When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.

The invention of closed circuit television (CCTV) has initiated a new trend in high security by video surveillance. More recently, CCTV cameras have been incorporating wireless LAN technology for data transfer purposes by using on chip memory storage until the time of update. In this thesis, short range communication such as Bluetooth low energy (Bluetooth smart) is used in order to perform simple I/O applications. The two important components of the project are the camera and the Bluetooth module box. An external antenna is designed for the connectivity box and the operating range of the box is deduced by using link budget. The blue cool connectivity box is assessed by defining the capabilities of the box, i.e., simple I/O operations. Field test measurements for the designed antenna provide optimum communication range. The thesis also reviews software simulation tools that are essential for antenna design and path loss modelling. The efficiency of simulated measurements versus real-time measurements are also assessed. The primary target of the thesis is to detail the design of a cost-effective antenna based on link budget calculations and perform basic I/O tasks wirelessly between the blue cool connectivity box and the camera. It is concluded that in future works, advanced operations can be added on to the existing model. It is also suggested that a model for multi floor communication can be designed.

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' 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.

Inkjet printing is an attractive patterning technology that has received tremendous interest as a mass fabrication method for a variety of electronic devices due to its manufacturing exibility and low-cost feature. However, the printing facilities that are being used, especially the inkjet printer, are very expensive. This thesis introduces an extremely cost-friendly inkjet printing method using a printer that costs less than $100. In order to verify its reliability, linearly and circularly polarized (CPd) planar and conformal microstrip antennas were fabricated using this printing method, and their measurement results were compared with copper microstrip antennas. The result shows that the printed microstrip antennas have similar performances to those of the copper antennas except for lower efficiency. The effects of the conductivity and thickness of the ink layer on the antenna properties were studied, and it is found that the conductivity is the main factor affecting the radiation efficiency, though thicker ink yields more effective antennas. This thesis also presents the detailed antenna design for a sub-payload. The sub-payload is a cylindrical structure with a diameter of six inches and a height of four inches. It has four booms coming out from the surface, which are used to measure the variations of the energy flow into the upper atmosphere in and around the aurora. The sub-payload has two types of antennas: linearly polarized (LPd) S-band antennas and right-hand circularly polarized (RHCPd) GPS antennas. Each type of antenna has various requirements to be fully functional for specific research tasks. The thesis includes the design methods of each type of antenna, challenges that were confronted, and the possible solutions that were proposed. As a practical application, the inkjet printing method was conveniently applied in validating some of the antenna designs.

A novel microstrip patch antenna topology is presented for achieving a dual-band response with arbitrarily closely spaced resonances. This topology is based on a coupled transmission line structure in order to take advantage of the separation in propagation constants for parallel (even-mode) and anti-parallel (odd-mode) current modes. Applying a metamaterials inspired design approach, periodic reactive load­ings are used to design the underlying transmission line to have specific propagation constants necessary to realize a desired separation between two resonant frequencies. Using a single probe feed for a finite coupled line segment, both even-and odd-mode resonances can be excited to radiate efficiently at their respective design frequencies. The efficiency of the odd-mode radiation is enhanced by separating the two lines, while strong coupling is maintained by inserting a series of narrowly-separated thin loops between them. Several example resonant antenna designs, in the 2.45 GHz band, are presented. The directivities of these microstrip patch antennas are enhanced by optimizing the physical length of the resonant structure. For a resonant antenna obtained by cas­cading several unit cells of reactively loaded microstrip segments, dispersion analysis is employed for the unit-cell design. Maximum directivity is achieved by choosing the overall physical length to be slightly less than a half wavelength in free space at the design frequency. This gain optimization is applied to three coupled-line antennas, as well as a single resonance patch. Excellent agreement is observed between simulated and measured responses across all designs. The potential of loading the coupled line structure with active components is also explored. Varactor diodes are placed on coupled-line structures in two configurations. In one configuration, both resonant frequencies are affected. In the other configura­tion, only the odd-mode characteristics are reconfigured. In this way, the resonant frequency of either one or both modes can be adjusted by applying a DC bias voltage to the varactor diode loading elements. Two antennas, one employing each of these topologies, were designed and fabricated. Control of the resonant frequency over the predicted range through applying a bias voltage is observed with the fabricated prototypes.

Yes / Microstrip patch antennas with harmonic suppression are designed and optimised, using a genetic algorithm and applying a novel adaptive meshing program to generate a wire-grid simulation. A coaxially-fed air-dielectric patch antenna design with a folded patch was investigated. It was confirmed that antennas with excellent performances could be designed by this method. / MSCRC

The Range Limited Antenna (RLA) is a device, which accurately estimates the range of incoming signals and rejects those that arrive from outside a certain, pre-determined range. This task is accomplished by using two multi-element arrays and applying direction finding (DF) algorithms on each of them. Rectangular, single-layer, coax-fed patch antennas are used as array elements for the specific purpose of tracking cell phones operating in the PCS band inside a given building. It is vital to ensure that the patch antenna is designed in such a manner that it resonates at the desired frequency. This thesis introduces the Agilent High Frequency Structure Simulator (HFSS) as an effective tool for modeling electromagnetic structures. It presents a comprehensive and meticulous description of the process of modeling a rectangular coax-fed patch antenna in HFSS. Plots of S-parameter values are calculated and are compared with WIPL-D, which is another simulation software program, and with measurements performed at the George Washington University. Various important parameters of the HFSS simulation are varied and their effects are investigated to provide a deeper understanding of the program. / Master of Science

Heterogeneous mixtures have the potential to be used as synthetic substrates for antenna applications giving the antenna designer new degrees of freedom to control the permittivity and/or permeability in three dimensions such as by a smooth variation of the density of the inclusions, the height of the substrate and the manufacture the whole antenna system in one process. Electromagnetic, fabrication, environmental, time and cost advantages are potential especially when combined with nano-fabrication techniques. Readily available and cheap materials such as Polyethylene and Copper can be used in creating these heterogeneous materials. These advantages have been further explained in this thesis. In this thesis, the research presented is on canonical, numerical and measurement analysis on heterogeneous mixtures that can be used as substrates for microwave applications. It is hypothesised that heterogeneous mixtures can be used to design bespoke artificial dielectric substrates for say, patch antennas. The canonical equations from published literature describing the effective permittivity, ε_eff and effective permeability, μ_eff of heterogeneous mixtures have been extensively examined and compared with each other. Several simulations of homogenous and heterogeneous media have been carried out and an extraction/inversion algorithm applied to find their ε_eff and μ_eff. Parametric studies have been presented to show how the different variables of the equations and the simulations affect the accuracy of the results. The extracted results from the inversion process showed very good agreement with the known values of the homogenous media. Numerically and canonically computed values of ε_eff and μ_eff of various heterogeneous media were shown to have good agreement. The fabrication techniques used in creating the samples used in this research were examined, along with the different measurement methods used in characterising their electromagnetic properties via simulations and measurements. The challenges faced with these measurement methods were explained including the possible sources of error. Patch antennas were used to investigate how the performance of an antenna may be affected by heterogeneous media with metallic inclusions. The performance of the patch antenna was not inhibited by the presence of the metallic inclusions in close proximity. The patch measurement was also used as a measurement technique in determining the ε_eff of the samples.

In this dissertation, many novel low-cost planar antenna designs are presented for on-vehicle applications. Promising planar antennas showing the desired broadside and omnidirectional radiation patterns and having low-profile configurations are demonstrated. Also, studies on controlling the radiation patterns are conducted. Details of the measured and simulated results of the studied antennas are presented and discussed.

This thesis presents design, fabrication and testing of a number of multi-frequency band microstrip-fed re-configurable microstrip patch antennas. All re-configurable antennas are designed to change from one resonance frequency to another by an electronic control of RF MEMS switches, one at a time. Besides a fixed size slot on the patch, switches are placed in insets for satisfying better input match at each resonance frequency individually. Also some switches are placed into the slot for adding another resonance frequency to change the effective slot-length like effective inset length changing.To actuate the RF MEMS switches in the configured way, DC-stubs are also designed to apply required potential difference between switch ports and the carrier. These stubs exhibit RF-open at switch side to prevent any RF leakage, and DCground on the other side. That RF short-to-open conversion is accomplished together with feed structure / with a taper depending on the feed network selected. All devices introduced here are built by Microwave Research Group in Electrical and Electronics Department, Middle East Technical University. Depending on the sensitivity of structure, some devices are built by RF MEMS group in Microelectronic Production Plant for MEMS (METU &amp / #8211 / MET) during the thesis study. Therefore this study is the continuation of the first national work on fabrication of RF MEMS devices.