Insights into dynamic tuning of magnetic-resonant wireless power transfer receivers based on switch-mode gyrators

Magnetic-resonant wireless power transfer (WPT) has become a reliable contactless source of power for a wide range of applications. WPT spans different power levels ranging from low-power implantable devices up to high-power electric vehicles (EV) battery charging. The transmission range and efficiency of WPT have been reasonably enhanced by resonating the transmitter and receiver coils at a common frequency. Nevertheless, matching between resonance in the transmitter and receiver is quite cumbersome, particularly in single-transmitter multi-receiver systems. The resonance frequency in transmitter and receiver tank circuits has to be perfectly matched, otherwise power transfer capability is greatly degraded. This paper discusses the mistuning effect of parallel-compensated receivers, and thereof a novel dynamic frequency tuning method and related circuit topology and control is proposed and characterized in the system application. The proposed method is based on the concept of switch-mode gyrator emulating variable lossless inductors oriented to enable self-tunability in WPT receiversPeer ReviewedPostprint (published version

Quasi-digital low-dropout voltage regulators uses controlled pass transistors

This article presents a low quiescent current output capacitorless quasi-digital CMOS LDO regulator with controlled pass transistors according to load demands. The pass transistor of the LDO is broken up to two smaller sizes based on a breakup criterion defined here, which considers the maximum output voltage variations to different load current steps to find the suitable current boundary for breaking up. This criterion shows that low load conditions will cause more output variations and settling time if the pass transistor is used in its maximum size. Therefore, using one smaller transistor for low load currents, and another one larger for higher currents, is the best trade-off between output variations, complexity, and power dissipation. The proposed LDO regulator has been designed and post-simulated in HSPICE in a 0.35 µm CMOS process to supply a load current between 0-100 mA while consumes 7.6 µA quiescent current. The results reveal 46% and 69% improvement on the output voltage variations and settling time, respectively.Postprint (published version

Diseño Microelectrónico de Controladores para Convertidores Conmutados Continua-Continua

Postprint (published version

Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects

While monolithic satellite missions still pose significant advantages in terms of accuracy and operations, novel distributed architectures are promising improved flexibility, responsiveness, and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance satellites are becoming feasible and advantageous alternatives requiring the adoption of new operation paradigms that enhance their autonomy. While autonomy is a notion that is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy is also presented as a necessary feature to bring new distributed Earth observation functions (which require coordination and collaboration mechanisms) and to allow for novel structural functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission Planning and Scheduling (MPS) frameworks are then presented as a key component to implement autonomous operations in satellite missions. An exhaustive knowledge classification explores the design aspects of MPS for DSS, and conceptually groups them into: components and organizational paradigms; problem modeling and representation; optimization techniques and metaheuristics; execution and runtime characteristics and the notions of tasks, resources, and constraints. This paper concludes by proposing future strands of work devoted to study the trade-offs of autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that consider some of the limitations of small spacecraft technologies.Postprint (author's final draft

A PLL control for self-tuning of parallel wireless power transfer receivers utilizing switch-mode gyrator emulated inductors

In multiple receivers wireless power transfer (WPT) systems, it is preferable to retune the resonant frequency of every receiver to the transmitter operating frequency in front of frequency mismatches. This paper discusses a proposal for electronic tuning for WPT receivers by means of a variable active switch-mode inductance. The proposed method benefits from the gyrator concept to emulate a variable inductance. Instead of the conventional approach of linear amplifier based implementation of a gyrator, a switch-mode gyrator circuit is exploited for more efficient operation. Additionally, a PLL-like control is presented to enable self-tuning for the receiver resonant tank. Furthermore, a design-space characterization for the system dynamic behavior has been discussed to show the control robustness and the instabilities (including slow-scale and fast-scale chaotic instabilities) it may undergo.Peer ReviewedPostprint (published version

Quasi–digital low–dropout voltage regulators uses controlled pass transistors

This article presents a low quiescent current outputcapacitorless quasi-digital CMOS LDO regulator with controlled pass transistors according to load demands. The pass transistor of the LDO is broken up to two smaller sizes based on a breakup criterion defined here, which considers the maximum output voltage variations to different load current steps to find the suitable current boundary for breaking up. This criterion shows that low load conditions will cause more output variations and settling time if the pass transistor is used in its maximum size. Therefore, using one smaller transistor for low load currents, and another one larger for higher currents, is the best trade-off between output variations, complexity, and power dissipation. The proposed LDO regulator has been designed and post-simulated in HSPICE in a 0.35 µm CMOS process to supply a load current between 0-100 mA while consumes 7.6 µA quiescent current. The results reveal 46% and 69% improvement on the output voltage variations and settling time, respectively.Postprint (published version

Tunable wide-band second-order all-pass filter-based time delay cell using active inductor

This paper presents a CMOS RF second-order voltage-mode all-pass filter (APF) as a time delay cell. The proposed filter benefits from a simple structure; consisting of one transistor, three resistors, and one grounded capacitor and inductor. The filter reaches a group delay of 60 ps over a 10 GHz bandwidth, while achieving maximum delay-bandwidth-product (DBW) and it consumes only 10.3 mW power. On the other hand, an active inductor is used in the APF instead of a passive RLC tank in order to control the time delay and improve the size. In this case, the power consumption increases while time delay can be tuned. The proposed APF is designed and simulated in a TSMC 180 nm CMOS process.Postprint (published version

Improved current-source sizing for high-speed high-accuracy current steering d/a converters

This paper describes a design methodology for the basic current source cell circuit of high-speed high-accuracy current steering DIA conveners taking into account mismatching in all the transistors of the cell. Previous works consider arbitrary safety margins in the sizing process. The presented approach allows a more accurale selection of the optimal design point. The design methodology is illustrated for a particular design of a 0.35pm CMOS 12-bit 400 MHz current-steering segmented DIA converter.Postprint (published version

A comparison of analytical models for resonant inductive coupling wireless power transfer

Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high e±ciencies (above 40%) at large distances compared to the antenna dimensions, which has exponentially increased the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary ¯eld, di®erent approaches have been proposed to predict the behaviour of these systems from physical theory of resonators, reflected load theory and the circuit point of view. However, the relation between these methods is still obscure. In this article, we compare the results of these models to find the effciency of a Resonant Inductive Coupling WPT system under Steady-State sonditions and to analyze the relation between the optimal load values obtained from this perspectives and the ones obtained using impedance matching techniques.Peer ReviewedPostprint (published version

Applying autonomy to distributed satellite systems

The need for autonomy in several fields of aerospace engineering has become apparent and widely accepted during the last decade. Autonomy promises to improve the systems' performances, their robustness and tolerance to failures, reduce operational costs and, ultimately increase the intelligence of the system. Many are the researchers that have tackled the design and implementation of autonomy technologies for system-specific purposes: from the control of a UAV fleet or the coordination of a team of robots, to the implementation of spacecraft FDIR techniques. In the area of satellite missions, autonomous systems may drastically reduce their response times when in the presence of internal perturbations (e.g. subsystem failures), or external changes (i.e. changes in the environment) and may allow new monitoring approaches such as the on-board identification of interesting targets (e.g. autonomous detection of natural disasters, crop and forest change detection, etc.) Autonomy has been deemed essential in the design and deployment of several distributed satellite architectures, especially for Earth Observation applications. The latter systems, grounded on small spacecraft technologies, potentially present node heterogeneity at the functional level as well as in terms of computational and communication capabilities. This, combined with some of their network characteristics (which are dynamic and are affected by the node's orbital properties) and architectural aspects (potentially hierarchically structured and composed of a massive number of spacecraft), enforces the need of autonomous operations. Finally, the absence of autonomy in Distributed Satellite Systems (DSS) architectures, not only could compromise their controllability but could complicate the operational requirements unnecessarily. This presentation is aimed at gathering the design, functional and execution aspects of autonomous mission planning software for DSS architectures and to identifying open issues that still need to be solved. In the context of distributed satellite architectures, autonomy may be translated as the capability of the system to plan its own activities and observational requests with minimum human intervention. Mission Planning and scheduling Systems (MPS) have been exhaustively explored to provide this capability to the system. Their design, modelling and execution characteristics, however, are particular to the missions for which they were developed and are usually not targeted for new and complex functions that next-generation architectures are aimed to address (e.g. multi-point observations, synchronization of nodes, exchange and management of infrastructure resources, on-board generation of observational requests, self-healing properties, etc.) Some authors have scrupulously identified the commonalities of MPS for monolithic satellite missions, but their characteristics and requirements for DSS are still unexplored. Because of that, this presentation will emphasize their characteristics in that specific context. Leveraging from the commonalities found in several MPS designs, this presentation will summarize: (a) their fundamental design approaches, ranging from the implementation of negotiation protocols, or multi-agent paradigms to bio-inspired and self-organizing applications; (b) their problem, resource and task modelling, including common algorithms and optimization schemes; and (c) their runtime characteristics (i.e. reactive or deliberative, centralized or distributed). From there, the presentation will conclude discussing the open questions and unsolved features with a focus on small-satellite limitations, network issues and collaborative task requirements, and will propose a roadmap for their resolution.Postprint (author's final draft