Massachusetts Institute of Technology

The Brigham and Women's Hospital, Inc.

Carnegie Mellon University

Fadel Adib

Yunfei Ma

Nicholas Selby

Dina Katabi

Zhihong Luo

Unsoo Ha

Junshan Leng

Carlo Giovanni Traverso

Reza Ghaffarivardavagh

Zachary Edward Kabelac

Qiping Zhang

Manish Singh

Alaa Khaddaj

Junsu Jang

Osvy Rodriguez

Sayed Saad Afzal

Tzu Ming Hsu

Tara Boroushaki

Zexuan Zhong

Christoph Steiger

Shyamnath Gollakota

Piotr Indyk

Haitham Zuhair Al-Hassanieh

Srinivasan Seshan

Francesco Tonolini

Isaac S Perper

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.

Methods and apparatus for wideband acoustic communication

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. The systems and techniques described herein find use in many applications including robotic retrieval tasks in complex environments such as warehouses, manufacturing plants, and smart homes.

Robotic grasping via RF-visual sensing and learning

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.

Methods and apparatus for acoustic backscatter communication

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.

Contactless seismocardiography

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.

System and method for location determination and robot control

Underwater transducer for wide-band communication

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.

Methods and apparatus for wideband localization

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.

Methods and apparatus for radio frequency sensing in diverse environments

An underwater transmitter may generate underwater pressure waves that encode bits of data. The pressure waves may travel to, and created minute vibrations in, the water's surface. An airborne radar may detect radar signals that reflect from the water's surface. The surface vibrations may modulate the phase of the reflected radar signal. The radar receiver may, based on the variation in the phase of the reflected radar signal, decode the data that was initially encoded in the underwater pressure waves. The underwater pressure waves may be frequency modulated, such as by orthogonal frequency-division multiplexing. Alternatively, the surface vibrations may be detected by a camera, interferometer or other light sensor. Alternatively, the pressure waves may propagate through a media other than water. For instance, the pressure waves may propagate through bodily tissue, or may propagate through oil or a liquid fracking mixture in an oil or gas well.

Methods and apparatus for cross-medium communication

Multiple antennas of a beamformer may simultaneously transmit wireless signals at different frequencies. The signals may comprise synchronized, identical wireless commands, each at a different carrier frequency. The transmitted signals may constructively and destructively interfere with each other at a receiver antenna, to form a beat signal. When the transmitted signals constructively interfere, the beat signal may cause a voltage in the receiver to exceed a threshold voltage. The threshold voltage may be a minimum voltage at which a device, which is operatively connected to the receiver antenna, is able to perform energy harvesting or wireless communication. The beamformer may operate under blind channel conditions, because the transmitted frequencies may be selected in such a way as to maximize peak power delivered under all possible channel conditions. The beamformer may deliver wireless power to a sensor or actuator that is located deep inside bodily tissue.

Methods and apparatus for multi-frequency beamforming

A method for monitoring periodic motions of one or more subjects uses signal reflections from the subjects. The method includes emitting a transmitted signal from a transmitting antenna and receiving a received signal at one or more receiving antennas. The received signal includes a combination of a number of reflections of the transmitted signal, at least some of which are associated with the subjects. The received signal, including the reflections, is processed to determine an estimate of a fundamental frequency of the periodic motions.

Vital signs monitoring via radio reflections

A wideband, radio-frequency localization system may estimate the one-dimensional, two-dimensional or three-dimensional position and trajectory of a static or moving object. These estimates may have a high spatial accuracy and low latency. The localization may be determined based on phase or amplitude of a wideband signal in each frequency band in a set of multiple frequency bands. The localization may be based on a single shot of measurements across a wide band of radio frequencies, without frequency hopping. The measurements of the wideband signal may be taken over time and over space at multiple receivers. The localization may be based on measurements taken while a backscatter node remains in a first reflective state or in a second reflective state, rather than when the backscatter node is transitioning between reflective states. In some cases, the localization achieves sub-centimeter spatial resolution in each of three spatial dimensions.

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Cambridge, MA, United States of America

Fadel Adib