Abstract: A LADAR system includes a transmitter configured to emit a directed optical signal. The LADAR system includes an optical aperture through which the directed optical signal is emitted. The optical aperture receives a return optical signal that is based on the directed optical signal. The system includes a detector to generate a measurement by comparing an attribute of the return optical signal to a predefined threshold. The measurement is based on an amount of backscatter in the return optical signal. The system includes an obstructive element that is controllable, based on the measurement, to move either into or out of a path of the return optical signal. The obstructive element is configured to block the return optical signal at least partly. The system includes a focal plane located in the path of the return optical signal. The obstructive element is disposed between the optical aperture and the focal plane.

Abstract: A LADAR system includes a transmitter configured to emit a directed optical signal. The LADAR system includes a shared optical aperture through which the directed optical signal is emitted. The shared optical aperture includes a first pupil plane. The shared optical aperture receives a return optical signal that is based on the directed optical signal. The system includes a mirror with a hole through which the directed optical signal passes. The mirror also reflects the return optical signal towards an imager. The imager receives the return optical signal and generates an image. The image is based on a portion of the return optical signal. The system also includes a partial aperture obscuration at a second pupil plane. The partial aperture obscuration may block a portion of internal backscatter in the return optical signal. The system also includes a focal plane to record the image.

Abstract: A global positioning system (GPS) receiver and system for determining a geographical location associated with the GPS receiver using less than four GPS signals. The system can comprise a constraint module configured to receive one or more constraints that describe at least one characteristic of a GPS receiver when a number of GPS satellites within a line of sight to the GPS receiver is below a defined value. The system can further comprise a pseudo range calculation module configured to calculate a plurality of pseudo ranges between the GPS receiver and the number GPS satellites, wherein the plurality of pseudo ranges are to various orbital positions of the GPS satellites over a period of time; and a geographical location module configured to determine the geographical location of the GPS receiver using the plurality of pseudo ranges and known constraints of motion associated with the GPS receiver.

Abstract: A LADAR system includes a transmitter configured to emit a directed optical signal. The LADAR system includes a shared optical aperture through which the directed optical signal is emitted. The shared optical aperture includes a first pupil plane. The shared optical aperture receives a return optical signal that is based on the directed optical signal. The system includes a mirror with a hole through which the directed optical signal passes. The mirror also reflects the return optical signal towards an imager. The imager receives the return optical signal and generates an image. The image is based on a portion of the return optical signal. The system also includes a partial aperture obscuration at a second pupil plane. The partial aperture obscuration may block a portion of internal backscatter in the return optical signal. The system also includes a focal plane to record the image.

Abstract: A LADAR system includes a transmitter configured to emit a directed optical signal. The LADAR system includes an optical aperture through which the directed optical signal is emitted. The optical aperture receives a return optical signal that is based on the directed optical signal. The system includes a detector to generate a measurement by comparing an attribute of the return optical signal to a predefined threshold. The measurement is based on an amount of backscatter in the return optical signal. The system includes an obstructive element that is controllable, based on the measurement, to move either into or out of a path of the return optical signal. The obstructive element is configured to block the return optical signal at least partly. The system includes a focal plane located in the path of the return optical signal. The obstructive element is disposed between the optical aperture and the focal plane.

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 system for tracking targets. A sequence of sensor observations is processed with two thresholds, including a first threshold, and a second threshold, higher than the first threshold. Signals that exceed the first threshold are identified as low-confidence target detections and stored for possible future use. When a signal exceeds the higher second threshold, it is identified as a high-confidence detection, and one or more candidate tracks are formed, including the high-confidence detection and one or more low-confidence detections from within a neighborhood of the high-confidence detection.

Abstract: Technology for determining a geographical location of a ground receiver is disclosed. A plurality of radio frequency (RF) signals from a plurality of RF signal carriers may be received at the ground receiver. The plurality of RF signal carriers may include satellites operated by a foreign entity or non-global positioning system (non-GPS) satellites. The ground receiver may measure a Doppler shift associated with each of the plurality of RF signals. The geographical location of the ground receiver may be determined in X, Y and Z coordinates based in part on the Doppler shift associated with each of the plurality of RF signals.

Abstract: A radio frequency system. In some embodiments, the system includes a one-bit receiver, and the one-bit receiver includes a digital pseudo random noise generator, a one-bit digital to analog converter, a power combiner, a one-bit analog to digital converter, and a digital subtraction circuit. The digital pseudo random noise generator produces a signal added to the received signal before analog to digital conversion. After analog to digital conversion, a delayed version of the dither is subtracted from the digital signal.

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: A radio frequency system. In some embodiments, the system includes a one-bit receiver, and the one-bit receiver includes a digital pseudo random noise generator, a one-bit digital to analog converter, a power combiner, a one-bit analog to digital converter, and a digital subtraction circuit. The digital pseudo random noise generator produces a signal added to the received signal before analog to digital conversion. After analog to digital conversion, a delayed version of the dither is subtracted from the digital signal.

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 digital receiver includes a digital synthesizer that generates a local oscillating (LO) signal at a selected frequency, and a signal mixer that receives an input signal and generates a mixed output signal in response to shifting a phase of the input signal based on the frequency of the LO signal. A multi-mode dynamic channelizer is selectively operable in a first mode and a second mode. The first mode generates a plurality of individual channels having a channel size defined by a bandwidth and a gain, and the second mode generates a parallelization of a selected channel. In response to operating in the second mode, the multi-mode dynamic channelizer adjusts at least one of the bandwidth and the gain of the selected channel based on the mixed output signal to change the channel size of the selected channel.

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: Devices and methods of providing response pulses in response to threat pulses are general described. The threat pulses are detected, identified and validity determined using reprogrammable firmware. Threat pulses are extracted from memory and the amplitude, frequency, phase, length and timing modified to generate a coherent set of superposed response pulses in response to the threat pulses. The modifications are calculated in situ using parameterization, rather than being based on tables. Multiple response pulses in response to different threat pulses are simultaneously generated, combined and transmitted in a single channel. Partial pulse capability and the capability to create a weighted and modulated composition of multiple response pulses is provided.

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.