Optically Transparent Antennas and Filters

As society continues to increase its demand for wireless network access, more antennas, base stations, and network access points is a must. By integrating these antennas into existing infrastructure, such as buildings, cars, and street lights, network engineers can begin to meet these demands. In order to integrate antennas into windows, optical transparency is paramount. Optically transparent antennas are currently created through materials known as Transparent Conductive Oxides (TCOs). TCOs are doped metal oxides that have high optical transmittance and low electrical resistivity. TCOs are employed in flat panel displays, touch sensitive control panels, and electromagnetic shielding windows. The most popular material in use, is called Indium Tin Oxide (ITO). ITO however, is becoming expensive to extract, and from mass production, it is becoming scarce. Therefore, an alternative to ITO is needed. Gallium Zinc Oxide (GZO) is an optimal substitute for ITO because it is in the same element group and has comparable conductivity/resistivity values. We have successfully fabricated an optically transparent antenna resonating at 2.4 GHz (Wi-Fi) and two transparent frequency selective surfaces at 27.5 GHz (proposed 5G). Optically transparent antennas allows a promising future in wireless technology such as smart windows, eyeglass telemetry, and even transparent RFID tags.https://scholarscompass.vcu.edu/capstone/1182/thumbnail.jp

Transparent Antennas for Solar Cell Integration

Transparent patch antennas are microstrip patch antennas that have a certain level of optical transparency. Highly transparent patch antennas are potentially suitable for integration with solar panels of small satellites, which are becoming increasingly important in space exploration. Traditional patch antennas employed on small satellites compete with solar cells for surface area. However, a transparent patch antenna can be placed directly on top of solar cells and resolve the issue of competing for limited surface real estate. For such an integration, a high optical transparency of the patch antenna is required from the solar cells\u27 point of view. On the other hand, the antenna should possess at least acceptable radiation properties at the same time. This dissertation focuses on some of the most important concerns from the perspective of small satellite applications. For example, an optimization method to simultaneously improve both optical transparency and radiation efficiency of the antenna is studied. Active integrated antenna design method is extended to meshed patch applications in an attempt to improve the overall power efficiency of the front end communication subsystem. As is well known, circular polarization is immune from Faraday rotation effect in the ionosphere and thus can avoid a 3-dB loss in geo-satellite communication. Therefore, this research also aims to present design methods for circularly polarized meshed patch antennas. Moreover, a meshed patch antenna capable of supporting a high communication data rate is investigated. Lastly, other types of transparent patch antennas are also analyzed and compared to meshed patches. In summary, many properties of transparent patch antennas are examined in order to meet different design requirements

Exploitation of Transparent Conductive Oxides in the Implementation of a Window-Integrated Wireless Sensor Node

Exploitation of transparent conductive oxides (TCO) to implement an energy-autonomous sensor node for a wireless sensor network (WSN) is studied and a practical solution presented. In the practical implementations, flexible and rigid substrates that is polyimide and glass, are coated with TCO, namely aluminum doped zinc oxide (AZO). AZO-coated flexible substrates are used to form thermoelectric generators (TEG) that produce electricity for the sensor electronics of the node from thermal gradients on a window. As the second solution to utilize AZO, its conductive properties are exploited to implement transparent antennas for the sensor node. Antennas for a UHF RFID transponder and the Bluetooth radio of the node are implemented. A prototype of a flexible transparent TEG, with the area of 67 cm2 when folded, was measured to produce power of 1.6 uW with a temperature difference of 43 K. A radiation efficiency of -9.1 dB was measured for the transparent RFID antenna prototype with the center frequency of 900 MHz. Radiation efficiencies between -3.8 dB and -0.4 dB, depending on the substrate, were obtained for the 2.45 GHz Bluetooth antenna.Comment: 10 pages, 14 figures, last author version accepted for publication in IEEE Sensors Journa

Development of Robust Transparent Conformal Antennas Based on Conductive Mesh-Polymer Composite for Unobtrusive Wearable Applications

© 1963-2012 IEEE. In this paper, a detailed investigation of the realization of conformal wearable transparent antennas by integrating conductive mesh with polymer has been presented. The proposed realization method is much simpler and more cost-effective than the existing realization methods of transparent antennas, and the prototype fabricated from the selected composite materials is more flexible and robust in bending operations than other transparent antennas. In this paper, the mechanical, electrical, and optical characteristics of the proposed composite material have been investigated to analyze its suitability for transparent flexible antenna realization. For concept demonstration, a prototype of a dual-band antenna operating at 2.33-2.53 GHz and 4.7-5.6 GHz has been fabricated and tested. These frequencies cover both the instrument, scientific, and measurement (ISM) and the wireless local area network (WLAN) bands. Full ground plane is utilized in the antenna design for on-body operations. The suitability of the antenna for wearable applications has been investigated by measuring its performance under physical deformation and testing its performance on phantom. Next, the RF performance of the antenna has been improved by using two layers of conductor to form the radiating element. Although transparency is slightly compromised, the double-layer element improves the gain and efficiency of the antenna

Optically Transparent Antennas and Filters for Smart City Communication

Incremental usage of mobile devices demand a new generation of wireless networks (5G) to provide faster data rates, more reliable coverage, monitor city infrastructure usage, and increase network capacity. The frequencies proposed for the upcoming 5G network would result in shorter broadcast distances and network dead zones, countered by incorporating transparent antennas into glass high rises. Transparent antennas possess, however a major challenge: low gain. This lower gain can be countered by means of employing antennas in an antenna array, boosting the gain and even giving the array the ability to beam form for the upcoming 5G network. The 5G dead zones can be countered with strategically placed transparent reflectors embedded into the glass surfaces of city high-rises. This dissertation shows there are significant effects due to the transparent antennas’ carrier concentration and film thickness. Changes in film conductivity and thicknesses results in shifts for filter and antenna resonances. A 4x1 GZO antenna array was constructed to operate at 5.8 GHz, and the results show approximately 10dBi of lower aperture gain between a copper version of the array and the GZO version of the array. However, the 4x1 GZO array shows an approximate 12dBi increase in gain over a single GZO antenna element. The technology developed in this dissertation has a broader impact other than for smart cities and the upcoming 5G network. Transparent antenna arrays offer sight insensitive military communication systems and eye-worn medical and commercial devices to monitor eye health and other various health signs

Miniature transparent UWB antenna with tunable notch for green wireless applications

Copyright @ 2011 IEEEA miniature transparent UWB antenna with tunable notch that can be incorporated with a solar panel for harnessing solar energy has been proposed and presented. The antenna demonstrates a good omni-directional radiation pattern throughout the FCC bandwidth of 3.1 – 10.6 GHz and a comparable gain making it a good candidate for future green wireless applications

A non-thermal soldering technique to improve polymer based antenna performance

Copyright @ 2010 EuMCA non-thermal soldering technique using cold solder or electrically conductive epoxy for connecting SMA connectors to polymer based antennas is proposed in this paper. The proposed technique prevents damage to the polymer due to the solder iron heat and also the loss of efficiency through the use of indirect connections of the coaxial feed via copper pads glued to the antenna. The direct connection of the feed points via SMA connectors on to a transparent antenna designed on AgHT-8 material has been demonstrated. The method can also be applied to solder the coaxial feed points directly to the antenna instead of using copper pads which will introduce additional reflection losses. The technique involves the use of colder soldering instead of hot soldering so as to not damage the polymer based antenna as well as improve the efficiency of the antenna

A novel technique to improve gain in transparent UWB antennas

A novel technique to improve the performance of AgHT-8 transparent polymer antennas is proposed in this paper. A spit-ring resonator is introduced on the radiating patch to enhance gain. The resonator basically concentrates the radiating energy to the central area of the patch thus improving gain. The designed antenna demonstrates good gain while maintaining the original transparency of the material. Such an antenna inscribed on the commercially available AgHT-8 sun shielding film material makes it a viable option for wireless applications like in-house base stations and applications requiring fast data rate transfers which can be mounted on windows and glass panels. © 2011 IEEE.Solutia Inc., St. Louis, Missouri, US

Analysis of Optically Transparent Antennas Designed from Different Transparent Conductors

This master’s thesis work presents an investigative study about the performance of transparent antennas. The antennas have been fabricated using two advanced transparent conductive films (TCF) namely Nano-C Hybrid and Silver-Nanowire (AgNW). Nano-C Hybrid is a new transparent conductive film which combines thin conductors like Carbon Nanotube and Silver Nanowire. The antennas made from Nano-C Hybrid and AgNW are of monopole types and are mounted on a ground plane made out of a printed circuit board and the antennas are excited using an SMA connector through that printed circuit board. Simulation works have been performed to find out the optimum length-to-width ratio for the monopoles so that they can be used to design an antenna that radiates at the desired frequency. It has been found that the length needs to be 1.25 times higher than the width of the monopole in order to reduce the loss resistance of the designed antenna. The antennas can operate in a wide range of frequencies, but performance varies marginally based on the material that has been used to fabricate them. The tested transparent antennas have shown promising results which prove that these transparent films can be considered as viable antenna design materials for various applications such as wireless communication technology. Simulation and experimental measurements indicate the gain of the transparent antennas is enhanced by widening and stacking the TCFs. There is a trade-off between the efficiency of the antenna and the transparency as stacking the TCFs reduces the transparency. Among the two transparent conductive materials tested during this research, the comparatively new material, Nano-C Hybrid, proves to be a potential competitor against commercially used Indium Tin Oxide (ITO) and AgNW in terms of transparency, conductivity, power handling capability, and usability

ALUMINUM ZINC OXIDE (AZO) OPTIMIZATION PROCESS FOR USE IN OPTICALLY TRANSPARENT ANTENNAS

The importance of having an optimal material for fabricating Optically Transparent Antennas (OTAs) is crucial for designing highly efficient antennas that can be integrated with photovoltaics. Transparent Conductor Oxides (TCOs) are promising for OTA fabrication due to their capability of being simultaneously transparent at optical frequencies and conductive within the radio frequency (RF) range. In this work, a new material was developed and optimized to be used for fabricating an optically transparent antenna on a solar cell. Aluminum and Zinc Oxide were co-sputtered onto Si and onto a polycrystalline photovoltaic cell and then annealed between 350°C and 450°C for 24 and 48 h in N2 ambient. The annealing process ensured the formation of the Aluminum Zinc Oxide (AZO) with a DC conductivity of 3.48×〖10〗^5 S⁄cm and a transparency of 86% for a thickness between 350 and 750 nm. This new AZO material was shown to be capable of yielding high levels of conductivity at RF frequencies and excellent transmittance at optical frequencies. The material was tested and validated by performing RF characterization, and by fabricating and testing different optically transparent antennas. The details of the fabrication process, its optimization process, the design of the optical antennas are presented in details and discussed. The material was tested and validated by performing RF characterization, and by fabricating and testing different OTA designs