1,720,969 research outputs found
1-D Combline Leaky-Wave Antenna With the Open-Stopband Suppressed: Design Considerations and Comparisons With Measurements
No full textThe design of a 1-D planar periodic combline leaky-wave antenna that avoids the open-stopband effects as the beam is scanned through broadside is discussed and verified experimentally. This antenna radiates from nearly resonant stubs, which ensures a small leakage constant and hence a high directivity, and shows a single beam scanning through its n = -1 space harmonic in the X-band frequency range. The open-stopband suppression is obtained by applying a recently proposed matching technique within the unit cell [1] that is experimentally validated here for the first time. Measurements are made of the phase and leakage constants, the S-parameters, and the realized gain patterns. Comparisons are made with numerical values obtained from specialized and commercial software and very good agreement is found in all cases
1-D Combline Leaky-Wave Antenna With the Open-Stopband Suppressed: Design Considerations and Comparisons With Measurements
No full textThe design of a 1-D planar periodic combline leaky-wave antenna that avoids the open-stopband effects as the beam is scanned through broadside is discussed and verified experimentally. This antenna radiates from nearly resonant stubs, which ensures a small leakage constant and hence a high directivity, and shows a single beam scanning through its n = -1 space harmonic in the X-band frequency range. The open-stopband suppression is obtained by applying a recently proposed matching technique within the unit cell [1] that is experimentally validated here for the first time. Measurements are made of the phase and leakage constants, the S-parameters, and the realized gain patterns. Comparisons are made with numerical values obtained from specialized and commercial software and very good agreement is found in all cases
A Novel Technique for Open-Stopband Suppression in 1-D Periodic Printed Leaky-Wave Antennas
No full textA novel technique for the elimination of the open stopband in one-dimensional periodic printed leaky-wave antennas is presented. A quarter-wave transformer, or alternatively a matching stub, is introduced into the unit cell of the antenna, which forces the Bloch-wave impedance of the structure to remain real and non-zero at broadside. The effectiveness of the proposed technique is first demonstrated on a printed periodic microstrip leaky-wave antenna consisting of a single radiating stub per unit cell, which exhibits a significant stopband at broadside. The technique is then also applied to a structure consisting of two radiating stubs per unit cell, which is capable of mitigating, but not eliminating, the open stopband. In both cases the open stopband at broadside is completely suppressed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analysis and design, of a microstrip patch antenna for harmonic tuning in a high-efficiency integrated microwave transmitter
No full textA microstrip patch antenna is designed to serve as both the radiator and the harmonic tuner of a power amplifier in a high-efficiency transmitter operating in the Ku-band. A circular-sector patch is used in conjunction with a double tuning stub in order to synthesize the optimal complex input impedance as a load for the power amplifier at the operating frequency. A compact filter is further inserted in the line that feeds the patch in order to achieve a complete impedance mismatch at the third harmonic frequency. Numerical full-wave simulations are reported for both the input impedance and the radiation pattern of the antenna, which confirm the effectiveness of the proposed design
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Regularization of Mixed-Potential Layered-Media Green's Functions for Efficient Interpolation Procedures in Planar Periodic Structures
No full textThe problem of improving the computational efficiency in the numerical analysis of planar periodic structures is investigated here using the mixed-potential integral-equation (WILE) approach. A new regularization of the periodic Green's functions (PGFs) that are involved in the analysis of multilayered structures is introduced, based on the effective-medium concept. This regularization involves extracting the singularities of the PGFs up to second-order terms. The resulting regularized PGF is very smooth and amenable to interpolation. Thus, optimized interpolation procedures for the PGFs can be applied, resulting in a considerable reduction of computation time without any significant effect on the accuracy. Another benefit of the regularization is that it significantly enhances the convergence of the series for both the vector- and scalar-potential PGFs. The theoretical formulation is fully validated with various numerical results for both two-dimensional (2-D) and one-dimensional (1-D) layered-media periodic structures
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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