Microstrip Yagi array for MSAT vehicle antenna application

A microstrip Yagi array was developed for the MSAT system as a low-cost mechanically steered medium-gain vehicle antenna. Because its parasitic reflector and director patches are not connected to any of the RF power distributing circuit, while still contributing to achieve the MSAT required directional beam, the antenna becomes a very efficient radiating system. With the complete monopulse beamforming circuit etched on a thin stripline board, the planar microstrip Yagi array is capable of achieving a very low profile. A theoretical model using the Method of Moments was developed to facilitate the ease of design and understanding of this antenna

Radiation and Scattering by Infinite Microstrip Patch Arrays on Anisotropic Substrates

An analysis is presented of an infinite array of printed patches on a grounded anisotropic-dielectric slab. The array is considered as both a transmitter fed by idealized probes and as a scatterer of plane waves. For the transmitter case, the input reflection coefficient versus incident angle is computed for various loads and substrates. The theory in both cases is confirmed by comparing its limit to isotropic cases with previous analyses. The inputs to the analysis are the substrate parameters, the array grid geometry, the patch dimensions including probe position, and the probe load impedance, which is assumed conjugate matched at broadside for the transmit case

Optimum Shape Synthesis of Maximum Gain Omnidirectional Antennas

Using characteristic mode shape synthesis, some antenna surfaces and their current distributions are found which produce maximum realizable gain for rotationally symmetric omnidirectional antennas. The same shape synthesis method fails to produce antennas which have maximum endfire gain

Performance evaluation of analog beamforming with hardware impairments for mmW massive MIMO communication in an urban scenario

[EN] The use of massive multiple-input multiple-output (MIMO) techniques for communication at millimeter-Wave (mmW) frequency bands has become a key enabler to meet the data rate demands of the upcoming fifth generation (5G) cellular systems. In particular, analog and hybrid beamforming solutions are receiving increasing attention as less expensive and more power efficient alternatives to fully digital precoding schemes. Despite their proven good performance in simple setups, their suitability for realistic cellular systems with many interfering base stations and users is still unclear. Furthermore, the performance of massive MIMO beamforming and precoding methods are in practice also affected by practical limitations and hardware constraints. In this sense, this paper assesses the performance of digital precoding and analog beamforming in an urban cellular system with an accurate mmW channel model under both ideal and realistic assumptions. The results show that analog beamforming can reach the performance of fully digital maximum ratio transmission under line of sight conditions and with a sufficient number of parallel radio-frequency (RF) chains, especially when the practical limitations of outdated channel information and per antenna power constraints are considered. This work also shows the impact of the phase shifter errors and combiner losses introduced by real phase shifter and combiner implementations over analog beamforming, where the former ones have minor impact on the performance, while the latter ones determine the optimum number of RF chains to be used in practice.The research done by P. Baracca, V. Braun, and H. Halbauer leading to these results received funding from the European Commission H2020 programme under grant agreement number 671650 (mmMAGIC project). The work carried out at the Universitat Politècnica de València was supported by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R) by the European FEDER funds.Giménez Colás, S.; Roger Varea, S.; Baracca, P.; Martín-Sacristán, D.; Monserrat Del Río, JF.; Braun, V.; Halbauer, H. (2016). Performance evaluation of analog beamforming with hardware impairments for mmW massive MIMO communication in an urban scenario. Sensors. 16(10):1-17. https://doi.org/10.3390/s16101555S117161

Micro-combs: a novel generation of optical sources

The quest towards the integration of ultra-fast, high-precision optical clocks is reflected in the large number of high-impact papers on the topic published in the last few years. This interest has been catalysed by the impact that high-precision optical frequency combs (OFCs) have had on metrology and spectroscopy in the last decade [1–5]. OFCs are often referred to as optical rulers: their spectra consist of a precise sequence of discrete and equally-spaced spectral lines that represent precise marks in frequency. Their importance was recognised worldwide with the 2005 Nobel Prize being awarded to T.W. Hänsch and J. Hall for their breakthrough in OFC science [5]. They demonstrated that a coherent OFC source with a large spectrum – covering at least one octave – can be stabilised with a self-referenced approach, where the frequency and the phase do not vary and are completely determined by the source physical parameters. These fully stabilised OFCs solved the challenge of directly measuring optical frequencies and are now exploited as the most accurate time references available, ready to replace the current standard for time. Very recent advancements in the fabrication technology of optical micro-cavities [6] are contributing to the development of OFC sources. These efforts may open up the way to realise ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates, in the form of compact and integrated devices. Indeed, the fabrication of high-quality factor (high-Q) micro-resonators, capable of dramatically amplifying the optical field, can be considered a photonics breakthrough that has boosted not only the scientific investigation of OFC sources [7–13] but also of optical sensors and compact light modulators [6,14]

Microwave engineering

The 4th edition of this classic text provides a thorough coverage of RF and microwave engineering concepts, starting from fundamental principles of electrical engineering, with applications to microwave circuits and devices of practical importance.  Coverage includes microwave network analysis, impedance matching, directional couplers and hybrids, microwave filters, ferrite devices, noise, nonlinear effects, and the design of microwave oscillators, amplifiers, and mixers. Material on microwave and RF systems includes wireless communications, radar, radiometry, and radiation hazards. A larg

Microwave Engineering ed.3

xvii, 699 hlm, Ilust, 24 c