Structural behaviour of beam with HDPE plastic balls subjected to flexure load

This paper presents the structural behavior of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results are analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failur

An Electronically Reconfigurable Patch Antenna Design for Polarization Diversity with Fixed Resonant Frequency

In this paper, an electronically polarization reconfigurable circular patch antenna with fixed resonant frequency operating at Wireless Local Area Network (WLAN) frequency band (2.4-2.48 GHz) is presented. The structure of the proposed design consists of a circular patch as a radiating element fed by coaxial probe, cooperated with four equal-length slits etched on the edge along x-axis and y-axis. A total of four switches was used and embedded across the slits at specific locations, thus controlled the length of the slits. By activating and deactivating the switches (ON and OFF) across the slits, the current on the patch is changed, thus modifying the electric field and polarization of the antenna. Consequently, the polarization excited by the proposed antenna can be switched into three types, either linear polarization, left-hand circular polarization or right-hand circular polarization. This paper proposes a simple approach that able to switch the polarizations and excited at the same operating frequency. Simulated and measured results of ideal case (using copper strip switches) and real case (using PIN diode switches) are compared and presented to demonstrate the performance of the antenna

Agregado de antenas 2x2 compolarização circular dual para constelações de satélites LEO

Although communications technologies are in rapid development, there are still many remote regions that aren’t covered by telecommunication services. LEO satellite constellations are being used to address this issue by aiming to provide continuous and high-capacity global communication services. Satellite communications are usually made using frequencies near the Ka band, with higher frequencies for the uplink and lower frequencies for the downlink. The antenna developed in the course of this dissertation was chosen to operate at 20GHz, enabling its implementation for downlink communications. Furthermore, circular polarized antennas are useful in satellite communications for versatility by being able to receive other polarizations. The proposed antenna is a dual-fed square patch, with aperture coupled feed, incorporated with a quadrature hybrid coupler as the feed and later included in a 2x2 array. This antenna has the possibility of being left or right circularly polarized by choosing the feeding port. The structures presented were modeled progressively by simulation, in several stages, and so the evolution of the results could be analyzed as the antenna got more complex. After designing the antenna it was later fabricated, and measurements were taken for validation.Apesar das tecnologias de comunicações estarem em rápido desenvolvimento, ainda há muitas regiões remotas que não são abrangidas por serviços de telecomunicações. Constelações de satélites LEO estão a ser usados para abordar este problema, com o objetivo de providenciar serviços de comunicação globais contínuos e de alta capacidade. As comunicações satélite são usualmente feitas perto da banda Ka, com frequências mais altas para o uplink e mais baixas para o downlink. A antena desenvolvida nesta dissertação foi projetada para operar a 20GHz, podendo ser implementada para as comunicações downlink. Adicionalmente, antenas com polarização circular são úteis em comunicações satélites pela versatilidade de serem capazes de receber outras polarizações. A antena proposta é uma patch quadrada com alimentação por acoplamento através de fenda, em dois pontos ortogonais, integrada com um acoplador híbrido em quadratura e mais tarde incluída num array 2x2. Esta antena tem a possibilidade de ter polarização circular esquerda ou direita consoante a escolha do porto de alimentação. As estruturas apresentadas foram modeladas progressivamente por simulação, em várias fases, e por isso a evolução dos resultados puderam ser analisados à medida que a antena ficava mais complexa. Depois a antena projetada foi fabricada e foram efetuadas medições para validação.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Design of a Multiband Stacked Microstrip Patch Antenna for Satellite Communications Application

In this thesis, a multiband stacked patch antenna for satellite communications is proposed. Since handheld devices used for satellite communications are mainly monopole antennas, this thesis explores the possibilities of developing a microstrip patch antenna that can be integrated in the satellite communications’ handheld devices. Therefore, a designed antenna for satellite communications that operates around the two bands 1.487 GHz and 1.578 GHz is proposed. The antenna composes of two stacked patches with total dimensions of 45 x 45 mm and 40 x 40 mm for the lower and upper patches, respectively, separated by FR_4 as a dielectric material. The proposed antenna is designed using the method of moments simulator of ADS and the simulations results show good performance in satellite communications bands with gain of 3.42 dBi and circular polarization from 1.453 GHz to 1.478 GHz. Additionally, the antenna shows multiple matching frequencies that can be used for other purposes along with the satellite communications. Moreover, this antenna is simple, easy to fabricate and manufacture, and implement on different devices comparing to other monopole antennas that serve the same purpose

A Novel QWT Fed Penta- Band Microstrip Patch Antenna for Various Wireless Applications

A conventional patch antenna is initially designed with edge fed feeding. The four edges of patch are chamfered to make it octagon shaped. Further four slots two in horizontal and two oriented vertically are etched on the patch. A H shaped Slot is created on Ground. The result is a multi- resonant antenna for SATCOM and RADAR applications. The use of flexible substrate is to suit the chosen wireless applications. The optimized antenna model with its vital parameters are  presented in this paper

Rectangular shaped microstrip patch antenna with multiple slits and slots

This paper presents a complex microstrip patch antenna design for Ku-band satellite communication applications. FR4 and RogerRT6002 have alternatively been used as substrates having dielectric constant of 4.4 and 2.94 respectively. The patch ground and feedlines are made of copper. The proposed antenna is unique in shape with rectangular slots. The performance of the antenna has been analyzed in terms of far field gain. The most significant results were obtained using FR4 substrate, which gave a gain of 7.88 dB, at 11.32 GHz and a reflection coefficient of -10.48 dB. The final microstrip patch antenna design was simulated, built and tested. Simulated and measured S11 frequencies perfectly match at 11.32 GHz with simulated and measured magnitudes of 10.48 dB and -29.64 dB respectively

Single-, Dual- and Triple-band Frequency Reconfigurable Antenna

The paper presents a frequency reconfigurable slot dipole antenna. The antenna is capable of being switched between single-band, dual-band or triple-band operation. The antenna incorporates three pairs of pin-diodes which are located within the dipole arms. The antenna was designed to operate at 2.4 GHz, 3.5 GHz and 5.2 GHz using the aid of CST Microwave Studio. The average measured gains are 1.54, 2.92 and 1.89 dBi for low, mid and high band respectively. A prototype was then constructed in order to verify the performance of the device. A good level of agreement was observed between simulation and measurement

Development of planar filters and diplexers for wireless transceiver front ends

The central theme of this work is the design of compact microstrip bandpass filters and diplexers and the investigation of applications of these circuits in integrated transceiver RF front-end. The core of this thesis therefore presents the following stages of the work: - Analysis of coupled pseudo-interdigital resonators and lines; formulation of approximate transmission zero conditions and the investigation of coupling between these two resonators and related structures. - Development of compact, low loss and high selectivity microstrip pseudointerdigital bandpass filters. The design procedure of the filter consists of three simple steps, starting from the design of a parallel-coupled bandpass filter using the image parameter method applied to coupled microstrip lines. The development of compact microstrip diplexers composed of these filters uses the optimized common-transformer diplexing technique. An experimental verification of the developed filters and diplexers is made. - Investigation of the use of stepped impedance resonators (SIR) for the design of pseudo-interdigital bandpass filters with advanced characteristics. The design of compact dual-band filter using SIR. The investigation of possible improvement of the stopband of bandpass filters using bandstop generating structures. The application of SIR, defected ground structures (DGS), spur-lines, and opencircuited stubs in the design of compact bandpass filters with improved stopband. - The application of the proposed filters and diplexers in the design of integrated antenna filters and antenna diplexers. Improvement of performance of patch antennas, such as suppression of spurious harmonics of single-band antenna and improvement of bandwidth and selectivity of dual-band antenna, as a result of integration with filters. Separation of antennas’ bands and reduction of component count in integrated antenna diplexer