Abstract: A system and method for detecting targets with radar signals are disclosed which include a receiver configured to receive a radar signal and generate a first return vector having four elements representing four channels of a full-polarimetric radar reading, and a four-dimensional polarization filter applied to the first return vector, the four-dimensional polarization filter configured to arrange the first return vector in a column of four elements according to polarimetric components associated with of respective transmit/receive channels, take an inner product of a selected vector with the column, derive a projection coefficient by dividing the inner product by a magnitude of the selected vector, and produce an output by subtracting a product of the projection coefficient and the selected vector from the column.

Abstract: A system for calibrating multi-port radio devices may include a radio device and circuitry. In one example, the radio device may include a reference port and a plurality of ports characterized by one or more radio-frequency (RF) imbalances relative to one another. Additionally or alternatively, the circuitry may be configured to calibrate the radio device by compensating for the one or more RF imbalances based at least in part on the reference port. Various other apparatuses, systems, and methods are also disclosed.

Abstract: A system and method for detecting targets with radar signals are disclosed which include a receiver configured to receive a radar signal on orthogonally-polarized channels and generate a receiver return vector from the received radar signal, a range filter configured to filter reflections in the receiver return vector at a selected range bin, and a polarization filter configured to filter an identified interference signal from a return of the range filter.

Abstract: A system for improving resolution of frequency-dependent objects in radar contexts may include a radar device configured to transmit a radar signal and receive a return of the radar signal. In one example, the system may also include circuitry configured to generate a first data set representative of a range profile based at least in part on the return and/or generate a second data set representative of the range profile by applying at least one shift to the first data set. Additionally or alternatively, the circuitry may be further configured to characterize at least one frequency-dependent object detected in the range profile based at least in part on the first data set and the second data set. Various other apparatuses, systems, and methods are also disclosed.

Abstract: Devices and techniques for authenticating wireless communications are disclosed. In some embodiments, the techniques can be performed by a network access point that includes a receiver to receive a wireless signal from a remote device. The network access point can also include a processor to calculate polarization data for the wireless signal and to determine whether the polarization data includes at least one characteristic that corresponds to a characteristic of a stored authenticated polarization signature.

Abstract: Methods and systems for sensing a physiological characteristic of a subject. At least one receiver antenna can be provided in proximity to a portion of the subject's body to obtain at least one receiver signal resulting from at least one transmitter signal that has propagated to the receiver antenna and has been reflected, diffracted, scattered, or transmitted by or through the portion of the subject's body. One or more coherent signal pairs can be formed. Then, amplitude and phase information of a plurality of frequency components for each signal pair can be determined. A set of comparison values can be determined for each signal pair by comparing respective frequency component phases and respective frequency component amplitudes of the signals. Physiological characteristics of the subject can then be determined from these comparison values.

Abstract: Devices and techniques for authenticating wireless communications are disclosed. In some embodiments, the techniques can be performed by a network access point that includes a receiver to receive a wireless signal from a remote device. The network access point can also include a processor to calculate polarization data for the wireless signal and to determine whether the polarization data includes at least one characteristic that corresponds to a characteristic of a stored authenticated polarization signature.

Abstract: Systems and methods for improving isolation between a cosite transmitter-receiver system. The transmitter may send a first plurality of transmit signals from multiple transmit ports. The first plurality of transmit signals may be related to one another by a first set of complex weights. The receiver may detect channel-impaired versions of the first plurality of transmit signals at one or more receive ports. The receiver may analyze channel-impaired versions of the first plurality of transmit signals to estimate channel state information. The transmitter may use the channel state information to determine a second set of complex weights which will reduce the power received at one or more ports of the receiver when applied to a second plurality of transmit signals. The second set of complex weights may vary with frequency.

Abstract: A signal source association method and receiver. A receiver can be used to detect a plurality of signals transmitted from a plurality of transmission sources. The receiver can determine amplitude and phase information for a plurality of frequency components of each of the plurality of signals. The receiver can also determine a set of comparison values by comparing the respective amplitude and phase information from one or more pairs of the plurality of signals. Finally, the receiver can associate one of the signals with one of the plurality of transmission sources using the set of comparison values. The comparison values can comprise Stokes parameters and the one or more pairs of the plurality of signals can comprise a pair of orthogonally polarized signals or a pair of signals detected from spatially-separated antennas.

Abstract: A multi-port transmitter can synthesize and send a first plurality of transmit signals having a separability characteristic which permits them to be differentiated from one another. A receiver can then detect one or more receiver signals which include one or more combinations of received versions of the first plurality of transmit signals. The receiver may use the separability characteristic to determine the received versions of the first plurality of transmit signals from the one or more receiver signals. Then, the receiver may determine an estimated signal corresponding to the estimated receiver response to a second plurality of virtual transmit signals which comprise a combination of the first plurality of transmit signals. Determining the estimated signal may include forming a combination of the received versions of the first plurality of transmit signals.

Abstract: Systems and methods for analyzing a characteristic of a transmitter, a receiver, or a propagation channel are disclosed. At least one receiver signal resulting from at least one transmitter signal that has propagated through a propagation channel can be obtained. A first signal pair can be formed from a first receiver signal and a first transmitter signal, or from first and second receiver signals obtained from spatially-separated receiver antennas, or from first and second receiver signals which are attributable to different transmitter signals. Amplitude and phase information of a plurality of frequency components for each signal in the first signal pair can be determined. A set of comparison values for the first signal pair can be determined by comparing respective frequency component phases or respective frequency component amplitudes. A characteristic of the set of comparison values can then be analyzed.

Abstract: Methods and systems for sensing a physiological characteristic of a subject. At least one receiver antenna can be provided in proximity to a portion of the subject's body to obtain at least one receiver signal resulting from at least one transmitter signal that has propagated to the receiver antenna and has been reflected, diffracted, scattered, or transmitted by or through the portion of the subject's body. One or more coherent signal pairs can be formed. Then, amplitude and phase information of a plurality of frequency components for each signal pair can be determined. A set of comparison values can be determined for each signal pair by comparing respective frequency component phases and respective frequency component amplitudes of the signals. Physiological characteristics of the subject can then be determined from these comparison values.

Abstract: Systems and methods for monitoring rotating machinery are disclosed. Transmitter and receiver antennas can be provided with access to the rotating machinery. At least one receiver signal resulting from at least one transmitter signal that has propagated through a portion of the rotating machinery can be obtained. A first signal pair can be formed from a first receiver signal and a first transmitter signal, or from first and second receiver signals obtained from spatially-separated receiver antennas, or from first and second receiver signals which are attributable to different transmitter signals. Amplitude and phase information of a plurality of frequency components for each signal in the first signal pair can be determined. A set of comparison values for the first signal pair can be determined by comparing respective frequency component phases or respective frequency component amplitudes. A characteristic of the rotating machinery can then be analyzed using the comparison values.

Abstract: A system and method for detection of complex sinusoidal signals. The method can include obtaining a set of complex-valued samples of one or more signals, in the presence of unknown noise, using a plurality of sensors. The presence of ? candidate complex sinusoids can be assumed. Then, ? candidate complex sinusoids in the set of complex-valued samples can be estimated. The method can include comparing a measurement of the energy of the ? estimated candidate complex sinusoids with a threshold value. Based on the comparison, a determination can be made whether to assume a different number of candidate complex sinusoids and repeat the estimation and the comparison steps, or to specify the estimated ? candidate complex sinusoids as detected complex sinusoids. The threshold value can be determined using a penalty value which reduces the probability of overestimating the number of complex sinusoids.

Abstract: Systems and methods for performing energy efficient communication. A transceiver for use in a point-to-point packet-based communication link with packet erasures is described. The transceiver can include a data source to provide bits of data for transmission to a remote device. The transceiver can map the bits of data to symbols in a constellation according to a modulation scheme and can provide the symbols on one or more subcarriers. The transceiver can include co-located orthogonally polarized antenna elements or spatially separated antenna elements or both. The symbols can be transmitted in packets via one or more of the antenna elements. The transceiver can determine a metric of average transmit energy per bit successfully decoded, and not erased, at the remote device and can adjust transmission powers at the antenna elements to reduce the average transmit energy per successfully decoded and unerased bit.

Abstract: A system and method of identifying changes utilizing radio frequency polarization includes receiving a reflected and/or transmitted polarized radio frequency signal at a receiver, filtering, amplifying and conditioning the received signal, converting the received signal from an analog format to a digital format, processing the digital signal to elicit a polarization mode dispersion feature of the received signal, and comparing the polarization mode dispersion features to a known calibration to detect a change in a characteristic of the target object.

Abstract: Systems and methods for improving isolation between a cosite transmitter-receiver system. The transmitter may send a first plurality of transmit signals from multiple transmit ports. The first plurality of transmit signals may be related to one another by a first set of complex weights. The receiver may detect channel-impaired versions of the first plurality of transmit signals at one or more receive ports. The receiver may analyze channel-impaired versions of the first plurality of transmit signals to estimate channel state information. The transmitter may use the channel state information to determine a second set of complex weights which will reduce the power received at one or more ports of the receiver when applied to a second plurality of transmit signals. The second set of complex weights may vary with frequency.

Abstract: A multi-port transmitter can synthesize and send a first plurality of transmit signals having a separability characteristic which permits them to be differentiated from one another. A receiver can then detect one or more receiver signals which include one or more combinations of received versions of the first plurality of transmit signals. The receiver may use the separability characteristic to determine the received versions of the first plurality of transmit signals from the one or more receiver signals. Then, the receiver may determine an estimated signal corresponding to the estimated receiver response to a second plurality of virtual transmit signals which comprise a combination of the first plurality of transmit signals. Determining the estimated signal may include forming a combination of the received versions of the first plurality of transmit signals.

Abstract: Systems and methods for monitoring rotating machinery are disclosed. Transmitter and receiver antennas can be provided with access to the rotating machinery. At least one receiver signal resulting from at least one transmitter signal that has propagated through a portion of the rotating machinery can be obtained. A first signal pair can be formed from a first receiver signal and a first transmitter signal, or from first and second receiver signals obtained from spatially-separated receiver antennas, or from first and second receiver signals which are attributable to different transmitter signals. Amplitude and phase information of a plurality of frequency components for each signal in the first signal pair can be determined. A set of comparison values for the first signal pair can be determined by comparing respective frequency component phases or respective frequency component amplitudes. A characteristic of the rotating machinery can then be analyzed using the comparison values.

Abstract: Systems and methods for analyzing a characteristic of a transmitter, a receiver, or a propagation channel are disclosed. At least one receiver signal resulting from at least one transmitter signal that has propagated through a propagation channel can be obtained. A first signal pair can be formed from a first receiver signal and a first transmitter signal, or from first and second receiver signals obtained from spatially-separated receiver antennas, or from first and second receiver signals which are attributable to different transmitter signals. Amplitude and phase information of a plurality of frequency components for each signal in the first signal pair can be determined. A set of comparison values for the first signal pair can be determined by comparing respective frequency component phases or respective frequency component amplitudes. A characteristic of the set of comparison values can then be analyzed.