Input Power Level Research Articles

Analysis and Design of a Resonant Power Converter With a Wide Input Voltage Range for AC/DC Applications

Resonant converter topologies have the ability to eliminate switching losses through zero-voltage switching (ZVS), making them well-suited for switching operation in the MHz frequency range. However, these types of converters are traditionally very sensitive to changes in input voltage and power level, making them unsuitable as power factor correcting ac–dc converters. This article presents a thorough analysis of the operation of a class DE converter in order to derive a set of conditions under which it can achieve a constant input impedance over a wide input-voltage range (60–325 Vdc) with a constant output voltage (450 Vdc) and, thus, be operated as a power factor correctional (PFC) converter, while maintaining ZVS across the full range. The operation is experimentally verified under dc–dc operation for different power levels at a series of input voltages within the specified range. The implemented prototype achieves conversion efficiencies of up to 94% and handles up to 105-W power at a switching frequency of 2 MHz and above, while achieving constant input impedance over the full input-voltage range, enabling its use as a power factor correcting converter.

A Modified Poly-Harmonic Distortion Model Based on the Canonical Piecewise Linear Functions for GaN HEMTs

A novel, large-signal behavioral modeling methodology for Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs), based on the canonical piecewise-linear (CPL) functions, is presented in this paper. The proposed new model employs the poly-harmonic distortion (PHD) model framework, making use of the CPL functions for interpolation of the amplitude of the dominant input signal. The CPL method is also applied to the quadratic PHD (QPHD) model framework, allowing for application to devices operating under high (greater than 3 dB) compression levels. Compared with the standard PHD/QPHD models, which require lengthy tables of parameter values to account for the varying large signal input power(s), the models described in this paper are able to predict transistor behavior at different levels of input power, from the linear region to the strongly nonlinear region (where gain compression exceeds 1 dB), with one single set of model coefficients. The basic theory of the proposed model for both RF and dc responses is provided in the paper. The proposed modeling technique is validated through simulated and experimental data from separate 6 W and 10 W GaN HEMT devices, over a wide range of load conditions and power levels. In addition, a two-dimensional polynomial-based model is used for performance comparison, with the proposed method providing comparable accuracy while requiring significantly fewer model coefficients.

Design of Compact Dual-Band RF Rectifiers for Wireless Power Transfer and Energy Harvesting

In this paper, we propose a compact dual-band impedance matching network (DBIMN) for radio frequency (RF) rectifiers. The DBIMN is achieved with a single-stage T-type network, with only three segments of the transmission line. We investigate the closed-form design equations, as a design guideline of the DBIMN. In addition, we propose the design methodology of the rectifier using the DBIMN. For validation, we design two dual-band rectifiers (0.915 and 2.45 GHz), for different input power levels. The rectifier with high input power level, is designed for a wireless power transmission (WPT) system. With a 12 dBm input power, the measured power conversion efficiencies (PCEs) are 81.7 and 73.1% at the working frequencies. The PCEs becomes 69.2 and 64.1% (at −1 dBm input power) for the low-power input rectifier that can be used in an RF energy harvesting (RF-EH) system. The simulated and measured results match each other well. Compared with previous designs, the proposed designs have advantages in compactness and high efficiency.

A Sensitive Triple-Band Rectifier for Energy Harvesting Applications

This paper presents a novel sensitive triple-band power rectifier for RF energy harvesting systems. The proposed rectifier can simultaneously harvest RF energy from GSM-900, GSM-1800, and Wi-Fi-2450 bands at relatively low and medium ambient power densities. Previously, a few multi-band rectennas have been reached a stable conversion efficiency overall frequency bands of interest because of the nonlinearity and the distinct input impedance of the rectifying circuit at these frequencies. The originality of this paper is on the improved impedance matching technique that enhances the efficiency and performance of the rectifier. The proposed high-efficiency triple-band rectifier consists of three parallel branches. Each branch comprises an input matching circuit designed to provide maximum RF power transferred to rectifying diodes, a single voltage doubler using Schottky diode HSMS-2852, and a DC-pass filter to smooth the DC output voltage. A prototype of the proposed rectifier circuit is fabricated and tested to verify its performance against the simulation results. With an optimum load resistance of 3.8 kΩ at -10 dBm input power level, the measured RF to DC conversion efficiency achieves 33.7%, 21.8%, and 20% at 0.9, 1.8 and 2.45 GHz respectively. The efficiency is above 46.5 % overall bands of interest under 0 dBm input power.

Behavioral Modeling of GaN Doherty Power Amplifiers Using Memoryless Polar Domain Functions and Deep Neural Networks

In this paper, novel Doherty Power Amplifier (DPA) models are presented. The motivation behind the proposed models is to accurately predict static nonlinearities in the compression regions of the carrier and peaking amplifiers. DPAs suffer from a nonlinearity that originates from the carrier amplifier, and a second more pronounced nonlinearity generated at the full compression region following the turn-on of the peaking amplifier. Moreover, these distortions are often observed at different input power levels depending on whether the AM-AM or the AM-PM characteristic is considered. Therefore, the proposed static model is based on independent modeling of the memoryless gain in the polar domain. The static model of the memoryless AM-AM and AM-PM characteristics is augmented with either memory polynomials or deep neural network functions for memory effects modeling. The methodology of building the proposed models and the achieved results are discussed in this paper. The MP based proposed model achieves an NMSE as low as -45.3dB with only 78 model parameters, while the DNN based model achieves an NMSE as low as -46.1dB with only 156 model parameters. However, the DNN based model achieves the best model resilience to changes in the identification data.

Carbon dioxide conversion in an atmospheric pressure microwave plasma reactor: Improving efficiencies by enhancing afterglow quenching

Microwave plasma is effective for decomposing CO2, which is a major contributor to global warming. Atmospheric pressure microwave plasma is of particular interest due to its vacuum-free configuration. Here, we investigated the CO2 conversion performance of a microwave plasma system operating at atmospheric pressure. CO2 conversion efficiency and energy efficiency were measured for various CO2 flow rates and input power levels. Lower CO2 flow and higher power yielded an enhanced CO2 conversion efficiency and lower energy efficiency. The afterglow temperature in the reactor was also measured. At a specific energy input (SEI) of 7.25 eV/molecule, a temperature of 1342 K was observed 12 cm below the gas injection nozzle. To improve the efficiencies of the plasma system, we propose an afterglow quenching method with enhanced heat transfer characteristics. This was achieved using a water-cooled quenching rod inserted into the plasma reactor to cool the afterglow gas stream, thus limiting the recombination reaction of CO to form CO2. At a SEI of 7.22 eV/molecule, CO2 conversion increased from 30.1% to 36.1% with the quenching rod; at 2.46 eV/molecule, the increment of CO2 conversion efficiency was 29 %. An energy efficiency of 28.9 % was achieved using an SEI of 1.19 eV/molecule. By tracking down the heat loss to cooling water flowing through the applicator, exhaust port, and quenching rod, we determined the energy distribution from the plasma plume to the exit gas stream. The quenching rod increased the chemical enthalpy of the product gas by reducing CO recombination.

RF Energy Harvesting using Wireless Sensor Network for Low Power Applications

The evolution of telecommunications systems emphasizes the importance of RF energy in the surroundings. This energy can be utilized for less power device namely wireless sensor network. The performance of small DC/RF converter is calculated in this paper in sequence to enslave the WSN performance for energy recovered. Specially to attain the performance in GSM band the efficient rectifier is achieved. Based on the selection of rectifying diode the design methodology works and causes the losses in rectifying antenna. By employing the slope method the advantageous performance is obtained in Advanced Design System (ADS) software. Implementing Schottky diodes in rectifier and voltage doubler HSMS 2850 is used. RF/DC conversion the maximum efficiency is 38% is achieved with 10dBm input power level. A uniform distribution of sensor node with network loads is utilized to control the WSN performance of Base station location as well as distance. For such reason Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is utilized.

WIDEBAND TRANSFORMER FOR MATCHING OF LOW-IMPEDANCE LOADS IN VERY HIGH FREQUENCY RANGE

The article presents the results of preliminary research in the wideband transformer development for matching low-ohms loads in the very high frequency band with the use of a coupled transmission lines. The transmission line was produced with the using of a polyimide in the form of flexible printed circuit board. This way may be useful for wideband matching different cascades with custom values of input and output impedance in the wide band of frequencies and powers with use of a defining impedance capability with a load character in mind. On the first stage, the computer simulation of transformer with a transformer ratio 4:1 in the band (40–240 MHz) was completed for limiting values of input and output resistances – 50 and 12,5 Ohms respectively. Results of simulation give us the data about constructive parameters of the transmission line. The measurement technique for insertion loss was worked out. The reason of that is an impossibility of appliance standard methods with using a network vector analyzer. The prototyping was done and values of the standing wave ratio and inserting losses were obtained for different levels of the input power. According to received data, it can be affirmed, that the manufactured transformer provides the standing wave ratio better (lower) that two. Inserting losses vary from 0,02 to 1,54 dB depending from a input power level (1– 1000 mW). The obtained results afford ground for working continuation in this field – a development of wideband transformers for matching of low-ohms loads.

Improved analytical approach for studying the effect of diode power detector modelling on six-port communication receiver performance

Purpose The purpose of this paper is to study the effect of diode power detector modelling on six-port communication receiver performance. Design/methodology/approach Based on proposed and conventional squared diode model, six-port receiver’s demodulation and its error vector magnitude (EVM) performance due to hardware impairments are studied. Through considering both the models, the accuracy of proposed power detector model is compared to the squared model, and then both results are validated with envelope simulation (ENV) in advanced design system (ADS). Findings Comparing the numerical results with envelope simulation results proved that the proposed model is much more accurate than the conventional squared model for a wide range of input power levels. Originality/value Studying the receiver’s performance numerically, by considering the new proposed analytical approach for diode power detectors which is more accurate than the conventional squared model.

Development of the Concept of High-Power Microwave Oscillators with Phase Locking by an External Signal

By simulations and experiments we develop a method for generation phase locking of a Ka-band subgigawatt nonstationary relativistic backward-wave oscillator (BWO) with an external radio pulse, the duration of which is considerably greater than the pulse duration of a driven BWO. The level of input power (about 20 kW), which provided phase locking with a total spread of about 1.2 rad, is determined both for the case of competition with an electromagnetic disturbance from a steep front of the beam current and the case of a slow current rise without phase locking in the self-excitation mode. The phase locking effect is achieved with a significant difference in the frequencies of the external radio pulse and driven BWO (about 1 GHz) and hence differs from the amplification mode.

Dielectric-Loaded Conformal Microstrip Antennas for Versatile In-Body Applications

Wireless implantable bioelectronics and accurate in vivo characterization of path loss require efficient and robust in-body antennas. Loading electric antennas with the effective permittivities higher than that of surrounding tissues are a promising solution. In this letter, proof-of-concept conformal microstrip antennas are proposed. The antennas are optimized for a standard impedance of 50 $\Omega$ and operate in all high-water-content tissues. Integral ground plane shields the antenna from inner circuitry. The radiation efficiencies are 0.4%, 2.2%, and 1.2% for the (434, 868, and 1400) MHz designs, respectively, when computed in a $\varnothing$ 100 mm spherical phantom with muscle-equivalent properties. The efficiencies are compared to the fundamental limitations and closely approach them. Specific absorption rates are evaluated, and the corresponding maximum input power levels are established. Prototypes are fabricated and characterized to validate the design.

Experimental and Numerical Investigations on a Phase Change Material Based Heat Sink with Symbiotically Joined Heat Pipe

This paper reports the results of experimental and numerical investigations on a phase change material based heat sink, with a compact heat pipe as the thermal performance enhancer. The evaporator of heat pipe is placed in such a way that, it is in symbiotic association with the phase change material in the heat sink. Visualization studies and numerical simulations are carried out using a digital camera and enthalpy porosity formulation with equivalent thermal conductivity model respectively. Parametric studies are carried out at 33, 66 and 99% fill ratios of phase change material and at power levels of 6, 8 and 10 W. The heat sink with heat pipe shows superior performance at all fill ratios of the phase change material and for all input power levels over the heat sink without the heat pipe. Experiments are also conducted on a heat sink with radial plate fins as an embedded thermal performance enhancer. Results are very encouraging with the heat sink coupled with the heat pipe showing an enhancement up to 30% and 175% in the time to reach set points during charging and discharging cycles respectively, and in overall effectiveness, it shows 3.58 times enhancement over the heat sink with embedded thermal performance enhancers.

Nonlinear performance and small signal model of junction-less microring modulator

In this paper, we have studied the nonlinear performance and modeled the junction-less microring modulator (JL-MRM) designed on the standard silicon-on-insulator (SOI) platform. The JL-MRM utilizes the electrostatic doping effect to achieve the free carrier plasma dispersion effect in a silicon waveguide. A compact voltage-dependent steady-state model is analytically derived for JL-MRM. Using the compact steady-state model, closed-form expressions for the on–off extinction ratio (ER), optical modulation amplitude (OMA), and the quality of resonance (Q-factor) are also presented. We have also analyzed the nonlinear and chirp performance of JL-MRM. A small signal model for the MRM is also analyzed. The proposed device is simulated using commercially available TCAD and mode solver tools. Simulation results show that for a JL-MRM with 8.75 μm radius, the on–off ER and insertion loss (IL) are 20.5 dB and 1.98 dB, respectively. The estimated Q-value for MRM is approximately 11,630. From the proposed small signal model, the estimated 3-dB bandwidth, chirp parameter, and Q-value are found to be 28.29 GHz, -0.19, and 9979, respectively. From the nonlinear analysis, we also found that the proposed MRM for the input power level of 0 dBm offers approximately 82.15 dB.Hz1/2 and 109.87 dB.Hz2/3 of spurious free dynamic range (SFDR) for second harmonic and third harmonic distortions, respectively.

Design, Analysis, and Performance Evaluation of a UHF RFID Forward-Link Repeater

The range of UHF-RFID systems, involving passive tags, is typically limited by the tag’s RF harvesting circuitry. In this paper a forward-link UHF RFID repeater is proposed. The repeater amplifies the reader-to-tag carrier signal. Then, a passive RFID tag can be successfully identified from a much larger distance, compared to current technology, by exploiting the sensitivity of the reader. The proposed repeater consists of low-cost components; namely a pair of antennas, a low-noise amplifier and passive electronics. The proposed design also accounts for out-of-band emissions and the limitations posed by the maximum effective isotropic radiated power of the EPC UHF Gen2 standard. In contrast to prior-art, it can be deployed with any commercial RFID reader. Link-budget analysis reveals i) that the location of the repeater is of great importance to the system, ii) the range depends on the reverse link and not on the forward, as in typical RFID technology and iii) optimum performance can be achieved with bistatic RFID readers and RFID tags, capable of harvesting RF power at higher input power-levels. It is shown that with common, commercial, monostatic RFID technology, a maximum range of 80m can be achieved. By deploying bistatic configurations, which allow for improved reader’s sensitivity, the read-range could be extended to 350m. By “tuning” the tag’s front-end to achieve good matching for increased incident power levels, the expected range could be increased to 2km. Experimental results validate the performance of the proposed repeater and reveal how the link budget is affected by the tag’s front-end. 73m measured range is experimentally achieved with commercial monostatic RFID equipment.

A compact energy harvesting multiband rectenna based on metamaterial complementary split ring resonator antenna and modified hybrid junction ring rectifier

This article presents an improved wireless energy harvesting multiband rectifying antenna. The proposed design is based on an original optimized bidirectional complimentary split ring resonator (CSRR) metamaterial multiband antenna and a modified hybrid junction ring rectifier with four rectifying branches. It harvests the ambient radiofrequency radiations at GSM, 1.8 GHz; UMTS, 2.1 GHz; WiFi, 2.45 GHz; and 4G-2.6 GHz GSM bands. The created prototypes are printed on a 1.57-mm-thickness FR4 substrate and achieve the needed dimensional optimization in both antenna and rectifier. The CSRR antenna accomplished a maximum harvesting realized gain of 2.41, 2.26, 1.58, and 2.69 dB on the aforementioned frequency bands, respectively, 63.75% of antenna size reduction, and 23.62% rectifier size reduction regarding the conventional designs. The hybrid ring junction is used to independently match the subrectifiers at each frequency band. The realized rectenna has been accurately tested in both controlled and outdoor environments, achieving a 67.6% peak efficiency at 1.8 GHz frequency band for an input power level of 10 dBm. It powered up a digital batteryless watch in the outdoor experiment.

A High-Efficiency Rectifier With Ultra-Wide Input Power Range Based on Cooperative Structure

As the most critical component of wireless power transfer (WPT) and wireless energy harvesting (WEH) systems, the rectifier is required to exhibit excellent performance. Most existing works focus on improvement in efficiency and bandwidth for a given input power level. However, in practice, the input power level is usually unpredictable. Therefore, a rectifier which exhibits high efficiency over a wide range of input power is highly desirable. But existing structures can only achieve limited input power range with a complex configuration. A novel cooperative structure using two diodes with diverse characteristics is proposed to solve these problems. Theoretical analysis and a comparison of performances with conventional ones are carried out. For validation in different application scenarios, two rectifiers operating at 2.4 GHz were designed, fabricated, and measured. For the proposed rectifier I, the measured efficiency is larger than 60% over an input power range from 3.5 to 25.2 dBm. While for rectifier II, the measured efficiency remains over 50% with input power from −6 to 26.5 dBm. These results demonstrated the effectiveness of the proposed structure in extending the input power range, especially for the low power region. Furthermore, the application in a WPT system was also demonstrated.

Design of a 900 MHz Dual-Mode SWIPT for Low-Power IoT Devices

This paper presents a duty cycle-based, dual-mode simultaneous wireless information and power transceiver (SWIPT) for Internet of Things (IoT) devices in which a sensor node monitors the received power and adaptively controls the single-tone or multitone communication mode. An adaptive power-splitting (PS) ratio control scheme distributes the received radio frequency (RF) energy between the energy harvesting (EH) path and the information decoding (ID) path. The proposed SWIPT enables the self-powering of an ID transceiver above 20 dBm input power, leading to a battery-free network. The optimized PS ratio of 0.44 enables it to provide sufficient harvested energy for self-powering and energy-neutral operation of the ID transceiver. The ID transceiver can demodulate the amplitude-shift keying (ASK) and the binary phase-shift keying (BPSK) signals. Moreover, for low-input power level, a peak-to-average power ratio (PAPR) scheme based on multitone is also proposed for demodulation of the information-carrying RF signals. Due to the limited power, information is transmitted in uplink by backscatter modulation instead of RF signaling. To validate our proposed SWIPT architecture, a SWIPT printed circuit board (PCB) was designed with a multitone SWIPT board at 900 MHz. The demodulation of multitone by PAPR was verified separately on the PCB. Results showed the measured sensitivity of the SWIPT to be −7 dBm, and the measured peak power efficiency of the RF energy harvester was 69% at 20 dBm input power level. The power consumption of the injection-locked oscillator (ILO)-based phase detection path was 13.6 mW, and it could be supplied from the EH path when the input power level was high. The ID path could demodulate 4-ASK- and BPSK-modulated signals at the same time, thus receiving 3 bits from the demodulation process. Maximum data rate of 4 Mbps was achieved in the measurement.

A survey on low power RF rectifiers efficiency for low cost energy harvesting applications

In this paper the analysis, simulation and prototyping of radio frequency rectifier topologies for ambient energy harvesting applications are evaluated, highlighting the effects of input power levels below −10 dBm. The equivalent diode impedance model is taken into consideration for better interpreting its effects when attached to each rectifier topology. Furthermore, the output capacitance modeling and its effects over the rectifier efficiency are discussed for different capacitance types, including a radial stub. A prototype of the most prominent topology was built on a low cost FR-4 substrate for RF harvesting in the range of −10 to −20 dBm, resulting in an approximate efficiency between 40% and 25%, respectively.

1.25 GHz – 3.3 GHz broadband solid state power amplifier for L and S bands applications

The research of a single stage broadband solid-state power amplifier based on ATF13876 transistor, which operates in the frequency ranging from 1.25 GHz ~3.3 GHz is presented in this paper. To achieve the broadband performance of the operating bandwidth, a multi-section quarter wave impedance transformer and an approximate transformation of previously synthesized lumped elements into transmission lines are adopted. With neatly design of broadband matching networks and biasing circuit, excellent matching performances and unconditionally stability are achieved over the whole operating bandwidth with a maximum gain of 17.2 dB. The large signal simulation shows that the proposed circuit reaches a saturated output power of 18.12 dBm with a maximum PAE of 27.55% and a 1-dB compression point at 5 dBm input power level. Considering the wide frequency coverage, the features of the proposed design compares favorably with the contemporary state-of-the-art.

Multipower-Level Hysteresis Control for the Class E DC–DC Converters

Featured with simple topology and easy realization of zero-voltage-switching, the Class E dc-dc converter is preferable for very high-frequency application. In this article, a multipower-level (MPL) hysteresis control is proposed for the Class E dc-dc converter, in which, multiple switching frequencies are selected for obtaining multiple input power levels, and the two adjacent input powers closest to the load power are chosen to synthesize the load power. Compared with the on-off control, which has only two input power levels, i.e., the input power in on mode and zero power in off mode, the MPL hysteresis control reduces the modulation frequency, and thus reducing the mode transition losses. Meanwhile, the conduction losses are also reduced. As a result, the efficiency of the converter is greatly improved. The parameters design and the switching frequencies selection for the Class E dc-dc converter with MPL hysteresis control are presented. Finally, a prototype of 10-W Class E dc-dc converter with 9-18 V input is fabricated and tested in the lab, and the experimental results are provided to verify the effectiveness of the proposed MPL hysteresis control scheme.