A Method to Include Antenna Pattern Characteristics in UWB System Design

In UWB system design and optimization, antennas are usually represented by a single transfer function relating the input voltage to the radiated electric field in the free space. However, the transfer function of planar ultra-wideband antennas depends on not only frequency but also direction. In this paper we present a strategy that helps the UWB system designer to select the best transfer function (and the best reference direction) for the antenna. In the process we demonstrate that good pattern stability of a UWB antenna within a particular band is advantageous to ease the complexities in the selection of the transfer function. We have thus emphasized the importance of having stable patterns for UWB antennas. Pulse optimization algorithms that meet FCC spectrum requirements are presented as examples

Design, Modeling, and Evaluation of the Eddy Current Sensor Deeply Implanted in the Human Body.

Joint replacement surgeries have enabled motion for millions of people suffering from arthritis or grave injuries. However, over 10% of these surgeries are revision surgeries. We have first analyzed the data from the worldwide orthopedic registers and concluded that the micromotion of orthopedic implants is the major reason for revisions. Then, we propose the use of inductive eddy current sensors for in vivo micromotion detection of the order of tens of μ m. To design and evaluate its characteristics, we have developed efficient strategies for the accurate numerical simulation of eddy current sensors implanted in the human body. We present the response of the eddy current sensor as a function of its frequency and position based on the robust curve fit analysis. Sensitivity and Sensitivity Range parameters are defined for the present context and are evaluated. The proposed sensors are fabricated and tested in the bovine leg

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

Shared-aperture dual-band dual-polarization array using sandwiched stacked patch

An L/C dual-band dual-polarized (DBDP) shared aperture microstrip array is proposed in the paper. In the array, the sandwiched stacked patch is employed for the L-band element to exploit the bandwidth for given element thickness. Several key issues regarding the proposed structure are discussed, including: 1) benefit of proposed L band sandwiched stacked patch; 2) C-band feeding method; 3) radiation performance in both bands. A prototype array of L/C DBDP sandwiched stacked patch is designed and fabricated to verify the feasibility of the proposed structure, where the measured data are presented in the paper. © 2010 EMW Publishing. All Rights Reserved

Additively Manufactured Perforated Superstrate to Improve Directive Radiation Characteristics of Electromagnetic Source

© 2013 IEEE. Additively manufactured perforated superstrate (AMPS) is presented to realize directive radio frequency (RF) front-end antennas. The superstrate comprises spatially distributed dielectric unit-cell elements with square perforations, which creates a pre-defined transmission phase delay pattern in the propagating electric field. The proposed square perforation has superior transmission phase characteristics compared to traditionally machined circular perforations and full-wave simulations based parametric analysis has been performed to highlight this supremacy. The AMPS is used with a classical electromagnetic-bandgap resonator antenna (ERA) to improve its directive radiation characteristics. A prototype is developed using the most common, low-cost and easily accessible Acrylonitrile Butadiene Styrene (ABS) filament. The prototype was rapidly fabricated in less than five hours and weighs 139.3 g., which corresponds to the material cost of only 2.1 USD. The AMPS has remarkably improved the radiation performance of ERA by increasing its far-field directivity from 12.67 dB to 21.12 dB and reducing side-lobe level from-7.3 dB to-17.2 dB

A Robust, Flexible and Frequency Reconfigurable Antenna with Flexible Superstrate and Substrate

This paper presents a frequency reconfigurable circular patch antenna having dielectric superstrate to tune the operating frequency and increase the realized gain of the antenna. The antenna is designed with highly flexible, robust and inexpensive materials. The antenna is basically a circular microstrip patch antenna having a flexible superstrate, the antenna is designed in such a way that the height from the patch surface to the superstrate can be varied, which subsequently changes the resonance frequency of the antenna. This mechanical reconfigurable technique appears to be a simple and effective method of frequency tuning operation of a flexible antenna. Moreover, the utilization of the superstrate improves the gain and efficiency of the antenna. Numerical investigations of the design are demonstrated in this paper

A stripline-based planar wideband feed for high-gain antennas with partially reflecting superstructure

© 2019 by the authors. This paper presents a new planar feeding structure for wideband resonant-cavity antennas (RCAs). The feeding structure consists of two stacked dielectric slabs with an air-gap in between. A U-shaped slot, etched in the top metal-cladding over the upper dielectric slab, is fed by a planar stripline printed on the back side of the dielectric slab. The lower dielectric slab backed by a ground plane, is used to reduce back radiation. To validate the wideband performance of the new structure, in an RCA configuration, it was integrated with a wideband all-dielectric single-layer partially reflecting superstructure (PRS) with a transverse permittivity gradient (TPG). The single-layer RCA fed by the U-slot feeding structure demonstrated a peak directivity of 18.5 dBi with a 3 dB directivity bandwidth of 32%. An RCA prototype was fabricated and experimental results are presented

All-metal wideband metasurface for near-field transformation of medium-to-high gain electromagnetic sources

Electromagnetic (EM) metasurfaces are essential in a wide range of EM engineering applications, from incorporated into antenna designs to separate devices like radome. Near-field manipulators are a class of metasurfaces engineered to tailor an EM source's radiation patterns by manipulating its near-field components. They can be made of all-dielectric, hybrid, or all-metal materials; however, simultaneously delivering a set of desired specifications by an all-metal structure is more challenging due to limitations of a substrate-less configuration. The existing near-field phase manipulators have at least one of the following limitations; expensive dielectric-based prototyping, subject to ray tracing approximation and conditions, narrowband performance, costly manufacturing, and polarization dependence. In contrast, we propose an all-metal wideband phase correcting structure (AWPCS) with none of these limitations and is designed based on the relative phase error extracted by post-processing the actual near-field distributions of any EM sources. Hence, it is applicable to any antennas, including those that cannot be accurately analyzed with ray-tracing, particularly for near-field analysis. To experimentally verify the wideband performance of the AWPCS, a shortened horn antenna with a large apex angle and a non-uniform near-field phase distribution is used as an EM source for the AWPCS. The measured results verify a significant improvement in the antenna's aperture phase distribution in a large frequency band of 25%

Cross-Entropy Method for Design and Optimization of Pixelated Metasurfaces

© 2013 IEEE. Electromagnetic metasurfaces are planar two-dimensional metamaterials, typically of subwavelength thickness. Unit cell elements of different shapes have been widely explored, including electric and magnetic dipoles, patches, arbitrary geometries and pixelated surfaces. Although pixelated metasurfaces have a great advantage of geometric versatility, their design and analysis requires algorithmic approach. One of the techniques for their design is via evolutionary simulation-driven optimization. Since full-wave electromagnetic simulations are time-consuming, optimization methods with fast convergence properties are preferable. In this article, we demonstrate the application of the cross-entropy optimization method to design of artificial magnetic conductors (AMCs) and thin printed phase shifters. Single-frequency AMCs at 10 GHz (X band) and dual-frequency AMCs at 8 and 12 GHz (X and Ku band) were produced that are more manufacturing-friendly, and thus cost effective, than previously reported AMCs. We also show that phase-shifting unit cells with transmission magnitudes over 0.9 (linear) can be designed using the proposed optimization technique. Other potential applications of these unit cells are in phase-correcting and beam-steering metasurfaces

A System-Level Overview of Near-Field Meta-Steering

The paper provides a system-level overview of Near-Field Meta-Steering (NFMS) technology. The NFMS is upcoming antenna beam-steering method that uses the physical rotation of pair of thin metasurfaces that are placed in very close proximity to a high-gain feeding base antenna. This method neither uses any active radio frequency (RF) components nor physical tilting of any antenna part. It is for these reasons that this method yield antenna systems that superior to traditional electronically scanned phased array and mechanically rotated beamsteering antennas. The antenna systems can be developed for a range of applications including inflight connectivity, low-cost satellite terminal antennas to provide connectivity at remote places, and high-power micro- and millimetre-wave applications. The dynamic phase transformation that is achieved by the rotation of two metasurfaces, in a proof-of-concept prototype reported in 2017, indicate that an antenna beam can be scanned in a conical region having an apex angle of 102°