Abstract: Femto-satellites are very small satellites that can be deployed in constellations from a larger mothership satellite for distributed measurement. They are too small to accommodate the GNSS receivers that many satellites use for navigation, but they can be located with an electromagnetic beam from the mothership satellite. The mothership satellite scans this beam across a constellation of femto-satellites. When the beam scans across a particular femto-satellite, the femto-satellite transmits an acknowledgement to the mothership satellite, e.g., by retroreflecting the beam or via a separate radio link. The beam can be modulated with commands for the femto-satellite, such as to make a measurement or transmit previously acquired data, as well with commands for determining the femto-satellite's location, such as a time stamp or beam pointing information.

Abstract: Compositions are provided that include a first product with a physical unclonable function (PUF) tag including silk particles conformably and directly attached to the first product, wherein the PUF tag cannot be reattached to a second product once removed from the first product.

Abstract: Systems and methods for implementing confidential communications between nodes of a network provide reduced power consumption, require less memory, and provide improved security, relative to previously-known systems and method. Preferred embodiments implement protocol functions in hardware, as opposed to software, to yield some or all of the foregoing improvements. Some embodiments use a hashing circuit for multiple purposes, while maintaining its ability to compute successive intermediate hash values. Some embodiments improve security of systems using circuits configured to leverage a favorable data format.

Abstract: Efficient and reliable transmission of information from sparse sources over wireless channels in wireless signal networks (WSNs). WSN nodes employ an “integrated signal representation-to-modulation” scheme to describe a sparse signal acquired from a sensor so as to ensure robustness against channel errors across a wide range of signal to noise (SNR) values in a rateless fashion. In one example, sparse signal samples are linearly transformed such that the total number of bits representing the sparse signal is reduced. The linearly-transformed signal samples are directly mapped to a modulation constellation to provide a succession of modulation symbols. A carrier wave is modulated in phase and/or frequency according to the succession of the modulation symbols to generate an encoded carrier wave representing the sparse analog signal. In one aspect, an order of the modulation constellation is based on the precision (e.g., number of bits) of each of the linearly-transformed signal samples.

Abstract: Systems and methods for implementing confidential communications between nodes of a network provide reduced power consumption, require less memory, and provide improved security, relative to previously-known systems and method. Preferred embodiments implement protocol functions in hardware, as opposed to software, to yield some or all of the foregoing improvements. Some embodiments use a hashing circuit for multiple purposes, while maintaining its ability to compute successive intermediate hash values. Some embodiments improve security of systems using circuits configured to leverage a favorable data format.

Abstract: Wireless charging of portable electronic devices is carried out by detecting load variations caused by the device and dynamically compensating for these variations during charging to increase system efficiency and regulate delivered power. In some embodiments, load variations are tracked by comparing a feedback signal to a value range and determining whether the feedback value is higher than, lower than, or within the range of values. This information is then used to modify one or more parameters associated with a power amplifier in a transmitter device.

Abstract: The disclosure features systems for providing auditory signals to a subject. The systems include a sensor front-end circuit configured to be connected to an acoustic sensor and to convert analog signals received from the acoustic sensor to digital electric signals. The systems further include a sound processor circuit configured to be connected to the sensor front-end circuit and receive the electric signals provided by the sensor front end circuit. The sound processor includes multiple filters that spectrally decompose the received electrical signals into multiple spectral channels during operation of the system. The multiple spectral channels include at least a low frequency channel and a high frequency channel and the sound processor circuit is configured to operate the low frequency channel at a sample rate lower than a sample rate of the high frequency channel.

Abstract: In one aspect, the disclosure features systems for providing auditory signals to a subject. The systems include a sensor front-end circuit configured to be connected to an acoustic sensor and to convert analog signals received from the acoustic sensor to digital electric signals. The systems further include a sound processor circuit configured to be connected to the sensor front-end circuit and receive the electric signals provided by the sensor front end circuit. The sound processor includes multiple filters that spectrally decompose the received electrical signals into multiple spectral channels during operation of the system. The multiple spectral channels include at least a low frequency channel and a high frequency channel and the sound processor circuit is configured to operate the low frequency channel at a sample rate lower than a sample rate of the high frequency channel.

Abstract: Efficient and reliable transmission of information from sparse sources over wireless channels in wireless signal networks (WSNs). WSN nodes employ an “integrated signal representation-to-modulation” scheme to describe a sparse signal acquired from a sensor so as to ensure robustness against channel errors across a wide range of signal to noise (SNR) values in a rateless fashion. In one example, sparse signal samples are linearly transformed such that the total number of bits representing the sparse signal is reduced. The linearly-transformed signal samples are directly mapped to a modulation constellation to provide a succession of modulation symbols. A carrier wave is modulated in phase and/or frequency according to the succession of the modulation symbols to generate an encoded carrier wave representing the sparse analog signal. In one aspect, an order of the modulation constellation is based on the precision (e.g., number of bits) of each of the linearly-transformed signal samples.

Abstract: A time-interleaved (TI) analog-to-digital converter (ADC) architecture employs a low resolution coarse ADC channel that samples an input analog signal at a Nyquist rate and facilitates background calibration of timing-skew error without interrupting normal operation to sample/convert the input signal. The coarse ADC channel provides a timing reference for multiple higher resolution TI ADC channels that respectively sample the input signal at a lower sampling rate. The coarse ADC digital output is compared to respective TI ADC digital outputs to variably adjust in time corresponding sampling clocks of the TI ADC channels so as to substantially align them with the sampling clock of the coarse ADC channel, thus reducing timing-skew error. In one example, the coarse ADC output provides the most significant bits (MSBs) of the respective TI ADC digital outputs to further improve conversion speed and reduce power consumption in these channels.

Abstract: In one aspect, the disclosure features systems for providing auditory signals to a subject. The systems include a sensor front-end circuit configured to be connected to an acoustic sensor and to convert analog signals received from the acoustic sensor to digital electric signals. The systems further include a sound processor circuit configured to be connected to the sensor front-end circuit and receive the electric signals provided by the sensor front end circuit. The sound processor includes multiple filters that spectrally decompose the received electrical signals into multiple spectral channels during operation of the system. The multiple spectral channels include at least a low frequency channel and a high frequency channel and the sound processor circuit is configured to operate the low frequency channel at a sample rate lower than a sample rate of the high frequency channel.

Abstract: Wireless charging of portable electronic devices is carried out by detecting load variations caused by the device and dynamically compensating for these variations during charging to increase system efficiency and regulate delivered power. In some embodiments, load variations are tracked by comparing a feedback signal to a value range and determining whether the feedback value is higher than, lower than, or within the range of values. This information is then used to modify one or more parameters associated with a power amplifier in a transmitter device.

Abstract: This disclosure describes techniques and systems for extracting energy from the endocochlear potential (EP) in animal subjects (e.g., human subjects) and using the extracted energy to operate circuits (e.g., electronic device, sensors, and transmitters). The subject matter of this disclosure is embodied, for example, in a system for extracting energy from an endocochlear potential of an animal, wherein the system includes a pair of electrodes, and a circuit coupled to the pair of electrodes. The circuit includes a boost converter, an energy buffer component configured to receive voltage from the boost converter, a start-up rectifier configured to provide voltage to the energy buffer component, and a control component configured to provide control signals to the boost converter. The power extracted from the endocochlear potential is equal or larger than the quiescent power of the circuit.

Abstract: An ASIC for monitoring wideband GHz spectrum to sense respective frequency components present in the spectrum. The ASIC implements Fast Fourier Transform (FFT) techniques to facilitate identification of one or more frequency components of a sparse signal after the signal is sub-sampled at a rate below the Nyquist criterion. The ASIC computes a first Fast Fourier Transform (FFT) of a first sub-sampled set of samples of a time-varying signal representing the monitored spectrum and sampled at a first sampling rate, and further computes a second FFT of a second sub-sampled set of samples of the time-varying signal sampled at a second sampling rate different from the first sampling rate. In one example, each of the first FFT and the second FFT is a low-radix FFT to facilitate a low-power and low-cost ASIC implementation of wideband spectrum sensing.

Abstract: A time-interleaved (TI) analog-to-digital converter (ADC) architecture employs a low resolution coarse ADC channel that samples an input analog signal at a Nyquist rate and facilitates background calibration of timing-skew error without interrupting normal operation to sample/convert the input signal. The coarse ADC channel provides a timing reference for multiple higher resolution TI ADC channels that respectively sample the input signal at a lower sampling rate. The coarse ADC digital output is compared to respective TI ADC digital outputs to variably adjust in time corresponding sampling clocks of the TI ADC channels so as to substantially align them with the sampling clock of the coarse ADC channel, thus reducing timing-skew error. In one example, the coarse ADC output provides the most significant bits (MSBs) of the respective TI ADC digital outputs to further improve conversion speed and reduce power consumption in these channels.

Abstract: An ASIC for monitoring wideband GHz spectrum to sense respective frequency components present in the spectrum. The ASIC implements Fast Fourier Transform (FFT) techniques to facilitate identification of one or more frequency components of a sparse signal after the signal is sub-sampled at a rate below the Nyquist criterion. The ASIC computes a first Fast Fourier Transform (FFT) of a first sub-sampled set of samples of a time-varying signal representing the monitored spectrum and sampled at a first sampling rate, and further computes a second FFT of a second sub-sampled set of samples of the time-varying signal sampled at a second sampling rate different from the first sampling rate. In one example, each of the first FFT and the second FFT is a low-radix FFT to facilitate a low-power and low-cost ASIC implementation of wideband spectrum sensing.

Abstract: This disclosure describes techniques and systems for extracting energy from the endocochlear potential (EP) in animal subjects (e.g., human subjects) and using the extracted energy to operate circuits (e.g., electronic device, sensors, and transmitters). The subject matter of this disclosure is embodied, for example, in a system for extracting energy from an endocochlear potential of an animal, wherein the system includes a pair of electrodes, and a circuit coupled to the pair of electrodes. The circuit includes a boost converter, an energy buffer component configured to receive voltage from the boost converter, a start-up rectifier configured to provide voltage to the energy buffer component, and a control component configured to provide control signals to the boost converter. The power extracted from the endocochlear potential is equal or larger than the quiescent power of the circuit.

Abstract: An energy harvesting system is provided that includes a startup module for starting the energy harvesting system operation from a completely OFF state. The startup module uses mechanical vibrations due to motion to trigger a switch which permits the startup module to charge one or more first capacitive elements so to as reach a first defined voltage. A storage module buffers energy obtained from a thermoelectric harvester to be used by a load device. The storage module commences storing energy from the thermoelectric harvester when the first defined voltage has been reached allowing charging of one or more second capacitive elements to reach a second defined voltage. A DC-DC converter module provides regulated voltage to the load device after energy has been transferred from the thermoelectric harvester. The DC-DC converter module determines whether the second defined voltage has been reached and releases stored energy in the one or more first capacitive elements and the load device.

Abstract: An energy harvesting system is provided that includes a startup module for starting the energy harvesting system operation from a completely OFF state. The startup module uses mechanical vibrations due to motion to trigger a switch which permits the startup module to charge one or more first capacitive elements so to as reach a first defined voltage. A storage module buffers energy obtained from a thermoelectric harvester to be used by a load device. The storage module commences storing energy from the thermoelectric harvester when the first defined voltage has been reached allowing charging of one or more second capacitive elements to reach a second defined voltage. A DC-DC converter module provides regulated voltage to the load device after energy has been transferred from the thermoelectric harvester. The DC-DC converter module determines whether the second defined voltage has been reached and releases stored energy in the one or more first capacitive elements and the load device.

Abstract: An energy harvester circuit is provided. The energy harvester circuit includes a harvesting module for extracting energy from an ambient source. A bias flip module manages the manner in which voltage across the harvesting module transitions when input current from the harvesting module changes direction so as to allow a majority of the charge available from the harvesting module to be extracted. A voltage transitioning module is shared amongst one or more DC-DC converters for efficient energy management.