bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Noise and Measurements
Authors: Chang Heng‐Chia 
Published: December 2024

Abstract
The phase of the electric signals or electromagnetic fields from the circuits and devices is often modulated or demodulated with important information in modern communication systems. However, there are always some random fluctuations in the phase of the signals caused by thermal noise (thermal motion of the carriers), or shot noise (discrete properties of the electric current sources), or several other mechanisms inside the devices, circuits, wired or wireless medium. The term phase noise is used for describing such short‐term random fluctuations of the signals. In this chapter the author especially describes the phase noise in the oscillators, because most of the phase noise sources in the communication systems come from the oscillators. The author explains the oscillator phase noise by theory, describes several techniques to improve phase noise, and illustrates several popular measurement techniques. The author concludes this chapter with some references for the interested readers to study by themselves the phase noise and the related measurement techniques further.
Radio‐Frequency‐Integrated Circuits
Authors: Chongcheawchamnan M. , Karacaoglu U. , Amsdon T. J. , Robertson I. D. 
Published: December 2024

Abstract
This chapter gives an overview of the technology and design of radiofrequency (RF)‐integrated circuits in silicon technology. These circuits have transformed the field of wireless communications, forming the heart of sophisticated multiple‐input, multiple‐output RF transceivers for use in cellular handsets. The technology is now starting to transform new fields in the millimeter‐wave frequency range, enabling it to be used for new consumer applications such as radars for autonomous cars. The chapter describes the key active device technologies and passive components before going on to describe the state of the art in circuit design techniques. There are separate sections dedicated to the design of amplifiers, oscillators, mixers and modulators, and integrated transceivers. A final section gives an introduction to the importance of taking the packaging into account at the chip design and layout stage, as well as describing the rapidly emerging field of RF system‐in‐package technology, where sophisticated millimeter‐wave antenna arrays can be integrated with active circuits. The chapter includes 180 references to research papers describing advanced techniques developed in both industry and academia.
Variable‐Frequency Oscillators
Authors: Gutierrez Germán 
Published: December 2024

Abstract
Oscillators are abundant around us. Most oscillators are of two basic kinds: sinusoidal and relaxation. This chapter covers the main topologies for all popular oscillators and the ways to make their frequency of oscillation variable. The description is independent of frequency and can be applied from very‐low‐frequency to microwave oscillators. Mechanical examples give a very simple explanation for the mechanism of oscillators and the concept of resonance.

An
oscillator
is defined as anything that swings back and forth like a pendulum (vibrates) or travels back and forth between two points. An
electronic oscillator
is a device used for producing alternating current (e.g., a radio frequency or audio frequency generator).
Frequency
is the number of times that a periodic function repeats the same sequence of values during a unit of time or the number of complete oscillations of a wave per second.

Oscillators are abundant all around us: light, sound, the rotation of the Earth, electric AC power, heartbeats, musical instruments, motors, microprocessor clocks, etc. Some of these oscillatory systems have variable frequencies, and some have fixed frequency. We will first describe all the different types of electronic oscillators to appreciate what determines their operating frequency and how it can be varied.
Voltage‐to‐Frequency Converters
Authors: Vidal‐Verdú Fernando , Navas‐González Rafael , Delgado‐Restituto Manuel , Rodríguez‐Vázquez Angel 
Published: December 2024

Abstract
Voltage‐to‐frequency converters (VFCs) typically employ relaxation oscillators to generate an output signal whose frequency depends linearly on an input voltage. VFCs are data converters; that is, they are designed to codify the input voltage by means of the output frequency. Hence, they have strong requirements regarding linearity, dynamic range, and stability. On the other hand, compared to other converters, they have the advantage of low cost, particularly for large resolutions; 13‐bit resolution is typical, and more than 20 bits are feasible. However, in such a case, several milliseconds may be necessary to complete the conversion—the smaller the resolution, the shorter the conversion time.
The serial frequency modulated output provided by VFCs is particularly well suited for telemetry, to send the outcome of a measurement by wire, radio, or fiber optic links. After the frequency‐modulated signal is received, it can be easily codified into a digital word, or converted back into a voltage by a frequency‐to‐voltage converter (FVC). This type of output simplifies galvanic isolation through the use of either an optocoupler or a magnetic coupler.
This chapter deals first with the concepts behind voltage‐to‐frequency conversion and then describes the main types of VFCs on the market, their limitations, and main applications. FVCs are also briefly described in the chapter.
RF Biometrics
Authors: Pizzillo Thomas J. 
Published: December 2024

Abstract
This report is a concise summary of research on radio frequency (RF) biometrics published in the open literature and informed by my own research as the Principal Investigator of the United States Army Research Laboratory's RF Biometrics program between 2007 and 2012. I provide a functional definition of RF Biometrics and define a concept of operations to provide context for the cited research. I explore the origins and evolution of RF Biometrics particularly in the context of security and defense applications, and provide a brief assessment of the current and future trends for RF Biometrics.
Antenna Booster Technology
Authors: Anguera Jaume , Andújar Aurora 
Published: December 2024

Abstract

Small and multiband antennas are always playing a predominant role in wireless communications to provide range, connectivity, and ensure battery life. In this regard, antenna booster technology features small size (∼
λ
/30), multiband, and multi‐radio behavior and at the same time easy to be embedded into a wireless device due to its chip‐like nature. The design of antenna systems radically differs from those based on conventional antenna design relying on shaping the geometry of the antenna to determine the frequencies of operation. On the contrary, with the antenna booster technology approach, the frequencies of operation are determined by the designer thanks to the combination of an antenna booster and a matching network. By doing so, all the complexity in the antenna part is removed and most of the intelligence is translated into the matching network. This enables making an antenna booster 10 times smaller than other antennas while flexibly adapting to any wireless protocol and device. Besides, reconfigurability can be combined with the matching network increasing the flexibility to adapt to any frequency band. Antenna booster technology is finding its applications in the design of wireless devices needing operation in the frequency range from 0.4 to 10 GHz.
The Use of Photonics for Analog RF Applications
Authors: Devgan Preetpaul S. 
Published: December 2024

Abstract
This chapter reviews the use of photonics for RF and microwave applications. As the need for more bandwidth increases, higher frequencies are being accessed. Photonics provides advantages over electronics at operating frequencies in the microwave and millimeter wave bands. This chapter provides examples of applications where photonics can be used. These applications include radio over fiber links, low phase noise clock signals, clock synchronization and simultaneous transmission and reception of RF signals. Photonics can address these applications and many more future use cases.
Collaborative Spectrum Sharing
Authors: Pham Quan , Shea John M. , Wong Tan F. 
Published: December 2024

Abstract
Explosion of the multitude of current and future wireless services has motivated the search for more efficient ways to allocate spectrum than fixed channel allocations enforced by regulatory agencies. In particular, dynamic spectrum‐sharing techniques allow spectrum to be assigned or selected for use based on the users and demand in a given geographic region. In this chapter, we consider collaborative spectrum sharing (CSS), in which users or networks share information about their spectrum needs and usage to facilitate efficient use of spectrum resources. We provide an ontology of CSS approaches and give an overview of previous CSS research. Then, we provide a more in‐depth discussion of the roles of CSS in two different example systems. The first is the Citizen Broadband Radio Service (CBRS), which is a system established by the Federal Communications Commission (FCC) in the United States, and which uses a centralized, hierarchical approach to CSS. The second is the Spectrum Collaboration Challenge (SC2), which was a competition run by the Defense Advanced Research Projects Agency (DARPA) in the United States to develop intelligent radios systems for CSS. In contrast to CBRS, the SC2 enforces a distributed, unified approach to CSS. The chapter concludes with a brief discussion of the progress and challenges in implementing CSS.
Full‐Duplex Communications Antennas
Authors: Smida Besma , Khaledian Seiran , Farzami Farhad , Atiqul Islam Md , Erricolo Danilo 
Published: December 2024

Abstract
Single‐antenna in‐band full‐duplex communication technology has the potential to substantially increase spectral efficiency. However, the implementation of full‐duplex systems is constrained by the cancellation of self‐interference (SI). This chapter provides an overview of all methodologies used to maintain a low level of SI in real‐time. First, a new analog SI cancellation technique is proposed. A radiofrequency (RF) circulator is used to separate transmitted (Tx) and received (Rx) signals. Instead of estimating the SI signals and subtracting them from the Rx signals, the inherent secondary SI signals at the circulator, reflected by the antenna, is used to cancel the primary SI signals leaked from the Tx port to the Rx port. The frequency response of the secondary SI signals is modified through a reconfigurable impedance mismatched terminal (IMT) circuit, which consists of two varactor diodes at the antenna port. The IMT adjustability makes it robust to antenna input impedance variations and fabrication errors.
Second, a comprehensive residual SI model based on a direct‐conversion transceiver structure considering nonlinearities of all the transceiver radio frequency components, in‐phase/quadrature (IQ) imbalances, phase noise effect, and receiver noise figure is offered. A more appropriate digital SI cancellation approach considering receiver chain RF and baseband (BB) nonlinearities is proposed to validate this model.
Finally, a prototype of the proposed technique at 2.45 GHz is analyzed and fabricated. An analog cancellation exceeding 40 dB over 65 MHz of bandwidth is achieved. The performance of the digital cancellation strategy is investigated and it achieves 20 dB more cancellation compared to existing methods.
Long‐Cycle Stable Zn2+ Storage in 2D Conductive Metal–Organic Frameworks via Exclusive Ligand Redox Mechanism
Authors: Liu Shuai , Kong Fantao , Chen Xiaofang , Song Erhong , Huang Aisheng 
Published: December 2024

Abstract2D conductive metal–organic frameworks (2D c‐MOFs) have emerged as novel cathode materials in the development of rechargeable aqueous zinc‐ion batteries (ZIBs) because of its integrated multiple redox‐active moieties. However, the redox of the metal nodes usually leads to the collapse of the c‐MOF structure during Zn2+ insertion/extraction process, thereby curtailing its cycling lifespan. Herein, a triphenylene‐catecholate‐based 2D c‐MOF (Zn‐HHTP) is fabricated by chelating the inactive Zn nodes, endowing the structural stability during charge and discharge processes only through ligand redox. The 1D open channel of Zn‐HHTP facilitates rapid insertion and extraction of zinc ions, thus enabling stable working of ZIBs at high rates. Impressively, Zn‐HHTP as cathode in ZIBs exhibits an ultra‐long cycling stability with capacity retention of 86.6% after 4000 cycles at the current density of 4 A g−1, exceeding the other MOF‐based cathodes ever reported. Density functional theory (DFT) calculations combined with ex situ X‐ray photo‐electron spectroscopy (XPS) further elucidate the redox mechanism between catechol and benzene ring of HHTP during the successive insertion/extraction of Zn2+, due to their comparatively negative electrostatic potentials. This work provides a new strategy to prolong the cycling capability of ZIBs by utilizing the highly active non‐metallic redox moieties in 2D c‐MOFs.
Constructing RuNi‐MoO2 Heterojunction with Optimal Built‐In Electrical Field for Efficient Hydrogen Production in Anion Exchange Membrane Water Electrolyzer
Authors: Guo Peng , Zhang Pengan , Cao Shoufu , Huang Wenjing , Lu Xiaoqing , Zhang Bo , Chen Weizhe , Zhang Youzi , Wang Yijin , Zou Ruiqing , Li Xuanhua 
Published: December 2024

AbstractWater electrolysis in alkaline media, demonstrating robust facility and cheap electrolyzer construction, are regarded as a promising strategy for industrial green hydrogen generation. Exploring effective alkaline hydrogen evolution electrocatalysts is remained an obstacle to date, which requires additional effort to obtain active hydrogen by water dissociation and promote the following unfavorable hydrogen coupling for further H2 release. Herein, the MoO2 supported RuNi nanoparticle (RuNi‐MoO2) is constructed as an efficient electrocatalyst for hydrogen evolution. Experimental and theoretical analysis demonstrate that the optimized built‐in electric field at the interface between MoO2 and RuNi alloy simultaneously accelerates the water dissociation kinetics and hydrogen spillover. It attains the current densities of 10 and 100 mA cm−2 at ultralow potential of −0.019 and −0.086 V versus RHE, respectively, along with rapid water cleavage kinetics, which even surpasses the commercial Pt/C. The constructing anion exchange membrane water electrolyzer adopting the RuNi‐MoO2 as a cathode electrocatalyst attains an industrial current density of 1 A cm−2 at a low voltage of 1.71 V and steadily operates over 1000 h with a large current density over 1 A cm−2.
Self‐Actuated Clot‐Piercing Nanoassembly Enabling Adaptable Drug Activation and Synergistic Thrombus Ablation
Authors: Zhang Hongyuan , Zhang Sen , Liu Shuwei , Fang Mingzhu , Wang Yuequan , Zhang Shenwu , Sun Jin , He Zhonggui , Luo Cong 
Published: December 2024

AbstractClinical thrombus therapy continues to be challenged by unsatisfactory antithrombotic outcomes and high bleeding risk. Rational design of prodrugs for thrombolytic agents is expected to ameliorate this situation. Nevertheless, a significant obstacle is the inadequate penetration of prodrugs and prodrug‐engineered nanomedicines, which hampers their effective interaction with the excessive stimuli produced in thrombi, resulting in suboptimal drug activation. Herein, a clot‐piercing nanoassembly is reported to facilitate photothermal clot penetration, adaptable drug activation, anti‐inflammatory action, and synergetic antithrombotic therapy, the nanoassembly is molecularly co‐assembled using a photothermal photosensitizer and a reactive oxygen species (ROS)‐sensitive antiplatelet dimeric prodrug. The nanoassembly demonstrates multiple advantages, including facile fabrication, high drug co‐loading capacity, long circulation time in the blood, thrombus‐targeting accumulation, photothermal‐potentiated clot‐piercing deep penetration, on‐demand prodrug activation in response to high H2O2 concentrations inside the clots, and anti‐inflammatory/antiplatelet synergy. These advantages result in significantly enhanced antithrombotic efficacy in vivo with favorable safety. This study presents a new paradigm for the development of prodrug‐driven antithrombotic nanomedicines.
Medium‐Entropy Engineering of Magnetism in Layered Antiferromagnet CuxNi2(1‐x)CrxP2S6
Authors: Upreti Dinesh , Basnet Rabindra , Sharma M. M. , Chhetri Santosh Karki , Acharya Gokul , Nabi Md Rafique Un , Sakon Josh , Benamara Mourad , Mortazavi Mansour , Hu Jin 
Published: December 2024

AbstractAntiferromagnetic van der Waals‐type M2P2X6 compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions in M2P2X6. Here, we report co‐substitution of Cu1+ and Cr3+ for Ni2+ in Ni2P2S6, creating CuxNi2(1‐x)CrxP2S6 medium‐entropy alloys spanning a full substitution range (x = 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co‐substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light‐matter interaction and high‐temperature ferroelectricity, can enable multifunctional device applications.
Looking Back the Nonlinear Optical Crystals in a Functionalized Unit's Perspective
Authors: Mutailipu Miriding , Li Junjie , Pan Shilie 
Published: December 2024

AbstractNonlinear optics, signifying a revolutionary paradigm change within the realm of optics, has ushered in a transformative era by employing the nonlinear optical crystals to manipulate and harness the laser power for at least six decades. The most exciting aspects of nonlinear optical (NLO)crystal is the repercussions of bonding over extended functionalized units to external force and how slight alterations at the atomic scale can result in huge changes in the macroscopic properties. However, to date, precisely controlling the functionalized unit and its potential to induce directed property is, yet, not fully realized. Here, the NLO crystals are explored and prospected from the viewpoint of a functionalized unit, with an emphasis on the application of functionalized units in material design to control and regulate key optical properties and start regulating their functions. An introduction of anionic group theory is started here, which considers the functional unit to be primary, then turns to a discussion of functionalized unit modification through emerging design strategies and how this facilitates the design of new NLO materials. Additional breakthroughs in rational design strategy to fully functionalize the groups are covered, including integration, preferential arrangement induction, microcosmic performance maximization for functionalized units as well as the supports of these for new materials discovery with a theoretical method. Beyond the gratifying achievements made, some future perspectives to move NLO crystals a step forward are finally provided.
A Nattokinase‐Loaded Nanozyme for Alleviating Acute Myocardial Infarction via Thrombolysis and Antioxidation
Authors: Shi Yingchao , Liu Chuanfen , Gui Yuesheng , Guo Yike , Zhang Yuanhao , Pan Jiangpeng , Tang Hao , Gao Chuanyu , Xing Junyue , Han Yu , Jiang Wei 
Published: December 2024

AbstractAcute myocardial infarction (MI) induced by thrombus formation is a prevalent cardiovascular disorder, and thrombolytic therapy continues to be a principal treatment modality. Prior research indicates a substantial association among MI, thrombosis, and the activation of oxidative stress pathways. The effectiveness of current thrombolytic drugs is relatively constrained, and the need for innovative and versatile thrombolytic medications remains critical. Nattokinase (NK) is a naturally‐occurring enzyme known for its thrombolytic characteristics. Nonetheless, nattokinase's limited stability and susceptibility to inactivation in biological systems have impeded its clinical utility. This study designs a manganese oxide nanozyme (MnOx) loaded with NK (MnOx@NK), which exhibits both antioxidant and thrombolytic function. The administration of MnOx@NK through tail vein injection significantly restores vascular function and further reduces myocardial injury in a mouse model of myocardial infarction, demonstrating a pronounced protective effect against oxidative stress. These findings indicate that nattokinase‐loaded nanozymes can be a promising approach for treating acute myocardial infarction, providing a new strategy for clinical application.
Large Area Near‐Field Thermophotovoltaics for Low Temperature Applications
Authors: Selvidge Jennifer , France Ryan M. , Goldsmith John , Solanki Parth , Steiner Myles A. , Tervo Eric J. 
Published: December 2024

AbstractThermophotovoltaics, devices that convert thermal infrared photons to electricity, offer a key pathway for a variety of critical renewable energy technologies including thermal energy storage, waste heat recovery, and direct solar‐thermal power generation. However, conventional far‐field devices struggle to generate reasonable powers at lower temperatures. Near‐field thermophotovoltaics provide a pathway to substantially higher powers by leveraging photon tunneling effects. Here a large area near‐field thermophotovoltaic device is presented, created with an epitaxial co‐fabrication approach, that consists of a self‐supported 0.28 cm2 emitter‐cell pair with a 150 nm gap. The device generates 1.22 mW at 460 °C, a 25‐fold increase over the same cell measured in a far‐field configuration. Furthermore, the near‐field device demonstrates short circuit current densities greater than the far‐field photocurrent limit at all the temperatures tested, confirming the role of photon tunneling effects in the performance enhancement. Modeling suggests several practical directions for cell improvements and further increases in power density. These results highlight the promise of near‐field thermophotovoltaics, especially for low temperature applications.