Beam broadened radial line slot array antenna for fifth generation (5g) mobile broadband communication

Radial line slot array antenna with broad beam is easily realized at frequencies in the lower part of super high frequency band. But emerging broadband mobile communication systems like the fifth generation target frequencies in the upper part of the band and beyond. Therefore, this paper presents the design of beam broadened radial line slot array antenna at 28 GHz for fifth generation broadband mobile communication system. Surface slot distribution synthesis was carried on beam squinted standard single layer radial line slot array design to achieve the broad beam. Using computer simulation technology microwave studio 2014 software, 85 mm radius antenna having polypropylene (ɛr = 2.33) as cavity material was realized. Simulated results shows a gain of 15.8 dB, impedance bandwidth of 1.6 GHz, radiation efficiency of 96 % and 3 dB half power beamwidth of up to 32.3o

Optimization of a linearly polarized radial line slot array antenna design for direct broadcast satellite services

Azimuthal components of beam squint design techniques for Linearly Polarized Radial Line Slot Array (LP-RLSA) antena was in the past chosen arbitrarily, which accounted for waste of quality design/simulation time and by extension the entire fabrication processes when poor design parameter is selected arbitrarily. This thesis introduces a more scientific method of identification and selection of azimuthal components (SØ) as a function of phi (Ø), thetaT (ƟT) and phiT (ØT) respectively via a numerical technique, which identifies optimal design parameters and formulates optimal equations. The thesis further studies the behaviour of dielectrics as it relates to the performance of the LP-RLSA antenas and has put in place suitable dielectric permittivity values required at Ku Band (12.25 - 12.75) GHz. Thus, a directivity value of more than 33.00 dBi was achieved at a frequency of 12.4 GHz with a reflection coeficient value less than -23.26 dB and a bandwidth of about 41% of 500MHz required. A radiation efficiency value of about 67% was achieved. Relationships between half power beam width (HPBW), slot widths (w) and antenna directivity (D) were studied, a new directivity relationship resulting from the study was formulated for the Ku Band (12.25 - 12.75) GHz. Research on the Ka Band LP-RLSA antenna design as an emerging technology for future satellite DBS service application at (21.4 - 22.0) GHz was done; CST MWS simulations were used, about 4 dBi higher in value of simulated directivity was obtained compared to the Ku Band design (12.25 - 12.75) GHz of same dish size (600 mm), with a bandwidth of about 41% of the 600 MHz required for the Ka Band DBS application at 21.699 GHz and 36.2 dBi realized. Good return loss performance of the Ka and Ku Bands design was achieved. Measured results for the Ku Band are in excellent agreement with the simulation result

Relationship for slots width, antenna directivity, and the 3dB HPBW of an RLSA antenna at 12.4GHz using regression analysis

The quest to optimize performance of the radial line slots array (RLSA) antenna continued to unfold. Attempt is made at studying slots width variation in radial line slot array antenna (RLSA) and its effect on the 3dB half power beam width (3dB HPBW) in this submission. It is aimed at formulating a polynomial equation that best describes the relationship between them. The polynomial equation in turn relates to the directivity of the RLSA antenna. The minimum number of slots in the first ring were restricted to (n1) =12 and, (n1) =14, this is used to manipulate slots concentration on the radiating surface. The restriction is owed to the fact that much cluster of slots in the first ring resulted to a deteriorating performance in terms of directivity values recorded from CST 2012 simulations, for the 12.4 GHz regression analysis in this study. Results obtained from the polynomial equation formed were compared with measured and simulated directivity values and showed good agreement

Syntax and semantics question analysis using user modelling and relevance feedback

A Question Answering (QA) system aims to provide relevant answers to users’ natural language (NL) questions by consulting its knowledge base (KB). Providing users with the most relevant answers to their questions is an issue. Many answers returned are not relevant to the questions, and this issue is due to many factors. One such factor is the ambiguity yield during the semantic analysis of lexical extracted from the user’s question. The existing techniques did not consider some of the terms, called modifier terms, in the user’s question which are claimed to have a significant impact of returning the correct answer. The objective of this study is to present the syntax and semantic question analysis using user modelling (UM) and relevance feedback (RF). This analysis interprets all the modifier terms in the user’s question in order to yield correct answers. A combination of UM and RF is used to increase the accuracy of the returned answer. UM helps the QA system to understand the user’s question and manage for question adjustment. RF provides an extended framework for the QA system to avoid or remedy the ambiguity of the user’s question. The analysis utilizes Vector Space Model (VSM) to semantically interpret and correctly converts modifier terms into a quantifiable form. The finding of this analysis demonstrates a good precision percentage of 94.7% in returning relevant answers for each NL question

Aperture slot size effect to wide band open air gap radial-line slot array performance

A wideband open air gap radial line slot array (RLSA) antenna is presented for point-to-point application. This article investigates the optimum slot arrangement and the effect of slot width to the RLSA antenna. Eight models were developed and simulated with slot width taking range in values from 1 to 8 mm. Results from simulation shows optimum performance at 6-mm slot width. The 2-mm slot width gave similar performance to the 6-mm slot width in term of gain and directivity. Both antennas were fabricated and measured, from the measurement; a better return loss performance of about 28% was realized at 6-mm slot width when compared to 2-mm slot width RLSA. However, both antennas produced the same gain. A better sidelobe level of 2.9 dB was achieved with the 2-mm slot width antenn

Investigation on Multisampling Deadbeat Current Control With Time-Delay Compensation in Grid-Connected Inverter

The control of voltage source converters (VSCs) is now implemented on digital microprocessors. This digitalization has the drawback of time delay in the control loop. The goal of this research work was to investigate improvements that can be obtained from the combination of model-based and model-free time-delay compensation approaches. Deadbeat control (DBC) from model-based techniques and the method of moving the control variable’s sampling instants, or the pulse-width modulation (PWM) updating instants, from model-free time-delay compensation techniques, were put together as the proposed new method of time-delay compensation in this study. These controllers were thoroughly examined in terms of control algorithm design, system stability analysis, and sensitivity analysis of plant parameter perturbations. In addition, thorough Simulink-based computer simulations were conducted in this work to assess the performance of each controller. The proposed method compensated about 80 µs as compared with the time delay compensated by the conventional single-sampling method. This research work was limited to simulations only; hence, conducting experiments to further validate this research work could be a direction for further research