Ultrawideband antennas [[electronic resource] ] : design and applications / / Daniel Valderas ... [et al.]

• Record Nr.: UNINA9910463924203321
• Pubbl/distr/stampa: London, : Imperial College Press, 2011
• ISBN: 1-283-14337-2; 9786613143372; 1-61344-081-2; 1-84816-492-0
• Descrizione fisica: 1 online resource (210 p.)
• Altri autori (Persone): ValderasDaniel
• Disciplina: 621.382/4; 621.3824; 621.384135
• Soggetti: Ultra-wideband antennas; Ultra-wideband antennas - Design; Electronic books.
• Lingua di pubblicazione: Inglese
• Formato: Materiale a stampa
• Livello bibliografico: Monografia
• Note generali: Description based upon print version of record.
• Nota di bibliografia: Includes bibliographical references (p. 183-190) and index.
• Nota di contenuto: Foreword; Acknowledgements; Authors; Contents; 1. Introduction to Ultrawideband Systems Cong Ling; 1.1 Overview; 1.2 UWB Schemes; 1.2.1 Impulse radio/time hopping; 1.2.2 Direct sequence; 1.2.3 Frequency hopping; 1.2.4 OFDM; 1.3 Industry Standards; 1.3.1 Single band versus multiband; 1.3.2 Standards; 1.4 Applications; 1.5 Challenges; 2. Figures of Merit for UWB Antennas David Puente and Daniel Valderas; 2.1 Requirements for a UWB Antenna; 2.1.1 Efficiency and matching; 2.1.2 Signal distortion and dispersion (ringing); 2.1.3 Stability over frequency of the transmission-reception transfer function2.1.3.1. Constant transfer function: Pulses selected directly by the source; 2.1.3.2. Variable transfer function: Concept of the antenna as a filter; 2.2 UWB Antenna Parameters; 2.2.1 Variability in the frequency domain; 2.2.1.1. Magnitude of the transfer function; 2.2.1.1.1. Stability of the reflection coefficient; 2.2.1.1.2. Polarisation stability; 2.2.1.1.3. Gain stability and channel losses; 2.2.1.2. Transfer function phase: Group delay; 2.2.2 Variability in the time domain: Pulse ; distortion parameters; 2.2.2.1. Fidelity factor2.2.2.2. Time spread; 2.2.3 Variability in the space domain; 2.2.3.1. Statistical values; 2.2.3.1.1. Uniformity; 2.2.3.1.2. Spatially averaged transfer function (SATF); 2.2.3.1.3. Spatially averaged group delay (SAGD); 2.2.3.2. Correlation-based averages: Angular range; 2.3 Simulation in the Time Domain; 3. Classification of UWB Antennas David Puente and Daniel Valderas; 3.1 Helical Antennas; 3.2 Frequency-independent Antennas; 3.2.1 Spiral antennas; 3.2.2 Biconical antennas; 3.2.2.1. 3D biconical antennas; 3.2.2.2. 2D biconical antennas; 3.3 Log-periodic Antennas; 3.4 Horn Antennas3.4.1 3D horn antennas; 3.4.2 2D horn antennas; 3.5 UWB Antennas Derived from Resonant Antennas; 3.5.1 3D monopoles; 3.5.1.1. Modifications to the geometry; 3.5.1.1.1. Euclidean shapes; 3.5.1.1.2. Computer optimisation; 3.5.1.1.3. Partial variation on a Euclidean shape; 3.5.1.2. Changes in current distribution; 3.5.1.2.1. Use of parasitic elements; 3.5.1.2.2. Use of a short-circuit pin; 3.5.1.2.3. Asymmetric feed; 3.5.1.2.4. Double feed; 3.5.2 2D resonant antennas; 3.5.2.1. Full 2D monopoles; 3.5.2.2. Slot antennas; 3.6 Conclusions; 4. UWB Monopole Antenna Analysis Daniel Valderas and Juan I. Sancho4.1 Introduction; 4.2 Current-conductive Parts on Planar Monopole Antennas; 4.2.1 Currents parallel and perpendicular to the ground plane: A working hypothesis; 4.2.2 Non-radiating currents in a PMA; 4.3 Transmission Line Model for UWB Monopole Antennas; 4.3.1 General description; 4.3.2 Description of the model; 4.3.2.1. Transmission line; 4.3.2.2. Radiating structure; 4.3.3 Purpose of the analogy; 4.3.4 Graphical approach: The Smith Chart; 4.4 Design Based on TLM; 4.4.1 Design of an UWB-PMA antenna with a given bandwidth; 4.4.2 Design of an UWB-PMA antenna having a maximised bandwidth
• Sommario/riassunto: Ultrawideband (UWB) technology, positioned as the cutting edge of research and development, paves the way to meet the emerging demands set by broadband wireless applications, such as high-speed data transmission, medical imaging, short-range radars, electromagnetic testing, etc. This breathtaking resource builds upon the basics of UWB technology to provide a complete compilation of figures of merit along with a vital state-of-the-art of the different antenna alternatives that are to be employed according to the specific application. Without excessive recourse to mathematics, this volume emphas

σ- and π-Hole Interactions

• Record Nr.: UNINA9910557727903321
• Autore: Frontera Antonio
• Pubbl/distr/stampa: Basel, Switzerland, : MDPI - Multidisciplinary Digital Publishing Institute, 2021
• Descrizione fisica: 1 online resource (212 p.)
• Soggetti: Biology, life sciences; Research & information: general; Research and information: general
• Lingua di pubblicazione: Inglese
• Formato: Materiale a stampa
• Livello bibliografico: Monografia
• Sommario/riassunto: This book describes unconventional noncovalent interactions and analyzes their importance for crystal growth in organic and hybrid organic-inorganic systems. Several examples illustrate how the combination of theory and experiment allows rationalizing the strength and directionality of noncovalent interactions. This book elegantly describes the results of a survey of X-ray structures of main group element compounds (M = Sn, Pb As, Sb, Bi, and Te) exhibiting intermolecular M•••Se noncovalent interactions in one of its chapters. Moreover, it provides a consistent description of noncovalent interactions, covering most groups of the periodic table. The interactions are described and discussed using their trivial names. That is, a comprehensive and accurate description is provided for alkali, alkaline earth, regium, spodium, triel, tetrel, pnictogen, chalcogen, halogen, and aerogen bonding interactions. No other book is available covering such an extensive number of interactions and examples where these interactions are relevant. relevant.