System Level Design Considerations Research Articles

Chemistries and materials for atmospheric water harvesting.

Atmospheric water harvesting (AWH) is recognized as a crucial strategy to address the global challenge of water scarcity by tapping into the vast reserves of atmospheric moisture for potable water supply. Within this domain, sorbents lie in the core of AWH technologies as they possess broad adaptability across a wide spectrum of humidity levels, underpinned by the cyclic sorption and desorption processes of sorbents, necessitating a multi-scale viewpoint regarding the rational material and chemical selection and design. This Invited Review delves into the essential sorption mechanisms observed across various classes of sorbent systems, emphasizing the water-sorbent interactions and the progression of water networks. A special focus is placed on the insights derived from isotherm profiles, which elucidate sorbent structures and sorption dynamics. From these foundational principles, we derive material and chemical design guidelines and identify key tuning factors from a structural-functional perspective across multiple material systems, addressing their fundamental chemistries and unique attributes. The review further navigates through system-level design considerations to optimize water production efficiency. This review aims to equip researchers in the field of AWH with a thorough understanding of the water-sorbent interactions, material design principles, and system-level considerations essential for advancing this technology.

Miniaturized Energy Harvesting Systems Using Switched-Capacitor DC-DC Converters

This tutorial brief reviews highly-integrated switched-capacitor (SC) DC-DC converter topologies for miniaturized energy harvesting (EH) IoT systems. Aiming to provide a concise overview of SC converter-based EH interfaces, we first discuss the system level design considerations for energy balancing between source, storage, and load under different environmental conditions. The key factors dominating the energy extraction and power conversion efficiencies, including the source adaptation strategies and SC power stage intrinsic losses, are outlined to establish a fundamental understanding on the EH system performance. After studying different state-of-the-art SC topologies in terms of their rational boost voltage conversion ratio (VCR) generation flexibility, loss characteristics, and implementation tradeoffs, we further introduce two advanced SC converter-based EH system examples, highlighting the SC converter operation in enhancing the EH system functionality and performance. The pros and cons of different SC converter topologies for EH systems will also be discussed.

Integrated phase-sensitive photonic sensors: a system design tutorial

Photonic integration has seen tremendous progress over the previous decade, and several integration platforms have reached industrial maturity. This evolution has prepared the ground for miniaturized photonic sensors that lend themselves to efficient analysis of gaseous and liquid media, exploiting large interactions lengths of guided light with surrounding analytes, possibly mediated by chemically functionalized waveguide surfaces. Among the various sensor concepts, phase-sensitive approaches are particularly attractive: offering a flexible choice of the operation wavelength, these schemes are amenable to large-scale integration on mature technology platforms such as silicon photonics or silicon nitride ( S i 3 N 4 ) that have been developed in the context of tele- and data-communication applications. This paves the path toward miniaturized and robust sensor systems that offer outstanding scalability and that are perfectly suited for high-volume applications in life sciences, industrial process analytics, or consumer products. However, as the maturity of the underlying photonic integrated circuits (PICs) increases, system-level aspects of mass-deployable sensors gain importance. These aspects include, e.g., robust system concepts that can be operated outside controlled laboratory environments as well as readout schemes that can be implemented based on low-cost light sources, without the need for benchtop-type tunable lasers as typically used in scientific demonstrations. It is, thus, the goal of this tutorial to provide a holistic system model that allows us to better understand and to quantitatively benchmark the viability and performance of different phase-sensitive photonic sensor concepts under the stringent limitations of mass-deployable miniaturized systems. Specifically, we explain and formulate a generally applicable theoretical framework that allows for a quantitatively reliable end-to-end analysis of the overall signal chain. Building upon this framework, we identify and explain the most important technical parameters of the system, comprising the photonic sensor circuit, the light source, and the detector, as well as the readout and control scheme. We quantify and compare the achievable performance and the limitations that are associated with specific sensor structures based on Mach–Zehnder interferometers (MZIs) or high-Q optical ring resonators (RRs), and we condense our findings by formulating design guidelines both for sensor concepts. As a particularly attractive example, we discuss an MZI-based sensor implementation, relying on a vertical-cavity surface-emitting laser (VCSEL) as a power-efficient low-cost light source in combination with a simple and robust readout and control scheme. In contrast to RR-based sensor implementations, MZIs can be resilient to laser frequency noise, at the cost of a slightly lower sensitivity and a moderately increased footprint. To facilitate the application of our model, we provide a MATLAB-based application that visualizes the underlying physical principles and that can be readily used to estimate the achievable performance of a specific sensor system. The system-level design considerations are complemented by an overview of additional aspects that are important for successful sensor system implementation such as the design of the underlying waveguides, photonic system assembly concepts, and schemes for analyte handling.

An Untethered Soft Robot Based on Liquid Crystal Elastomers.

An untethered, soft robot using liquid crystal elastomer (LCE) actuators, onboard power, and wireless Bluetooth control was developed. LCE actuators were thermally triggered using Joule heating and demonstrated an ∼5 N force pull capacity per LCE. A >20% repeatable strain was demonstrated over >100 cycles with minimal loss of strain at high cycle numbers. The LCE actuators were horizontally oriented to maximize conversion of LCE contraction to overall robot movement. A battery and control board were integrated into the body of the robot, which allowed for Bluetooth control of the LCE on/off cycle. System level programming and design were implemented to offset the slow recovery associated with LCE actuators. The multiple LCE actuator legs were programmed to allow individual control of on/off cycles for each leg. LCE leg actuation was alternated between inner and outer legs to provide horizontal movement with minimized loss of motion during the LCE recovery cycle by actuating one set of legs during the recovery cycle of the other set for a maximum movement speed of 1.27 cm/min. Path control was also demonstrated by turning the robot by actuating two LCE legs on one side of the robot. The robot was able to pull up to 1400 g in ideal frictional conditions, allowing the possibility of payload transport, additional battery storage, or onboard sensors. Additional design considerations are discussed to further improve overall robot speed in the future by combining system and material level design considerations.

Design Considerations of Distributed and Centralized Switched-Capacitor Converters for Power Supply On-Chip

On-chip power supply distribution faces the challenges of high and fast-changing load current, limited metal layers and decoupling capacitors, efficiency, and thermal issues. This paper mainly discusses system-level design considerations of both distributed and centralized fully integrated voltage regulators. In particular, a ring-shaped switched-capacitor dc-dc converter that has a unity-gain frequency a few times higher than its switching frequency is introduced with comprehensive considerations, and optimizing the number of time-interleaving phases (power cells) is detailed. Design issues such as on-chip power-rail routing parasitics, input capacitor and input ripple, and phase mismatch between power cells are addressed. Furthermore, a couple of possible extensions of the converter-ring architecture are proposed, which include power management of the active-matrix light-emitting diode array in a microdisplay system, cascading multiple nMOS-LDO regulators for granular power, and on-chip power converter grid with flipped-chip packaging.

Circuit and System Designs of Ultra-Low Power Sensor Nodes With Illustration in a Miniaturized GNSS Logger for Position Tracking: Part II—Data Communication, Energy Harvesting, Power Management, and Digital Circuits

This two-part paper reviews recent innovations in circuit design that have accelerated the miniaturization of sensor nodes. In this second part of the paper, we focus on key building blocks of miniaturized sensor nodes, such as data transceivers, energy harvesters, power management units, and digital logic circuits. System level design considerations are also discussed to provide guidelines for the design of a miniaturized system. As an example prototype design, a 2.7-cm3 global navigation satellite system (GNSS) logger is proposed. This paper includes a die-stacked sensor platform composed of an ARM cortex M0 processor, energy harvester, power management unit, solar cell, optical receiver, sensor layer, and RF transmitter that exploits the discussed design techniques for ultra-low power operation. The GNSS logger can store GNSS signals of >1 k positions on a single battery charging without additional energy harvesting.

System-Level Design Considerations for Digital Pre-Distortion of Wireless Base Station Transmitters

Over the past 25 years or so there has been much interest in the use of digital pre-distortion (DPD) techniques for the linearization of RF and microwave power amplifiers. In this paper, we describe the important system and hardware requirements for the four main subsystems found in the DPD linearized transmitter: RF/analog, data converters, digital signal processing, and the DPD architecture and algorithms, and illustrate how the overall DPD system architecture is influenced by the design choices that may be made in each of these subsystems. We shall also consider the challenges presented to future applications of DPD systems for wireless communications, such as higher operating frequencies, wider signal bandwidths, greater spectral efficiency signals, resulting in higher peak-to-average power ratios, multiband and multimode operation, lower power consumption requirements, faster adaption, and how these affect the system design choices.

Compressive Channel Estimation and Tracking for Large Arrays in mm-Wave Picocells

We propose and investigate a compressive architecture for estimation and tracking of sparse spatial channels in millimeter (mm) wave picocellular networks. The base stations are equipped with antenna arrays with a large number of elements (which can fit within compact form factors because of the small carrier wavelength) and employ radio frequency (RF) beamforming, so that standard least squares adaptation techniques (which require access to individual antenna elements) are not applicable. We focus on the downlink, and show that "compressive beacons," transmitted using pseudorandom phase settings at the base station array, and compressively processed using pseudorandom phase settings at the mobile array, provide information sufficient for accurate estimation of the two-dimensional (2D) spatial frequencies associated with the directions of departure of the dominant rays from the base station, and the associated complex gains. This compressive approach is compatible with coarse phase-only control, and is based on a near-optimal sequential algorithm for frequency estimation which can exploit the geometric continuity of the channel across successive beaconing intervals to reduce the overhead to less than 1% even for very large (32 x 32) arrays. Compressive beaconing is essentially omnidirectional, and hence does not enjoy the SNR and spatial reuse benefits of beamforming obtained during data transmission. We therefore discuss system level design considerations for ensuring that the beacon SNR is sufficient for accurate channel estimation, and that inter-cell beacon interference is controlled by an appropriate reuse scheme.

Compressed Sensing System Considerations for ECG and EMG Wireless Biosensors

Compressed sensing (CS) is an emerging signal processing paradigm that enables sub-Nyquist processing of sparse signals such as electrocardiogram (ECG) and electromyogram (EMG) biosignals. Consequently, it can be applied to biosignal acquisition systems to reduce the data rate to realize ultra-low-power performance. CS is compared to conventional and adaptive sampling techniques and several system-level design considerations are presented for CS acquisition systems including sparsity and compression limits, thresholding techniques, encoder bit-precision requirements, and signal recovery algorithms. Simulation studies show that compression factors greater than 16X are achievable for ECG and EMG signals with signal-to-quantization noise ratios greater than 60 dB.

AN EFFICIENT DESIGN FOR MOTION-JPEG2000 SYSTEM IN REAL-TIME VIDEO ENCODING

Motion-JPEG2000 is derived from Part 1 of the JPEG2000 standard and provides high quality image compression in video coding system. This paper presents a real-time Motion-JPEG2000 encoding which is built on a fixed-point digital signal processor (DSP) as a single-chip implementation. The design addresses on the system-level design considerations. Among several modules in JPEG2000, Embedded Block Coding with Optimized Truncation (EBCOT) algorithm contains the highest computation complexity and also becomes the bottleneck of JPEG2000. Two speed-improved methods are proposed to significantly reduce the processing time of EBCOT. The fast algorithm is used by processing the three coding passes in sequential and is very suitable to the execution on programming-based processor. For Motion-JPEG2000 implementation, a real-time encoding system is built on the single-chip DSP processor without any extra hardware support. The optimization techniques are also applied to enhance the performance. Due to the contribution on algorithm and implementation issue, the complexity of Motion-JPEG2000 is largely reduced. Simulation results show that the proposed system can process 30 frames per second in CIF size (352 × 288 pixels) with 4:2:0 video sequences. For SDTV size resolution (760 × 480 pixels), the system can achieve near 20 frames per second.

A Highly Integrated Power Management IC for Advanced Mobile Applications

Wireless communication now has the speed and power to converge seamlessly with other consumer and business electronics. However, battery technology has not kept pace with advancement in circuit technology. As a result, design of power management is becoming a more complex problem for this new generation of wireless devices with converged voice, data, and multimedia. In this paper, a highly integrated power management IC (PMIC) is presented which enables mobile devices that are more cost effective, thinner and more compact with better power efficiency. The overall architecture and system level design considerations are described. The design details of two key building blocks - low-dropout linear regulator (LDO) and switch-mode DC-DC converter - are also discussed, including a novel frequency compensation method for LDO.

A review of distributed power systems. Part II. High frequency AC distributed power systems

The present development state in high frequency (HF) AC distributed power systems (DPS) is reviewed. First, background and motivations of developing HF AC-DPS are addressed. Two types of basic HF AC-DPSs based on sine wave and square/PWM (pulsewidth modulated) wave bus are described, and the system level design considerations are discussed. Further, the issues and challenges in this research area are identified. These issues include high electromagnetic interference (EMI) level, difficulty to back up power, nonredundant system structure and limited post-regulation capability, etc. Finally, a viable HF AC-DPS is proposed, which is expected to yield effective EMI trade-off and system redundancy

A review of distributed power systems part I: DC distributed power system

The present development state in DC distributed power systems (DPS) is comprehensively reviewed in this tutorial. Basic distributed structures and their characteristics are described. The system level design considerations are discussed. The profile of current technologies is drawn. Finally, the issues and challenges in this research area are identified. These issues include not only improving efficiency, but also increased concerns regarding the cost and complexity of power supplying systems.

Providing multimedia communications services from high altitude platforms

AbstractSystem level design considerations for high altitude platforms operating in the mm‐wave bands are examined. Propagation effects in these bands are outlined, followed by a brief introduction to different platform scenarios. Ground‐based and platform‐based fixed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The effects on performance of platform displacement from its desired location with both fixed and steerable antennas are also examined. It is shown that steerable antennas are of most use when fixed stations are immediately below the platform, with no benefit for fixed stations on the edge of coverage. The bandwidths required to serve several traffic distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The effects of temporal changes in the spatial traffic distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes. Copyright © 2001 John Wiley & Sons, Ltd.