Experimental analysis of power control and element spacing for unobtrusive MIMO antenna systems

With ever-increasing demand for wireless communications, spectral efficiency and power management are of great importance. Mobile nodes in an ad hoc network are limited by the available power, interference, and shared communication resources. Research shows that multiple-input multiple-output (MIMO) communication systems can increase capacity and mitigate interference by exploiting the multi-path nature of wireless energy. This increase in capacity is realized with an array of antennas that can transmit multiple uncorrelated streams. In order to achieve theoretical gains in capacity, several practical problems must be considered. This dissertation presents solutions to create higher quality communication systems in MIMO ad hoc networks through power management, antenna array spacing, and unobtrusive conductive polymer antennas.To show how co-channel interference can be managed in ad hoc networks, the experimental performance of several power control methods are demonstrated. These experiments were made with a multiple antenna software defined radio (SDR) testbed and verified with electro-magnetic ray tracing. In addition, the spacing between antenna array elements directly impacts the wireless channel. An analysis of the wireless channel is presented to show the impact of the antenna spacing and cochannel interference on the network capacity. A method for selecting the best antenna spacing is also described based upon the channel analysis. Finally, due to the size of mobile devices, it is difficult to incorporate MIMO systems into small form factors. A transparent, conformal antenna array was fabricated to demonstrate that antennas can be developed to fit into small form factors and perform at a high level.Ph.D., Electrical Engineering -- Drexel University, 200

Circularly polarized multiple input multiple output transparent antenna

Circular polarization technology can improve mobile connectivity and mitigate signal losses caused by absorption, reflection and refraction by utilizing all planes in transmitting waves. In this thesis, Circularly Polarized (CP) transparent antenna designs are investigated for broadband applications. Two designs are introduced namely Single Input Single Output (SISO) and Multiple Input Multiple Output (MIMO) transparent antennas. A silver coated polyester film which is a Transparent Conductive Oxide (TCO) in the shape of film is incorporated in both designs. The film is cut according to design and attached to a glass substrate. SISO antenna is fed by Coplanar Waveguide (CPW) with a circular ring patch radiating element. The existence of tapered split gap and the inequality in CPW ground arm’s length has contributed to a 3 dB axial ratio bandwidth from 5.4 to 6.2 GHz. Results show that the proposed antenna has a gain of 0.92 dB and an efficiency of 14% at 5.8 GHz. It is shown that the electron mobility, a parameter that is determined by the material development is a primary limiting factor seen from the 14% efficiency of transparent antenna. The proposed antenna obtained a reflection coefficient response from 2.55 to 6 GHz which covers the desired frequency band. MIMO is designed by combining two aforesaid SISO CP antenna designs, mirrored 180° at y-axis and separated by 1 mm. Measurement results show |S11| and |S22| bandwidth from 2.65 to 6.23 GHz with good isolation of 27 dB at the 5.8 GHz band. Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG) and Diversity Gain (DG) with measurement values of 0.0007, 0 dB and 10 dB accordingly were discussed in the thesis. These values were calculated using scattering parameters data obtained from the measurement. Both designs are meeting the objectives of this project

Efficiency of a compact elliptical planar ultra-wideband antenna based on conductive polymers

Extent: 11p.A planar antenna for ultra-wideband (UWB) applications covering the 3.1–10.6 GHz range has been designed as a test bed for efficiency measurements of antennas manufactured using polymer conductors. Two types of conductive polymers, PEDOT and PPy (polypyrrole), with very different thicknesses and conductivities have been selected as conductors for the radiating elements. A comparison between measured radiation patterns of the conductive polymers and a copper reference antenna allows to estimate the conductor losses of the two types of conductive polymers. For a 158 μm thick PPy polymer, an efficiency of almost 80% can be observed over the whole UWB spectrum. For a 7 μm thick PEDOT layer, an average efficiency of 26.6% demonstrates, considering the room for improvement, the potential of this type of versatile materials as flexible printable alternative to conductive metallic paints. The paper demonstrates that, even though the PEDOT conductivity is an order of magnitude larger than that of PPy, the thicker PPy layer leads to much higher efficiency over the whole UWB frequency range. This result highlights that high efficiency can be achieved not only through high conductivity, but also through a sufficiently thick layer of conductive polymers.Thomas Kaufmann, Akhilesh Verma, Van-Tan Truong, Bo Weng, Roderick Shepherd, and Christophe Fumeau

Diode-switched thermal-transfer printed antenna on flexible substrate

We demonstrate that diode-switching can be used to introduce frequency agility into antennas produced by thermal transfer printing. Our particular example is a triangular Sierpinski fractal pattern with two PIN diodes to switch between operation optimised for the 800 MHz UHF band (diodes on) and the 2400 MHz ISM band (diodes off). Our measured results show an improvement in S11 in the UHF band from -2 dB to -28 dB, and from -7 dB to -30 dB at 2400 MHz, when switching the diodes appropriately. The measured bandwidth is 200 (1000) MHz, and the measured directivity is 3.1dB (5.2dB) while the measured gain is -5.2dB (6.7dB) for the diodes on(off)

A Coplanar Edge-Fed Optically-Transparent Microstrip Patch Antenna Operating in the 5-6 GHz Frequency Spectrum

As wireless communications infiltrates our daily lives, there is a growing need for unobtrusive antennas. Utilizing optically transparent and electrically conductive material for antenna fabrication satisfies this demand. Optically transparent antennas have infiltrated applications in wireless communications where it is desired to reduce an antenna\u27s visual or spatial impact. Their use in automotive applications preserves car aesthetics, while their integration onto solar cells of small satellites reduces size and thus weight. This work presents the development of a coplanar edge-fed optically transparent microstrip patch antenna, composed of highly conductive thin mesh wires designed to operate in the 5 to 6 GHz band, to be used in a phased array for beamforming and beamsteering applications. A simulation-based analysis of two edge-fed feeding mechanisms showed an inset feed outperforms a quarter-wavelength impedance transformer under optically transparent mesh material design limitations. From the results of the simulation, an optically transparent microstrip patch antenna was fabricated, and its performance was shown to be comparable to an antenna composed of solid copper

Smart nanotextiles for communication

Together with wireless technology, advances in nanotechnology and rapid and scalable synthesis of nanomaterials including the 2D graphene has transformed the realms of biomedical sciences. Recent research in the areas of drug delivery, cancer therapy, bio-sensing and bio-imaging have exploited the unique structural and physiological features of graphene and its different forms. Along with the Graphene, several other nanomaterials including carbon nanotubes (CNTs), make excellent candidates for applications associated with loading of drugs, cellular imaging, sensing other molecules and in-vivo cancer studies due to their biocompatibility and stability. Assimilating from the fundamentals of electromagnetic, wireless communication, medical and material science, a novel concept of nanonetworks was first introduced in 2008, which stems from the concept that a collection of nanodevices have the potential to harness the innate communication capabilities of the human body, thereby allowing them to cooperate and share information. It is anticipated that the advanced healthcare diagnosis can be realised if an efficient communication mechanism and data transfer are established between these nanodevices. The human body is a good example of a naturally existing communication network. For instance, the nervous system is composed of nerve cells, i.e. neurons that communicate the external stimulus to the brain and enable the communication between different systems by conveying information with a molecular impulse signal known as a spike. The human body needs communication amongst different cells to survive, the proposed intra- and inter-body nanonetworks ensure their stability without mechanically (or physically) disturbing the harmony of the in-built molecular structure of the body. Moreover, in several cases, the medicine technology fails to understand the root cause of the problem but once we have a monitoring network established in our body, we can extract various unknowns and treat them effectively. The vision of nanoscale networking attempts to achieve the functionality and performance of the internet with the exception that node size is measured in nanometres and channels are physically separated by up to hundreds or thousands of nanometres. In addition, nodes are assumed to be mobile and rapidly deployable. Nodes (or nanodevices) are expected to be either self-powered or spread in and around the specific location. In a visionary sense, an ultimate application of nanoscale networking would be an automated process, where the nano-nodes are in motion communicating in a complex dynamic environment of living organisms monitoring diseased or sensitive parts of the body