Supporting circular polarisation in single-layer, single-feed, compact patch antennas is a challenging task, especially when improved bandwidths are required. The difficulty lies in simultaneously obtaining good axial ratio (AR) and impedance matching performance over the required bandwidth. Several broadband,thick-substrate circularly polarised (CP) patch designs have appeared in the literature, but their complex fabrication might not be suitable for harsh environments requiring mechanical simplicity or for high-frequency applications at X-band or higher. In this study, the authors propose a novel solution to this problem: the CP half E-shaped patch antenna. This antenna is able to utilise thick substrates to meet the bandwidth requirements of many potential applications. Furthermore, the design can be fabricated on a single-layer and uses reasonably sized gaps and line widths, making for a fabrication-friendly design. Their design example shows 5.3% AR and impedance matching bandwidth at a thickness near a tenth of a wavelength. The S11 < − 10 dB bandwidth is 35%. Their particular design example has dimensions that fit within 45% × 39% of a free-space wavelength. Furthermore, they provide an important comparison discussing the differences in operation between the linearly polarised half E-shaped patch, CP E-shaped patch, and CP half E-shaped patch.

This paper proposes a new circuit model for E-shaped patch antennas (ESPA) using the multiconductor transmission line mode theory (the modal theory). First, radiation and transmission line modes generated on the ESPA are described, and an equivalent circuit is derived from the modal theory. The equivalent circuit is analyzed in detail to obtain wideband and multiband characteristics. For wideband ESPAs, the theoretical maximum bandwidth is derived under VSWR criterion. Dual-band ESPA is also discussed theoretically. Finally, impedance characteristics obtained by the circuit model are compared with full-wave electromagnetic simulations and measurements.

A novel broadband RHCP/LHCP reconfigurable patch antenna array using an E-shaped patch antenna element is investigated. By applying particle swarm optimization (PSO), a challenging, combined S 11 -AR bandwidth of 17% was achieved and verified through measurement for the isolated element using MEMS switches at an overall substrate thickness of 0.092λ 0 . The achieved bandwidth is significantly higher than the current state-of-the-art in single-layer, single-feed circularly polarized (CP) patch element designs with similar substrate thickness. A small percentage of the upper frequency band experiences a pronounced beam squint similar to other thick substrate CP patch antennas. To overcome the beam squint, a novel rotated-element configuration is implemented to force pattern symmetry. Derivations of pattern symmetry and network effects are also shown. The final design prototype using rotated elements provides a measured 20% S 11 -AR bandwidth with good radiation pattern stability.

Reconfigurable antennas offer attractive potential solutions to solve the challenging antenna problems related to cognitive radio systems using the ability to switch patterns, frequency, and polarization. In this paper, a novel frequency reconfigurable E-shaped patch design is proposed for possible applications in cognitive radio systems. This paper provides a methodology to design reconfigurable antennas with radio frequency microelectromechanical system (RF-MEMS) switches using particle swarm optimization, a nature-inspired optimization technique. By adding RF-MEMS switches to dynamically change the slot dimensions, one can achieve wide bandwidth which is nearly double the original E-shaped patch bandwidth. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2 GHz to 3.2 GHz (50% impedance bandwidth at 2.4 GHz ) is obtained. RF-MEMS switch circuit models are incorporated into the optimization as they more effectively represent the actual switch effects. A prototype of the final optimized design is developed and measurements demonstrate good agreement with simulations.

This paper presents a detailed numerical electromagnetic characterization of GaAs photovoltaic (PV) nanopillar array solar cells recently developed for solar energy harvesting. Through electromagnetic theory, full-wave simulations, and an optical measurement, a deeper understanding of the electromagnetic operation of these nanostructure arrays is achieved by revealing the mechanisms that allow for its inherent improvement of optical absorption over conventional PV solar cells. Initial investigations include incorporating and verifying material optical properties through measurements of bulk GaAs samples, simulating the effects of nanopillar geometry and configuration, and an analysis of the optical absorption mechanism of the nanopillar arrays through the graphical visualization of the electric fields in the vicinity of the nanopillars. These investigations will offer critical insights into the effects of pillar dimensions and configuration that can significantly increase optical solar energy absorption approximately 1.5 times that of conventional solar cells spanning the entire visible spectrum and for angles of incidence up to 60 $^{\circ}$ . Furthermore, comparisons between nanopillar arrays with and without substrates will demonstrate the mechanism that drives the efficient optical absorption. In addition, the importance of the nanopillar structure (i.e., dimensions) and reflecting substrate in providing energy coupling and improving the air-to-array interface will be discussed.

Wireless identification and sensing systems are emerging in everyday use and the demand for ubiquitous automatic cognition and wireless sensing is growing rapidly [1,2].For example, passive sensors are critical and highly desirable in remote sensing platforms, where long term environment controlling and monitoring take place.Important features for

This paper experimentally demonstrates the use of a microstrip reflectarray as a low-profile planar substitute to a conic section subreflector (hyperboloidal type) in a symmetric dual reflector system at Ku-band. At first, a brief discussion on the simulation and measurement techniques utilized in the paper is provided. A nominal dual reflector Cassegrain system is synthesized through simulations where a feed horn is used to illuminate the hyperboloidal subreflector. Next, a flat metallic subreflector is placed at the subreflector location. This is a critical task as it shows the importance of phase compensation. Due to the flat subreflector, the feed is defocused from the image of the focus and creates phase aberration, leading to beam bifurcation, pattern degradation, and performance deterioration of the dual reflector system. A planar microstrip patch-type subreflectarray is then designed to mimic a hyperboloidal subreflector. Ray tracing is applied to the subreflector-feed system to calculate the phase needed to compensate for the axial defocusing of the feed. A prototype subreflectarray based on the ray-optics approach is fabricated. Radiation pattern measurements and back-projection holographic diagnostics demonstrate that the subreflectarray acts as a hyperboloidal subreflector and restores the antenna performance with a well-defined main beam and low side lobes.

This article presents a unique point of view for microstrip reflectarrays. Through the effective utilization of graphical visualization of the scattered fields from the reflectarrays, one can gain insightful understanding into the fundamental workings of these antennas. The most important part of the reflectarray analysis and design is the accurate characterization of the individual reflectarray element for reflection phase performance. Using this visualization approach, reflectarray elements are characterized in unit-cell environments. This exercise aids in identifying the important geometrical parameters of the element that contribute to the reflection phase shift. These elements are then placed in an actual reflectarray environment, and the performance of the reflectarray is evaluated through full-wave electromagnetic simulations and measurements. It is validated that this technique can be successfully used to analyze, design, and potentially diagnose reflectarray antennas.

Understanding the enhancement of optical absorption in nanostructure photovoltaic (PV) solar cells, specifically GaAs core-shell nanopillar arrays, is accomplished through the full-wave electromagnetic characterization of the optical electric fields. Inherent advantageous electromagnetic properties of reduced reflection, increased absorption, and angle of incidence independence can be understood through the absorption mechanism that is a function of the interaction of the incident electric field with the nanopillar structure, materials, and configuration. The role of nanopillar structure versus the role of the nanopillar materials in optical absorption will be revealed by comparing nanopillars using purely perfectly electric conducting (PEC) materials with that of nanopillars using semiconductor material. Also, further development of nanopillar design will be suggested from an absorption aspect.

This paper presents the application of sub-reflectarray for main reflector antenna distortion compensation through simulations and measurements. A distorted dual reflector Cassegrain system is used for this study. A sub-reflectarray is used as the subreflector to form the compact Cassegrain system. A metallic ring-type distortion is created on the main reflector surface that severely distorts the radiation performance of the dual reflector system. A hybrid HFSS/PO simulation approach was used for the design and analysis. The distortions are corrected using sub-reflectarray approach by employing conjugate field matching method. A sub-reflectarray was designed and built. Bipolar planar near-field measurements are performed to measure the radiation patterns of the whole system. The sub-reflectarray compensation technique shows improved system performance in terms of higher directivity and lower side lobes.

This paper summarizes the primary features inherent in current optimization methods typically applied to antenna designs and demonstrates their effectiveness by applying particle swarm optimization (PSO), a nature-inspired global optimization technique, to novel antenna design solutions in wireless communications. The concept of the PSO technique is briefly introduced and an outline of the important parameters that are utilized is summarized. Next, an implementation strategy combining PSO with numerical algorithms for electromagnetic solutions, namely the finite element method (FEM) and the method of moments (MoM), is discussed. In both realizations (PSO-FEM and PSO-MoM), the PSO technique drives the design variables, such as the antenna dimensions, geometrical features, etc., and the full-wave electromagnetic analysis engines evaluate the fitness function for the optimizer. Optimized antenna designs including a multiband handset antenna and an E-shaped patch antenna for circularly polarized (CP) applications are presented. Measurement results of prototype optimized designs are shown to demonstrate the functionality and effectiveness of the methodologies presented in this paper.

This paper presents the design of a frequency reconfigurable wideband E-shaped patch antenna using particle swarm optimization. Ideal switches are used to demonstrate proof of concept of frequency reconfigurability. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2GHz to 3.25GHz (53% total bandwidth) is obtained. A prototype of the design is developed and measurements are performed.

Achieving circular polarization (CP) diversity for single port patch antennas presents a difficult challenge for broadband communication systems. In light of this, we propose a novel optimized broadband polarization (RHCP/LHCP) reconfigurable antenna using the E-shaped patch topology. We have used a nature inspired optimization technique, Particle Swarm Optimization, to realize a novel broadband switchable design which provides 14% impedance/axial ratio bandwidth. As a concept verification, we demonstrate our design using ideal switch models through simulation and measurement of the radiation pattern, axial ratio, and impedance matching. Our design demonstrates excellent performance, and good agreement between simulation and measurement was observed. Overall, broadband CP diversity has been realized with our single feed E-shaped patch design, and active RF switches can effectively be implemented into this design.

This paper presents the design of a smart diagnostic capsule system with novel antenna and nano-biosensors. The design of the novel miniaturized antenna addresses some of the challenges in the current capsule diagnostic systems namely potential capsule miniaturization, wireless link robustness for efficient medical data transfer. The implementation of nano-biosensors can help in sensing of clinically relevant molecular-level biomarkers in vivo which a big improvement over current capsule systems. Initial antenna and nano-biosensor designs will be discussed followed by a brief technology outlook.

This paper presents surface distortion detection and identification using bipolar measurements and microwave holography on a compact sub-reflectarray Cassegrain system. A ring-type distortion is added to the Cassegrain system which affects the performance of the overall system. Using microwave holographic diagnostics and measurements, the ring distortion is identified and its effect on the overall system is analyzed.

In the recent past, nanostructured photovoltaics research has gathered significant momentum due to the promise of high efficiency solar cell designs. In lieu of this nascent technology, this paper investigates the electromagnetic performance of Gallium Arsenide (GaAs) superquadric nanostructures for future solar cell designs. The superquadric function allows for the investigation of different shapes ranging from hexagonal nanopyramid to a hexagonal nanopillar array. The presence of nanostructures reduces the optical reflection and increases absorption as compared to conventional flat cell geometries. Different superquadric nanostructures are compared for their reflection performance properties. The elliptical superquadric nanostructures are used as a baseline for different parametric studies and some observations are made.