Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Antenna Design Concepts Based on Transformation Electromagnetics Approach

Using the idea of wave manipulation via coordinate transformation, we demonstrate the design of novel antenna concepts. The manipulation is enabled by composite metamaterials that realize the space coordinate transformation. We present the design, realization and characterization of three types of antennas: a directive, a steered beam and a quasi-isotropic one. Numerical simulations together with experimental measurements are performed in order to validate the concept. Near-field cartography and far-field pattern measurements performed on a fabricated prototype agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation can be transformed at ease into a desired one by modifying the electromagnetic properties of the space around it. This idea can find various applications in novel antenna design techniques for aeronautical, telecommunication and transport domains

Compact-Size Low-Profile Wideband Circularly Polarized Omnidirectional Patch Antenna With Reconfigurable Polarizations

A compact-size low-profile wideband circularly polarized (CP) omnidirectional antenna with reconfigurable polarizations is presented in this communication. This design is based on a low-profile omnidirectional CP antenna which consists of a vertically polarized microstrip patch antenna working in TM01/TM02 modes and sequentially bended slots etched on the ground plane for radiating horizontally polarized electric field. The combined radiation from both the microstrip patch and the slots leads to a CP omnidirectional radiation pattern. The polarization reconfigurability is realized by introducing PIN diodes on the slots. By electronically controlling the states of the PIN diodes, the effective orientation of the slots on ground plane can be changed dynamically and the polarization of antenna can be altered between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The proposed antenna exhibits a wide-operational bandwidth of 19.8% (2.09-2.55 GHz) with both axial ratio below 3 dB and return loss above 10 dB when radiates either LHCP or RHCP waves. Experimental results show good agreement with the simulation results. The present design has a compact size, a thickness of only 0.024? and exhibits stable CP omnidirectional conical-beam radiation patterns within the entire operating frequency band with good circular polarization

A Compact Tri-band Printed Antenna for MIMO Applications

In this paper, a compact tri-band printed multi-input multi-output (MIMO) antenna with high isolation is presented to operate within WLAN and WiMAX frequency bands. By adopting a rectangular open-ended slot combined with a rectangular strip with an inverted L-shaped open-ended slot, three operating frequency bands can be obtained. The proposed compact MIMO antenna occupies an overall size of 19×33 mm2. Good port-to-port isolation is obtained. The simulated and measured results show that the presented antenna is suitable for multiband MIMO applications

Dual-band Omnidirectional Circularly Polarized Antenna

A dual-band omnidirectional circularly polarized antenna is proposed. The antenna comprises back-to-back microstrip patches fed by a coplanar waveguide. A very low frequency ratio of 1.182 has been achieved, which can be easily tuned by adjusting four lumped capacitors incorporated into the antenna. An analysis of the omnidirectional circular polarization mechanism as well the dual band operation is provided and confirmed by numerical and experimental data. Key parameters to tune the resonant frequencies and the axial ratio have been identified. The prototype antenna provides omnidirectional circular polarization in one plane with cross polar isolation better than 12 dB for both frequency bands

Series-Fed Omnidirectional mm-Wave Dipole Array

THE rapid expansion in the millimeter-wave (mm-wave) frequency domain has completely changed the course of wireless communication. One of the most important steps to make smart cities, the Internet-of-Things (IoT), smart homes, and vehicular communication a reality is to use mm-wave frequencies for wireless applications. The rise in the number of wireless appliances has also led to a rise in data traffic [1]. The adoption of mm-wave frequencies enabled several gigahertz of bandwidth, allowing data rate and latency limits to be exceeded. The availability of a broad electromagnetic spectrum and frequency reusability are the most important characteristics of mm-wave deployment [2]. Although mm-wave systems have a shorter effective communication distance than microwave systems due to increased propagation loss, they are sufficient to cover small cells that span hundreds of meters [3]. So, the use of mm-wave systems in providing high-speed wireless connectivity in indoor venues, such as shopping centers, stadiums, and auditoriums, is very effective. To satisfy the network coverage in such scenarios, omnidirectional antennas for mm-wave frequencies are key. High gain antennas are also required to mitigate losses due to obstacles, including walls, buildings, and trees, which makes the mm-wave bands more beneficial as larger antenna arrays can be realized in small form factor

Genetic Algorithm Optimization of a High-Directivity Microstrip Patch Antenna Having a Rectangular Profile

A single high-directivity microstrip patch antenna (MPA) having a rectangular profile, which can substitute a linear array is proposed. It is designed by using genetic algorithms with the advantage of not requiring a feeding network. The patch fits inside an area of 2.54λ x 0.25λ, resulting in a broadside pattern with a directivity of 12 dBi and a fractional impedance bandwidth of 4%. The antenna is fabricated and the measurements are in good agreement with the simulated results. The genetic MPA provides a similar directivity as linear arrays using a corporate or series feeding, with the advantage that the genetic MPA results in more bandwidth