Abstract: Described herein is a retroreflective underwater backscatter node comprising a receiver that receives an incoming acoustic signal from a first direction; a reflector that reflects back an incoming acoustic signal in a second direction; and a modulator coupled to the reflector to modulate the reflected incoming acoustic signal as a back-scattered signal. In some embodiments, the first direction and second direction are substantially the same such that the retroreflective underwater backscatter node retro-directs an incoming acoustic signal as a back-scattered signal and incoming and back-scattered acoustic signals propagate in the same but substantially opposite directions.

Abstract: According to one aspect of the disclosure, a mobile augmented reality (AR) system can include: a receiver configured to receive radio frequency (RF) signals from one or more items located within an environment; a tracking module configured to generate tracking data responsive to a location of the system within the environment over time; a display device; and one or more processors configured to determine a location of at least one of the one or more items within the environment using the received RF signals and the tracking data, and generate a visual representation of the location of the at least one item for display on the display device.

Abstract: According to one aspect of the disclosure, a method for measuring stress of a subject includes: transmitting, by a sensor, a wireless signal within an environment comprising the subject: measuring reflections of the wireless signal to generate a physiological signal responsive to changes in distance between the subject and the sensor over time: processing the physiological signal to extract feature data of the subject; and providing the feature data as input to a stress classification network to determine a stress level of the subject.

Abstract: An ultra-wide bandwidth acoustic transducer may include multiple layers, including an inner piezoelectric layer, a polymer coupling layer and an outer piezoelectric layer. The polymer layer may be located between, and may be bonded to, the inner and outer piezoelectric layers. The transducer may have multiple eigenfrequencies of vibration. These eigenfrequencies may include primary resonant frequencies of the inner and outer piezoelectric layers respectively and may also include resonant frequencies that arise due to coupling between the layers. An acoustic backscatter system may employ such a transducer in backscatter nodes as well as in a transmitter. The multiple eigenfrequencies may enable the system to perform spread-spectrum communication at a high throughput. These multiple eigenfrequencies may also enable each backscatter node to shift frequency of an uplink signal, which in turn may enable the system to mitigate self-interference and to decode concurrent signals from multiple backscatter nodes.

Abstract: Described is the design, implementation, and evaluation of a robotic system configured to search for and retrieve RFID-tagged items in line-of-sight, non-line-of-sight, and fully-occluded settings. The robotic system comprises a robotic arm having a camera and antenna strapped around a portion thereof (e.g. a gripper) and a controller configured to receive information from the camera and (radio frequency) RF information via the antenna and configured to use the information provided thereto to implement a method that geometrically fuses at least RF and visual information. This technique reduces uncertainty about the location of a target object even when the object is fully occluded. Also described is a reinforcement-learning network that uses fused RF-visual information to efficiently localize, maneuver toward, and grasp a target object.

Abstract: A communication system may communicate by backscattered acoustic signals that propagate through a liquid or solid. In this system, one or more transmitters may transmit acoustic signals that travel to, and are reflected by, an acoustic backscatter node. The backscatter node may modulate the amplitude and/or phase of the reflected acoustic signals, by varying the acoustic reflectance of a piezoelectric transducer onboard the node. The modulated signals that reflect from the backscatter node may travel to a microphone and may be decoded. The backscatter node may include sensors, and the uplink signals may encode sensor readings. The backscatter node may harvest energy from the downlink acoustic signals, enabling the node and the sensors to be battery-free. Multiple backscatter nodes may communicate concurrently at different acoustic frequencies. To achieve this, each node may have a matching circuit with a different resonant frequency.

Abstract: A control system and method locates a partially or fully occluded target object in an area of interest. The location of the occluded object may be determined using visual information from a vision sensor and RF-based location information. Determining the location of the target object in this manner may effectively allow the control system to “see through” obstructions that are occluding the object. Model-based and/or deep-learning techniques may then be employed to move a robot into range relative to the target object to perform a predetermined (e.g., grasping) operation. This operation may be performed while the object is still in the occluded state or after a decluttering operation has been performed to remove one or more obstructions that are occluding light-of-sight vision to the object.

Abstract: A control system and method locates a partially or fully occluded target object in an area of interest. The location of the occluded object may be determined using visual information from a vision sensor and RF-based location information. Determining the location of the target object in this manner may effectively allow the control system to “see through” obstructions that are occluding the object. Model-based and/or deep-learning techniques may then be employed to move a robot into range relative to the target object to perform a predetermined (e.g., grasping) operation. This operation may be performed while the object is still in the occluded state or after a decluttering operation has been performed to remove one or more obstructions that are occluding light-of-sight vision to the object.

Abstract: Described herein is a retroreflective underwater backscatter node comprising a receiver that receives an incoming acoustic signal from a first direction; a reflector that reflects back an incoming acoustic signal in a second direction; and a modulator coupled to the reflector to modulate the reflected incoming acoustic signal as a back-scattered signal. In some embodiments, the first direction and second direction are substantially the same such that the retroreflective underwater backscatter node retro-directs an incoming acoustic signal as a back-scattered signal and incoming and back-scattered acoustic signals propagate in the same but substantially opposite directions.

Abstract: A handheld system radio frequency identification (RFID) system for fine-grained RFID localization of an RFID target. Also disclosed is a mechanism for localizing RFID targets at all orientations through software-controlled polarization of two LP antennas. The system may detect an RFID target using a generated circularly polarized (CP) RF signal and accurately localize the RFID target using a generated linearly polarized (LP) signal. The disclosed systems and techniques discover and localize RFID concurrently and regardless of RFID target orientation.

Abstract: According to one aspect of the disclosure, a mobile augmented reality (AR) system can include: a receiver configured to receive radio frequency (RF) signals from one or more items located within an environment; a tracking module configured to generate tracking data responsive to a location of the system within the environment over time; a display device; and one or more processors configured to determine a location of at least one of the one or more items within the environment using the received RF signals and the tracking data, and generate a visual representation of the location of the at least one item for display on the display device.

Abstract: A contactless sensor includes a cardiac beamformer, a wireless-to- seismocardiogram translator, and an automatic labeler. The cardiac beamformer determines at least one beam for receiving wireless signals generated based on movement of a heart. The at least one beam is generated based on phase information and a heart signal extracted from a time-domain signal generated from one or more receiver elements. The wireless-to-seismocardiogram translator implements a convolutional neural network to transform time-series data detected from the at least one beam to a seismocardiogram. The automatic labeler identifies and labels one or more micro-cardiac events in the time-series data. The cardiac beamformer may be considered an optional feature in one or more implementations.

Abstract: An ultra-wide bandwidth acoustic transducer may include multiple layers, including an inner piezoelectric layer, a polymer coupling layer and an outer piezoelectric layer. The polymer layer may be located between, and may be bonded to, the inner and outer piezoelectric layers. The transducer may have multiple eigenfrequencies of vibration. These eigenfrequencies may include primary resonant frequencies of the inner and outer piezoelectric layers respectively and may also include resonant frequencies that arise due to coupling between the layers. An acoustic backscatter system may employ such a transducer in backscatter nodes as well as in a transmitter. The multiple eigenfrequencies may enable the system to perform spread-spectrum communication at a high throughput. These multiple eigenfrequencies may also enable each backscatter node to shift frequency of an uplink signal, which in turn may enable the system to mitigate self-interference and to decode concurrent signals from multiple backscatter nodes.

Abstract: An ultra-wide bandwidth acoustic transducer may include multiple layers, including an inner piezoelectric layer, a polymer coupling layer and an outer piezoelectric layer. The polymer layer may be located between, and may be bonded to, the inner and outer piezoelectric layers. The transducer may have multiple eigenfrequencies of vibration. These eigenfrequencies may include primary resonant frequencies of the inner and outer piezoelectric layers respectively and may also include resonant frequencies that arise due to coupling between the layers. An acoustic backscatter system may employ such a transducer in backscatter nodes as well as in a transmitter. The multiple eigenfrequencies may enable the system to perform spread-spectrum communication at a high throughput. These multiple eigenfrequencies may also enable each backscatter node to shift frequency of an uplink signal, which in turn may enable the system to mitigate self-interference and to decode concurrent signals from multiple backscatter nodes.

Abstract: A transceiver may wirelessly transmit a communication signal at a first frequency and a sensing signal at a second frequency. The communication signal may include a command that causes a backscatter node to modulate impedance of an antenna, and thereby modulate reflectivity of the backscatter node. The communication signal may also deliver wireless power to the backscatter node. While the impedance is being modulated in response to the command, the transceiver may transmit the sensing signal and measure wireless reflections. The power of the sensing signal may be much lower than that of the communication signal. The transceiver may frequency hop the sensing signal in a wide band of frequencies and take measurements at each frequency in the hopping. Based on the measurements, a computer may determine time-of-flight or phase of a reflected signal from the backscatter node and may estimate location of the backscatter node with sub-centimeter precision.

Abstract: Described is the design, implementation, and evaluation of a robotic system configured to search for and retrieve RFID-tagged items in line-of-sight, non-line-of-sight, and fully-occluded settings. The robotic system comprises a robotic arm having a camera and antenna strapped around a portion thereof (e.g. a gripper) and a controller configured to receive information from the camera and (radio frequency) RF information via the antenna and configured to use the information provided thereto to implement a method that geometrically fuses at least RF and visual information. This technique reduces uncertainty about the location of a target object even when the object is fully occluded. Also described is a reinforcement-learning network that uses fused RF-visual information to efficiently localize, maneuver toward, and grasp a target object.

Abstract: A communication system may communicate by backscattered acoustic signals that propagate through a liquid or solid. In this system, one or more transmitters may transmit acoustic signals that travel to, and are reflected by, an acoustic backscatter node. The backscatter node may modulate the amplitude and/or phase of the reflected acoustic signals, by varying the acoustic reflectance of a piezoelectric transducer onboard the node. The modulated signals that reflect from the backscatter node may travel to a microphone and may be decoded. The backscatter node may include sensors, and the uplink signals may encode sensor readings. The backscatter node may harvest energy from the downlink acoustic signals, enabling the node and the sensors to be battery-free. Multiple backscatter nodes may communicate concurrently at different acoustic frequencies. To achieve this, each node may have a matching circuit with a different resonant frequency.

Abstract: A communication system may communicate by backscattered acoustic signals that propagate through a liquid or solid. In this system, one or more transmitters may transmit acoustic signals that travel to, and are reflected by, an acoustic backscatter node. The backscatter node may modulate the amplitude and/or phase of the reflected acoustic signals, by varying the acoustic reflectance of a piezoelectric transducer onboard the node. The modulated signals that reflect from the backscatter node may travel to a microphone and may be decoded. The backscatter node may include sensors, and the uplink signals may encode sensor readings. The backscatter node may harvest energy from the downlink acoustic signals, enabling the node and the sensors to be battery-free. Multiple backscatter nodes may communicate concurrently at different acoustic frequencies. To achieve this, each node may have a matching circuit with a different resonant frequency.

Abstract: A control system and method locates a partially or fully occluded target object in an area of interest. The location of the occluded object may be determined using visual information from a vision sensor and RF-based location information. Determining the location of the target object in this manner may effectively allow the control system to “see through” obstructions that are occluding the object. Model-based and/or deep-learning techniques may then be employed to move a robot into range relative to the target object to perform a predetermined (e.g., grasping) operation. This operation may be performed while the object is still in the occluded state or after a decluttering operation has been performed to remove one or more obstructions that are occluding light-of-sight vision to the object.

Abstract: A system may sense the contents of a closed container, by analyzing a wireless signal that reflects from an RFID tag on the outside of the container. The frequency response of the tag's antenna may be affected by the relative permittivity of the contents and by the tag's environment. The frequency response may be measured in a line-of-sight environment and in a multipath environment. Channel estimates may be calculated, based on the measurements. Channel ratios may be calculated by dividing line-of-sight channel estimates by multipath channel estimates. The resulting channel ratios may be fed into a variational autoencoder, which in turn generates synthetic data that contains information about multipath environments but not the contents. The output of the variational autoencoder may be converted into synthetic channel estimates, which may in turn be employed for anomaly detection, or to train a classifier to classify contents of the container.