrix of the various outputs of the range-Doppler cells that are to be weighted. The constraint parameters are specified in terms of the ambiguity function of the transmitted waveform. Synthetically generated covariance matrices or combinations of measured and synthetic matrices can also be used to produce desired modifications to the resulting range-Doppler response of the adapted process.
摘要:
Dipole detection and localization systems and methods employing improved processing techniques. The first processing technique provides for higher spatial resolution by implementing maximum likelihood beamforming processing to detect and locate a dipole in a manner analogous to the processing of wave propagation phenomena. The high resolution technique is comprised of using data derived from an array of magnetic sensors that is arranged in the form of a vector of coefficients in lieu of a matrix. This vector can be either the magnetic field components or the Anderson function expansion coefficients and is used to form a dyadic matrix, to which a multiple of an identity matrix is added to prevent singularity. The second improvement uses more than three Anderson function expansions to achieve detection and localization of the dipole. The use of more than three Anderson functions more effectively normalizes the noise dependence by providing better noise representations, and provides for detection and localization of multipoles. The third improvement provides for multiple-pass multiple-target processing of data measured by the array of sensors. First, the location of the largest dipole in the field-space of the array is determined, and its moment and orientation are determined. The field due to a dipole at that location and orientation is then removed from the measurement data and the process is repeated. The field is removed by subtracting out its contribution at each of the sensors in the array, and then estimating the location of the next largest dipole. Simulations have shown that this process provides the ability to resolve multiple dipoles, when applied as many times as is needed.