Cylindrical Electromagnetic Bandgap Research Articles

Beam Switching Dual Polarized Antenna Array With Reconfigurable Radial Waveguide Power Dividers

In this paper, we propose a new method for designing dual polarized beam switching antennas by using reconfigurable radial waveguides excited by central probes and feeding multiple radiating elements. The power distribution of the radiating elements is controlled by cylindrical electromagnetic bandgap structures made of metallic wires loaded with PIN diodes. The proposed technique allows azimuth beam switching and multiple beams, with arbitrary and well controlled polarizations, using low dc voltage. First, a new rectangular periodic structure is used as a model for analyzing the transmission and reflection coefficients for different diode states. Then, numerical and experimental results are presented for a reconfigurable radial waveguide power divider and for the radiating elements. Finally, numerical and experimental results are presented and discussed for a complete dual polarized antenna operating at wireless local area network (WLAN) 5 GHz band (5.18–5.825 GHz).

Design of Rectangular Microstrip Patch Antenna by Improving the Performance Parameters with EBG Structures

In this paper, the execution of rectangular patch antenna is mended applying a newly cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed in the driven terminal. This EBG structure, when constituted with microstrip patch antenna to radiation pattern and return loss got from menstruation appearance a better impedance matching and a gain enhancement of the directed antenna. The gain utilizing the designed structure has been found to be 5.5123dB, which are merits for transmitting data over a retentive distance. Wideband antenna detects its applications in mobile sensors, data ingathering and tracking diligence.

Analysis of a Rectangular Microstrip Patch Antenna with EBG Structures

In this paper, the execution of rectangular patch antenna is mended applying a newly cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed by the driven terminal. This EBG structure, when comprised with microstrip patch antenna to radiation pattern and return loss got from menstruation appearance a better impedance matching and a gain enhancement of the aimed antenna. The gain using the designed structure has been found to be 7.73dB, which are merits for transmitting data over a long distance. Wideband antenna finds its applications in mobile sensors, data ingathering and tracking applications.

Resonances and Field Enhancement in Cylindrical Electromagnetic Bandgap Structures

Resonances and Field Enhancement in Cylindrical Electromagnetic Bandgap Structures

Directivity of radiation of a dipole source coupled to cylindrical electromagnetic bandgap structures

Cylindrical electromagnetic bandgap structures excited by a dipole source are analyzed by a rigorous semi-analytical method using the T-matrix approach and reflection and transmission matrices of cylindrical harmonic wave expansions as the basis. Resonance and stopband characteristics in the transmission spectra of the cylindrical bandgap structures for the excited cylindrical harmonic waves are studied. The relationship between the transmission spectra of the cylindrical harmonic waves and the radiation patterns of the dipole source in both H-plane and E-plane is numerically investigated for three different configurations of cylindrical bandgap structures and different locations of the dipole source with respect to the cylindrical bandgap structures.

Analysis of Radiation from Line Source Located in Cylindrical Electromagnetic Bandgap Structures with Defects

A semi-analytical approach for analyzing the electromagnetic radiation of a line source in cylindrical electromagnetic bandgap (EBG) structure is presented. The cylindrical structure is composed of circular rods periodically distributed along concentrically layered circular rings. The method uses the T-matrix of a circular rod in isolation, the reflection and transmission matrices of a cylindrical array expressed in terms of the cylindrical waves as the basis, and the generalized reflection and transmission matrices for a layered cylindrical structure. Using the proposed method, the radiated field from a line source placed inside a three-layered cylindrical EBG structure with defects is investigated. The defects are created by removing the particular circular rods from each circular ring. The structure is prominent from the viewpoint of flexible design of the directive antennas. Numerical examples demonstrate that the cylindrical EBG structures are very effective at forming and controlling the directed beam in the radiated fields.

Narrow-beam azimuthally omni-directional millimetre-wave antenna using freeformed cylindrical woodpile cavity

A freeformed cylindrical electromagnetic bandgap (EBG) structure and its application for millimetre-wave antennas are presented. The cylindrical EBG structure is fabricated using the extrusion freeforming technique in which the design is downloaded directly to a building platform. The fabricated cylindrical woodpile exhibits bandgap characteristics around 95 GHz and is used for realising a resonant cavity antenna. The fabricated antenna achieves a narrow beam with 6.5 measured half-power beam-width in the elevation plane without using an array configuration. The overall antenna gain is approximately 5 dBi at 94.2 GHz, suitable for future short-range gigabit wireless communications.

Hybrid Dielectric Resonator Antenna With Circular Mushroom-Like Structure for Gain Improvement

In this paper, the performance of a cylindrical dielectric resonator antenna (DRA) is improved using a new cylindrical electromagnetic bandgap substrate. The DRA is fed by a coaxial probe and integrated within a cylindrical electromagnetic bandgap (EBG) substrate to increase the antenna gain. The cylindrical electromagnetic bandgap structure is composed of two distinctive periodic structures. The first structure is made of metallic rings, while the second is formed of grounding vias, which are placed radially and circularly. To describe and optimize this EBG stucture, a parametric study using a finite integration method was carried out. Furthermore, an antenna prototype was fabricated and measured to validate the proposed concept. The radiation patterns and return loss obtained from measurements demonstrate a good performance in terms of impedance matching and gain enhancement.

Cylindrical EBG antenna for short range gigabit wireless communications at millimetre-wave bands

An omnidirectional millimetre-wave antenna based on a cylindrical electromagnetic bandgap (EBG) resonator is presented. The cylindrical woodpile is fabricated using the ceramic extrusion freeforming technique with high purity alumina powder. The designed antenna can achieve a narrow beam with 6.5° measured half power beam-width in the elevation plane without using an array configuration. The overall antenna gain is approximately 5 dBi at 94.2 GHz, suitable for future short range gigabit wireless communications.

Multibeam Antenna for Telecommunications Networks Using Cylindrical EBG Structure

We present in this letter the study of a multibeam antenna for telecommunication networks by using cylindrical electromagnetic band-gap (EBG) structures. The EBG structure behaves as a partially reflecting surface (PRS) and enhances the directivity of a simple radiating source. We begin by presenting the principle of the multibeam antenna, and then we present a first version, conceived to operate in WiMAX band [5.45.7] GHz. Simulation results of this antenna will show us that the strong mutual coupling between the different excitation sources of the EBG structure badly influences its performance. In order to reduce the mutual coupling, metallic walls are inserted between the excitation sources. Moreover, excitation sources have been changed to improve the radiation performance of the antenna. A prototype of the final antenna is fabricated to validate our simulation results, and the measurements results are compared to the simulated ones.

Reconfigurable Beamwidth Antenna Based on Active Partially Reflective Surfaces

This letter presents a new method to design a new reconfigurable antenna by using an active cylindrical electromagnetic band-gap (EBG) structure for wireless communication systems. The antenna provides a reconfigurable elevation beamwidth while the azimuth radiation pattern maintained omnidirectional. The EBG structure that is composed of periodic discontinuous metallic strips and PIN diodes behaves as an active partially reflecting surface (PRS). By changing the diode states, the reflection coefficient of the structure is controlled so that the radiation beamwidth and directivity of the antenna can be reconfigured. To validate the proposed concept, the final prototype is fabricated, and measurement results are also presented and discussed.

Gain Enhancement of a Microstrip Patch Antenna Using a Cylindrical Electromagnetic Crystal Substrate

The performance of a circular microstrip patch antenna is improved using a new cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed by a coaxial probe and is integrated within a cylindrical electromagnetic bandgap substrate, based on the mushroom-like substrate, to increase the antenna gain. The cylindrical electromagnetic bandgap structure is a combination of two periodic structures with different periods. One is made of metallic rings and the other of grounding vias, which are disposed such as to form a radially and circularly periodic structure. A parametric analysis using a full-wave method was carried out in order to design the EBG structure. With the proposed concept, an antenna prototype was fabricated and tested. The radiation patterns and return loss obtained from measurements show a good impedance matching and a gain enhancement of the proposed antenna.

Metallic Cylindrical EBG Structures With Defects: Directivity Analysis and Design Optimization

An analysis is presented of the directivity and the design optimization of cylindrical electromagnetic band gap (CEBG) structures constituted of metallic wires and with defects. The directivity is studied for different transversal periods, radial periods and numbers of rings. In the proposed configuration, the defects are designed by removing multiple wires, such as to form a horn-shaped aperture inside the periodic structure. From numerical results, obtained with a home-made finite difference time domain (FDTD) code, it is shown that the structures with defects present a directive beam in the stop-bands of the corresponding structures without defects. The radiation characteristics of the CEBG material are compared with those of an equivalent-plane sectoral horn to explain the directivity mechanism. An optimization method is also proposed for minimizing the number of wires. To validate the analysis, an optimized directive antenna with a dipole as an excitation source was fabricated and measured.

Omnidirectional Electromagnetic Band Gap Antenna for Base Station Applications

This letter presents the study of metallic omnidirectional electromagnetic band gap (EBG) antennas with an omnidirectional pattern in the azimuth plane for base station applications. The technique used to solve the matching problem, generally encountered with this type of antenna is also detailed. A cylindrical EBG antenna for HiperLAN2 applications [5.15-5.35] GHz has been designed and its performances are disclosed. Finally, a prototype has been realized and the experimental measurements are compared to the simulated ones.

Omnidirectional Cylindrical Electromagnetic Bandgap Antenna With Dual Polarization

This paper describes the method of design of an electromagnetic bandgap antenna. This antenna is able to radiate in vertical, horizontal, and dual polarization with an omnidirectional pattern in azimuth. Through the given abacuses, it is possible to conceive the structure to obtain specific performances in each polarization. To illustrate this purpose, a dual polarization antenna, operating in the lower HiperLAN frequency band, i.e., 5.15-5.35 GHz, is presented.

Dispersion Characteristics of a Cylindrical Electromagnetic Band Gap Structure

In this letter, a new analytical expression for the dispersion equation of radially periodic structures is derived. The periodic structure is considered as a set of parallel cylindrical frequency selective surfaces, and the dispersion equation is calculated by using a transmission line model. Using this result, the dispersion proprieties of cylindrical electromagnetic bandgap structures composed of continuous or discontinuous metallic wires are presented. It is shown that the band structures of these materials can be determined by using the proposed dispersion equation. Cylindrical periodic materials have potential applications for designing directive antennas, circular high impedance surfaces, or agile antennas

Technique for Reducing the Power Supply in Reconfigurable Cylindrical Electromagnetic Bandgap Structures

In this letter, a new design of cylindrical electromagnetic bandgap (CEBG) structures is proposed in order to reduce the power supply used to control active elements in EBG-based reconfigurable antennas. The proposed configuration uses structures of discontinuous wires with defects consisting of continuous wires. To examine its performances, numerical simulations were carried out using a finite-difference time-domain (FDTD) code, for the structure without active elements. The obtained results show that the new configuration allows to obtain a directive beam in the pass-band of the all continuous-wires structure. This work has potential application for designing an antenna with a directive pattern able to turn over 360deg range

Analysis and Design of a Cylindrical EBG-Based Directive Antenna

In this paper, a cylindrical electromagnetic bandgap (CEBG) structure composed of infinite metallic wires is analyzed, designed and used as a model to develop a new reconfigurable directive antenna. This structure is circularly and radially periodic, and it is excited at its center using an omnidirectional source. The analysis is based on calculating the transmission and reflection coefficients of a single cylindrical frequency selective surface (FSS) and then, considering only the fundamental mode interaction, deducing the frequency response of the CEBG structure composed of multiple cylindrical FSSs. For this structure, new analytical formulas are derived, and their accuracy is assessed compared to those obtained by the finite-difference time-domain method. As in rectangularly periodic structure case, the frequency response of the CEBG structure exhibits pass-bands and bandgaps, and it is possible to obtain directive beams by introducing defects in the periodic structure. Using this concept, a new antenna was developed to obtain a controllable directive beam. An antenna prototype, without control, was designed, fabricated, and tested. An excellent agreement was obtained between theory and experiment for both return loss and radiation patterns.

Cylindrical electromagnetic bandgap structures for directive base station antennas

This work presents a new method to realize directive base station antennas by incorporating cylindrical electromagnetic bandgap (EBG) structures. The EBG structure behaves as a partially reflecting surface (PRS) and significantly enhances the E-plane directivity of a simple radiating dipole positioned in front of a metallic cylinder. A novel cylindrical antenna that operates at 2.4 GHz is simulated and presented.