Total Average Power Research Articles

A Novel 3-Way Dual-Band Doherty Power Amplifier for Enhanced Concurrent Operation

This article presents the architecture and design methodology for a new type of dual-band Doherty power amplifier (DB-DPA), referred to as 3-Way DB-DPA, which consists of a main amplifier for each band and an auxiliary amplifier handling both bands. The 3-Way DB-DPA improves the average drain efficiency in concurrent dual-band operation compared to the traditional 2-Way DB-DPA, by avoiding early clipping in the main amplifiers, while benefiting from load—pulling from the auxiliary power amplifier (PA). This improvement is verified in theory and simulation at the current-source reference planes and in measurement with a fabricated 1.5- and 2-GHz dual-band PA. A statistical analysis using 2-D continuous-wave (CW) signals with long-term evolution (LTE) probability distribution functions (PDFs) is performed and demonstrated an improvement in the concurrent average efficiency by 15 percentage points compared to the conventional 2-Way DB-DPA. In nonconcurrent operation, the measured CW drain efficiency in the lower band (1.5 GHz) is 82.8% at peak and 66.6% at 9.6-dB backoff, and the measured CW drain efficiency in the upper band (2.0 GHz) is 70.0% at peak and 48.4% at 9.4-dB backoff. The CW concurrent-balanced drain efficiency reaches 66.2/52.0% in the 3-Way DB-DPA at 3-/6-dB backoff. In single-band operation at 1.5/2.0 GHz, the average power and average drain efficiency after linearization by digital predistortion (DPD) are 35.1/37.4 dBm and 65.0/53.7%, respectively, for an LTE signal with 10-MHz bandwidth and 6.1-dB peak-to-average power ratio (PAPR). In concurrent operation, the 3-Way DB-DPA is driven by two 10-MHz LTE uncorrelated signals at 1.5 GHz with 6.86-dB PAPR and at 2.0 GHz with 6.26-dB PAPR, and the average total power and average concurrent drain efficiency after DPD are 37.5 dBm and 54.24%, respectively.

BER Performance Analysis for Downlink Nonorthogonal Multiple Access With Error Propagation Mitigated Method in Visible Light Communications

In order to mitigate the error propagation (EP) effect on the bit error rate (BER) performance due to the imperfect successive interference cancellation for the non-orthogonal multiple access (NOMA)-based visible light communication (VLC) downlinks, adjustable bit rate superposition coding (ABRSC) and sample-and-sum successive interference cancellation (SSSIC) decoding schemes are proposed in this paper. Based on the modified fixed-power allocation (MFPA) strategy, the closed-form expressions of BER are derived for the two-user case with on-off keying, and further extended to the multi-user scenario. The residual probability of EP is introduced and derived to theoretically assess the effectiveness of the proposed ABRSC and SSSIC schemes. Monte Carlo simulation is also conducted to validate the analytical BER results. The BER performance of the NOMA-based VLC system with multiple users is further analyzed and discussed in detail. It is found that under the total average optical transmission power constraint, the allocated average optical transmission power to current user should be higher than that to all rest of users, i.e., the power allocation factor (PAF) is supposed to be greater than 1/2, in order to avoid the error floor issue of current user, hence facilitating the successful implementation of SSSIC. Besides, increasing the bit-rate factor (BRF) could mitigate the effect of EP, and larger BRF leads to more efficient outcomes in alleviating the effect of EP.

Study of power flow mechanism of capacitive power transfer system based on Poynting vector analysis

In this paper, the power flow mechanism of a typical Capacitive Power Transfer (CPT) system is studied by analysing the electric field, magnetic field, and Poynting vector, to determine the power distribution as well as the average power flow to the load. It is found that the average power from the source flows along the wires on the transmitting side and passes the external areas of the coupling plates mainly along the channel between the two coupling pairs (instead of going through the air gaps in between), then converges along the wires before reaching the load. The average power calculated by integrating the real part of the Poynting vector across a defined power flow plane at the receiving end is consistent with CST (Computer Simulation Technology) simulation, circuit analysis, and practical measurements of the CPT system. Although the power density described by Poynting vector changes with the separation distance between the two coupling pairs, the total average power keeps approximately constant because the power flow area changes accordingly. Compared to the traditional lumped circuit analysis, the Poynting vector analysis shows the power distribution around the coupling plates in relation to their physical configuration. This research reveals the power flow mechanism and distribution in a CPT system from field point of view, which is useful to gain deeper understanding of the CPT system beyond the traditional circuit theory and would also be helpful to improve practical system design in the future.

Beam quality and efficiency of ns-pulsed high-power mid-IR ZGP OPOs compared in linear and non-planar ring resonators.

We compare the performance of ns-pulsed mid-infrared optical parametric oscillators (OPOs) based on ZGP crystals in a simple linear cavity and two non-planar image-rotating resonators. Our 2 μm pump source is a 68 W 10 kHz diffraction limited Ho:LLF MOPA system. In a linear cavity, it allows us to generate up to 38 W of the total average power with M2<2.2 from the ZGP OPO in the 3-5 μm range. Beam quality and stability are significantly improved in both types of non-planar ring resonators (M2<1.8 in RISTRA and M2<1.4 in FIRE), while the total average power is above 21 W. Factors influencing the beam quality such as average power and pump repetition rate are studied in detail.

InAs/InP quantum dash buried heterostructure mode-locked laser for high capacity fiber-wireless integrated 5G new radio fronthaul systems.

We have developed and experimentally demonstrated a highly coherent and low noise InP-based InAs quantum dash (QDash) buried heterostructure (BH) C-band passively mode-locked laser (MLL) with a pulse repetition rate of 25 GHz for fiber-wireless integrated fronthaul 5G new radio (NR) systems. The device features a broadband spectrum providing over 46 equally spaced highly coherent and low noise optical channels with an optical phase noise and integrated relative intensity noise (RIN) over a frequency range of 10 MHz to 20 GHz for each individual channel typically less than 466.5 kHz and -130 dB/Hz, respectively, and an average total output power of ∼50 mW per facet. Moreover, the device exhibits low RF phase noise with measured RF beat-note linewidth down to 3 kHz and estimated timing jitter between any two adjacent channels of 5.5 fs. By using this QDash BH MLL device, we have successfully demonstrated broadband optical heterodyne based radio-over-fiber (RoF) fronthaul wireless links at 5G NR in the underutilized spectrum of around 25 GHz with a total bit rate of 16-Gb/s. The device performance is experimentally evaluated in an end-to-end fiber-wireless system in real-time in terms of error vector magnitude (EVM) and bit error rate (BER) by generating, transmitting and detecting 4-Gbaud 16-QAM RF signals over 0.5-m to 2-m free-space indoor wireless channel through a total length of 25.22 km standard single mode fiber (SSMF) with EVM and BER under 8.4% and 2.9 × 10-5, respectively. The intrinsic characteristics of the device in conjunction with its system transmission performance indicate that QDash BH MLLs can be readily used in fiber-wireless integrated systems of 5G and beyond wireless communication networks.

Multi-objective fault-tolerant optimization algorithm for deployment of IoT applications on fog computing infrastructure

Nowadays, fog computing as a complementary facility of cloud computing has attracted great attentions in research communities because it has extraordinary potential to provide resources and processing services requested for applications at the edge network near to users. Recent researchers focus on how efficiently engage edge networks capabilities for execution and supporting of IoT applications and associated requirement. However, inefficient deployment of applications’ components on fog computing infrastructure results bandwidth and resource wastage, maximum power consumption, and unpleasant quality of service (QoS) level. This paper considers reduction of bandwidth wastage in regards to application components dependency in their distributed deployment. On the other hand, the service reliability is declined if an application’s components are deployed on a single node for the sake of power consumption management viewpoint. Therefore, a mechanism for tackling single point of failure and application reliability enhancement against failure are presented. Then, the components deployment is formulated to a multi-objective optimization problem with minimization perspective of both power consumption and total latency between each pair of components associated to applications. To solve this combinatorial optimization problem, a multi-objective cuckoo search algorithm (MOCSA) is presented. To validate the work, this algorithm is assessed in different conditions against some state-of the arts. The simulation results prove the amount 42%, 29%, 46%, 13%, and 5% improvement of proposed MOCSA in terms of average overall latency respectively against MOGWO, MOGWO-I, MOPSO, MOBA, and NSGA-II algorithms. Also, in term of average total power consumption the improvement is about 43%, 28%, 41%, 30%, and 32% respectively.

Improving frictional performance of ring-liner system under cylinder deactivation conditions by surface texturing

In this study, a method of surface texture is considered to improve the frictional performance of the ring-liner system (i.e. RLS) under the conditions of cylinder deactivation (i.e. CDA). To assess the effectiveness of the method, a lubrication model is developed with considerations of the liner deformation, the actual rheological properties of lubricant, and the lubricant transport. By solving the model numerically, the friction reduction effect of surface texture for the RLS under the CDA is investigated. The results show that the surface texture can improve the friction properties significantly. For a six-cylinder gasoline engine, 7.57% and 7.28% decreases in the total average friction loss and power loss are observed when the RLS under the CDA is surface textured.

Power-Efficient Wireless Streaming of Multi-Quality Tiled 360 VR Video in MIMO-OFDMA Systems

In this paper, we study the optimal wireless streaming of a multi-quality tiled 360 virtual reality (VR) video from a multi-antenna server to multiple single-antenna users in a multiple-input multiple-output (MIMO)-orthogonal frequency division multiple access (OFDMA) system. In the scenario without user transcoding, we jointly optimize beamforming and subcarrier, transmission power, and rate allocation to minimize the total transmission power. This problem is a challenging mixed discrete-continuous optimization problem. We obtain a globally optimal solution for small multicast groups, an asymptotically optimal solution for a large antenna array, and a suboptimal solution for the general case. In the scenario with user transcoding, we jointly optimize the quality level selection, beamforming, and subcarrier, transmission power, and rate allocation to minimize the weighted sum of the average total transmission power and the transcoding power. This problem is a two-timescale mixed discrete-continuous optimization problem, which is even more challenging than the problem for the scenario without user transcoding. We obtain a globally optimal solution for small multicast groups, an asymptotically optimal solution for a large antenna array, and a low-complexity suboptimal solution for the general case. Finally, numerical results demonstrate the significant gains of proposed solutions over the existing solutions.

The Influence of Nordic Walking on Isokinetic Trunk Muscle Endurance and Sagittal Spinal Curvatures in Women after Breast Cancer Treatment: Age-Specific Indicators.

Nordic walking (NW) is a popular form of rehabilitation. NW improves psychophysical condition in breast cancer (BC) survivors. This study aimed to analyze the effects of NW on functional and postural changes of the trunk in women of different ages after BC. We hypothesized that an age relationship would be found. BC survivors (n = 39) were stratified by age as “middle- aged” (45–59 years) or “older” (60–75 years), then randomly allocated to the training intervention. A study group (SG, n = 19) participated in NW and a control group (CG, n = 20) performed general gymnastics. The sagittal spinal curvatures and isokinetic trunk muscle endurance were recorded at two time points, pre- and post-training intervention. Significant within NW group changes (p < 0.05) were found for the total work (TW) and average power (AP) of trunk flexors and extensors and the upper thoracic angle in middle-aged women. In older Nordic walkers, significant increases in TW and AP of the trunk flexor muscles were observed, with a negative increase in the trunk inclination angle. In CG, no significant functional or postural changes were observed in response to general gymnastics. NW improved both functional and postural changes in middle-aged women. This study identified the limitations of NW training in older women.

Methodology for estimating reception efficiency of mutually correlated or in- phase signals at diversity transmission

The article describes and theoretically substantiates the potential technical capabilities of spatially separated earth stations (ES). When several ESs emit in-phase or mutually pairwise correlated signals in the direction of one received antenna of the object, the total level of the sum of emissions at its output (at the input of the receiving path) may be several times higher than the sum of the powers of these signals. In this regard, the article investigates the influence of the phase difference of the transmitted signals on the value of their total average power at the input of the receiving path. In the case of addition of common-mode signals, a formula is used to calculate in which the power of harmonic radiation is proportional to the square of the sum of the amplitude of the common-mode signals. This paradox is also valid for pairwise cross-correlated signals. The presented technique for evaluatingтthe effectivenessтallows one to establish not only the dependence of the energy ratios on the nonтenergy parameter, but also to determine the number of low-power ESs required to ensureтthe required signal level at the input of the receiving device. The use of the presented technique makes it possible to evaluate the efficiency of receiving a combined high-power signal for a differentтnumber of emitters that form in-phase or pairwise mutual correlation of signals at the receiving point.

RIATA: A Reinforcement Learning-Based Intelligent Routing Update Scheme for Future Generation IoT Networks

Future generation Internet of Things (IoT) communication infrastructure is expected to pave the path for innovative applications like smart cities, smart grids, smart industries, and smart healthcare. To support these diverse applications, the communication protocols are required to be adaptive and intelligent. At the network layer, an efficient and lightweight algorithm known as trickle-timer is designed to perform the route updates and it utilizes control messages to share the updated route information between IoT nodes. Trickle-timer tends to generate higher control overhead ratio and achieves lower reliability. Therefore, this article aims to propose an RL-based Intelligent Adaptive Trickle-Timer Algorithm (RIATA). The proposed algorithm performs three-fold optimization of the trickle-timer algorithm. Firstly, the RIATA assigns higher probability to control message transmission to nodes that have received an inconsistent control message in the past intervals. Secondly, the RIATA utilizes RL to learn the optimal policy to transmit or suppress a control message in the current network environment. Lastly, the RIATA selects an adaptive redundancy constant value to avoid unnecessary transmissions of control messages. Simulation results show that RIATA outperforms the other state-of-the-art mechanisms in terms of reducing control overhead ratio by an average of 21%, decreasing the average total power consumption by 10%, and increasing the packet delivery ratio by 4% on an average.

161 W middle infrared ZnGeP2 MOPA system pumped by 300 W-class Ho:YAG MOPA system.

We demonstrated a high-power Q-switched two-stage Ho:YAG master-oscillator power-amplifier (MOPA) system dual-end pumped by Tm:YLF lasers. A new method was introduced by rotating and swapping spatial axial directions of pump beams to improve the beam quality of the Ho:YAG oscillator and first-stage amplifier. Two parallel second-stage Ho:YAG amplifiers were employed to output high power. A total maximum average output power of 332 W at 2091 nm with pulse repetition frequency of 20 kHz was achieved. Then a ZnGeP2 MOPA system was demonstrated using the Ho:YAG MOPA as the pump source. A maximum average output power of 161 W at 3-5 µm was obtained with 290 W incident Ho pump power, corresponding to beam quality factors M2 of 3.42 and 3.83 for horizontal and vertical directions, respectively.

Demonstration of a kilowatt average power, 1 J, green laser.

A λ=515nm laser generating joule-level pulses at 1 kHz repetition rate was demonstrated by frequency doubling 1.2 J, 2 ns temporally shaped square pulses from a cryogenically cooled Yb:YAG laser in an LBO crystal. A doubling efficiency of 78% resulted in 0.94 J second-harmonic pulses at 1 kHz. The unconverted light interacted with a second LBO crystal to generate >100mJ second-harmonic pulses to reach a total green average power of 1.04 kW. A conversion efficiency of 89% was achieved for 0.58 J green pulses at 1 kHz. These results open the possibility to pump high energy femtosecond lasers at kilohertz repetition rates.

A loss of neuronal inhibition best explains EEG abnormalities in preclinical Alzheimer’s disease: A multiscale computational modeling study

AbstractBackgroundA better understanding of the earliest functional brain changes in human preclinical Alzheimer’s Disease (AD) may improve diagnosis and intervention. Evidence accumulating from experimental neurophysiological research illustrates that neuronal excitation/inhibition imbalance is an early sign of AD (Palop and Mucke, 2016). However, how this microscale phenomenon relates to the typical changes in oscillatory activity during preclinical AD stages at the macroscale as assessed by electroencephalography/magnetoencephalography (EEG/MEG), remains unclear. This computational modeling study of a network of coupled neural masses aims to find the most probable pathophysiologic mechanism by linking the microscopic level of neurons with the macroscopic level of observable human brain dynamics.MethodThe brain dynamics simulation model consists of 78 neural mass models (describing regional brain activity), coupled according to human DTI‐based structural network topology (Ponten et al., 2010). The model produces EEG‐like data that can be analyzed the same way as patient recordings. We first examined the effect of gradually increasing or decreasing global excitability of either inhibitory or excitatory neurons on overall oscillatory behavior (average total and relative power, peak frequency and spike density), by changing the average membrane threshold potential. Consequently, these four different scenarios were compared with (CSF) amyloid‐positive mild cognitively impaired (MCI) patient data (Gouw et al., 2017) to identify the most compatible underlying mechanism.ResultThe results confirm previous literature (Isaacson and Scanziani 2011), showing an overall stronger effect of changes to inhibitory neurons on oscillatory activity compared to excitatory neurons. Simulating a decrease in inhibition of the network is associated to a reduction in peak frequency, lower relative alpha power and higher relative theta power, which best matches to preclinical AD data (Gouw et al., 2017). The decreased inhibition scenario resulted furthermore in a strong increase in total power and the highest spike density levels.ConclusionThis study provides theoretical support for the hypothesis that inhibitory (inter)neuron dysfunction is one possible mechanism underlying cortical oscillatory activity changes and a hyperactive network in early AD, in line with recent insights from experimental animal studies.

Fiber-laser-pumped high-repetition-rate picosecond optical parametric generation and amplification in MgO:PPLN.

We report the generation of tunable high-repetition-rate picosecond pulses in the near-infrared at high average power with record conversion efficiency using single-pass optical parametric generation (OPG) and amplification (OPA) in MgO:PPLN, for the first time, to the best of our knowledge. By deploying a mode-locked Yb-fiber laser at 1064 nm providing 21 ps pump pulses at 80 MHz, and a cascade of two 50-mm-long MgO:PPLN crystals, we generate up to 8.3 W of total average output power at a conversion efficiency of 59% over a tunable range of 513 nm, across 1902-2415 nm, with a record threshold as low as 600 mW (7.5 nJ). The two-stage OPG-OPA scheme provides control over fine wavelength tuning and output spectral bandwidths, enabled by the independent control of phase-matching in each crystal. The OPG-OPA output exhibits high spatial beam quality and excellent passive power and central wavelength stability better than 0.9% rms and 0.1% rms, respectively, over 1 hour. The output pulses have a duration of ∼11ps, with a 10 dB bandwidth of ∼350nm at 2107 nm.

Controllable duration and repetition-rate picosecond pulses from a high-average-power OP-GaAs OPO.

We report an orientation-patterned gallium arsenide (OP-GaAs) optical parametric oscillator (OPO) offering a high degree of temporal flexibility with controllable pulse repetition rates from 100 MHz to 1 GHz and pulse durations from ∼95 ps to ∼1.1 ns. The maximum average power of 9.2-W signal (3.3 μm) and 4.5-W idler (4.9 μm) was obtained at a repetition rate of 100 MHz and a pulse duration of ∼95 ps, with a pump power of 34.3 W and at a slope efficiency of 45.4%. The corresponding total average output power of 13.7 W is the highest power achieved to date from an OP-GaAs OPO, to the best of our knowledge.

A Capacitive Pressure Sensor Interface IC with Wireless Power and Data Transfer.

This paper presents a capacitive pressure sensor interface circuit design in 180 nm XH018 CMOS technology for an implantable capacitive pressure sensor, which has a wireless power supply and wireless data transfer function. It integrates full-bridge rectifiers, shorting control switches, low-dropout regulators, bandgap references, analog front end, single slope analog to digital converter (ADC), I2C, and an RC oscillator. The low-dropout regulators regulate the wireless power supply coming from the rectifier and provide a stable and accurate 1.8 V DC voltage to other blocks. The capacitance of the pressure sensor is sampled to a discrete voltage by the analog front end. The single slope ADC converts the discrete voltage into 11 bits of digital data, which is then converted into 1 kbps serial data out by the I2C block. The “1” of serial data is modulated to a 500 kHz digital signal that is used to control the shorting switch for wireless data transfer via inductive back scatter. This capacitive pressure sensor interface IC has a resolution of 0.98 mmHg (1.4 fF), average total power consumption of 7.8 mW, and ±3.2% accuracy at the worst case under a −20 to 80 °C temperature range, which improves to ±0.86% when operated between 20 and 60 °C.

Analyzing the ignition differences between conventional spark discharges and nanosecond-pulsed high-frequency discharges

New methods of energy deposition using nanosecond-pulsed high-frequency discharges (NPHFD) have shown promise in igniting fuel-lean conditions. This work compared an NPHFD ignition system to a conventional, capacitive discharge system in a flowing environment under matching total energy and average power conditions. The results showed that, in every case, matching the average power and deposited energy between the two systems resulted in similar trends in kernel radius growth, time to minimum growth rate, and kernel radius at which minimum growth rate occurs. These results were used as a baseline for comparison for the lower average power NPHFD test conditions. Decreasing the power of the NPHFD system while maintaining the total energy deposited allowed kernel growth to be aided by flow advection, resulting in a ∼38% increase in the streamwise radius as compared to the baseline. The larger kernel size comes at the expense of the kernel taking ∼20% longer to transition to a self-propagating flame that occurs at a radius that is ∼72% larger than the respective values for the baseline condition. This behavior is due to the long duration of the discharge and the low energy density per unit volume in the fluid, respectively. The benefit of the larger kernel size comes at the cost of reliability. Therefore, in combustor conditions with strong external quenching physics, depositing the most energy in the shortest time will be optimal. Conversely, for kernels in the presence of mild turbulence, the average power can be decreased, and flow advection can be utilized to grow the kernel over a longer duration without risk of extinction.

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

Summary As the share of variable renewable energy (VRE) grows in the electric grid, so does the risk of curtailment. While energy storage and hydrogen production have been proposed as solutions to the curtailment problem, they often pose technological and economic challenges. Here, we analyze the potential of data center load migration for mitigating curtailment and greenhouse gas (GHG) emissions. Using historical hourly electricity generation, curtailment, and typical data center server utilization data, we simulate the effect of migrating data center workloads from the fossil-fuel-heavy PJM to the renewable-heavy CAISO. The results show that load migration within the existing data center capacity during the curtailment hours in CAISO has the potential to reduce 113–239 KtCO2e per year of GHG emissions and absorb up to 62% of the total curtailment with negative abatement costs in 2019. Our study demonstrates the overlooked role that data centers can play for VRE integration and GHG emissions mitigation.

A synergetic hybrid mechanism of piezoelectric and triboelectric for galloping wind energy harvesting

Small-scale wind energy harvesting, which can replace batteries to power small electronic devices and realize self-powered systems, has been extensively studied. To improve the working wind-speed range and output power of small-scale wind energy generation systems, we propose a synergetic hybrid piezoelectric and triboelectric mechanism for galloping wind energy harvesting. In this mechanism, a piezoelectric energy harvester (PEH) works in the vibration area and starts working at low wind speeds, while triboelectric nanogenerators work at the vibration boundaries and cooperate with the PEH at high wind speeds. The triboelectric nanogenerator boundaries can (1) constrain the maximum deformation of the beam at high wind speeds to avoid damage to the PEH, (2) increase the vibration frequency to enhance the electromechanical conversion efficiency, and (3) allow the PEH to have a low equivalent stiffness to work effectively at low wind speeds. A dynamic model is presented to characterize the synergetic hybrid piezoelectric–triboelectric wind energy harvester (SHPTWEH) and this is verified by experiments. The results show that the triboelectric nanogenerator boundaries greatly expand the effective working wind-speed range, and the total average power output by the prototype SHPTWEH was 0.24 mW at a wind speed of 14 m/s, which was 2.3 times that of the PEH alone.