Electromagnetic Band-Gaps Structure In Microwave Device Design

The research in the field of electromagnetic band gap or well known as EBG structure has becoming attractive in antenna community. This structure has a unique property such as the ability to suppress the propagation of surface wave in specific operating frequency defined by the EBG structure itself. The electromagnetic band gap structure always used as a part of antenna structure in order to improve the performance of the antenna especially for improves the gain and radiation pattern. In this project, microstrip antenna is used due to the advantages such as easy and cheap fabrication, light weight, low profile and can easily integrated with microwave circuit. This project involves the investigation of various EBG structure and the integration of the EBG structure with various antenna design through the simulation and fabrication process. The simulation is done by using microwave office software (MWO) and CST. The fabrication process involves the photo etching technique while the substrate used for antenna fabrication is FR4 board which has relative permittivity 4.7 and tangent loss 0.019. From the simulation done, most of the antenna which has been incorporated with EBG structure show the enhancement of the performance in term of radiation pattern, gain and return loss, S11. The 1 dB gain increment is noticed for microstrip array antenna with incorporated with EBG structure. The radiation pattern also improves where the side and back lobes are decreasing by using EBG structure surrounding the patch antenna. Other than that, the EBG structure also can be used as a band reject especially for ultra wide band application which operates at very wide frequency ranges. The simulation and measurement result for ultra wide band with and without band rejection has been shown in this thesis

Active beamforming network design

This paper describe the design and implementation of multi beam antenna array using active beam forming network for wireless local area networks (WLAN) operating at 2.4 GHz band frequency. In this paper, four beam patterns generated by incorporated a rectangular patch antenna array with active beam forming network using switch line phase shifter. The radiation patterns measurement of multibeam antenna using active beam forming is compared with passive beam forming network using butler matrix. It shows that the multibeam antenna can be produced using this active beam forming network by switching the RF diode towards the required phase shift of the circuit. The comparison between active and passive beamforming have been made and discuss

Single-band Zigzag Dipole Artificial Magnetic Conductor

A new Artificial Magnetic Conductor (AMC) structure called zigzag dipole is discussed. Based on the 0.92GHz straight dipole AMC, the zigzag dipole AMC operating at 0.92GHz, 2.45GHz and 5.8GHz are carried out using TLC-32 and RF-35 boards. This AMC structure is designed based on the characterization of a unit cell using a transient solver of Computer Simulation Technology (CST) software. The simulated results such as the reflection phase, reflection magnitude, surface impedance, bandgap and electric field for each single-band AMC are presented in this paper. From the results gained it shows that, the bandwidth of the AMC will increase when the frequency is increased. It is also proved that these AMC are not providing the bandgap at their resonance. The zigzag dipole AMC is carried out to minimize the AMC size and to be suitable for UHF RFID applications

Wideband Sierpinski carpet monopole antenna

This paper described the design and fabrication of the fractal Sierpenksi carpet monopole antenna. The properties of antennas such as bandwidth and radiation pattern have been investigated. Wide bandwidth with input return loss of -10 dB has been achieved from 1 GHz to 10 GHz using this fractal antenna. The radiation patterns have been investigated at 2.73 GHz and 4.29 GHz. The cross polar isolation is in the range of -20 dB for both frequencies. The radiation pattern is in the direction of the main lobe

Performance Evaluation of Two Port and Four Port Measurement for Twisted Pair Cable

A balance-unbalance (balun) transformer is commonly used to connect the balance 100 Ohm twisted pair cable to the unbalance 50 Ohm network analyzer ports, but due to the limitations of the core (i.e. ferrite) inside the balun, the balun can only effectively operates at a certain band of frequencies. This limitation can be eliminated by using a 4-port vector network analyzer (VNA) which is done by connecting the VNA’s ports to each conductor end. The extracted S-parameters will then be transformed to a 2-port S-parameters in differential mode at both ports. To validate the measurement technique, S-parameter measurement by using the 4-Port Network Analyzer without any balun will be compared to the measurement which used the 2-Port Network Analyzer with the balun transformers. Two twisted pair cable distances are selected as reference which are 500, and 1000 meters with nominal copper diameter of 0.5mm. Based on the measurement results, the 4-ports measurement shows good correlation with the 2-ports measurement especially at 500m distance. This shows that the 4-ports measurement setup is suitable to be used to measure twisted pair copper cable and possible to measure at a higher frequency band such as up to 500 MHz but at a shorter twisted pair cable distance

The good, the bad, and the ugly: divorced mothers’ experiences with coparenting

This study produces a grounded theory of how 20 predominantly White, well-educated women experienced sharing physical custody of their children with their former partners after divorce or separation. Three patterns of coparenting were identified in the data: continuously contentious, always amicable, and bad to better. Five negative factors and three positive factors that influenced mothers’ coparenting relationships were identified. The type of relationship women had with their ex-partners was related to how they shared custody of their children (e.g., how they exchanged their children). The findings of this study suggest that shared physical custody relationships are dynamic and can vary greatly

A comparison of various double loops frequency selective surfaces in terms of angular stability

This paper presents the comparison of Frequency Selective Surfaces (FSS) structure performance based on three different double loops: square, circular and hexagonal structures. The simulation process of the double loops FFS structures are carried out by using the Computer Simulation Technology (CST) Microwave Studio software. The dielectric substrate used in the simulation is the FR-4 lossy substrate

Design of Triple-band Dipole-type Antenna with Dual-band Artificial Magnetic Conductor Structure

A design of dual-band high-impedance surface called Artificial Magnetic Conductor (AMC) is presented. The AMC is designed to resonate at 0.92GHz and 2.45GHz. In this paper also, the design parameters that influence the AMC frequencies are discussed. The designed AMC then is incorporated with the designed triple-band printed dipole antenna (operating at 0.92GHz, 2.45GHz and 5.8GHz). Here, the performance of the dipole antenna with 2 and 4 unit cells of 0.92GHz and 2.45GHz AMC ground plane are presented. The reported results show that, by applying the AMC structure as a ground plane for the printed dipole antenna, the gain of the dipole antenna can be increased due to the attracting feature of the AMC surface that provide in-phase reflected waves with the incident waves

Keberkesanan penggunaan edubase dalam kalangan pelajar teknikal yang berbeza gaya kognitif, afektif dan psikomotor di Politeknik Malaysia

Bahan bantu pengajaran yang digunakan secara bersesuaian dengan pelajar menyumbang kepada perkembangan pembelajaran mereka. Dalam dunia pendidikan teknikal, aspek kognitif dan psikomotor turut memberi kesan kepada kualiti pembelajaran pelajar. Kajian ini membincangkan tentang kesan penggunaan EDUBASE terhadap pencapaian dan minat pelajar yang mempunyai gaya kognitif, afektif dan psikomotor yang berbeza dalam topik Electromagnetism. Seramai 70 orang pelajar politeknik yang terdiri daripada 33 pelajar kumpulan rawatan dan 37 pelajar kumpulan kawalan telah terlibat dalam kajian yang menggunakan kaedah kuasi-ekperimen ini. Ujian kognitif, psikomotor, ujian pra-pasca dan kaji selidik telah diagihkan untuk memantau kesan penggunaan EDUBASE terhadap pelajar. Dapatan kajian ini telah dianalisis dengan menggunakan statistik MANCOVA, korelasi Pearson dan skor min. Hasil dapatan dalam kajian ini menunjukkan bahawa terdapat perbezaan yang tidak signifikan secara statistik bagi skor pelajar kumpulan kawalan dan kumpulan rawatan. Namun, skor min menunjukkan kumpulan rawatan memberikan skor yang lebih cemerlang dan minat mereka juga turut meningkat dalam topik pembelajaran tersebut berbanding pelajar yang mengaplikasikan pembelajaran secara konvensional. Selain itu, hasil dapatan kajian juga menunjukkan terdapat hubungan yang signifikan terhadap minat dan pencapaian. Di samping itu, EDUBASE yang diaplikasikan telah memenuhi keperluan dan minat pelajar. Secara ringkasnya, hasil kajian ini menunjukkan bahawa penggunaan EDUBASE sebagai alat bahan bantu mengajar dilihat berkesan dalam memberikan kecemerlangan pencapaian dan meningkatkan minat pelajar politeknik terhadap topik Electromagnetism

UHF RFID antenna tag design and analysis for antenna miniaturization

This paper proposes four designs of UHF RFID antenna tag with two different radiating element, copper and aluminum, for antenna miniaturization. The main contribution of this work is the unique design that involves a meander line traced in a variety shape of a bowtie antenna. The UHF RFID band is achieved by reshaping a 900 MHz straight line dipole antenna into the form of a bowtie, thus reducing the size of the antenna significantly while maintaining the operating frequency. The effectiveness of the method is tested in multiple steps. First, the antenna tag designs are run through CST software simulations and optimized to achieve desired outcome. Next, the designs are transferred to Silhouette Studio software to be fabricated using a cutting machine, and finally measured using a vector network analyzer. The comparison between the measurement result of the reflection coefficient and the radiation pattern to their respective simulation results shows that they have a good agreement between each other. With further research and improvements, the size of the antenna tag could be further reduced while maintaining or even improving the performance of the antenna tag