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

Circularly Polarized Stack-Patch Microstrip Array Antenna for ETS-VIII Applications

By using the H-IIA Launch Vehicle No. 11 from the Tanegashima Space Center, in the south of Kagoshima Prefecture Japan, ETS-VIII (Engineering Test Satellite VIII) has been launched successfully in the end of 2006. The ETS-VIII is one of the largest geostationary Sband satellites in the world to meet future requirements of voice and data communications, broadcasting and global positioning [1]. Backward-looking, there are various types of antennas which developed aiming at ETS-VIII [2]-[5]. A part of the antennas [3] have been experimented outdoor by use of a pseudo-satellite station. Moreover, in order to obtain a good performance antenna to clarify suitably result on frequency characteristic, return loss, and radiation pattern, and also to obtain a simple configuration such as small, light and low profile, a left-handed circularly polarized stack-patch microstrip array antenna is proposed. The antenna was calculated by the Method of Moments using probe-fed pentagonal array antenna as radiating patch and triangular array antenna as parasitic patch with dielectric relative permittivity 2.17 and loss tangent 0.0009. In this paper, it discuss about the performances of antenna above at El=48° both of calculation and measurement results, the examined of performance beam antenna at low elevation, and the performances of antennas to take in signal from ETS-VIII satellites. The measured results at El=48° agree well with the calculated results of 5 dBic gain, and the 3-dB axial ratio beamwidth of the whole azimuth range about more of 120° for each beam coverage in the conical-cut direction satisfy for ETS-VIII applications

Ultra-wideband antennas

The focus of UWB antenna research activity has matured in recent years and currently mainly concentrates on applications such as biomedicine and security. Early UWB antenna designs were driven by the FCC allocation of spectrum in 2002 and focussed on obtaining wide impedance bandwidths with reasonable group delay characteristics. Many of these were simple planar monopoles antennas with canonical geometries. The emergence of new applications channelled the emphasis towards miniaturisation and integration into devices. This required optimisation of the antenna geometries to ensure that good system performance is achieved from the integrated antenna. Many optimisation techniques are available including the spline technique to generate the outline of the antenna element and ground plane. Simple methods based on genetic algorithms are employed and evolutionary algorithms which are capable of optimising for multiple goals are beneficial when multiple antenna parameters are simultaneously investigated. These techniques have proven advantageous especially when time-domain performance is critical and provide solutions for both single-ended and differential feed arrangements. The main applications using UWB channels in the 3.1 GHz −10.6 GHz spectrum are localization and tracking applications, mainly employing impulse radio UWB imaging, and generally using linear polarization. However circularly-polarized UWB antennas have been developed, both directional and omnidirectional and are being investigated across various systems

Advanced Circularly Polarised Microstrip Patch Antennas

The thesis describes outcomes of research on advanced circularly polarised antennas. The proposed designs are intended for integration into small mobile devices, therefore low profile and easy manufacturability are key parameters, along with good CP radiation properties. The designs were validated by simulation and measurement, and are also backed by theory and design guidelines. The primary focus is on the development of planar omnidirectional circularly polarised antennas, which are fabricated using multilayer PCB techniques and thus are lightweight and cost-efficient. Unlike in classical microstrip patch antenna designs, the groundplane of the proposed antenna was substantially reduced. This helps to achieve an omnidirectional circular polarisation pattern and miniaturize the antenna, however at the cost of increased feed circuit complexity. The basic design, its advantages and disadvantages are discussed in Section 3. In the next step, the omnidirectional circularly polarised antenna was extended with additional, advanced features. A miniaturized version is investigated, which offers a 20% footprint reduction by folding parts of the patch underneath itself. Further miniaturization is possible by increasing the dielectric constant of the substrate. A method to adjust the omnidirectional circularly polarised antenna performance by trimming four lumped capacitors is also investigated. Manufacturing inaccuracy in large scale production may cause some of the units to radiate outside of the desired frequencies. By integrating four trimmed capacitors into the antenna it can be precisely tuned to the desired band. Simulated results demonstrate this property by trimming the antenna between GPS L1 band (centre frequency at 1.575 GHz) and Galileo/Beidou-2 E2 band (1.561 GHz). Furthermore, a dual-band omnidirectional circularly polarised antenna is presented, which employs slots and capacitor loading to steer the current path of the first and second resonant mode. The design offers a small frequency ratio of 1.182. The methods to obtain a planar omnidirectional circularly polarised antenna have been further advanced to propose a reconfigurable antenna. The beam reconfiguration is capable of rotating it dipole-like radiation pattern around an axis, thus allowing reception or transmission from any spherical angle. The switching method is simple and does not require any semiconductor devices. Finally, a dual circularly polarised antenna is presented, which achieves dual-polarisation by employing even and odd modes in a coplanar waveguide. This technique allows greater flexibility and size reduction of the feed network, as two signals can be transmitted by a single multi-mode transmission line. Simulated results demonstrate this property by trimming the antenna between GPS L1 band (centre frequency at 1.575 GHz) and Galileo/Beidou-2 E2 band (1.561 GHz). Furthermore, a dual-band omnidirectional circularly polarised antenna is presented, which employs slots and capacitor loading to steer the current path of the first and second resonant mode. The design offers a small frequency ratio of 1.182. The methods to obtain a planar omnidirectional circularly polarised antenna have been further advanced to propose a reconfigurable antenna. The beam reconfiguration is capable of rotating it dipole-like radiation pattern around an axis, thus allowing reception or transmission from any spherical angle. The switching method is simple and does not require any semiconductor devices. Finally, a dual circularly polarised antenna is presented, which achieves dual-polarisation by employing even and odd modes in a coplanar waveguide. This technique allows greater flexibility and size reduction of the feed network, as two signals can be transmitted by a single multi-mode transmission line

Omnidirectional GPS antenna for Vorsat

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201

Design and development of triangular, spiral, and fractal antennas for radio frequency identification tags

This dissertation reports on the design and development of three compact, non-meandered microstrip patch antennas for ultra high frequency (UHF) radio frequency identification (RFID) applications. The monopole antennas considered in this work are an inset-fed triangular antenna, one arm Archimedes spiral antenna and a Half-Sierpinski fractal antenna. These antennas with small length to width ratios (\u3c 2/1), can be the preferred choice, in the tagging of small size consumer end products, over the ubiquitous meandered dipole antenna (length/width \u3e 5/1), which is often the antenna of choice, due to its high gain for UHF RFID applications. The lengths and widths of all three antennas are less than 5.5 cm. Earlier reports of planar antennas for RFID applications in the UHF range have lengths larger than 9 cm on one side or are developed on a rigid substrate. All three antennas have a surface area of about 30 cm2 and are designed for a flexible polyimide substrate. The new antennas satisfy the requirement of a voltage standing wave ratio (VSWR) \u3c 2 and exhibit a gain close to or greater than 0 dBi at the operation frequency of 915 MHz. All three antennas have a return-loss less than -10 dB at 915 MHz and a -10 dB bandwidth greater than 12 MHz. While the triangular and spiral antennas display peak gains of over 2 dBi, the fractal antenna has a gain close to 0 dBi (-0.64 dBi). The effect of ground geometry on the radiation performance of the antennas has been analyzed using ANSOFT Designer software. Slots, aligned to the top patch were introduced in the antenna ground plane to increase the gain of the antennas. The fabricated and tested antennas were then employed in the transmission-delay-line-based passive radio-frequency identification tag. The location of the antenna with respect to the transmission line on the tag was found to affect the radiation pattern of the antenna. A circular disc monopole antenna having a gain of 8.88 dBi and having a -10 dB bandwidth greater than 300 MHz was employed to transmit and receive the interrogating and back-scattered signals, respectively. The generation of bits, employing On-Off Keying (OOK) modulation technique was successfully demonstrated. The tag, fabricated with the triangular antenna is found to perform the best

Spectral Signature Modification By Application Of Infrared Frequency-selective Surfaces

It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the millimeter-wave spectral regime, but is a challenging technology to scale for IR application. Incorporation of thin films and FSS antenna elements on a surface permits the signature of a surface to be changed in a deterministic manner. In the seminal application of this work, both technologies are integrated to comprise a circuit-analog absorbing IR FSS. The design and modeling of surface treatments are accomplished using commercially-available electromagnetic simulation software. Fabrication of microstructured antenna arrays is accomplished via microlithographic technology, particularly using an industrial direct-write electron-beam lithography system. Comprehensive measurement methods are utilized to study the patterned surfaces, including infrared spectral radiometry and Fourier-transform infrared spectrometry. These systems allow for direct and complementary spectral signature measurements--the radiometer measures the absorption or emission of the surface, and the spectrometer measures its transmission and reflection. For the circuit-analog absorbing square-loop IR FSS, the spectral modulation in emission is measured to be greater than 85% at resonance. Other desirable modifications of surface signature are also explored; these include the ability to filter radiation based on its polarization orientation and the ability to dynamically tune the surface signature. An array of spiral FSS elements allows for circular polarization conditioning. Three techniques for tuning the IR FSS signature via voltage application are explored, including the incorporation of a pn junction substrate, a piezoelectric substrate and a liquid crystal superstrate. These studies will ignite future explorations of IR FSS technology, enabling various unique applications

State-of-the-Art Antenna Technology for Cloud Radio Access Networks (C-RANs)

The cloud radio access network (C-RAN) is one of the most efficient, low-cost, and energy-efficient radio access techniques proposed as a potential candidate for the implementation of next-generation (NGN) mobile base stations (BSs). A high-performance C-RAN requires an exceptional broadband radio frequency (RF) front end that cannot be guaranteed without remarkable antenna elements. In response, we present state-of-the-art antenna elements that are potential candidates for the implementation of the C-RAN’s RF front end. We present an overview of C-RAN technology and different types of planar antennas operating at the future proposed fifth-generation (5G) bands that may include the following: (i) ultra-wide band (UWB) (3–12 GHz), (ii) 28/38 GHz, and (iii) 60-GHz radio. Further, we propose different planar antennas suitable for the implementation of C-RAN systems. We design, simulate, and optimize the proposed antennas according to the desired specifications covering the required frequency bands. The key design parameters are calculated, analyzed, and discussed. In our research work, the proposed antennas are lightweight, low-cost, and easy to integrate with other microwave and millimeter-wave (MMW) circuits. We also consider different implementation strategies that can be helpful in the execution of large-scale multiple-input multiple-output (MIMO) networks