Load Modulation Research Articles

A Broadband Switched-Transformer Digital Power Amplifier for Deep Back-Off Efficiency Enhancement

This article presents a switched-transformer-based polar Doherty digital power amplifier (DPA) for deep back-off efficiency enhancement. A single-transformer-footprint parallel-combining transformer (PCT) power combiner is introduced for 1.3-3.5-GHz wide frequency coverage, dynamic load modulation at 0-/6-/12-/18-dB power back-off (PBO) levels, and an ultracompact die size. Implemented in 40-nm CMOS, the DPA is powered by a 1.1-V supply and only occupies 0.7 × 1.15 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> chip area. It achieves 21.4-dBm peak power with the power added efficiencies (PAEs) of 31.3%, 27.7%, 16.6%, and 7.7% for 0-/6-/12-/18-dB PBOs at 1.5 GHz. With 20-MHz 64QAM long term evolution (LTE) signal, the DPA achieves P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> of 15.2 dBm and the average PAE of 25.3% with -32.5-dB error vector magnitude (EVM) at 1.5 GHz. Moreover, for 20-MHz 64 QAM WLAN signal, Pavg of 14.7 dBm with the average PAE of 20.1% is obtained with - 25-dB EVM at 2.4 GHz.

Pseudo-Doherty Load-Modulated Balanced Amplifier With Wide Bandwidth and Extended Power Back-Off Range

This article presents a novel architecture of load-modulated balanced amplifier (LMBA) with a unique load-modulation characteristic different from any existing LMBAs and Doherty power amplifiers (DPAs), which is named pseudo-Doherty LMBA (PD-LMBA). Based on a special combination of control amplifier (carrier) and balanced amplifier (peaking) together with proper phase and amplitude controls, an optimal load-modulation behavior can be achieved for PD-LMBA, leading to maximized efficiency over extended power back-off range. More importantly, the efficiency optimization can be achieved with only a static setting of phase offset at a given frequency, which greatly simplifies the complexity for phase control. Furthermore, the cooperations of the carrier and peaking amplifiers in PD-LMBA are fully decoupled, thus lifting the fundamental bandwidth barrier imposed on the Doherty-based active load modulation. Upon theoretical proof of these discoveries, a wideband RF-input PD-LMBA is physically developed using the GaN technology for experimental demonstration. The prototype achieves a highly efficient performance from 1.5 to 2.7 GHz, e.g., 58%-72% of efficiency at 42.5-dBm peak power and 47%-58% at 10-dB output back-off (OBO). When stimulated by a 10-MHz long term evolution (LTE) signal with a 9.5-dB peak-to-average power ratio (PAPR), the developed PD-LMBA achieves an efficiency of 44%-53% over the entire bandwidth at an average output power of around 33 dBm.

A Dual-Band Outphasing Power Amplifier Based on Noncommensurate Transmission Line Concept

This article proposes a design methodology of dual-band outphasing power amplifier (OPA) based on two noncommensurate transmission lines (NCTLs). The devised NCTLs are used to replace the imperative reactance compensation and impedance matching networks in a conventional design. In virtue of this, the overall complexity of the combiner can be greatly reduced without sacrificing the load modulation effect. To support operations at two distinct frequencies, the conceptual NCTLs are further realized using two dual-band stub-loaded transmission lines. Comprehensive theoretical analysis is given to describe the proposed scheme and to illustrate how the electrical parameters of essential elements are determined. As a proof of concept, an OPA prototype operating at 2.6 and 3.5 GHz is fabricated. The implemented PA based on two 10-W GaN high electron mobility transistor (HEMTs) achieves 44.8 and 44.2-dBm maximum output power, and 74.5% and 62.1% peak drain efficiencies under continuous wave excitation at these two independent frequencies. At 6-dB output back-off points, the corresponding efficiencies reach 63.8% and 54.9%, respectively.

Neural-Network-Based Digital Predistortion for Active Antenna Arrays Under Load Modulation

In this letter, we propose an efficient solution to linearize mmWave active antenna array transmitters that suffer from beam-dependent load modulation. We consider a dense neural network that is capable of modeling the correlation between the nonlinear distortion characteristics among different beams. This allows providing consistently good linearization regardless of the beamforming direction, thus avoiding the necessity of executing continuous digital predistortion parameter learning. The proposed solution is validated, conforming to 5G new radio transmit signal quality requirements, with extensive over-the-air RF measurements utilizing a state-of-the-art 64-element active antenna array operating at 28-GHz carrier frequency.

Automatic Detection System for Abnormal Storage of Sensitive Data in Coastal Port Network Communication

Wang, Z., 2020. Automatic detection system for abnormal storage of sensitive data in coastal port network communication. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 868–872. Coconut Creek (Florida), ISSN 0749-0208.In order to effectively prevent the security threat of data storage in network communication and improve the accuracy of anomaly detection, an automatic anomaly detection system for sensitive data storage in coastal port network communication based on Linux platform is proposed and designed. The system is divided into data acquisition, protocol analysis, rule loading, exception detection, console and other functional modules. Among them, the data acquisition module mainly discusses the optional method of capturing data packets and BPF capture mechanism. The acquired network packets are processed by protocol analysis module and converted into data that can be easily analyzed; the rule description language is designed in the rule loading module to effectively discover and warn the abnormal behaviors by matching with the established rules; the information entropy is used to extract the behavioral characteristic parameters of network traffic in the abnormal detection part, and the detection process and detection method are discussed. The console module is designed as a web page based on WebSocket communication protocol, which is convenient to control the detection system across platforms. Experimental results show that the system has strong detection performance, high accuracy and reliability.

Single-Switch Open-Circuit Diagnosis Method Based on Average Voltage Vector for Three-Level T-Type Inverter

Fault-tolerant control strategy plays a significant role in improving the reliability of three-level T-type inverter where fault diagnosis method is the key and a research hotspot. Load power factor variation and modulation index regulation have great effect on conventional load current based diagnosis methods. Therefore, this article proposes a novel voltage vector based method for single-switch open-circuit fault diagnosis in three-level T-type inverter. Average output voltage vector calculated by voltages between dc-link neutral-point and bridge output terminals is taken as the eigenvector in the procedure and failed switch can be located by three diagnosis variables including angle of eigenvector, normalized modulus of eigenvector, and neutral-point potential. These variables will be some certain values under circuit fault, which are defined as eigenvalues. The vector trajectory prediction technology is utilized for threshold setting, by which the diagnosis is suitable for different power factors and different modulation indices. The strategy of redundant vector replacement is applied to realize fault-tolerant operation and verifying the proposed scheme. Simulations and experiments are carried out to illustrate the superiorities of the proposal.

Visual working-memory capacity load does not modulate distractor processing.

Over the last decade, researchers have explored the influence of visual working-memory (WM) load on selective attention in general, by focusing on the modulation of visual WM load on distractor processing in perception. However, there were three distinct hypotheses (perceptual-load hypothesis, resolution hypothesis, and domain-specific hypothesis) with different predictions. While the perceptual-load hypothesis suggests that visual WM capacity load serves as a type of perceptual load, the latter two hypotheses consider visual WM capacity load acting as a type of central executive load, with a constraint that the domain-specific hypothesis claimed that only a content overlap existed between WM load and the perceptual task. By adding a flanker task into the maintenance phase of visual WM, here we attempted to understand the influence of visual WM load on distractor processing. We systematically manipulated the parameters of the task setting between WM and flanker tasks (Experiments 1-4), the perceptual load of flanker task (Experiment 5), the settings of the flanker stimuli and the WM load (Experiment 6), and the content overlap between WM task and flanker task and the exposure time of flanker task (Experiments 7, 8, and 9). However, in 11 out of 12 sub-experiments we consistently found that the visual WM load did not modulate the distractor processing. The implications of these findings are discussed.

Bandwidth Enhancement of Doherty Power Amplifier Using Modified Load Modulation Network

A novel Doherty power amplifier (DPA) architecture with extended bandwidth is presented in this paper. A modified load modulation network is introduced to provide impedance condition required by the Doherty operation in a wide frequency range. Analytical parameter solutions of the proposed load modulation network and the related load modulation process are presented. A DPA with 2.80-3.55 GHz bandwidth utilizing commercial GaN transistors is implemented. The fabricated DPA attains a measured 9.3-11.1 gain and 43.0-45.0 dBm saturated power. 50.0-60.6% and 66-78% drain efficiency is obtained at 6 dB output power back-off and saturation throughout the designed band, respectively. Moreover, the back-off drain efficiencies are higher than 55% within 700 MHz bandwidth. When driven by a 6-carrier 120 MHz OFDM signal with 7.0 dB peak to average power ratio, the proposed DPA achieves adjacent channel leakage ratio of better than −50 dBc after digital pre-distortion (DPD) at 3.20 GHz with average efficiency of 53.3%.

A Coupler-Based Differential mm-Wave Doherty Power Amplifier With Impedance Inverting and Scaling Baluns

Designing Doherty power amplifiers (PAs) at high millimeter-wave (mm-Wave) range remains a major challenge because most Doherty combiners at this frequency band are inefficient. To resolve this bottleneck, we analyze balun response under load variation and subsequently propose the Doherty PA architecture with impedance inverting and scaling baluns that perform active load modulation on differential PAs and delivers combined power to a single-ended load. At the PA output/input stage, instead of utilizing the transformer-based balun commonly used at RF and low mm-Wave frequencies, we explore the coupler-based balun to resonate out the device parasitic capacitance and achieve well-balanced differential to single-ended conversion at high mm-Wave frequencies. Based on the coupled-line theory and our analysis, we derive the [Y] matrix of the coupler-based balun and originate various solutions for baluns that can invert or scale impedance. From this derivation, we conceive a canonical form of impedance inverting baluns when the electrical length of coupled lines equals 45°. We also propose a close-formed solution for the coupler-based impedance scaling balun that is electrically equivalent to an idealistic transformer in series with a small inductance. We then combine the proposed impedance inverting and scaling balun structures to construct a Doherty network that exhibits desirable Doherty active load modulation and occupies a single-transformer footprint. On the active circuit design, we employ the adaptive biasing circuit for both driver and PA stages of the auxiliary PA to enhance the main and auxiliary cooperation. Using a 45-nm GlobalFoundries CMOS SOI process, we fabricate a proof-of-concept Doherty PA that demonstrates 20.1-dBm $P_{\mathrm {sat}}$ , 19.3dBm OP1,dB, 26% peak power-added efficiency (PAE), and 16.6% PAE at 7-dB power back-off (PBO) from OP1 dB at 60 GHz. Our results indicate a substantial PAE enhancement at PBO and a state-of-the-art modulation efficiency achieved when transmitting digital pre-distortion (DPD)-free 64-QAM-modulated signals.

Investigating cognitive load modulation of distractor processing using pupillary luminance responses in the anti-saccade paradigm.

Observers must select goal-directed stimuli in lieu of distractors in the environment for preferential information processing. This selection, according to the load theory of attention, is modulated by cognitive load, involving the frontal cortices, with more significant distractor interference under high cognitive load, with strained executive control resources. Evidence in support of this theory exists; however, working memory tasks were predominately used in these investigations. The influence of other types of cognitive load on distractor processing is largely unknown. An interleaved pro- and anti-saccade task has often been used to investigate executive control in which subjects are instructed in advance to either automatically look at the peripheral stimulus (pro-saccade), or to suppress the automatic response and voluntarily look in the direction opposite of the stimulus (anti-saccade). Distinct frontal preparatory activity has been clearly characterized during preparation for pro- and anti-saccades, with higher inhibition-related activity in preparation for anti-saccades than pro-saccades. Here, we used an interleaved pro- and anti-saccade paradigm to investigate the modulation of distractor interference by cognitive load in a group of 24 healthy young adults. Luminant distractors were used to evoke automatic pupillary responses to evaluate distractor processing. Greater pupillary dilation following dark distractor presentation was observed in the anti-saccade than the pro-saccade preparation. These effects, however, were absent in pupillary constriction following bright distractors. Together, our results support the load theory of attention, importantly highlighting the potential of using involuntary changes in pupil size to objectively investigate attentional selection under load.

Discovery of Cryptic Largimycins in Streptomyces Reveals Novel Biosynthetic Avenues Enriching the Structural Diversity of the Leinamycin Family.

Largimycins are hybrid nonribosomal peptide-polyketides that constitute a new group of metabolites in the leinamycin family of natural products displaying unique structural features such as containing an oxazole instead of a thiazole ring or being oxime ester macrocycles, unprecedented in nature, rather than macrolactams. Their discovery in Streptomyces argillaceus and Streptomyces canus has relied on the activation of two homologous silent gene clusters by overexpressing a transcriptional activator and cultivating in specific media. The proposed biosynthesis of largimycins includes the key action of the oxidoreductase LrgO, responsible for the formation of the oxime group involved in macrocyclization, and two putative cryptic biosynthetic steps consisting of chlorination of l-Thr by the NRPS loading module and incorporation of an olefinic exomethylene group by LrgJ PKS. The discovery of largimycins uncovers novel biosynthetic avenues employed in nature to enrich the structural diversity of leinamycins and provides tools for combinatorial biosynthesis.

A technogenic load on the environmental components during the formation and accumulation of the waste in the North-Western Black Sea regions

The amount of the production and consumption waste generated and accumulated in a certain territory (in the region) can be considered as one of the indicators of a technogenic load on the environmental components. The processes of formation and accumulation of various wastes pose a threat to a state of all environmental components. The formation and, especially, the accumulation of production and consumption waste inevitably contaminate the soil cover.The problem of inefficient waste management is typical for the regions of Ukraine, and therefore the purpose of the work is to assess a level of a technogenic load on the environmental components by the indicators of the formation and accumulation of production waste and the consumption in the regions of the Northwest Black Sea. To evaluate and analyze a level of a technogenic load on the environment based on the principle of calculating a technogenic load module it is proposed to determine a module of a technogenic load on the geological environment, ie the most vulnerable component of the environment.It is established that the greatest load in the territory of the North-Western Black Sea is in the Mykolaiv region (due to industrial waste). The amount of the generated and accumulated waste exceeds the corresponding figures in the Odesa and Kherson regions. More than 95% are class IV hazardous waste. In almost all regions of the Northwest Black Sea, there has been a tendency of increasing a load, primarily due to the increased accumulation of the waste.It is suggested to determine a module of a technogenic load on the geological environment according to the waste generated and accumulated in the region.

A theoretical and experimental study of passive computational radio frequency identification tags

AbstractThe investigation and optimization of the RF frontend of radio frequency identification (RFID) tags represents a crucial topic when looking for an increased tag performance. This work studies the RF frontend of three state‐of‐the‐art passive computational RFID tags: AMS SL900a Dev Kit, Farsens Spider Eval, and WISP 5.1. Given a module‐based approach, the antenna, the matching network, the RF energy harvesting, and the load modulation are reviewed both theoretically and experimentally. The influence of a set of properties, corresponding to these modules, on the overall RFID tag performance is evaluated using a tag read range measurement.

Task load modulates tDCS effects on brain network for phonological processing

Motor participation in phonological processing can be modulated by task nature across the speech perception to speech production range. The pars opercularis of the left inferior frontal gyrus (LIFG) would be increasingly active across this range, because of changing motor demands. Here, we investigated with simultaneous tDCS and fMRI whether the task load modulation of tDCS effects translates into predictable patterns of functional connectivity. Findings were analysed under the “multi-node framework”, according to which task load and the network structure underlying cognitive functions are modulators of tDCS effects. In a within-subject study, participants (N = 20) performed categorical perception, lexical decision and word naming tasks [which differentially recruit the target of stimulation (LIFG)], which were repeatedly administered in three tDCS sessions (anodal, cathodal and sham). The LIFG, left superior temporal gyrus and their right homologues formed the target network subserving phonological processing. C-tDCS inhibition and A-tDCS excitation should increase with task load. Correspondingly, the larger the task load, the larger the relevance of the target for the task and smaller the room for compensation of C-tDCS inhibition by less relevant nodes. Functional connectivity analyses were performed with partial correlations, and network compensation globally inferred by comparing the relative number of significant connections each condition induced relative to sham. Overall, simultaneous tDCS and fMRI was adequate to show that motor participation in phonological processing is modulated by task nature. Network responses induced by C-tDCS across phonological processing tasks matched predictions. A-tDCS effects were attributed to optimisation of network efficiency.

Guest Editorial: Special Issue on IEEE RFID 2019 Conference

With the proliferation of the Internet of Things, there is an increased demand to enhance every day physical objects with sensors and communication abilities so that they can have digital counterparts (“digital twins”) in a connected world. While many solutions based on protocols such as ZigBee, Bluetooth, ANT, LoRa, LPWAN, NB-IoT, HaLow, etc. do exist, RFID technology presents a compelling alternative. Radio Frequency Identification (RFID) is a generic term for a variety of active and passive RF technologies. RFID transponders have varying degrees of sophistication and their design is often a tradeoff between functionality and cost. At one end of the spectrum, there are active RFID tags that offer on-board battery and memory, sensor integration, active RF transmitters and hence communication range up to kilometers albeit at increased costs. At the other end, passive and semi-passive RFID tags rely on a simple load modulation to backscatter ID and data back to the reader over several meters distance. Passive RFID tags, in particular, lend themselves well for applications needing large-scale, low-cost, automatic identification and are a good option for imparting digital identity to a host of physical assets. Industry alliances such as the NFC forum (for HF RFID) and the RAIN RFID alliance (for UHF RFID) have been formed to motivate and promote these efforts.

Local Estimation of Critical and Off-Peak Periods for Grid-Friendly Flexible Load Management

In the demand-side management (DSM) context, some appliances are remotely controlled by the utility or by end-users based on the expected aggregated consumption profile or day-ahead electricity rates. The main objective of these actions is to shift the load from critical to off-peak periods. This article proposes a novel approach to estimate in real time the load as seen by the distribution power network. The only requirement to perform this online estimation is the voltage measurement at the electrical board panel of the end-user building. The proposed method combines digital filtering, statistical process, and transient analysis to make possible the accurate identification of the corrective actions introduced by the voltage regulation system of the distribution network. Hence, this identification permits the estimation of the aggregated load profile. The method provides real-time information that can be used by the end-user or an automated energy management system to initiate demand response actions depending on the state of the grid, e.g., shaving, shifting, or modulation of the local load. Experimental data of three different locations permitted the validation of this novel approach, which enables the implementation of grid-friendly home energy managements systems with DSM functions at a very low cost for the utilities and end-users.

An integrated experimental system for gas hydrate drilling and production and a preliminary experiment of the depressurization method

The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device, and the resulted boundary effect is so obvious due to the small size of samples in the reaction kettle that the experimental results will be difficult to apply in the field. In this paper, an integrated experimental system for drilling and exploitation of gas hydrate is developed innovatively based on the idea of depressurization method and the technological process. This experimental system consists of high-pressure vesselmodule, drilling & extraction module, liquid supply module, gas supply module, confining pressure loading module, back-pressure control module, three-phase separation module, temperature control module, data acquisition module and an operational platform. The hydrate-bearing samples similar to marine hydrate formations were prepared inthe experimental system with the actual geological surroundings simulated. The electrical resistance tomography was used to real-time monitor the dynamic distribution of gas hydrate in sediments inside the high-pressure vessel (521 L). This experimental system can also simulate the process of wellbore drilling in hydrate reservoirs and depressurization extraction, and realize the real-time monitoring of parameters in the whole production process such as gas production, water production, sand production, temperature, pressure, etc. We carried out a preliminary experiment on the CO2 hydrate extraction via depressurization by using this experimental system. Fundamental procedures for data acquisition and analysis were established and verified. The variations of temperature and pressure fields and gas/water output behaviors in the reservoirs were both achieved. The results show that (1) the gas and water production rate fluctuate greatly even at a constant backpressure; (2) the reservoir temperature distribution is uneven during hydrate decomposition, and the maximum temperature is decreased by 5 °C, suggesting that the hydrate decomposition is heterogeneous and stochastic. The abundant and credible experimental results based on this system are expected to provide important data support for marine gas hydrate production tests.

Anoxia remediation and internal loading modulation in eutrophic lakes using geoengineering method based on oxygen nanobubbles

Benthic anoxia and internal P release, widely occurring in eutrophic lakes, are major factors threatening the health of aquatic ecosystems. In this paper, we experimentally evaluated the efficacy of a new type of “flock-lock” geoengineering method based on oxygen nanobubble technology to remediate sediment anoxia and reduce the internal P release in waters with and without algal blooms. Oxygen-carrying materials (OCM) modified from natural zeolites were used as capping agents and an oxygen-locking layer consists of OCM and the oxidized sediment was formed between anoxic sediment and overlying water. The synergy of diffusion and retention of oxygen in this layer contributes to both the increase of DO and reversal of anoxic conditions. By capping with OCM, the DO in overlying water improved instantly from around 1.5 mg/L to 3.5–4 mg/L and 5–6 mg/L in the systems with algal blooms and without algal blooms, respectively, and maintained throughout the incubation period. The oxygen penetration depth in the sediment can be significantly enhanced from around 0 cm to 3 cm and form an oxygen-locking layer at the end of the experiment by capping with OCM. The labile P was effectively retained via the re-oxidation of ferrous iron in this layer compared with the obvious release of labile P and Fe in control. More importantly, the oxygen depletion and labile P increase at the sediment-water interface caused by the decomposition of the deposited algal biomass can be substantially eliminated after capping with OCM. The study shed insights on the sustainable modulation of sediment anoxia and internal loading in eutrophic waters.

Impedance-Based Stability Analysis of Constant-Power-Source-Involved and Cascaded-Type DC Distributed Power Systems

This paper proposes impedance specifications for guaranteeing the stability of a cascaded-type DC distributed power system (DPS), which is formed by several cascaded voltage source modules, several load modules, and several constant power source modules. To analyze the stability of a cascaded-type DC DPS, there are conventional approaches like eigenvalue method, root-locus method, bode-diagram method and so on. However, the aforementioned stability analysis approaches will suffer from the incomplete system parameters if the modules of the DPS are designed modularly and independently. This paper defines time-invariant and decentralized impedance specifications for the modules of the cascaded-type DC DPS, where the impedance specifications are independent to each other. Thus, the modules of the cascaded-type DC DPS can be independently and modularly designed, as well the stability of the cascaded-type DC DPS can be guaranteed.

Техногенне навантаження на довкілля Миколаївської області

In assessing the state of the environment of the regions of Ukraine, the greatest attention is paid to the assessment of the level of pollution of natural environments. When assessing the level of anthropogenic environmental load, the load indices for its individual components are not usually separated. Most estimates are based on identifying indicators that determine the overall level of load for the region (the environment of the region). The Mykolaiv region is a highly developed industrial region of the country, characterized by significant recreational potential. The purpose of the performed research is to evaluate the technogenic load on the environmental components of Mykolaiv region over a long period. The module of technogenic loading was calculated for evaluation. In order to assess the load on individual components of the environment, it is proposed to also calculate individual load modules for the air pool, water bodies, and geological environment. The dominant sources of pollutants emissions into the air are mobile sources. Since 2012, as the number of stationary sources has increased, emissions have been significantly reduced. From 2000 to 2011, there was an increase in technogenic load on the air pool with a predominant influence of mobile sources, from 2012 — a decrease due to both types of emission sources. The main polluters of the water resources of the region are water utilities. The maximum water consumption is noted for production needs, the minimum — for agricultural needs. Indicators of water intake, water use and wastewater discharges decreased. The volume of discharges of wastewater and pollutants has decreased the level of load. The waste generated in the region is dominated by IV hazard class waste. The amount of waste accumulated exceeds the amount of waste generated by an order of magnitude. There is a steady tendency to increase the accumulated waste in the region. Since 2011, there has been an increase in technogenic load on the geological environment by the amount of waste. The greatest technogenic loading of Mykolaiv region undergoes on indicators of discharges of sewage and formation of waste.