Low Input Power Research Articles

An Energy-Efficient UWB Transmitter with Wireless Injection Locking for RF Energy-Harvesting Sensors.

An ultralow-power ultrawideband (UWB) transmitter with an energy-efficient injection-locked radio frequency (RF) clock harvester that generates a carrier from an RF signal is proposed for RF energy-harvesting Internet-of-Things (IoT) sensor applications. The energy-efficient RF clock harvester based on the injection-locked ring oscillator (ILRO) is proposed to achieve optimal locking range and minimum input sensitivity to obtain an injection-locked 450 MHz clock in ultralow-power operation. A current-starved inverter-based delay stage is adopted that allows delay adjustment by bias voltage to minimize dynamic current consumption while maintaining a constant delay regardless of changes in process, supply voltage, and temperature (PVT). To minimize static current consumption, a UWB transmitter based on a digital-based UWB pulse generator and a pulse-driven switching drive amplifier is proposed. The proposed injection-locked RF clock harvester achieves the best RF input sensitivity of −34 dBm at a power consumption of 2.03 μW, enabling energy-efficient clock harvesting from low RF input power. In ultralow-power operation, a 23.8% locking range is achieved at the RF injection power of −15 dBm to cope with frequency changes due to PVT variations. The proposed UWB transmitter with RF clock harvester achieves the lowest energy consumption per pulse with an average power consumption of 97.03 μW and an energy consumption of 19.41 pJ/pulse, enabling operation with the energy available in RF energy-harvesting applications.

Enhanced Pulse Compression within Sign-Alternating Dispersion Waveguides

We show theoretically and numerically how to optimize sign-alternating dispersion waveguides for maximum nonlinear pulse compression, while leveraging the substantial increase in bandwidth-to-input peak power advantage of these structures. We find that the spectral phase can converge to a parabolic profile independent of uncompensated higher-order dispersion. The combination of an easy to compress phase spectrum, with low input power requirements, then makes sign-alternating dispersion a scheme for high-quality nonlinear pulse compression that does not require high powered lasers, which is beneficial for instance in integrated photonic circuits. We also show a new nonlinear compression regime and soliton shaping dynamic only seen in sign-alternating dispersion waveguides. Through an example SiN-based integrated waveguide, we show that the dynamic enables the attainment of compression to two optical cycles at a pulse energy of 100 pJ which surpasses the compression achieved using similar parameters for a current state-of-the-art SiN system.

Developing multiplexed plasma micro-reactor for ozone intensification and wastewater treatment

The development of non-thermal plasma-based wastewater treatment technologies is a challenging topic of research these days. The conventional domestic ozonators based on corona, are susceptible to arcing, produce less ozone due to low input power, and yield larger bubbles limiting mass transfer rate. The article proposes a new design- multiplexed system containing six Corona-DBD hybrid packed-bed plasma micro-reactors connected in parallel to significantly improve the said design problems. The reactor gives enhanced ozone generation due to characteristics of corona (high concentration of radicals), DBD (homogeneous discharge), and packing material (stronger electric field). The diffuser configuration yields high number density of microbubbles enhancing mass transfer. The optimized multiplexed reactor improves ozone generation by 4.8 folds at 5.8 kVpk, 20 kHz, 76 mA, 1 LPM, and 5 cm electrode length producing 480.8 ppm ozone in 20 s. The reactor efficiency was evaluated using Methyl orange degradation. The energy yield of the plasma reactor was also evaluated for MO solution. At optimized reactor conditions, 86 % Methyl orange was removed at pH 3, 10 ppm, and 900 mL in 8 min, and COD was reduced to 74 %. The multiplexed design offers an effective replacement for conventional ozone generators for about 1 L capacity in less than 10 min.

Analysis and Design of Interleaved DCM Buck–Boost Derived Three-Phase PFC Converter for MEA

In more-electric aircraft (MEA), the synchronous generators are connected directly to the turbo engine to develop a constant-voltage variable-frequency (CVVF) ac supply bus. In addition, the MEA has adopted a high-voltage dc bus in its power system to cater to the various categories of load used by aircraft. Therefore, this change in power paradigm has created a requirement for ac-dc power factor correction (PFC) converters to convert CVVF ac to constant dc with high power quality in a reliable manner. In this article, a three-phase interleaved buck-boost-derived PFC converter is operated in discontinuous current conduction mode to realize the inherent unity power factor (UPF) operation for MEA wide range of supply frequency. The benefits of the proposed converter are higher power density, efficiency, and reliability. The advantages of the proposed converter are demonstrated by performing an analytical comparison with the single-cell three-phase buck-boost derived PFC converter and presented the relevant results. The experimental results from a 2.0-kW laboratory concept-proof hardware prototype have been provided to confirm the proposed converter UPF operation for a wide range of supply frequencies. A low input power factor of 0.9996 and a minimum current THD of 2.52% are recorded from the developed prototype.

Design and analysis of a novel four‐channel optical filter using ring resonators and line defects in photonic crystal microstructure

In this paper, we report a new design of an all-optical filter using photonic crystal microstructure. Ring resonators, line defects, scatterer rods, microcavities, and coupling rods are used to form the filter in order to extract specific wavelengths at the output channels. The well-known plane wave expansion method is used to calculate the photonic band diagram. The widely used finite-difference time-domain method is also applied to study the light propagation inside the filter. Our numerical results demonstrate that the proposed structure has high transmission power, high-quality factor, and low cross-talk. They reveal an optical signal centered at 1522 nm exits the first output channel, which has an output-to-input ratio (OIR) of 95 % with a bandwidth (FWHM) of 0.4 nm, and an optical signal centered at 1520.8 nm exits the second output channel with an OIR of 98 % and an FWHM of 0.5 nm. The third output channel can exit the optical signal centered at 1518.2 nm with an OIR of 78 % and an FWHM of 0.4 nm. Furthermore, the fourth channel will exit the optical signal at 1519.3 nm with an OIR of 56 % and an FWHM of 0.4 nm. Therefore, the quality factors of the first to fourth outputs of the filter are equal to 3805, 3041, 3795, and 3798, respectively. The first to fourth outputs’ cross-talk values are also − 37 dB, − 36 dB, − 41 dB, and − 38 dB, respectively, which confirm the least interference between output channels. Besides, linear dielectric rods form the filter design that leads to the filter’s appropriate performance at a low input power that is the most important benefit of this work compared to other recently published articles. The maximum rise time of the proposed filter for all output ports is less than 8 ps. The structure also has ​​375.84 µm2, which makes the filter easy to use in photonic integrated circuits.

A Light-Driven Vibrotactile Actuator with a Polymer Bimorph Film for Localized Haptic Rendering.

A vibrotactile actuator driven by light energy is developed to produce dynamic stimulations for haptic rendering on a thin-film structure. The actuator is constructed by adopting a thermal bimorph membrane structure of poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonate (PEDOT-Tos) coated onto a polyethylene terephthalate (PET) film. Upon irradiation of near-infrared (NIR) light, the light energy absorbed at the PEDOT-Tos layer is converted into thermoelastic bending deformation due to the mismatch in coefficient of thermal expansion between PEDOT-Tos and PET. Since the light-induced deformation is reversible, spatially localized, and rapidly controllable with designed light signals, the proposed actuator can produce vibrotactile stimulation over 10 dB at arbitrary areas in the human-sensitive frequency range from 125 to 300 Hz using a low input power of ∼2.6 mW mm-2, as compared with a complex electrical circuit and high input power needed to achieve such actuation performance. Together with its simple structure based on light-driven actuation, the advent of this actuator could open up new ways to achieve substantial advances in rendering textures at a flexible touch interface.

Phase-preserving NALM regenerator with lower input power by optimizing the nonreciprocal phase shifter

We propose a new nonlinear amplifying loop mirror (NALM)-based phase-preserving amplitude regenerator (so-called NP-NALM) by introducing a nonreciprocal phase shifter to further improve the regeneration performance. The theoretical model of the NP-NALM structure and the amplitude regeneration and phase-preserving conditions are presented. It is shown that the optimal working point power reduces with the increase of the nonreciprocal phase shift in the available range and the first working point power can be as low as 115 mW by optimizing the nonreciprocal phase shifter. We also investigate the cascaded NP-NALM transmission system for quadrature phase-shift keying signals with amplified spontaneous emission noise and the output error vector magnitude (EVM) can reduce to 23% from the EVM limit of 30%, corresponding to bit error ratio of 10-3 for the cascaded system without regeneration.

Application of induction heating in the FDM/FFF 3D manufacturing

This article addresses the problem of induction heating in its application to the FDM/FFF 3D manufacturing. One of the major problems of the FDM/FFF is the instability of layer-to-layer adhesion quality, and on the larger scale - maintaining the homogeneity of material inside the whole printed object. Approach for mitigating and/or resolving of those problems, based on the fast and reliable control of the extruded material temperature during the printing process was proposed. Such approach uses specially created testbed system, consists of the ultra-low weight induction heated nozzle and fast temperature controller. This equipment enables rapid heating and cooling of the nozzle at low input power. On the contrary, using of the nozzle with the minimal thermal mass poses the problems of maintaining even heat distribution on the nozzle surface, and therefore inside the heated material. Multiphysics FEM model for the electromagnetic and thermal problem for the proposed nozzle and inductor configuration was formulated, and numerically solved using COMSOL 5.2a. Parametric optimization of the inductor form and heating signal frequency was conducted. Series of the experiments with the optimized inductor construction were made using the proposed testbed, showing significant increase of the heating speed and uniform heat distribution on the nozzle surface, and therefore in the final printed object quality. Experimental data for the all stages of conducted research is provided.

Quad-Band Multiport Rectenna for RF Energy Harvesting in Ambient Environment

This article proposes a quad-band multiport harvester that can scavenge ambient radio frequency (RF) energy of available frequency bands (i.e. GSM-900, GSM-1800, 3G and Wi-Fi) efficiently. This design's novelty is the use of frequency-dependent multiple antenna ports that enables the harvester to fully exploit all available frequency bands, spatial diversity, and polarization for maximizing the harvested RF energy at a lower power density level in an ambient environment. Indistinctly, the proposed antenna consists of 8-port which maintain 0.33λ×0.33λ (i.e. wavelength λ calculated at 0.9 GHz in free space) average area per port and has achieved more than 35% relative bandwidth (BW) with a maximum gain of 6.5 dBi to cover the selected frequency bands. Besides, the proposed quad-band rectifier with a multi-stub impedance matching network is feasible for RF harvesting over the available ambient frequency bands. The proposed rectenna's measurement results show that the generated average dc output voltage is increased up to 0.750 V at a low RF input power density of -27 dBm for a load resistance of 2.11 kΩ. The overall dc rectification efficiency of the 8-port pixel harvester is also assessed and depicted to be 66.52% when the resultant RF input power density level is -27 dBm. Measurement in an ambient outdoor and controlled indoor environment is also conducted, demonstrating that the new 8-port pixel RF harvester can produce a dc output voltage of 0.797 V which is greater than some of the reference RF harvesters.

Simple Adaptive Rectifier with High Efficiency over a Range of 21 dBm Input Power for RF Energy Harvesting Applications

This paper presents a novel simple adaptive and efficient rectifier for Radio Frequency (RF) energy harvesting applications. Traditional rectifiers have maximum RF-DC Power Conversion Efficiency (PCE) over a narrow range of RF input power due to diode breakdown voltage restrictions. The proposed adaptive design helps to extend the PCE over a wider range of RF input power at 2.45GHz using a simple design. Two alternative paths arecontrolled depending on the RF input power level. Low input power levels activate the first path connected to a single rectifier; low power levels make the diode operate below its breakdown voltage and therefore avoiding PCE degradation. High input power levels activate the second path dividing it into three rectifiers. This keeps input power at each rectifier at a low power level to avoid exceeding the diode break down voltage. Simulated PCE of this work is kept above 50% over a range of 21.4 dBm input power from -0.8dBm to 20.6dBm.

Ultrafast reconfigurable nanoscale optical switch based on photonic crystal waveguide

We propose reconfigurable photonic switches with very low input power, ultracompact size, fast response, and low optical loss for high-speed optical network and on-chip interconnect applications. The photonic crystal waveguide-based nanostructure is used to realize the reconfigurable 3 × 3 and 4 × 4 optical switches. The two different operating wavelengths of 1550 and 1630 nm play a significant role in the nanophotonic switching platform. The reconfiguration of optical signal path is effectively attained using these wavelengths with low delay time and high data rate. The performance of nanoswitch parameters is numerically investigated by the finite-difference time-domain method. The proposed optical switch is designed with a low input power of 0.5 mW, fast response time of 607.33 fs, and high data rate of 1.646 Tbps. This high-performance device can be suitable for lightwave communication network, quantum computing, and nanoscale photonic integrated systems.

Effects of geometry and orientation of food products on heating uniformity during radio frequency heating

In radio frequency (RF) assisted heat treatment of food products, heating behavior depends on the composition and geometry of a product. In this study, the effect of salt added to a food simulant on its dielectric properties and penetration depth (dp) were determined across a temperature range from 5 to 80 °C. Three primitive geometries (cube, cylinder and sphere) of a food simulant having a standardised volume (3.98 × 10−4 m3) heated in a custom-built 50 Ω RF system to investigate the impact of sample geometry and orientation on power absorption and heating uniformity. Experimental results revealed vertical oriented cylinder samples followed by cubes showed better temperature uniformity. The temperature at the core of food simulant samples after 6 min RF heating using 500 W power was 44 ± 7.1 °C, 45.3 ± 0.9 °C and 52.9 ± 3.5 °C in cube, cylinder, and sphere sample, respectively. However, the sphere sample was characterized by having the hottest spot at the bottom section. RF power level also played a significant role in heating uniformity with lower power input resulting not only in a slower heating rate but also in less uniform temperature distribution. This study provided a potential insight on the use of food simulants for evaluating RF heating design and performances.

A Low Phase Noise All Cryogenic Microwave Oscillator Based on a Superconductor Resonator.

A 1-GHz full cryogenic oscillator is presented. The oscillator is based on a planar superconductor resonator featuring a loaded Q factor of 200 000 at low microwave input power (unloaded Q of 400 000) and on amplifying parts realized with SiGe bipolar transistors. The circuit is designed with a harmonic balance software and realized on an alumina substrate. A nonlinear model is extracted at low temperature both for the transistor and the resonator. This double nonlinearity increases the difficulty of the oscillator design and implies a strategy to limit the power inside the resonator. The vibrations of the cryogenerator are also a serious issue to get high performance. Finally, the oscillator features a phase noise of -112 dBc/Hz at 100-Hz offset frequency and a phase noise floor of -170 dBc/Hz (100-kHz offset) at a temperature of 65 K.

(Keynote) Decoupled Electrolysis for Water Splitting and Beyond

The storage of renewably-generated energy as hydrogen via the electrolysis of water is a fundamental cornerstone of a sustainable hydrogen economy. Conventional electrolysers usually require stable power inputs in order to operate effectively and safely and so may be unsuited to harnessing renewable power, which is often intermittent and diffuse. Electrolysis mediated by Electron-Coupled-Proton Buffers (see, for example: Nature Chem. 2013, 5, 403-409; Science, 2014, 345, 1326-1330; J. Am. Chem. Soc. 2016, 138, 6707–6710; Joule, 2018, 2, 1390-1395) has the potential to overcome some of the challenges surrounding electrolysis using low and/or sporadic power inputs (especially those related to gas crossover) as the use of Electron-Coupled-Proton Buffers allows the oxygen and hydrogen evolution reactions to be completely decoupled from one another. In this talk, we shall investigate these claims for decoupled electrolysis (Electrochim. Acta, 2020, 331, 135255) and also explore the use of Electron-Coupled-Proton Buffers in new contexts such as redox flow batteries (Nature Chem. 2018, 10, 1042-1047) and electrochemical CO2 reduction.

Experimental study on confinement effect of two-phase closed thermosyphon and heat transfer enhancement using cellulose nanofluid

This study experimentally investigated the confinement effect on the boiling regime of a two-phase closed thermosyphon and heat transfer enhancement using cellulose nanofiber fluid as the working fluid. The design lengths of the condenser, adiabatic, and evaporator sections of the experiment apparatus were 400, 150, 300 mm, respectively. The filling ratios were set to 0.25, 0.5, and 0.75. The applied input power was limited to 800 W owing to the heat resistance limit of the heating block, which supplies heat to the evaporator section. By applying Confinement number of 0.245 and using de-ionized water as the working fluid, the inner diameter of the channel was set to 11 mm. The boiling regime for each level of input power was determined using the surface temperature graph of the thermocouples attached to the evaporator section. It was observed that geyser boiling occurred at a low input power; in this regime, the surface temperature was observed to have a regular long-period oscillation with a large amplitude. Subsequently, the amount of heat increased, the amplitude remained the same, and the cycle length reduced. Churn boiling regime was observed at high input power, with the surface temperature having a very small and irregular amplitude. When the input power was further increased, dry out occurred and the surface temperature soared significantly. Using cellulose nanofiber fluid as a working fluid, the critical heat flux improved by a minimum of 14.3% and the boiling heat transfer coefficient improved by up to 71.74%, compared to water. In addition, aggregation and sedimentation phenomena, which are disadvantages of existing inorganic nanofluids, were not observed after repeated experiments.

Performance evaluation of the dense wavelength division multiplexing system using reconfigurable optical add/drop multiplexer based on digital switches

ROADM technology has reformed optical networking and an intimate part of recent optical communication offering enormous bandwidth for data conveyance at least expense. In this paper, reconfigurability in the dense wavelength division multiplexing system is analyzed with the placement of digital switches by varying the bit rate from 10 to 40 Gbps by adding and dropping certain wavelengths. The performance of the dense wavelength division multiplexing system is characterized in terms of the quality factor, bit error rate and optical signal to noise ratio. It is observed that the signal can be communicated over a distance of 780 km with 16 channels, 420 km with 32 channels and 300 km with 64 channels having a low input power of −10 dBm with an acceptable bit error rate and quality factor. Furthermore, the performance of the system is calculated by varying the number of fiber spans with input power of −10 dBm with a bit rate of 40 Gbps. This structural design permits for remote traffic provisioning at the wavelength level in network node, operation cost reduction, better consumption of communication bandwidth, simplification of network design and implementation.

Markov Decision Process Based Design of SWIPT Systems: Non-Linear EH Circuits, Memory, and Impedance Mismatch

In this paper, we study simultaneous wireless information and power transfer (SWIPT) systems employing practical non-linear energy harvester (EH) circuits. Since the voltage across the reactive elements of realistic EH circuits cannot drop or rise instantaneously, EHs have memory which we model with a Markov decision process (MDP). Moreover, since an analytical model that accurately models all non-linear effects and the unavoidable impedance mismatch of EHs is not tractable, we propose a learning based model for the EH circuit. We optimize the input signal distribution for maximization of the harvested power under a constraint on the minimum mutual information between transmitter (TX) and information receiver (IR). We distinguish the cases where the MDP state is known and not known at TX and IR. When the MDP state is known, the formulated optimization problem for the harvested power is convex. In contrast, if TX and IR do not know the MDP state, the resulting optimization problem is non-convex and solved via alternating optimization, which is shown to yield a limit point of the problem. Our simulation results reveal that the rate-power region of the considered SWIPT system depends on the symbol duration, the EH input power level, the EH impedance mismatch, and the type of EH circuit. In particular, a shorter symbol duration enables higher bit rates at the expense of a significant decrease in the average harvested power. Furthermore, whereas half-wave rectifiers outperform full-wave rectifiers in the low and medium input power regimes, full-wave rectifiers are preferable if the input power at the EH is high.

Simulation of low-noise amplifier with quantized ballistic nanowire channel

The concept of a cryogenic low-noise amplifier (LNA) using quantized conduction in a 1D channel is proposed and explored through simulations. A MOSFET with a 1D channel (nanowire) will exhibit the formation of plateaus in the current due to sub-band quantization at temperatures of below about 100 K and low drive bias. Using a ballistic 1D top-of-the-barrier model, we show that the current plateaus significantly enhance the transconductance, enabling low noise and high gain at low DC power dissipation—key characteristics for LNA applications such as quantum computing. The results indicate that cryogenic 1D ballistic MOSFETs may offer a significant improvement in noise performance and power dissipation (40x reduction) over traditional devices for cryogenic applications with low input power, such as quantum computing.

Compact Rectifier Circuit Design for Harvesting GSM/900 Ambient Energy

In this paper, a compact rectifier, capable of harvesting ambient radio frequency (RF) power is proposed. The total size of the rectifier is 45.4 mm × 7.8 mm × 1.6 mm, designed on FR-4 substrate using a single-stage voltage multiplier at 900 MHz. GSM/900 is among the favorable RF Energy Harvesting (RFEH) energy sources that span over a wide range with minimal path loss and high input power. The proposed RFEH rectifier achieves measured and simulated RF-to-dc (RF to direct current) power conversion efficiency (PCE) of 43.6% and 44.3% for 0 dBm input power, respectively. Additionally, the rectifier attained 3.1 V DC output voltage across 2 kΩ load terminal for 14 dBm and is capable of sensing low input power at −20 dBm. The work presents a compact rectifier to harvest RF energy at 900 MHz, making it a good candidate for low powered wireless communication systems as compares to the other state of the art rectifier.

Range-speed mapping and target-classification measurements of automotive targets using photonic-radar

The frequency-modulated continuous-wave radar is an ideal choice for autonomous vehicle and surveillance-related industries due to its ability to measure the relative target-velocity, target-range, and target-characterization. Unlike conventional microwave radar systems, the photonic radar has the potential to offer wider bandwidth to attain high range-resolution at low input power requirements. Subsequently, a frequency-modulated continuous-wave photonic-radar is developed to measure the target-range and velocity of the automotive mobile targets concurrently with acceptable rang resolution keeping in mind the needs of the state-of-the-art autonomous vehicle industry. Furthermore, the target-identification is also an important parameter to be measured to enable the futuristic autonomous vehicles for the recognition of the objects along with their dimensions. Therefore, the reported work is extended to characterize the target-objects by measuring the specular-reflectance, diffuse-reflectance, the ratio of horizontal-axis to vertical-axis, refractive index constants of the targets using the bidirectional reflectance distribution function. Furthermore, the reflectance properties of the target-objects are also measured with different operating wavelengths at different incident angles to assess the influence of the operating wavelength and the angle at which the radar-pulses incident on the surface of the targets. Moreover, to validate the performance of the demonstrated work, a comparison is also presented in distinction with the conventional microwave FMCW-RADAR.