Abstract: A system is provided that includes multiple analog-to-digital converters (ADCs), multiple antennas, and one or more processors. The one or more processors are configured, in a first mode of operation, to receive from the multiple ADCs samples of emissions received by one of the antennas and identify a signal of interest. The one or more processors are configured, in a second mode of operation, receive from the multiple ADCs samples of emissions received by the multiple antennas and identify an angle of arrival for the signal of interest.

Abstract: A direction finding interferometer shares receivers among antennas and aperiodically switches between those antennas. The phase differences for a subset of the antenna pairs are measured for each pulse and the results are combined with the results from subsequent pulses to resolve ambiguities. An angle of arrival common to two subsets of angles of arrival is the unambiguous angle of arrival.

Abstract: An advance warning system including an antenna pair and an RWR system to receive first, second and third signals for computing a frequency for all the signals and a phase difference between the signals. If the frequencies are within a threshold frequency difference and the phase difference is less than a threshold phase difference, two signals can be associated. If the frequencies are not within the threshold frequency difference, the RWR system generates a set of ambiguous angle of arrival AoA for the signals and correlates the two sets of ambiguous AoA to determine if there is a common AoA. If there is a common AoA, a third set of ambiguous angle of arrival AoA for a third signal is generated to determine if the three sets correlate. If there is a common AoA for all three signals, the three signals are associated.

Abstract: All of a plurality of analog-to-digital converters (ADCs) each operating in a first mode of operation within a spectrum of interest sample a signal received at one of a plurality of antennas, with the outputs of the ADCs processed to detect signals of interest based on a threshold. For each of the plurality of antennas, a corresponding one of the plurality of ADCs operating in a second mode of operation samples signals received at the one of the antennas such that signals received are sampled at all of the plurality of antennas, with the outputs of the ADCs processed to calculate an angle of arrival for at least one detected signal of interest using phase interferometry. Bandpass or non-uniform under-sampling may be employed to sample all of the antennas at a relatively low data rate.

Abstract: A system is provided that includes multiple analog-to-digital converters (ADCs), multiple antennas, and one or more processors. The one or more processors are configured, in a first mode of operation, to receive from the multiple ADCs samples of emissions received by one of the antennas and identify a signal of interest. The one or more processors are configured, in a second mode of operation, receive from the multiple ADCs samples of emissions received by the multiple antennas and identify an angle of arrival for the signal of interest.

Abstract: A direction finding interferometer shares receivers among antennas and aperiodically switches between those antennas. The phase differences for a subset of the antenna pairs are measured for each pulse and the results are combined with the results from subsequent pulses to resolve ambiguities. An angle of arrival common to two subsets of angles of arrival is the unambiguous angle of arrival.

Abstract: An advance warning system including an antenna pair and an RWR system to receive first, second and third signals for computing a frequency for all the signals and a phase difference between the signals. If the frequencies are within a threshold frequency difference and the phase difference is less than a threshold phase difference, two signals can be associated. If the frequencies are not within the threshold frequency difference, the RWR system generates a set of ambiguous angle of arrival AoA for the signals and correlates the two sets of ambiguous AoA to determine if there is a common AoA. If there is a common AoA, a third set of ambiguous angle of arrival AoA for a third signal is generated to determine if the three sets correlate. If there is a common AoA for all three signals, the three signals are associated.

Abstract: Systems and methods for determining an angle of arrival (AoA) of a signal received from an emitters at a pair of antennas spaced apart by more than one half wavelength of the received signal. Features of the signal are determined, including a phase difference between signal components detected at the antennas, and a time difference of arrival (TDOA) having a known measurement error. A set of TDOA possibilities bounded by the known TDOA measurement error and a set of AoA estimates using phase interferometry (PI) within the range are calculated. The TDOA set is iteratively reduced to determine a precise AoA estimate for the emitter.

Abstract: Methods and systems for determining an angle of arrival (AoA) of a RF emitter signal utilizing phase comparisons between pairs of antennas from among two closely spaced antenna elements and a third antenna element fixedly positioned more distant, and a combination of TDOA and PI techniques, to resolve PI ambiguities. Overlapping AoA ambiguity patterns with different angular spacings may be resolved by TDOA techniques. A span of TDOA AoA possibilities is obtained, centered at a solution to a TDOA angle calculation and bounded by a known TDOA measurement error range.

Abstract: Antenna systems and methods of detecting RF signals received from a field of view (FOV) are presented, employing intersecting fan beam pluralities formed by associated columns or rows of antenna elements and cross-correlation of components of the received radiation from the fan beam pluralities. The intersecting fan beams pluralities form pencil-like beams persistently spanning the FOV as desired. Angle(s) of arrival and frequency channels of incident RF signals may be determined through power estimation, ranking and filtering, and/or frequency channelization techniques. Higher sensitivity beams may be cued to more accurately characterize the incident signals.

Abstract: An imaging spectrometer and method are provided. In one example, the imaging spectrometer includes foreoptics positioned to receive electromagnetic radiation from a scene, a diffraction grating positioned to receive the electromagnetic radiation from the foreoptics and configured to disperse the electromagnetic radiation into a plurality of spectral bands, each spectral band corresponding to a diffraction grating order of the diffraction grating, and a single-band focal plane array configured to simultaneously receive from the diffraction grating overlapping spectra corresponding to at least two diffraction grating orders.

Abstract: Systems and methods for determining an angle of arrival (AoA) of a signal received from an emitters at a pair of antennas spaced apart by more than one half wavelength of the received signal. Features of the signal are determined, including a phase difference between signal components detected at the antennas, and a time difference of arrival (TDOA) having a known measurement error. A set of TDOA possibilities bounded by the known TDOA measurement error and a set of AoA estimates using phase interferometry (PI) within the range are calculated. The TDOA set is iteratively reduced to determine a precise AoA estimate for the emitter.

Abstract: Methods and systems for determining an angle of arrival (AoA) of a RF emitter signal utilizing phase comparisons between pairs of antennas from among two closely spaced antenna elements and a third antenna element fixedly positioned more distant, and a combination of TDOA and PI techniques, to resolve PI ambiguities. Overlapping AoA ambiguity patterns with different angular spacings may be resolved by TDOA techniques. A span of TDOA AoA possibilities is obtained, centered at a solution to a TDOA angle calculation and bounded by a known TDOA measurement error range.

Abstract: All of a plurality of analog-to-digital converters (ADCs) each operating in a first mode of operation within a spectrum of interest sample a signal received at one of a plurality of antennas, with the outputs of the ADCs processed to detect signals of interest based on a threshold. For each of the plurality of antennas, a corresponding one of the plurality of ADCs operating in a second mode of operation samples signals received at the one of the antennas such that signals received are sampled at all of the plurality of antennas, with the outputs of the ADCs processed to calculate an angle of arrival for at least one detected signal of interest using phase interferometry. Bandpass or non-uniform under-sampling may be employed to sample all of the antennas at a relatively low data rate.

Abstract: An imaging spectrometer and method are provided. In one example, the imaging spectrometer includes foreoptics positioned to receive electromagnetic radiation from a scene, a diffraction grating positioned to receive the electromagnetic radiation from the foreoptics and configured to disperse the electromagnetic radiation into a plurality of spectral bands, each spectral band corresponding to a diffraction grating order of the diffraction grating, and a single-band focal plane array configured to simultaneously receive from the diffraction grating overlapping spectra corresponding to at least two diffraction grating orders.

Abstract: A system for determining a direction for an electromagnetic signal. The system includes a receiving array antenna, including a plurality of antenna elements, each antenna element having a position in the receiving array antenna; a digitizer configured to receive an analog signal from each of the antenna elements, and to sample and digitize each of the analog signals to form a sequence of digitized samples from each of the analog signals; and a processing unit. The processing unit is configured to receive the sequences of sample values from the digitizer; and, for each direction of a plurality of hypothesized directions: combine the sample values from the plurality of antenna elements to form a single time record; fit the single time record with a combination of one or more functions of time; and identify a direction at which a measure of the magnitude of the linear combination is greatest.

Abstract: Antenna systems and methods of detecting RF signals received from a field of view (FOV) are presented, employing intersecting fan beam pluralities formed by associated columns or rows of antenna elements and cross-correlation of components of the received radiation from the fan beam pluralities. The intersecting fan beams pluralities form pencil-like beams persistently spanning the FOV as desired. Angle(s) of arrival and frequency channels of incident RF signals may be determined through power estimation, ranking and filtering, and/or frequency channelization techniques. Higher sensitivity beams may be cued to more accurately characterize the incident signals.

Abstract: A system for determining a direction for an electromagnetic signal. The system includes a receiving array antenna, including a plurality of antenna elements, each antenna element having a position in the receiving array antenna; a digitizer configured to receive an analog signal from each of the antenna elements, and to sample and digitize each of the analog signals to form a sequence of digitized samples from each of the analog signals; and a processing unit. The processing unit is configured to receive the sequences of sample values from the digitizer; and, for each direction of a plurality of hypothesized directions: combine the sample values from the plurality of antenna elements to form a single time record; fit the single time record with a combination of one or more functions of time; and identify a direction at which a measure of the magnitude of the linear combination is greatest.

Abstract: A method includes generating a sampling signal having a non-uniform sampling interval and sampling a received signal with an analog-to-digital converter (ADC) using the sampling signal. The method also includes mapping the sampled received signal onto a frequency grid of sinusoids, where each sinusoid has a signal amplitude and a signal phase. The method further includes estimating the signal amplitude and the signal phase for each sinusoid in the frequency grid. In addition, the method includes computing an average background power level and detecting signals with power higher than the average background power level. The non-uniform sampling interval varies predictably.

Abstract: Methods and systems are provided for estimating background spectral content in a hyperspectral imaging (HSI) scene. A HSI processor computes a scene covariance matrix for each of a plurality of sparsely sampled pixel sets, identifies and removes the spectral content of contaminating pixels from the covariance matrices, and checks the consistency among the plurality of decontaminated covariance matrices, iteratively re-sampling and re-computing said matrices until an acceptable consistency is achieved, and then computes a final decontaminated covariance matrix representative of the background spectral content of the scene. Alternate approaches to pixel sampling, and/or using fewer spectral dimensions than are available for the pixels are presented.