Abstract: In examples, Time-Reversal (TR) Orthogonal Frequency-Division Multiplexing (OFDM) communications employ adaptive filtering on a per-subcarrier basis. Matched filtering is used for subcarriers with poor transmission properties (such as relatively high channel attenuation), while inverse filtering is used for subcarriers with relatively good transmission properties (such as relatively low channel attenuation). Modulation order may be reduced for the subcarriers with poor properties (relative to the subcarriers with good properties). The discovery of subcarrier properties may be performed through the channel state information measured and reconciled from single- and/or bi-directional TR sounding signals. The discovery may be repeated, for example, performed continually. In response to changes in traffic and other environmental conditions, the system may be reconfigured dynamically with different subcarriers selected for matched and inverse filtering.

Abstract: In examples, two arrays of Radio Frequency nodes achieve enhanced beamforming for communications between the arrays by successively sending sounding signals from one array to the other array. Each sounding signal sent by the first of the two arrays is beamformed through time reversal of an immediately preceding sounding signal received by the first array from the second array, and each sounding signal (except the initial sounding signal) sent by the second array is beamformed through time reversal of an immediately preceding sounding signal received by the second array from the first array. The initial sounding signal sent by the second array may be omnidirectional, beamformed through a guesstimate, random, predetermined, or determined through a search of the area where the arrays are located. With sufficient beamfocusing, the arrays may communicate by sending and receiving data from one array to the other array.

Abstract: Dynamic, untethered array nodes are frequency, phase, and time aligned/synchronized, and used to focus their transmissions of the same data coherently on a target or in the target's direction, using time reversal or directional beamforming. Information for alignment/synchronization may be sent from a master node of the array to other nodes, over non-RF links, such as optical and acoustic links. Some nodes may be connected directly to the master nodes, while other nodes may be connected to the master node through one or more transit nodes. A transit nodes may operate to (2) terminate the link when the alignment/synchronization information is intended for the node, and (2) pass through the alignment/synchronization information to another node without imposing its local clock properties on the passed through alignment/synchronization information. In this way, an end point node may be aligned/synchronized to the master node without a direct link between the two nodes.

Abstract: In examples, Radio Frequency nodes of an array are synchronized using Time-Reversal. A Master node (“Master”) of the array receives and captures a sounding signal emitted by a Slave node (“Slave”) of the array, downconverts it to baseband, Time-Reverses the downconverted signal, upconverts the Time-Reversed signal to the carrier frequency using the Master's clock so that the upconverted signal has phase property of the Master's clock, and transmits the resulting signal to the Slave. The Slave receives the signal from the Master, and adjusts the phase of the Slave's clock so that the phases of the two nodes are aligned. Once phases, frequencies, and time references of the array's nodes are aligned, the array may be used for coherent operation. In examples, the array is used to transmit Time-Reversed signals so that the signals from the array's nodes are spatially and temporally focused on a target.

Abstract: Dynamic, untethered array nodes are frequency, phase, and time aligned, and used to focus their transmissions of the same data coherently on a target, using time reversal. Alignment may be achieved separately for the radio frequency (RF) carriers and the data envelopes. Carrier alignment may be by phase conjugation. The data is distributed across the nodes. Data distribution and/or alignment may be performed by a Master node of the array. The nodes capture a sounding signal from the target, in the same time window. Each node converts the captured sounding signal to baseband, for example, using in-phase/quadrature downconversion. Each node stores the baseband samples of the sounding pulse. Each node convolves time-reversed samples of the sounding signal with the data, and upconverts the convolved data to radio frequency. The nodes emit their respective convolved and upconverted data so that the emissions focus coherently at the target.

Abstract: In examples, Radio Frequency Iterative Time-Reversal (RF-ITR) and singular value decomposition (SVD) are used by an array of nodes to characterize environment by identifying scatterer objects. The array may be ad hoc dynamic or stationary. The environment is cancelled from the RF-ITR by adjusting Time-Reversal (TR) prefilters, reducing illumination of the scatterer objects in the environment. This enables the RF-ITR process to focus on a moving target, which can then be sensed (discovered, identified, monitoring, tracked, and/or imaged). The moving target on which the RF-ITR process focuses may then be cancelled from the RF-ITR in the same way as the environment, allowing the RF-ITR to focus on another target. Multiple moving targets can thus be sensed. Defensive measures such as jamming may then be taken against the targets. ii The targets may be distinguished from the scatterer objects in the environment through differential, Doppler processing, and other classification techniques.

Abstract: In selected embodiments, a process of geolocation of a transmitter uses a receiver with an antenna array that is non-line-of-sight (NLoS) to the transmitter. A first plurality of scatterers within line-of-sight (LoS) of the array is located using multilateration based on time difference of arrival (TDoA) from the first scatterers, and applying a spatial consistency requirement. Time of emission/reflection from the first scatterers is also determined. The coordinates and timing of the first scatterers are used to locate either the transmitter or another set of scatterers, by applying multilateration to the TDoA at the first scatterers, and applying the spatial consistency requirement. The process is iteratively repeated until the transmitter is identified. The multilateration may be linearized without sacrificing precision. In each iteration, a non-singularity requirement is applied to ensure that the selected scatterers produce unambiguous results.

Abstract: Techniques, apparatus and systems for providing radio frequency wireless communications based on time reversal of the channel impulse response of an RF pulse in a transmission channel between an RF transmitter and an RF receiver to enhance reception and detection of an RF pulse at the RF receiver against various effects that can adversely affect and complicate the reception and detection of the RF pulse at the RF receiver.

Abstract: Methods, apparatus, and articles of manufacture make Geolocation of a source transmitter more difficult or impossible. Scatterers common to a source transmitter and an intended receiver are identified using a variety of techniques, such as iterative time reversal (ITR) and Singular Value Decomposition (SVD) of a scatter matrix. The source transmitter then uses time reversal and knowledge of the signatures of the scatterers to focus its transmissions on one or more of the scatterers, instead of the intended receiver. The source transmitter may have multiple antennas or antenna elements. The source transmitter and/or the intended receiver may include antenna elements with Near-Field Scatterers to enable spatial focusing below the diffraction limit at the frequencies of interest. The source transmitter may be a plurality of ad hoc nodes cooperating with each other.

Abstract: Selected embodiments use a relatively small image detector and a scanning mirror to obtain effective performance of a larger image detector. An imager with folded optics captures images of different field positions of a field of view (FOV), and stitches the images together for a larger image of the FOV. The stitched image is processed to identify portions of interest within the larger image, for example, using a cuing algorithm. The portions of interest are scanned again to capture enhanced quality images using, for example, longer dwell time for enhanced contrast. Another image of the FOV or a part of the FOV is stitched together using the enhanced quality images.

Abstract: Methods, apparatus, and articles of manufacture make Geolocation of a source transmitter more difficult or impossible. Scatterers common to a source transmitter and an intended receiver are identified using a variety of techniques, such as iterative time reversal (ITR) and Singular Value Decomposition (SVD) of a scatter matrix. The source transmitter then uses time reversal and knowledge of the signatures of the scatterers to focus its transmissions on one or more of the scatterers, instead of the intended receiver. The source transmitter may have multiple antennas or antenna elements. The source transmitter and/or the intended receiver may include antenna elements with Near-Field Scatterers to enable spatial focusing below the diffraction limit at the frequencies of interest. The source transmitter may be a plurality of ad hoc nodes cooperating with each other.

Abstract: Selected described embodiments include an imager providing concurrent wide field of view (WFOV) and foveated images. The imager includes a frontend optic configured to receive light from a scene. Corrective optics reduces distortions, and transmits the light to a beam splitter. One portion of the light exiting the beam splitter is focused on a WFOV image detector. A second portion of the light falls on a scanning mirror that can be configured to target a selected field position in the field of view. From the scanning mirror, the light passes through a magnifier and is corrected by an adaptive wavefront corrector. The corrector may be configured to correct aberrations corresponding to the particular field of view selected by the scanning mirror. The light from the wavefront corrector is focused on a foveated image detector. The images captured by the image detectors may be stored, processed, and transmitted to other systems.

Abstract: Dynamic, untethered array nodes with internal clocks are frequency, phase, and time aligned/synchronized, and used to focus their transmissions of the same payload data coherently on a target or in the target's direction, using time reversal or directional beamforming. Information for alignment/synchronization may be sent from a master node of the array to the slave nodes, over RF node-to-node links operating on different carrier or subcarrier frequencies. Additionally, the up- and down-communications on the RF links may use different frequencies. The RF links may also be used to distribute the payload data across the array. Because of frequency division on the RF links, interference is reduced or avoided, and the process of alignment/synchronization may be performed concurrently for several or all the slave nodes. The array may also operate collaboratively to receive data from the target.

Abstract: In selected embodiments, improved image restoration is realized using extensions of Wiener filtering combined with multiple image captures acquired after simple, fast reconfigurations of an optical imaging system. These reconfigurations may yield distinct OTF responses for each capture. The optical imaging system may reduce fabrication cost, power consumption, and/or system weight/volume by correcting significant optical aberrations. The system may be configured to perform independent correction of fields within the total field-of-regard. The system may also be configured to perform independent correction of different spectral bands.

Abstract: In selected embodiments, improved image restoration is realized using extensions of Wiener filtering combined with multiple image captures acquired after simple, fast reconfigurations of an optical imaging system. These reconfigurations may yield distinct OTF responses for each capture. The optical imaging system may reduce fabrication cost, power consumption, and/or system weight/volume by correcting significant optical aberrations. The system may be configured to perform independent correction of fields within the total field-of-regard. The system may also be configured to perform independent correction of different spectral bands.

Abstract: Dynamic, untethered array nodes are frequency, phase, and time aligned/synchronized, and used to focus their transmissions of the same data coherently on a target or in the target's direction, using time reversal or directional beamforming. Information for alignment/synchronization may be sent from a master node of the array to other nodes, over non-RF links, such as optical and acoustic links. Some nodes may be connected directly to the master nodes, while other nodes may be connected to the master node through one or more transit nodes. A transit nodes may operate to (2) terminate the link when the alignment/synchronization information is intended for the node, and (2) pass through the alignment/synchronization information to another node without imposing its local clock properties on the passed through alignment/synchronization information. In this way, an end point node may be aligned/synchronized to the master node without a direct link between the two nodes.

Abstract: Techniques, apparatus and systems for providing radio frequency wireless communications based on time reversal of the channel impulse response of an RF pulse in a transmission channel between an RF transmitter and an RF receiver to enhance reception and detection of an RF pulse at the RF receiver against various effects that can adversely affect and complicate the reception and detection of the RF pulse at the RF receiver.

Abstract: Techniques, apparatus and systems to provide carrier signal transmission in reciprocal transmission architecture networks for optical communications.

Abstract: Dynamic, untethered array nodes are frequency, phase, and time aligned, and used to focus their transmissions of the same data coherently on a target, using time reversal. Alignment may be achieved separately for the radio frequency (RF) carriers and the data envelopes. Carrier alignment may be by phase conjugation. The data is distributed across the nodes. Data distribution and/or alignment may be performed by a Master node of the array. The nodes capture a sounding signal from the target, in the same time window. Each node converts the captured sounding signal to baseband, for example, using in-phase/quadrature downconversion. Each node stores the baseband samples of the sounding pulse. Each node convolves time-reversed samples of the sounding signal with the data, and upconverts the convolved data to radio frequency. The nodes emit their respective convolved and upconverted data so that the emissions focus coherently at the target.

Abstract: Techniques, apparatuses and systems for providing communications based on time reversal of a channel impulse response of a pulse in a transmission channel between a transmitter and a receiver to enhance reception and detection of a pulse at the receiver against various effects that can adversely affect and complicate the reception and detection of the pulse at the receiver.