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This article presents a compact $2\times $ time-interleaved switched-capacitor (SC) digital-to-analog converter (DAC) for digital-intensive transmitter architectures. To minimize area and to leverage the strengths of FinFET technology, the implementation departs from the traditional current steering approach and consists mainly of inverters and sub-femtofarad SCs. The DAC’s architecture is based on parallel charge redistribution and separates level generation, pulse timing, and output power generation. The described 28-GS/s 8-bit prototype design occupies 0.03 mm2 in 16-nm CMOS and supports up to 0.32- $\textrm {V}_{\textrm {pp}}$ signal swing across its differential 100- ${\Omega }$ load. It achieves an SFDR $\geq 37$ dB and an IM $3\leq -45.6$ dBc across the first Nyquist zone while consuming 88 mW from a single 0.8-V supply.

Problem definition: The recent surge in demand for cloud services has posed a significant capacity-expansion problem for cloud infrastructure providers. Although the growth of demand for capacity attributes—for example, CPU and RAM—is disproportionate, these attributes are often provided in preconfigured packages (cluster-types), and the fixed ratio of attributes in a package does not match with the time-varying ratio of demand. We analyze a class of expansion policies to determine the timing and magnitude of expansions, using preconfigured cluster-types, and we examine the optimal configurations of the cluster-types. Academic/practical relevance: Cloud computing is a major technological advance that is influencing businesses significantly, giving rise to an emerging industry but also posing the above-noted capacity-expansion problem. To our knowledge, this is a new issue that has not been studied in the literature. Methodology: We consider growing demand for two attributes and analyze a class of policies that consist of capacity expansion cycles (CECs), whereby capacities are added through sequential or simultaneous replenishments of two configured cluster-types. Results: We first derive the optimal timing and magnitude of expansions for every CEC, and then we devise two algorithms, the dynamic-programming-based (DP) algorithm and the forward-looking (FL) heuristic, to determine the optimal cycle lengths. We also propose a cluster-selection heuristic for choosing the optimal configurations of the cluster-types. Managerial implications: The FL-heuristic is effective, easy to communicate, and can be used as an excellent starting point for the search of the DP-algorithm. Moreover, because there is a desire in practice to reduce the variety of cluster-types, we find conditions under which the employment of only two cluster-types is as efficient as the employment of many cluster-types. Finally, we provide useful guidelines for the optimal configurations of these two cluster-types.

In this paper we consider the impact of 3D printing, or additive manufacturing, on a simple supply chain, consisting of a manufacturer and retailer, that serves stochastic customer demand. 3D printing is a relatively new manufacturing technology that is attracting attention from many firms. However, the impact of 3D printing on operations and firm relationships in a supply chain is relatively unexplored in academic research. A unique aspect of 3D printers is that they can be installed at the retailer in a supply chain, a characteristic that we highlight in our paper since it enables the supply chain to be more responsive to demand. Consequently, 3D printers can be adopted by either the manufacturer or, in a more novel situation, the retailer; we analyze the equilibrium of Stackelberg games in both cases. We characterize the economic and competitive conditions where either firm adopts 3D printing, and show that under either scenario, it is possible for both firms to earn more profit than a benchmark system without 3D printing. We identify and quantify the positive benefits associated with 3D printing, for both firms in a simple supply chain, when either firm adopts this new manufacturing technology. In many cases, the scenario where the manufacturer adopts 3D printing and installs 3D printers at the retailer results in the best profit outcomes for the manufacturer. The retailer’s preference, however, depends on problem parameters. Therefore, supply chain managers should carefully consider the possibility of 3D printing products in their supply chain.

Non-reciprocal devices such as isolators and circulators are key enabling technologies for communication systems, both at microwave and optical frequencies. Although non-reciprocal devices based on magnetic effects are available for free-space and fibre-optic communication systems, their on-chip integration has been challenging, primarily due to the concomitant high insertion loss, weak magneto-optical effects and material incompatibility. We show that χ(3) nonlinear resonators can be used to achieve all-passive, low-loss, bias-free non-reciprocal transmission for applications in photonic systems such as chip-scale LiDAR. A multi-port nonlinear Fano resonator is used as an on-chip, non-reciprocal pulse router for frequency comb-based optical ranging. Because time-reversal symmetry imposes stringent limitations on the operating power range and transmission of a single nonlinear resonator, we implement a cascaded Fano–Lorentzian resonator system that overcomes these limitations and substantially improves the insertion loss and operating power range of current state-of-the-art devices. This work provides a platform-independent design for non-reciprocal transmission and routing that is ideally suited for photonic integration. Optical nonlinearity is exploited for non-reciprocal transmission and integrated frequency comb-based optical ranging.

The data rate-times-distance product in mm-wave dielectric waveguide (DWG) communication links is usually limited by waveguide dispersion. This letter presents the DWG’s baseband impulse response in the context of a homodyne receiver and introduces a continuous-time linear equalizer able to minimize such dispersion. The desired transfer function is implemented with inverter-based transconductance cells. The simulation and measurement results at 10-Gbps data rate show eye-opening improvement at two distances (10 and 15 m) and carrier frequencies (140 and 160 GHz). The equalizer occupies 80 $\times $ 32 ${\mu }\text{m}^{2}$ in GLOBALFOUNDRIES 22-nm FD-SOI.

Multi-modal imaging via thermoacoustic (TA) approaches provides contrast mechanisms differing from conventional ultrasound (US) imaging - opening up new applications like non-invasive, non-contact below-ground sensing. Due to the high correlation between soil moisture content and speed-of-sound (SoS), knowledge about the SoS in soil can be utilized to improve below-ground image reconstruction and soil moisture mapping at depth. In this work, we present multi-task deep learning networks to accurately predict arbitrarily varying SoS distributions in soil while concurrently reconstructing high-fidelity TA images of root structures. We deploy multi-task U-Net based fully convolutional neural networks trained using US data generated through TA simulations on a wheat root dataset. A multi-input, multi-output architecture performed best - achieving the highest root image contrast-to-noise ratio and lowest SoS mean absolute error.

Disclosed are systems for converting rotational momentum into linear propulsion. A propulsion system includes one or more thrust units with masses controllably driven by actuators to generate inertia that thrusts a vehicle with the propulsion system in a desired direction. The propulsion system can be configured to have multiple units, each configured to generate thrust in a desired direction and counteract or neutralize thrust in other directions. The propulsion system can generate thrust via two operational cycles and/or through continuous operation. The propulsion system may comprise two mirroring units, each configured to operate in mirrored synchrony to generate a net thrust in a desired direction and counteract or neutralize thrust in other or undesired directions.

Single modality wireless power has limited depth for mm-sized implants across air-tissue (e.g. retina implants) or skull-tissue interfaces because of high loss in tissue (RF, optical) or high reflection at the medium interface (ultrasound). The proposed RF-ultrasound (US) relay uses an RF link across the interface to a relay chip which rectifies the RF power and transmits focused ultrasound to the implant using a 6-channel phased array with 251% efficiency improvement at 2.5 cm over fixed focusing.

Signal distribution across a large aperture remains a major problem for millimeter-wave (mm-wave) arrays. This paper demonstrates a mm-wave non-radiative dielectric (NRD) waveguide that realizes flexible interconnect and low propagation loss. Two back-to-back grounded coplanar waveguides (CPW-G) are used for coupling from the printed circuit board (PCB) to the NRD waveguide as a forward-wave coupler. Due to the field distribution similarity of the longitudinal section electric (LSE) mode of the NRD waveguide to the quasi-TEM mode of the CPW-G, the proposed coupler achieves a smooth and efficient transition. Measurement results for PCB-NRD-PCB links at 60 GHz with 10-cm and 20-cm lengths are demonstrated. The measured propagation and coupling losses of the proposed NRD waveguide and coupler are 30.0 ±3.3 dB/m and 1.0 ±0.4 dB from 56 to 64 GHz. respectively.

Handheld microwave thermoacoustic imaging (TA) can be used to image subcutaneous vasculature for biometric authentication and to monitor blood-vessel health, but the system requires a compact silicon microwave power amplifier (PA) with peak output power on the order of 10 W to be portable, affordable, and ubiquitous. This work presents a 55nm BiCMOS 4.9 GHz PA with 37.3 dBm peak output power that operates at a pulse width of 50 ns - $2\ \mu\mathrm{s}$ for a duty cycle of 0.025 - 1%. The PA serves as the transmitter in a microwave TA system, which generates the first known TA images of tissue phantoms using a compact transmitter built on a silicon substrate.

Portable and easy-to-use imaging systems are in high demand for medical, security screening, nondestructive testing, and sensing applications. We present a new microwave-induced thermoacoustic imaging system with non-contact, airborne ultrasound (US) detection. In this system, a 2.7 GHz microwave excitation causes differential heating at interfaces with dielectric contrast, and the resulting US signal via the thermoacoustic effect travels out of the sample to the detector in air at a standoff. The 65 dB interface loss due to the impedance mismatch at the air-sample boundary is overcome with high-sensitivity capacitive micromachined ultrasonic transducers with minimum detectable pressures (MDPs) as low as ${278~\mu {\mathrm{ Pa}}_{\mathrm{ rms}}}$ and we explore two different designs—one operating at a center frequency of 71 kHz and another at a center frequency of 910 kHz. We further demonstrate that the air–sample interface presents a tradeoff with the advantage of improved resolution, as the change in wave velocity at the interface creates a strong focusing effect alongside the attenuation, resulting in axial resolutions more than $10\times $ smaller than that predicted by the traditional speed/bandwidth limit. A piecewise synthetic aperture radar (SAR) algorithm modified for US imaging and enhanced with signal processing techniques is used for image reconstruction, resulting in mm-scale lateral and axial image resolution. Finally, measurements are conducted to verify simulations and demonstrate successful system performance.

We present an ultralow-power millimeter-sized ultrasonic wake-up receiver (WuRx) that uses precharged ultrasonic transducers to wirelessly receive wake-up signatures. Our WuRx takes advantage of the low carrier frequency afforded by the low speed of sound to achieve high impedance, and thus high sensitivity, operation in a millimeter-sized form factor. We discuss the system-level considerations that arise from the use of ultrasound as a mode of signature transmission, including the choice of operating frequency and the effect of transducer miniaturization on WuRx sensitivity. We describe the design of the receiver electronics and support our case for ultrasonic wake-up with thorough wireless measurements of error rate and electrical characterization of multiple dice from the same wafer lot. The receiver electronics are fabricated in 65-nm CMOS technology, while the receiver transducer is fabricated by means of a custom in-house process. The receiver achieves a sensitivity of −59.7 dBm at a bit error rate (BER) of 10−3 with a power consumption of 8 nW and a footprint of 14.5 mm2. Our benchmarking shows that the proposed WuRx achieves the lowest system area/aperture of all RF and acoustic WuRxs in the literature (1.45 $\times $ smaller than the state of the art) while maintaining competitive sensitivity and power consumption.

In this paper, we demonstrate a proof-of-concept 130 GHz wireless 2x2 line-of-sight (LoS) multi-input multi-output (MIMO) transceiver using fully packaged transmit and receive arrays and scalable analog baseband processing. The link utilizes the Rayleigh criterion to transmit independent wireless streams over a LoS channel. The transmitter (TX) and receiver (RX) chips are fully packaged with integrated mm-wave antennas. The two-element QPSK TX array consumes 432 mW, while the entire four-channel QPSK MIMO RX consumes 630 mW and supports four concurrent 130 GHz mm-wave channels with a simulated passband bandwidth of 20 GHz. Wireless measurements demonstrate 32 Gbps QPSK transmission over 40 cm, allowing for a link efficiency of 83 pJ/ bit/ m and an energy efficiency of 33 pJ/ bit. Scaling the system from the two channels measured here to the four channels supported by the RX chip will double the data rate as well as the range reported.

This paper presents a compact DAC for digital-intensive transmitter architectures. To minimize area and to leverage the strengths of FinFET CMOS, the implementation departs from the traditional current steering approach and consists mainly of inverters and sub-femtofarad switched capacitors. The 14 GS/s 8-bit design occupies only 0.011 mm2 and supports up to 0.32 V pp signal swing across its differential 100 Ω load. It achieves IM3 < −45.3 dBc across the first Nyquist zone while consuming 50 mW from a single 0.8 V supply.

In this paper, we present the design and the analysis of an electrochemical circuit for measuring the concentrations of therapeutic drugs using structure-switching aptamers. Aptamers are single-stranded nucleic acids, whose sequence is selected to exhibit high affinity and specificity toward a molecular target, and change its conformation upon binding. This property, when coupled with a redox reporter and electrochemical detection, enables reagent-free biosensing with a sub-minute temporal resolution for in vivo therapeutic drug monitoring. Specifically, we design a chronoamperometry-based electrochemical circuit that measures the direct changes in the electron transfer (ET) kinetics of a methylene blue reporter conjugated at the distal-end of the aptamer. To overcome the high-frequency noise amplification issue when interfacing with a large-size (> 0.25 mm2) implantable electrode, we present a sample-and-hold (S/H) circuit technique in which the desired electrode potentials are held onto noiseless capacitors during the recording of the redox currents. This allows disconnecting the feedback amplifiers to avoid its noise injection while reducing the total power consumption. A prototype circuit implemented in 65-nm CMOS demonstrates a cell-capacitance-insensitive input-referred noise (IRN) current of 15.2 pArms at a 2.5-kHz filtering bandwidth. Tested in human whole blood samples, changes in the ET kinetics from the redox-labeled aminoglycoside aptamers at different kanamycin concentrations are measured from the recorded current waveforms. By employing principal component analysis (PCA) to compensate for the sampling errors, a detection limit (SNR = 1) of 3.1 uM under 1-sec acquisition is achieved at 0.22-mW power consumption., Submitted to IEEE Journal of Solid-State Circuits (JSSC). This is the initial submission version

Objective. Therapeutic applications of implantable active medical devices have improved the quality of patient life. Numerous on-going research in the field of neuromodulation and bioelectronic medicine are exploring the use of these implants for treating diseases and conditions. Miniaturized implantable medical devices that are wirelessly powered by ultrasound (US) can be placed close to the target sites deep inside the body for effective therapy with less invasiveness. In this study, we assessed the long-term in vivo performance of miniaturized US powered implants (UPI) using a rodent model. Approach. Prototype UPI devices were implanted in rodents and powered wirelessly using an unfocused US transmitter over 12 weeks, and the corresponding device output was recorded. Structural integrity of UPI before and after implantation was studied using scanning electron microscopy (SEM). We also conducted qualitative histological assessment of skin and muscle surrounding the UPI and compared it to naïve control and US exposed tissues. Main results. We found that it is feasible to power UPI devices wirelessly with US over long-term. The encapsulation of UPIs did not degrade over time and the tissues surrounding the UPI were comparable to both naïve control and US exposed tissues. Significance. This study is the first to assess the long-term performance of miniaturized UPI devices using a rodent model over 12-weeks. The set of tests used in this study can be extended to assess other US-powered miniaturized implants.

We demonstrate the working principle of a lithium niobate resonant photoelastic modulator. The optomechanical device can be integrated with a standard image sensor to convert it into a time-of-flight imaging system.

The impact of 3D printing, or additive manufacturing, on a supply chain, consisting of a manufacturer and retailer, that utilizes a wholesale-price contract and serves stochastic customer demand has been studied in this paper. 3D printing is an evolutionary manufacturing technology which is attracting many firms and governments. Its impact, however, on supply chains remains unexplored. A 3D printer can be purchased by either the manufacturer or, in a more novel situation, the retailer; we derive the equilibrium of Stackelberg games in both cases. We characterize the economic conditions where either firm adopts 3D printing; under a uniform distribution of demand, these conditions simplify to upper bounds on the acquisition cost of a 3D printer. If the firms do not naturally adopt 3D printing, we derive the minimum government subsidy that will induce each firm to adopt, and we find that the retailer subsidy is always at most the manufacturer subsidy. If the manufacturer adopts 3D printing, both firms benefit, with respect to a supply chain without 3D printing; however, the double marginalization effect is still present. If the retailer adopts 3D printing, the manufacturer benefits, but the retailer does not; however, the double marginalization effect is eliminated, and we discover that retailer 3D printing is a new mechanism for coordinating a supply chain. Thus, supply chain managers should carefully consider the possibility of a retailer manufacturing products via 3D printing.

We present an analytical framework for optimizing the efficiency of ultrasonic wireless power links for implantable devices scaled down to sub-mm dimensions. Key design insights and tradeoffs are considered for various parameters including the operating frequency, the transmission depth, the size of the transmitter, the impedance and the aperture efficiency of the miniaturized receiver, and the interface between the receiver and the power recovery chain on the implant. The performance of spherically focused transducers as ultrasonic transmitters is analyzed to study the limits and the tradeoffs. Two optimization methods are presented: “Focal Peak” sets the focus of transducers at target depths, and “Global Maximum” maximizes the efficiency globally with off-focus operation. The results are also compared to phased array implementations. To investigate the efficiency of implants, miniaturized receivers made from single crystalline piezoelectric material, PMN-PT, are used as they have resonances in the derived optimal carrier frequency range (~ l-2 MHz). A methodology to achieve an efficient interface to the power electronics is then provided using an optogenetic stimulator as an example platform. The analytical results are verified through both simulations and measurements. Finally, an example ultrasonic link using a spherical transmitter with a radius of 2 cm is demonstrated; link efficiencies of 1.93–0.23% are obtained at 6–10 cm depths with sub-mm receivers for the optogenetic application.

This letter presents a fully packaged 130-GHz QPSK transmitter (TX) with an on-package Vivaldi antenna for high-density dielectric waveguide (DWG) chip-to-chip and board-to-board interconnects. The TX chip contains a multiplier chain for the local oscillator path, up-conversion mixers, and a two-stage power amplifier. For testing, the chip also includes two $2^{7} - 1$ sequence-programmable high-speed pseudo-random bit generators, each capable of generating 18 Gb/s (limited by test equipment) at energy efficiency of 0.7 pJ/bit. The fully packaged TX achieves a data rate of 36 Gb/s over a 1-m-long DWG link, leading to energy efficiency of 6 pJ/bit.

Neurological implants that harvest ultrasound power have the potential to provide long-term stimulation without complications associated with battery power. An important safety question associated with long-term operation of the implant involves the heat generated by the interaction of the device with the ultrasound field. A study was performed in which the temperature rise generated by this interaction was measured. Informed by temperature data from thermocouples outside the ultrasound beam, a mathematical inverse method was used to determine the volume heat source generated by ultrasound absorption within the implant as well as the surface heat source generated within the viscous boundary layer on the surface of the implant. For the test implant used, it was determined that most of the heat was generated in the boundary layer, giving a maximum temperature rise ∼5 times that for absorption in an equivalent volume of soft tissue. This result illustrates that thermal safety guidelines based solely on ultrasound absorption of tissue alone are not sufficient. The method presented represents an alternative approach for quantifying ultrasound thermal effects in the presence of implants. The analysis shows a steady temperature rise of about 0.2 °C for every 100 mW/cm2 for the presented test implant.

OBJECTIVE The aim of the present study was to compare clinical features of patients with elevated serum digoxin concentrations who were treated with digoxin-Fab with those where the immunotherapy was not given by a tertiary hospital toxicology service. METHODS This was a retrospective series of patients with supratherapeutic serum digoxin concentrations referred to the toxicology service from August 2013 to October 2015. Data collected included demographics, presenting complaint, digoxin dose, other medications taken, serum digoxin, potassium and creatinine concentration on presentation and initial and post-digoxin-Fab heart rate. RESULTS There were 47 referrals. Digoxin-Fab was administered in 21 cases. It was given more commonly when the heart rate was 5.0 mmol/L. Patients receiving digoxin-Fab were more likely to be on maintenance therapy with beta-blockers or calcium channel blockers (95% vs 61%; OR 13.1; 95% CI 1.5-113) and/or potassium-sparing medications (95% vs 54%; OR 17.1; 95% CI 2.0-147). They had elevated serum creatinine (76% vs 42%; OR 8.2; 95% CI 1.9-34), higher serum potassium (median: 5.1 mmol/L vs 4.2 mmol/L, P = 0.02), higher serum digoxin concentration (median: 3.5 nmol/L vs 2.3 nmol/L, P = 0.02) and pretreatment heart rate

We propose the use of airborne ultrasound for wireless power transfer to mm-sized nodes, with intended application in the next generation of the Internet of Things (IoT). We show through simulation that ultrasonic power transfer can deliver 50 $\mu \text{W}$ to a mm-sized node 0.88 m away from a ~ 50-kHz, 25-cm2 transmitter array, with the peak pressure remaining below recommended limits in air, and with load power increasing with transmitter area. We report wireless power recovery measurements with a precharged capacitive micromachined ultrasonic transducer, demonstrating a load power of 5 $\mu \text{W}$ at a simulated distance of 1.05 m. We present aperture efficiency, dynamic range, and bias-free operation as key metrics for the comparison of transducers meant for wireless power recovery. We also argue that long-range wireless charging at the watt level is extremely challenging with existing technology and regulations. Finally, we compare our acoustic powering system with cutting edge electromagnetically powered nodes and show that ultrasound has many advantages over RF as a vehicle for power delivery. Our work sets the foundation for further research into ultrasonic wireless power transfer for the IoT.

Implantable medical devices (IMDs) and the concept of integrating electronics with the human body have been intriguing curiosities in medicine for many decades-slowly finding their way into mainstream medicine for several very specific conditions but not quite making it beyond "last resort" treatments. From the reality of today's cardiac pacemakers and deep-brain stimulation devices to the dream of sensor motes roaming around one's bloodstream (as described by researchers and writers like Isaac Asimov in his adaptation of Fantastic Voyage), the marriage of electronics and the human body has provided endless fascination for both science and science fiction alike. There is an abundance of potential applications, from electroceuticals to brain computer interfaces, and with advances in closed-loop systems and recent insights on neuromodulation, these devices are projected to make a huge impact on patient care for everything from neurological conditions all the way to diabetes and arthritis.

We assessed the effect of vitamin E and vitamin B (Vit E & Vit B) and their combination on sperm functional parameters in the rat varicocele model. Male rats (n = 120) were divided into control (n = 30), sham (n = 30) and varicocele induction (n = 60) groups. After 2 months, 10 rats from each group were sacrificed to verify varicocele model. This part of results showed that sperm parameters, DNA damage, lipid peroxidation and residual histone were adversely effected in the varicocele group. From the 50 remaining rats in varicocele group, 10 rats received Vit B complex (6, 9.6, 30.4, 9.6 and 0.006 mg/kg for B6, B2, B9, B1 and B12 respectively), 10 rats received Vit E (40 mg/kg), 10 rats received Vit B & E, 10 rats only received water and 10 rats were only received sesame oil as a solvent for Vit E, for 2 months. From 40 remaining rats in control and sham groups, 20 rats only received water and other 20 rats only received sesame oil for 2 months. Then, all the aforementioned parameters were assessed. These results showed that Vit B antioxidant was more efficient in improvement of sperm parameters, chromatin integrity and lipid peroxidation in varicocelized rats compared with Vit E.

Multi-access networking with miniaturized wireless implantable devices can enable and advance closed-loop medical applications to deliver precise diagnosis and treatment. Using ultrasound (US) for wireless implant systems is an advantageous approach as US can beamform with high spatial resolution to efficiently power and address multiple implants in the network. To demonstrate these capabilities, we use wirelessly powered mm-sized implants with bidirectional communication links; uplink data communication measurements are performed using time, spatial, and frequency-division multiplexing schemes in tissue phantom. A 32-channel linear transmitter array and an external receiver are used as a base station to network with two implants that are placed 6.5 cm deep and spaced less than 1 cm apart. Successful wireless powering and uplink data communication around 100 kbps with a measured bit error rate below 10(−4) are demonstrated for all three networking schemes, validating the multi-access networking feasibility of US wireless implant systems.

Non-invasive temperature monitoring of tissue at depth in real-time is critical to hyperthermia therapies such as high-intensity focused ultrasound. Knowledge of temperature allows for monitoring treatment as well as providing real-time feedback to adjust deposited power in order to maintain safe and effective temperatures. Microwave-induced thermoacoustic (TA) imaging, which combines the conductivity/dielectric contrast of microwave imaging with the resolution of ultrasound, shows potential for estimating temperature non-invasively in real-time by indirectly measuring the temperature dependent parameters from reconstructed images. In this work, we study the temperature dependent behavior of the generated pressure in the TA effect and experimentally demonstrate simultaneous imaging and temperature monitoring using TA imaging. The proof-of-concept experiments demonstrate millimeter spatial resolution while achieving degree-level accuracy.

Neuromodulation devices have been approved for the treatment of epilepsy and seizures, with many other applications currently under research investigation. These devices rely on implanted battery powered pulse generators, that require replacement over time. Miniaturized ultrasound powered implantable devices have the potential to eliminate the need for batteries in neuromodulation devices. While these devices have been assessed in vitro, long-term in vivo assessment is required to determine device safety and performance. In this study, we developed a multi-stage long-term test platform to assess the performance of miniaturized ultrasound powered implantable devices.

Nonreciprocal devices are crucial components for optical communications, nonlinear signal processing and all-optical circuits in silicon-compatible photonic platforms, but traditional techniques for achieving nonreciprocity and isolation have lacked CMOS compatibility. In recent work, we combined state-of-the-art fabrication and inverse design to demonstrate bias-free, low-loss nonreciprocal transmission in silicon integrated devices.

Miniaturized ultrasonic receivers are designed for efficient powering of implantable medical devices with reconfigurable power loads. Design parameters that affect the efficiency of these receivers under highly variable load conditions, including piezoelectric material, geometry, and operation frequency, are investigated. Measurements were performed to characterize electrical impedance and acoustic-to-electrical efficiency of ultrasonic receivers for off-resonance operation. Finally, we propose, analyze, and demonstrate adaptive matching and frequency tuning techniques using two different reconfigurable matching networks for typical implant loads from 10 $\mu \text{W}$ to 1 mW. Both simulations and measurements show a significant increase in total implant efficiency (up to 50 percentage points) over this load power range when operating off-resonance with the proposed matching networks.

We investigate the fundamental physical constraints and tradeoffs in common millimeter-wave dielectric waveguides proposed for high speed links. We consider waveguides with different geometries, dimensions and operating frequencies, and show that the capacity of optimized longer links is limited by the dispersion and not necessarily the loss. In our analysis, the required capacity and distance determine the choice of waveguide and the operating frequency, which would then determine the energy efficiency of the link. Our generic theoretical analyses are in agreement with the measurements presented in the recent literature.

Millimeter-sized and low-cost sensor nodes can enable future applications of the Internet of Things (IoT), for which the number of sensors is projected to grow to a trillion within the next decades. RF far-field power transfer is a potential technique for wirelessly powering these sensors since it offers flexible configuration of sensor networks, beamforming capability and a large power transfer range compared to near-field approaches. However, system design for RF power transfer needs to be completely rethought to enable this new paradigm of a trillion IoT sensors. This paper, therefore, presents a comprehensive, system-level analysis strategy and a modular framework for investigating the fundamental efficiency components in an RF power transfer chain. Through this detailed analysis, it is demonstrated that the optimal frequency is primarily determined by the antenna size and the quality factors $(Q)$ of components in the matching network. Millimeter-wave frequencies are shown to be optimal for powering mm-sized sensors for practical matching component $Q$ values. An intuitive explanation of our results is also provided, along with insights for the design and practical implementation of RF power transfer systems for the IoT space.

Article history: Received March 25, 2015 Received in revised format August 6 2015 Accepted August 17 2015 Available online August 18 2015 This paper presents a study on the effects of professional ethics and commitments on audit quality. The population of this survey includes all audit managers who were active in auditing official statements of different firms listed in Tehran Stock Exchange in 2014. The study designs a questionnaire in Likert scale and distributes it among 152 randomly selected managers. In our survey, professional ethics consists of four items including confidentiality and impartiality, professional competence, accountability and individual values while organizational commitment consists of three items including emotional commitment, continues commitment and fundamental commitment. Using Pearson correlation as well as regression models, the study has determined a positive and meaningful relationship between professional ethics as well as commitment and audit quality. Growing Science Ltd. All rights reserved. 5 © 201

This publisher’s note corrects the Funding section in Appl. Opt. 58, 2235 (2019)APOPAI0003-693510.1364/AO.58.002235.

Ahstract- This paper presents a compact RF-acoustics imaging system which adds RF spectroscopy capability for enhanced contrast and specificity in soft tissue imaging. A programmable, wideband, high power RF transmitter with 25.6 dBm across 1–3 GHz is designed in a 55-nm BiCMOS process enabling the system to operate across both conventional pulse mode as well as the SNR-enhancing coherent imaging mode. Measured reconstructed images at different RF excitation frequencies demonstrate the feasibility to distinguish materials based on the spectroscopic information, therefore opening the door to new spectroscopic feature sets in compact thermoacoustic imaging modalities.

We consider a communication channel where there is no common clock between the transmitter and the receiver. This is motivated by the recent interest in building system-on-chip radios for Internet of Things applications, which cannot rely on crystal oscillators for accurate timing. We identify two types of clock uncertainty in such systems: timing jitter, which occurs at a time scale faster than the communication duration (or equivalently blocklength); and clock drift, which occurs at a slower time scale. We study the zero-error capacity under both types of timing imperfections, and obtain optimal zero-error codes for some cases. Our results show that, as opposed to common practice, in the presence of clock drift it is highly suboptimal to try to learn and track the clock frequency at the receiver; rather, one can design codes that come close to the performance of perfectly synchronous communication systems without any clock synchronization at the receiver., accepted for publication in IEEE Transactions on Communications

Miniaturized minimally-invasive implants with wireless power and communication links have the potential to enable closed-loop treatments and precise diagnostics. As with wireless power transfer, robust wireless communication between implants and external transceivers presents challenges and tradeoffs with miniaturization and increasing depth. Both link efficiency and available bandwidth need to be considered for communication capacity. This paper analyzes and reviews active electromagnetic and ultrasonic communication links for implants. Example transmitter designs are presented for both types of links. Electromagnetic links for mm-sized implants have demonstrated high data rates sufficient for most applications up to Mbps range; nonetheless, they have so far been limited to depths under 5 cm. Ultrasonic links, on the other hand, have shown much deeper transmission depths, but with limited data rate due to their low operating frequency. Spatial multiplexing techniques are proposed to increase ultrasonic data rates without additional power or bandwidth.

The next generation of the Internet of Things is envisioned to include unobtrusive, distributed mm-sized nodes capable of sensing and communicating information about their surroundings. Wake-up receivers (WuRXs) — ultra-low-power receivers that monitor their environment for a wake-up signature — are an important part of this vision, as they can extend the lifetime of a wireless node by keeping it asleep until interrogated. The state of the art in WuRXs, measured in terms of sensitivity and power, has recently been advanced by streamlining the signal path to include fewer power-hungry gain stages and instead obtaining the gain at the chip-antenna interface [1,2]. This has led to excellent power-sensitivity performance, but the accompanying increase in size hampers the applicability of these techniques in size-conscious applications, such as surveillance, asset tracking, and ubiquitous sensing. Moreover, size-reduction methods based on RF antenna miniaturization are fundamentally limited by high antenna Qs at low size-to-wavelength ratios [3]; efficiently matching to these antennas requires, in turn, high-Q passives that are generally unavailable at mm-scale.

A first proof-of-concept mm-sized implantable device using ultrasonic power transfer and a hybrid bi-directional data communication link is presented. Ultrasonic power transfer enables miniaturization of the implant and operation deep inside the body, while still achieving safe and high power levels (100 $\mu$ W to a few mWs) required for most implant applications. The current implant prototype measures 4 mm $\times $ 7.8 mm and is comprised of a piezoelectric receiver, an IC designed in 65 nm CMOS process and an off-chip antenna. The IC can support a maximum DC load of 100 $\mu$ W for an incident acoustic intensity that is $\sim $ 5% of the FDA diagnostic limit. This demonstrates the feasibility of providing further higher available DC power, potentially opening up new implant applications. The proposed hybrid bi-directional data link consists of ultrasonic downlink and RF uplink. Falling edge of the ultrasound input is detected as downlink data. The implant transmits an ultra-wideband (UWB) pulse sequence as uplink data, demonstrating capability of implementing an energy-efficient M-ary PPM transmitter in the future.

A wireless-powered pad-less single-chip radio is implemented in 65 nm CMOS for applications in Internet of Things (IoT) and wireless tagging. This fully-self-sufficient mm-wave radio has no pads or external components (e.g., power supply), and the entire radio is a single chip with dimensions of 3.7 mm by 1.2 mm. To provide multi-access, and to mitigate interference, it uses two separate mm-wave bands for RX/TX and integrates both antennas to provide a measured communication range of 50 cm. The transmitter uses a modified Multipulse Pulse Position Modulation (MPPM) with 2 GHz of bandwidth on a 60 GHz carrier to communicate the data sequence as well as the local timing reference. The entire system operates with standby harvested power below 1.5 µW and achieves an aggregate data rate > 12 Mbps.

We investigate scaling of ultrasound-powered wireless receivers for efficient, miniaturized implantable medical devices. Single crystalline piezoelectric material, PMN-PT, is chosen in this study as it has low resonance frequency with scaled dimensions. For accurate modeling of sub-mm-sized receivers, we perform simulations using the finite element method, followed by validation with measurements. Results are presented for scaling of the resonance frequency, resistance at resonance, and aperture efficiency of PMN-PT receivers with thickness of 0.5 mm and widths ranging from 0.3 mm to 1.0 mm. Since optimizing the overall harvesting efficiency of an implant requires not only an efficient receiver but also an efficient interface to the power electronics, we analyze impedance matching efficiency between the receivers and the power electronics using optogenetic stimulation as an example application. Finally, we show the measurement of prototype implants with scaled receivers and discuss the trade-off between size and power harvesting efficiency of sub-mm wireless implants.

Capacitive micromachined ultrasonic transducers (CMUTs) are currently used in diagnostic ultrasound imaging systems, and are also attractive solutions for therapeutic and tracking applications in the body. Most CMUTs require a voltage bias for operation with high sensitivity and efficiency; this requirement can be inconvenient for some applications, such as catheter- and capsule-based endoscopy, while being prohibitive for others, such as wirelessly-powered millimeter-sized nodes for the Internet of Things. The use of pre-charged CMUTs, which can operate without a voltage bias, holds the potential to open up an entire class of previously inaccessible applications for CMUTs that are incompatible, due to issues of size, complexity, or safety, with a voltage bias. Pre-charging can also greatly increase the safety and simplicity of system-level design for applications that are compatible with a voltage bias, but that do not require tuning of the bias in the course of operation.

To overcome the limitations of conventional ultrasound endoscopy, we developed a capsule ultrasound (CUS) device: an ingestible and disposable pill to inspect the multiple layers of the entire gastrointestinal (GI) tract and to provide a convenient method for diagnosing GI diseases. The CUS device was composed of three building blocks: the cylindrical capacitive micromachined ultrasonic transducer (CMUT) array, imaging circuitry, and wireless transmitter. All of these three components were designed, fabricated and tested successfully. With low DC bias voltage, a single element of the CMUT array generated surface pressure over 700 kPa, with a 3 dB bandwidth greater than 80 percent. In the imaging circuitry, the high-voltage pulser generated a unipolar pulse up to 18 V with the pulse width varying from 77 ns to 125 ns, and the receiving channel included the TIA with a gain of 92.4 dB and a 3 dB bandwidth of 7.5 MHz, the TGC amplifier with 25 ns recovery time when switching between five gain levels, and the 20 MSample/s ADC with a signal-to-noise-and-distortion ratio (SNDR) of 46.5 dB. The wireless transmitter provided a data rate of 10 Mbps, with a measured bit error rate (BER) < 2110−7 through a link attenuation of 64 dB. The performance of a single element of CMUT array was tested with an imaging circuity channel, demonstrating a CMUT element surface pressure of greater than 290 kPa, a receive sensitivity of 300 μV/Pa and a minimal detectable pressure of 0.756 mPa per root Hertz.

Networks of miniaturized implantable medical devices (IMDs) capable of operating deep in the body are crucial for many novel diagnostic and therapeutic applications. An external portable base station to power, coordinate, and communicate with IMDs can enable these networks. Ultrasonic (US) wireless power transfer is utilized to shrink device dimensions, raise available power, and increase operation depth due to its small wavelength and low attenuation in the body. Building on previous demonstrations of US-powered IMDs for neuromodulation and active communication, we investigate and design an US linear array base station to interface with multiple implants. This allows for programmable focusing for multi-access control and higher power transfer efficiency (PTE), as well as bidirectional communication for closed-loop operation.

This paper presents the first fully ultrasonic (US) high-precision implantable sensor with active US links for power-up, data downlink, and data uplink. The packaged implant measures just 1.7×2.6×8.1mm3 and includes a custom IC, piezoelectric devices (piezos) designed for data/power links, and a pressure transducer (PT). Characterization is performed at a large depth of 12 cm, in a phantom material, giving a >10× improvement over state-of-the-art in both the depth/volume and energy per sample figures of merit. The IC has a front-end and 10-bit ADC which achieves a pressure LSB of 0.78 mmHg and full-scale range of 800 mmHg, exceeding specifications required for various pressure monitoring applications. The sample rate is externally controlled, up to 1 kHz, through the downlink, allowing power optimization for various applications.

Miniaturized wirelessly powered implants capable of operating and communicating deep in the body are necessary for the next-generation of diagnostics and therapeutics. A major challenge in developing these minimally invasive implants is the tradeoff between device size, functionality, and operating depth. Here, we review two different wireless powering methods, inductive and ultrasonic power transfer, examine how to analyze their power transfer efficiency, and evaluate their potential for powering implantable medical devices. In particular, we show how ultrasonic wireless power transfer can address these challenges due to its safety, low attenuation, and millimeter wavelengths in the body. Finally, we demonstrate two ultrasonically powered implants capable of active power harvesting and bidirectional communication for closed-loop operation while functioning through multiple centimeters of tissue.