Input Power Range Research Articles

Multitone Excitation Analysis in RF Energy Harvesters—Considerations and Limitations

The effect of multitone excitation on the dc response of a voltage-doubler radio frequency energy harvester is analyzed. Theoretical analysis as well as frequency and time domain (TD) simulations were conducted to clarify the findings. Measurements were also carried out to validate the results. The measured, simulations and theoretical results are in good agreement. This paper focuses on evaluating the performance of a voltage doubler rectifier under multitone excitation (input power is the same in the single-tone and multitone case). Based on TD and harmonic balance simulations, theoretical and measurement analyses, it is evident that the application of multiple tones simultaneously within the matched frequency band and with the same average available power results in a lower average output dc power when compared with the single-tone case with the same input power. This trend is evident over a broad low input power range of −50 to −10 dBm (0.01–100 $\boldsymbol {\mu }\text{W}$ ).

Experimental and Numerical Study Effect of Using Nanofluids in Perforated Plate Fin Heat Sink for Electronics Cooling

An experimental and numerical investigation of the effect of using two types of nanofluids with suspending of (Al2O3 and CuO) nanoparticles in deionized water with a volume fraction of (0.1% vol.), in addition to use three types of fin plate configurations of (smooth, perforated, and dimple plate) to study the heat transfer enhancement characteristics of commercial fin plate heat sink for cooling computer processing unit. All experimental tests under simulated conditions by using heat flux heater element with input power range of (5, 16, 35, 70, and 100 W). The experimental parameters calculated are such as water and nanofluid as coolant with Reynolds number of (7000, 8000, 9400 and 11300); the air is blown in the inlet duct across the heat sink with Reynolds number of (10500, 12300, 14200 and 16000). The distance fin-to-fin is kept constant at (2.00 mm), and the channel employed in this work has a square cross-section of (7 cm) inside. It was observed that the average effectiveness and Nusselt number of the nanofluids are higher compared with those of using conventional liquid cooling systems. However, the perforated fin plate showed higher air heat dissipation than the other configuration plate fin employed in this study. The experimental results were supported by numerical results which gave a good indication to heat transfer enhancement in studied ranges.

Development of a tunable low-frequency vibration energy harvester and its application to a self-contained wireless fatigue crack detection sensor

In this study, a tunable electromagnetic energy harvesting system, consisting of an energy harvester and energy harvesting circuits, is developed for harnessing energy from low-frequency vibration (below 10 Hz) of a bridge, and the harvesting system is integrated with a wireless fatigue crack detection sensor. The uniqueness of the proposed energy harvesting system includes that (1) the resonance frequencies of the proposed energy harvester can be readily tuned to the resonance frequencies of a host structure, (2) an improved energy harvesting efficiency compared to other electromagnetic energy harvesters is achieved in low-frequency and vibration, and (3) high-efficiency energy harvesting circuits for rectification are developed. Furthermore, the developed energy harvesting system is integrated with an on-site wireless sensor deployed on Yeongjong Grand Bridge in South Korea for online fatigue crack detection. To the best knowledge of the authors, this is the very first study where a series of low-frequency vibration energy harvesting, rectification, and battery charging processes are demonstrated under a real field condition. The field test conducted on Yeongjong Grand Bridge, where fatigue cracks have become of a great concern, shows that the proposed energy harvester can generate a peak voltage of 2.27 V and a root mean square voltage of 0.21 V from 0.18-m/s2 root mean square acceleration at 3.05 Hz. It is estimated the proposed energy harvesting system can harness around 67.90 J for 3 weeks and an average power of 37.42 µW. The battery life of the wireless sensor is expected to extend from 1.5 to 2.2 years. The proposed energy harvesting circuits, composed of the AC–DC and boost-up converters, exhibit up to 50% battery charging efficiency when the voltage generated by the proposed energy harvester is 200 mV or higher. The proposed boost-up converter has a 100 times wider input power range than a conventional boost-up converter with a similar efficiency.

Microstructure, Mechanical Properties, and Crack Propagation Behavior in High-Nb TiAl Alloys by Directional Solidification

Titanium aluminide (Ti-47Al-6Nb-0.1C) alloys were prepared using a cold crucible directional solidification technique with an input power range of 35 to 55 kW under a withdrawing velocity of 0.4 mm/min. The macro/microstructure was characterized, and the mechanical properties were evaluated. The results show that the directional solidification (DS) ingots exhibit β-solidification characteristics at an input power range of 35 to 55 kW, and a well-developed DS microstructure was acquired at an input power range of 40 and 45 kW. With the increasing input power, the lamellar spacing decreases, resulting in the increasing tendency in the average room-temperature yield strength. The steady-state creep rate strongly depends on the lamellar spacing, and the creep life depends on the DS microstructure. The well-developed DS alloy can significantly improve the creep properties but has little influence on the room-temperature tensile properties. Moreover, after testing the fracture toughness, the crack propagation showed interlamellar cracks, translamellar cracks, and intercolony boundary cracks that primarily propagated along the colony boundary after creep testing.

Two‐terminal InGaAs microwave amplifier

AbstractThe feasibility of using a 2‐terminal InGaAs planar Gunn structure as a microwave amplifier is proposed and verified. By achieving a pronounced negative differential resistance with a peak‐to‐valley current ratio of 1.20, our devices are able to amplify microwaves at a high gain of 17 dB. When compared with commonly used 3‐terminal transistor‐based microwave amplifiers, the proposed devices not only have a simple structure but also are capable of achieving high operating frequencies even with relatively large feature sizes. The device with a channel length of 4 μm has a positive gain up to about 77 GHz, and the 2‐μm device is able to amplify microwaves well beyond 110 GHz. Furthermore, the planar Gunn amplifier shows a good linearity over a wide input power range from −45 to about 0 dBm. A good operation stability has also been demonstrated despite having no substrate thinning and heat sink.

Analysis and experiment of a bio-inspired flyable micro flapping wing rotor

Inspired by insect flapping wings, a novel flapping wing rotor (FWR) has been developed for micro aerial vehicle (MAV) application. The FWR combines flapping with rotary kinematics of motions to achieve high agility and efficiency of flight. To demonstrate the feasibility of FWR flight and its potential MAV application, an extensive and comprehensive study has been performed. The study includes design, analysis, manufacture, experimental and flight test of a flyable micro FWR model of only 2.6 g weight. By experiment, the FWR kinematic motion and aerodynamic lift were measured using high speed camera and load cells. Within a range of input power, the difference between the measured aerodynamic force and the analytical results by a quasi-steady model was found to be within 3.1%–15.7%. It is noted that the FWR aeroelastic effect plays a significant role to obtain an ideal large angle of attack especially in up-stroke and enhance the FWR performance. Further analysis of the unsteady aerodynamic characteristics has been carried out based on the detailed airflow field of the FWR in a flapping cycle by CFD method. A successful vertical take-off and short hovering flight of the micro FWR model has been achieved for the first time in the research field. The flight test demonstrates the FWR feasibility and its unique feature of flight dynamics and stability for the first time. These characteristics have also been simulated by using ADAMS software interfaced with the aerodynamic model.

High-Efficiency Rectifier With Wide Input Power Range Based on Power Recycling

In this brief, a novel rectifier with power recycling based on a branch-line coupler is proposed to operate within a wide input power range. In the proposed topology, two output ports of the coupler are connected with two subrectifiers dealing with higher power level (main branches), while the isolation port is connected with the subrectifier dealing with lower power level (power recycling branch). By using the branch-line coupler, the power reflected from the two main branches can be efficiently transmitted to the power recycling branch. Consequently, the power can be reused and thus the RF-dc conversion efficiency can be improved. In this way, the rectifier can maintain high efficiency in a wide input power range. Theoretical analysis and performance comparison are carried out, which show that the proposed topology features recycling ability within a wide input power range. For validation, a rectifier working at 2.45 GHz is implemented and compared to other designs. The measured efficiency remains over 50% from 8.5 to 32.5 dBm, indicating that high efficiency can be obtained within wide input power range.

Channelized amplification of RF signal based on actively mode locked fiber laser

A new approach for implementing channelized radio frequency (RF) signals amplification based on actively mode locked laser (MLL) is proposed and demonstrated. The channelized amplification (CA) is based on the mode-locking gain of the fiber ring laser while the frequency of RF signal applied to Mach–Zehnder modulator (MZM) in the fiber laser matching the fundamental or harmonic of the laser cavity mode. The experimental results show that high RF regenerative gain with a maximum 44 dB and high Q factor normally greater than 105 can be achieved with this approach of CA. By electrically tuning the fiber delay line incorporated in the ring laser so as to scan the center frequency of the channelized amplifier, spectrum recognition of quadrature phase shift keying (QPSK) modulated electro-magnetic signal with low power density is successfully implemented. The limit of input power and linear operating dynamic range is also measured and discussed.

Fundamental bounds on the operation of Fano nonlinear isolators

Nonlinear isolators have attracted significant attention for their ability to break reciprocity and provide isolation without the need of an external bias. A popular approach for the design of such devices is based on Fano resonators, which, due to their sharp frequency response, can lead to very large isolation for moderate input intensities. Here, we show that, independent of their specific implementation, these devices are subject to fundamental bounds on the transmission coefficient in the forward direction versus their quality factor, input power, and nonreciprocal intensity range. Our analysis quantifies a general tradeoff between forward transmission and these metrics, stemming directly from time-reversal symmetry, and that unitary transmission is only possible for vanishing nonreciprocity. Our results also shed light on the operation of resonant nonlinear isolators, reveal their fundamental limitations, and provide indications on how it is possible to design nonlinear isolators with optimal performance.

Hydrodynamic characterization of dual-impeller submerged membrane bioreactor relevant to single-use bioreactor options

The flow characteristics e.g. velocity and velocity gradients in a conventional stirred sMBR with in-line tubular membrane module for integrated production and recovery of value-added material, are studied. Considering a hybrid vessel, the flow characteristics are conflicting parameters, viz. high shear is required for membrane walls and low shear required for microbial cells. Attempt is made to find a range of parameters that are balanced against known critical values. The task is resolved by numerical solution of a theoretical model of dual flat-blade impeller Biostat® 5L (T=0.16m, D=6.6cm) equipped with tubular membrane module (L=23cm, d=12mm) operating in non-Newtonian biofluid (flow index range, 0.34<n<0.78). CFD for gasöliquid cross-flow (e.g. EuöEu model) at Re∼103ö2×104 and mesh 106 cells is employed. In a study aimed at sMBR bulk and near-wall flow properties, the effect of gas flow at various tip velocity (1ö2.5m/s), sparging intensity (8ö16m/s) and rheology on shear is revealed. In a range of specific input power 102ö5×103W/m3, the bulk shear rate varied in the range 20ö60s−1 and mean wall shear varied between 600s−1 and 3000s−1. Wall shear stress non-uniformity in the range 1ö30N/m2 is registered. The gas phase is found to reduce wall shear, but to increase shear uniformity. In view of preserving cells’ viability, zonal shear rates of the vessel bulk and sparger openings were determined. Relating the data to similar results in single-use vessels, a correlation reported previously for bulk average shear rate γ˙ versus input power [γ˙=C(P/VR)1/3] is confirmed. A range of balanced bulk and wall shear relevant to hybrid operation is determined. In view of the reported scalability of the conventional MBR design and reusable bioreactors, the data could be used for extrapolation.

Prospects of Tunnel FETs in the Design of Power Management Circuits for Weak Energy Harvesting DC Sources

In this paper, a new tunnel FET (TFET)-based power management circuit (PMC) is proposed for weak dc energy harvesting sources. Thanks to their particular carrier injection mechanisms, TFETs can be used to design efficient energy harvesting circuits by enabling the power extraction from sources which are not only at very low voltage levels (sub-0.1 V) but also at very low power levels (a few nW). As TFET devices are designed as reverse-biased diodes, changes in conventional circuit topologies are required in order to take full advantage of these emerging devices. The circuit design techniques proposed in this paper represent an improvement in output voltage and input power range with respect to previously published TFET-based PMCs. Simulation results show that the TFET-based PMC can sustain itself from a 2.5 nW@50 mV dc source, powering a load at 0.5 V with 29% of efficiency.

Hybrid MZI-SOA InGaAs/InP Photonic Integrated Switches

A low-power, high-performance integrated 4 × 4 hybrid Mach–Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) optical switch is designed, fabricated, and characterized. The 4 mm × 6 mm device is fabricated using an active–passive integration scheme in an InGaAsP/InP foundry. MZIs are implemented as the main switching elements and short switchable SOAs are used to either compensate the loss or suppress the crosstalk. A dilated Benes architecture is implemented to reduce the crosstalk and offer rearrangeably nonblocking connections. The 4 × 4 switch exhibits a low 1.3–dB loss, a crosstalk ratio of −47 dB, and more than 13–dB input power dynamic range (IPDR) for a 0.5–dB power penalty at a 10–Gb/s signal rate. By active control of injection currents into the SOAs, a fixed output power is achieved for a 10-dB range of input power and the IPDR is extended by at least 4 dB. A 12-mA control current tolerance has been demonstrated for a 10-dB IPDR. The performance of a 16 × 16 switch is emulated by cascading two 4 × 4 chips. A record IPDR of 15 dB at a 1-dB penalty is achieved with a 0.6–dB power penalty floor.

Passively Q-switched S-band thulium fluoride fiberlaser with multi-walled carbon nanotube

A stable, passively Q-switched thulium fluoride fiber laser (TFFL) using a multi-walled carbon nanotube (MWCNT)-based saturable absorber (SA) for operation in the S-band region is proposed and demonstrated. The proposed TFFL has a central lasing wavelength of 1486.4 nm and an input power range of 87.1–126.6 mW. The output pulses have a repetition rate and pulse width range of 30.1–40.0 kHz and 9.0–3.2 μs, respectively, with a maximum pulse energy of 28.9 nJ. This is the first time, to the author’s knowledge, of the successful demonstration of a passively Q-switched S-band TFFL using an MWCNT-based SA.

High-Efficiency Microwave Rectifier With Less Sensitivity to Input Power Variation

In this letter, a novel microwave rectifier based on a power recycling network (PRN) is proposed, which features less sensitivity to input power variation. The PRN is connected to the microwave input of two parallel subrectifiers, realizing better matching over a wide power range. For validation, a 2.45-GHz rectifier incorporating the PRN is designed and implemented. The measured results show that the RF-dc conversion efficiency maintains over 50% and 70% within the input power range 10.5–31.8 and 21.7–30.1 dBm, respectively. Compared with the counterpart without the PRN, the operating power range is extended without degrading the maximum efficiency.

Hydropyrolysis of n-Hexane and Toluene to Acetylene in Rotating-Arc Plasma

Thermal plasma pyrolysis is a powerful technology for converting waste or low-value materials to valuable gaseous hydrocarbons. This paper presents for the first time the hydropyrolysis of n-hexane and toluene in a rotating-arc plasma reactor. Effects of the mole ratio of H/C in the feed, power input and magnetic induction were investigated to evaluate the reaction performance. A lower H/C ratio could lead to a lower yield of C2H2 and lower specific energy consumption, and there existed an optimum range of power input for both n-hexane and toluene pyrolysis within the investigated range. The yield of C2H2 in n-hexane and toluene pyrolysis could reach 85% and 68%, respectively, with respective specific energy consumption (SEC) of 13.8 kWh/kg·C2H2 and 19.9 kWh/kg·C2H2. Compared with the results reported in literature, the rotating-arc plasma process showed higher C2H2 yield and lower energy consumption, which is attributed to the better initial mixing of the reactant with the hot plasma gas and the more uniform temperature distribution.

Self-Biased Differential Rectifier With Enhanced Dynamic Range for Wireless Powering

A self-biased cross-coupled differential rectifier is proposed with enhanced power-conversion efficiency (PCE) over an extended range of input power. A prototype is designed for ultrahigh-frequency (UHF) 433-MHz radio-frequency power-harvesting applications and is implemented using a 0.18- $\mu\text{m}$ CMOS technology. The proposed rectifier architecture is compared with the conventional cross-coupled rectifier. It demonstrates an improvement of more than 40% in the rectifier PCE and an input power range extension of more than 50% relative to the conventional cross-coupled rectifier. A sensitivity of −15.2-dBm (30- $\mu\text{W}$ ) input power for 1-V output voltage and a peak PCE of 65% are achieved for a 50- $\text{k}\Omega$ load.

Analysis of free carrier effects on modulational instability in silicon-on-insulator nano-waveguides

We have numerically studied the effect of free-carrier-induced loss and dispersion on the modulational instability (MI) gain at low input powers in silicon-on-insulator (SOI) nanowaveguides with normal and anomalous second-order dispersion. We have shown that the free carriers affect the gain spectra even at low input powers. First time we have reported the gain in normal SOI nanowaveguides even in the absence of higher order dispersion parameters, which is due to the interaction of free-carrier-induced dispersion and nonlinearity. The MI gain in an anomalous SOI nanowaveguide vanishes even at a few milliwatt range of input power due to this interaction. We have shown that the gain could be achieved in an anomalous nanowaveguides by reducing the free carrier lifetime.

A Wide Input Range Dual-Path CMOS Rectifier for RF Energy Harvesting

This brief presents a dual-path CMOS rectifier with adaptive control for ultrahigh-frequency (UHF) RF energy harvesters. The input power range with high power conversion efficiency (high PCE) of the rectifier is extended by the proposed architecture, which includes a low-power path and a high-power path. The dual-path rectifier with an adaptive control circuit is fabricated in a 65-nm CMOS process. Operating at 900 MHz and driving a 147-kΩ load resistor, the measured PCE of this work can be maintained above 20% with an 11-dB input range from -16 to -5 dBm, while only an 8-dB input range can be achieved with traditional single-path rectifiers. A sensitivity of -17.7 dBm is measured with 1-V output voltage across a capacitive load.

浮動ヘッドスライダの接触過程におけるディスク微小うねり励振振動の解析

Vibration characteristics of a flying head slider in hard disk drives at touchdown attract strong interest because head‒disk spacing must be decreased to less than 1 nm in order to increase recording density. This study first evaluates head‒disk interfacial force based on rough surface adhesion contact models and a simple air-bearing force model. Then, microwavinessexcited vibration of single-degree-of-freedom slider model at touchdown was numerically simulated in more detail than the previous study. It was found that the slider exhibits a MW-excited vibration having low frequency components of less than 100 kHz at touchdown and shifts to severe contact state near the boundary of static instability onset. When a small static unstable region is generated by decreasing air-bearing stiffness ratio, the occurrence of the low frequency spacing variation is interrupted by temporal flying state (loss of contact). When the static unstable region further increases by decreasing air-bearing stiffness ratio, the spacing variation with low frequencies can appear only at the beginning of contact and immediately jumps to a light contact state and then shifts to a perfect flying state during a long input power range and eventually jumps to a heavy contact state. These calculated results seem to correspond to the actual slider dynamic behaviors at touchdown in the inner, outer and middle diameter regions. The possibility of surfing recording is discussed from the analytical and experimental evidences.

RF Power Analysis on 5.8 GHz Low-Power Amplifier Using Resonant Tunneling Diodes

This letter reports the analysis of RF power characteristics in a microwave amplifier using resonant tunneling diodes (RTDs). The implemented IC shows a return loss of more than 11 dB with a low dc-power consumption of 0.42 mW and a power gain of 8.6 dB at 5.8 GHz. The maximum linear RF output power with a uniform gain of 8.6 dB is measured to be −25.4 dBm at the same frequency. The gain hump phenomenon is observed in an input power range from −32 dBm to −16 dBm, and is shown to arise from a sudden movement of the operating point from the negative differential resistance (NDR) region to the positive differential resistance (PDR) region, based on a large-signal load-line analysis together with a harmonic balance simulation.