Circular polarised antenna fabricated with low-cost 3D and inkjet printing equipment

The fabrication of a patch antenna using low-cost 3D printing equipment is presented. A circular polarised (CP) patch antenna is manufactured by combining inkjet printing and stereolithography (SLA) technology. The substrate has been fabricated by curing photosensitive resin while the patch element of the antenna has been inkjet printed using silver ink. The printed antenna satisfies the required reflection coefficient, axial ratio and radiation pattern at 1575 MHz. The aim is to demonstrate an inexpensive technology that could be used for the fabrication of antennas on customised 3D printed substrates. The performance of the antenna is summarised through simulations and experimental results

Design and Optimization of Electromagnetic Band Gap Structures

Dizertační práce pojednává o návrhu a optimalizaci periodických struktur s elektromagnetickým zádržným pásmem (EBG – electromagnetic band gap) pro potlačení povrchových vln šířících se na elektricky tlustých dielektrických substrátech. Nepředvídatelné chování elektromagnetických vlastností těchto struktur v závislosti na parametrech elementární buňky činí jejích syntézi značně komplikovanou. Bez patřičného postupu je návrh EBG struktur metodou pokusu a omylu. V první části práce jsou shrnuty základní poznatky o šíření elektromagnetických vln v tzv. metamateriálech. Následně je diskutován správný způsob výpočtu disperzního diagramu ve vybraných komerčních programech. Jádrem dizertace je automatizovaný návrh a optimalizace EBG struktur využitím různých globálních optimalizačních algoritmů. Praktický význam vypracované metodiky je předveden na návrhových příkladech periodických struktur s redukovanými rozměry, dvoupásmovými EBG vlastnostmi, simultánním EBG a AMC (artificial magnetic conductor – umělý magnetický vodič) chováním a tzv. superstrátu. Poslední kapitola je věnována experimentálnímu ověření počítačových modelů.The thesis deals with the design and optimization of periodic structures for surface waves suppression on electrically dense dielectric substrates. The design of such structures is rather complicated due to the large factor of uncertainty how the electromagnetic band gap (EBG) properties change depending on the unit cell geometry. Without a proper approach, the design of EBGs is based on trial-and-error. In this thesis, the basic theory of electromagnetic wave propagation in metamaterials is presented first. Second, the correct dispersion diagram computation in the selected full-wave software tools is discussed. The main attention is turned then to the automated design and optimization of EBG structures using different global evolutionary algorithms. The practical exploitation of the developed technique is demonstrated on design examples of reduced-size and dual-band EBGs, periodic structures with simultaneous electromagnetic band gap and artificial magnetic conductor (AMC) properties and periodic structures acting as superstrates. The last chapter of the thesis is devoted to the experimental verification of computer models.

A Frequency and Polarization Reconfigurable Circularly Polarized Antenna Using Active EBG Structure for Satellite Navigation

This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90º from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3dB axial ratio (AR)bandwidth reaches 40% (1.03-1.54GHz), with good input matching(S11) and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP)

C Band Microstrip Patch Antenna with EBG & Superstrate Structure

EBG structure and a dielectric layer over a microstrip patch antenna have remarkable effect on its input characteristics and bandwidth. In proposed paper we studied both electromagnetic band-gap structure and a superstrate to increase the bandwidth of patch antenna. We measured bandwidth with and without EBG to design an Antenna for resonance frequency 4 GHz. And then implemented superstrate in EBG structure. This antenna designed on Ansoft HFSS designer software, impedance bandwidth ,VSWR ,return losses & smith charts are observed and experimentally studied. Details of simulated results are presented and discussed

Electromagnetic bandgap antennas and components for microwave and (Sub)millimeter wave applications

This paper reviews the primary application areas of electromagnetic bandgap (EBG) technology at microwave and (sub)millimeter wave frequencies. Examples of EBG configurations in the microwave region include array antennas, high precision GPS, mobile telephony, wearable antennas and diplexing antennas. In the submillimeter wave region a 500 GHz dipole configuration and a novel heterodyne mixer is shown for the first time. Some emphasis is also placed on EBG waveguides and filters. As most fundamental components will be available in EBG technology, a fully integrated receiver could be developed in order to take full advantage of this technology. True integration of passive and active components can now begin to materialise using EBG technology

Design of dualband antenna for RFID applications

This paper focuses on the design and fabrication of dual band antenna for UHF RFID and ISM RFID applications. The U-shaped patch loaded with dipole is introduced and investigated. The antenna can be performed dual-band frequencies at 0.915 GHz and 2.4 GHz required in RFID applications with reflection coefficient is less than -10 dB. The lower band can be varied by adjusting both dipole arms length and upper band is tuned by U-shaped patches. The gains of the design with a size 130   45  1.6 mm3  are performed 1.89 dB and 3.65 dB for single and dual band respectively. This compact and low cost dual band antenna also performed total efficiency greater than 80%. The design methodology and antenna measurement results are both presented and discussed in this letter

Artificial Magnetic Conductor Integrated Textile Monopole Antenna

Wearable antenna is a fast growing field in application-oriented research, which introduced a new generation of garments capable of monitoring wear health, as well as environmental states. This thesis is concerned with the design and fabrication of a compact textile wearable antenna at operating frequency within the Industrial, Scientific and Medical (ISM) band, intended for integration into a flight jacket of the astronaut inside the habitat. The antenna is integrated with artificial material known as High Impedance Surface (HIS) for performance enhancement. The purpose of the system is to constantly monitor vital signals of the astronauts. The entire design cycle of wearable Co-Planar Waveguide (CPW) fed monopole antenna, starting from simulation-based design to fabricated prototype and antenna testing under different conditions was carried out in this thesis. Because of the lossy nature of human body tissues, the radiation efficiency of the antenna will be reduced due to the absorption of the radiated energy. Hence, changes in the radiation characteristics of the wearable antenna like operating frequency, gain and impedance bandwidth will take place. To overcome these challenges, HIS has been suggested and integrated with the monopole antenna to isolate the antenna from the ambient environments. This wearable antenna was tested under real operating conditions such as bending and crumpling conditions. Moreover, as the antenna operates near human body tissues, Specific Absorption Rate (SAR) assessment is required to consider the safety concerns of the antenna system. SAR analysis based on simulation results has been carried out in this thesis to show a significant reduction in SAR with the usage of HIS in the antenna system

Improvement of a Circular Microstrip Antenna Excited by Four Feeds and Suspended with Artificial Magnetic Conductors

The proposed antenna is a circular microstrip structure excited by four feeds and suspended with artificial magnetic conductors (AMCs). The multifeed circular microstrip antennas can generate a high circularly polarized performance by using a different feed arrangement. AMC structures with a square, circular, or octagonal patch on a unit cell are designed and applied to circular microstrip patch antennas for the enhancement of antenna performance. It is found that simulated results of the proposed antenna are well suited. The properties of wide beamwidth with good axial ratio can be achieved when applying the proposed AMC structures to circular microstrip antennas. The antenna prototype was fabricated to validate simulated results