Linear and Non-Linear Synthesis of Unequally Spaced Time-Modulated Linear Arrays Using Evolutionary Algorithms

A novel method of designing unequally spaced time-modulated arrays (UESTMAs) by handling fewer optimization parameters with reduced problem dimension is presented in this paper. For synthesizing UESTMA, two design parameters, specifically, the non-linear parameter - element position, and the linear parameter – on-time durations are optimized in two steps. Different possible cases of linear and non-linear synthesis methods such as, position-only (PO), on-time only (OTO), position then on-time (PTOT), on-time then position (OTTP), and simultaneous position on-time (SPOT) are considered. To examine the performance of the synthesis methods, three global search stochastic algorithms based on differential evolution (DE), teaching-learning-based optimization (TLBO) and quantum particle swarm optimization (QPSO) have been employed to achieve the array pattern with significantly suppressed side lobe levels and sideband levels. Through comparative study, it is observed that the two step non-liner to linear synthesis method by fewer optimization parameters is efficient to provide better pattern with less computation time

Analysis and synthesis of antenna arrays with respect to mutual coupling and beamforming

ato práce se zabývá analýzou a syntézou (zejména liniových) anténních řad umístěných ve volném prostoru nebo nad nekonečnou zemní rovinou. K charakterizaci problému byla odvozena teorie a algoritmus implementován v programu MATLAB. Pro liniové anténní řady se vyvinutá metoda se vyznačuje velkou rychlostí z důvodu použití vhodné aproximace proudového obložení na jednotlivých prvcích řady. Pro analýzu řad jsou využity modální techniky, tj. řada je charakterizována maticemi o rozměru NxN (kde N je počet prvků v řadě) popisujícími její impedační a vyzařovací vlastnosti. Tyto matice jsou následně podrobeny modálním rozkladům, jejichž výsledek poskytuje optimální buzení elementů pro dosažení daných vlastností – rezonance řady, činitel jakosti, směrovost. Kromě semi-analytických metod aplikovaných na liniové řady byl rovněž vyvinut algoritmus využívající simulátor elektromagnetického pole CST MWS, jež je pomocí maker propojen s programem MATLAB. Takto je možné syntetizovat vyzařovací diagram řady s libovolným typem elementů, tj. nikoli jen s dipóly. Výše zmíněné metody jsou aplikovány a ověřeny na několika příkladech: Optimalizace Yagi-Uda antény s různou délkou elementů, Optimalizace šířky pásma a směrovosti řady nad zemní rovinou, Řízení směrovosti kruhové řady, Syntéza supersměrového buzení řady, Syntéza daného vyzařovacího diagramu řady včetně zahrnutí vzájemných vazeb. V neposlední řadě jsou tyto příklady a techniky inspirací pro návrh a výrobu anténní řady na frekvenci 26 GHz. Tato řada byla vyrobena, změřena a bude implementována spolu s optickým systémem, který bude tvořit napájecí a přenosovou část pro systém 5G.This work deals with the analysis and synthesis of (especially linear) antenna arrays located in free space or above the infinite ground plane. The theory and algorithm implemented in MATLAB were derived to characterize the problem. For linear antenna array the developed method is characterized by a high computational speed due to the use of suitable current distribution approximation on individual elements of the array. Modal techniques are used to analyze the array, i.e., the array is characterized by matrices of N x N dimension (where N is the number of elements) describing its impedance and radiation properties. These matrices are then subject to modal decomposition, the result which provides optimal excitation of the elements to achieve given properties - resonance, quality factor, directivity. In addition to semi-analytical methods applied to linear arrays, an algorithm using electromagnetic field simulator CST MWS, which is connected to MATLAB by macros, was also developed. In this way, it is possible to synthesize a radiation pattern of an array with any type of element, i.e., not just dipoles. The above methods are tested and validated on several examples: Optimization of Yagi-Uda antenna with different element lengths, Optimization of bandwidth and directivity of an array above ground plane, Directivity control of circular array, Synthesis of super-directivity excitation of an array, Synthesis of a given radiation pattern of an array, including the mutual coupling. Last but not least, these examples and techniques are an inspiration for the design and manufacture of the 26 GHz antenna array. This array has been manufactured, measured and will be implemented together with an optical system that will form the power and transmission part to the 5G system

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion