Digest - IEEE Antennas and Propagation Society. International Symposium

Summary form only given. The International Telecommunication Union (ITU) is the oldest specialized agency of the United Nations, far older, in fact, than the UN itself. The ITU is unique in the sense that while it is first and foremost an intergovernmental organization, it very much is a partnership between the public and private sectors. Indeed, given the explosive growth occurring in the telecommunication sector and the transformations occurring around the world, this partnership is its very strength. Radiocommunications is also playing an ever increasing role in the technological evolution which we are witnessing. This article reviews the history of the ITU, the changes in its structure and functioning and measures being considered to further adapt the ITU to the changing telecommunication environment.

Left-handed (LH) materials, first introduced theoretically in Veselago (1968), have spurred considerable excitement since the demonstration of their practical realizability. The unique properties of these metamaterials, verified by full-wave analysis in Caloz et al. (2001), are promising for a diversity of optical/microwave applications, such as new types of beam steerers, modulators, band-pass filters, superlenses, microwave couplers and antenna radomes. However, the LH structures presented so far are impractical for microwave applications, because of their too narrow bandwidth and too lossy characteristics, and alternative theories are desirable to gain a deeper insight into their behavior. We introduce here a transmission line (TL) approach of LH materials (Caloz et al. 2002), provide a method to realize an artificial lumped-element LH-TL and propose a microstrip implementation of this line.

Microstrip antennas consist of a planar resonant radiating element parallel to, but separated, from a ground plane by a thin dielectric substrate (t \ll \lambda). These antennas are very thin and consequently rugged and easy to mount. They may be fed from the back through the ground plane or from the edge by depositing microstrip lines on the dielectric substrate. Several varieties of microstrip antennas are discussed in this paper. Design procedures are given for both linearly and circularly polarized antennas. Measured patterns are presented for antennas from UHF throughCband.

Starting from the equivalence theorem any composite metallic and dielectric structure can be analyzed by using SIE (surface integral equations). Such integral equations are usually solved by MoM (method of moments). Most of the existing MoM methods for solving SIE are developed for BORs (bodies of revolution). There are only few such methods that can handle structures of arbitrary shape. These methods use sub-domain basis functions defined over triangles, requiring a very large number of unknowns even for the simplest problems. This paper presents a new MoM method for electromagnetic modeling of composite metallic and dielectric structures. The method uses entire-domain basis functions defined over bilinear surfaces, resulting in a remarkably small number of unknowns.

Genetic algorithms (GA) have proven to be a useful method of optimization for difficult and discontinuous multidimensional engineering problems. A new method of optimization, particle swarm optimization (PSO), is able to accomplish the same goal as GA optimization in a new and faster way. The purpose of this paper is to investigate the foundations and performance of the two algorithms when applied to the design of a profiled corrugated horn antenna. Also investigated is the possibility of hybridizing the two algorithms.

Metamaterial surfaces can be conceptualized by a 2-dimensional periodic arrangement of many small flat inclusions on an otherwise homogeneous host surface. The electromagnetic properties of such metamaterial plates, which can indeed be regarded as frequency-selective surfaces, are influenced by the shape and geometry of these inclusions. When a metamaterial surface is closely placed above a perfectly conducting plate, at a certain frequency band, this structure may possess a high surface impedance at its top surface, thus providing a high-impedance ground plane (HIGP). The center frequency and bandwidth over which such a high-impedance electromagnetic surface is achieved depend on inclusion shapes and compositions, among other parameters. By placing a resistive sheet on top of this surface, we can achieve a thin structure that can be an efficient absorber for incident electromagnetic energy.

This paper presents an overview of limitations imposed on the range performance of passive UHF RFID systems by such factors as tag characteristics, propagation environment, and RFID reader parameters

This paper introduces a novel nature-inspired global optimization technique, which we call Wind Driven Optimization. WDO is a population based iterative global optimization method, where the velocity and the position of wind controlled air parcels are updated based on the physical equations that govern atmospheric motion. The effectiveness of WDO as a tool in optimization problems is first shown with its performance on benchmark functions and then with its application to optimizing the design for a thin double-sided AMC surface at 10 GHz.

A microstrip reflectarray is a flat reflector antenna that can be conformally mounted onto its supporting structure without consuming a significant amount of real estate and without adding significant mass. The article concentrates on the bandwidth study of a form of reflectarray that uses identical patches with different-length transmission delay lines attached to compensate for the spatial phase delays. This antenna suffers from one major shortcoming, its limited bandwidth. A new concept of mechanically phased reflectarray is also presented.

In this paper we present the design, fabrication, and characterization of broadband and wide-angle metasurface-based optical waveplates. Such nanostructured waveplates are formed by an array of rectangular gold nanopatches on a solid gold layer backed glass spacer. Through engineering the anisotropic resonant response and inter-element coupling of the nanopatch array, highly efficient polarization conversion can be achieved to generate an arbitrary state-of-polarization in a broad wavelength and wide angular range. As a proof-of-concept example, a near-infrared quarter-wave metasurface waveplate is experimentally demonstrated, showing a polarization conversion ratio higher than 91% and energy efficiency over 86% within a wavelength range from 630 nm to 1290 nm.

In this paper, preliminary results and analysis of cloud attenuation on a Ka-band satellite propagation link in tropical island of Singapore are reported. The received signal by a ground-based beacon receiver at 18.9 GHz was processed with a sliding window technique to minimize the system and scintillation effects. The results show that the Ka-band cloud attenuation is highly correlated with the observed solar radiation.

This paper presents a study on randomly distributed planar antenna array elements for adaptive beamforming. A comparison between uniformly and randomly spaced antenna arrays is detailed by using the adaptive least mean square algorithm. The study is based on varying the number of elements of the random planar antenna array to obtain an optimal performance.

In this paper we present the circuit modeling and phase analysis of multilayer graphene on quartz. The multilayer graphene film is characterized by the total sheet resistance at low frequency which is decreased with increasing number of layers. The transmission phase variation is dominant by the thickness of quartz and has 360° phase inversion at resonant frequency. The reflection phase shows reduced variation range around resonance with decreased total sheet resistance, this effect can be applied to narrowband reflective phase shifter. The measured phase responses show a similar phase variation with quartz thickness but reveal a varied trend of the reflection phase with more layers.

This paper presents an experimental study on wireless power delivery to low-power mobile devices based on retro-reflective beamforming. In our scheme, a pilot signal comprised of an impulse train is broadcasted from a mobile device. The wireless charger analyzes the received pilot signal, and then accordingly constructs a focused power beam onto the mobile device. In our experiments, 14 mW out of the 1 Watt power transmitted from the charger is harvested by the mobile device 50-cm distance away, and the power beam is capable of tracking the device's location dynamically. In addition, since the pilot signal's spectrum covers a certain frequency range, the carrier of wireless power can be configured among multiple frequencies.

Built-in antennas in mobile equipment are often subject to changes in input impedance due to the proximity of objects, e.g. a user's hand/head, a desk, etc. To compensate this mismatch, an automatic tunable antenna system using Micro-Electro-Mechanical System (MEMS) variable capacitors and a probe is proposed in this paper. The system controls MEMS variable capacitors based on the received power of the probe and triggered by the Transmission Power Control (TPC). A prototype using a square-law detector, an Analog-to-Digital Converter (ADC), a Field Programmable Gate Array (FPGA) and a matching circuit containing MEMS variable capacitors is also demonstrated.

In this paper, PIN diode based reconfigurable mul- tiple input multiple output (MIMO) modified printed inverted F-shape antenna (PIFA) is presented. The proposed design is very versatile as it can be used to cover many frequency bands. The well known frequency bands covered are LTE 900 MHz, GSM 1800, WLAN 2450 MHz with several other bands as well. The proposed design provides at least 10 dB isolation between its antenna elements. The dimensions of the proposed design were 11×28 mm2with a ground plane area of 60×120 mm2.

Time-modulated arrays (TMAs) are antenna systems where the signals either transmitted or received by the elements of the array is multiplied by means of periodic functions (e.g., obtained by the on-off behavior of a set radio-frequency switches) in order to achieve advanced performance as compared to classical phased array architectures and enable new generation wireless services. In this abstract, a review of the advances in the framework of TMA synthesis and design at the ELEDIA Research Center of the University of Trento is given.

We propose a mixed order formulation of the combined field volume integral equation (CFVIE) for inhomogeneous anisotropic magnetodielectric objects. This method uses the Rao-Wilton-Glisson (RWG) basis functions to expand flux densities while second order curl conforming basis functions are used to expand vector potentials. In this case, both dielectric and magnetic contrasts of the objects can be accounted for in the CFVIE formulation. Moreover, correct boundary conditions are imposed on both flux densities and vector potentials. Finally, the stabilized bi-conjugate gradient fast Fourier transform (BCGS-FFT) method is employed to solve the integral equations. Numerical examples show that this method can handle large size objects with inhomogeneous or anisotropic magnetodielectric materials. The scattered fields calculated by this method have excellent agreement with both MIE solution and the results from commercial software.

In this paper, we present a graphene-based mantle cloak structure for both dielectric and conducting elliptical cylinders. The mantle cloak design is realized by means of a patterned metasurface formed by periodic sub-wavelength graphene nanopatches. Although the scattering behavior of an ellipse is dependent on the angle of incidence, it is shown that the cloak design is robust for any incident angle. The scattering behavior of the cloaked objects is analyzed by expressing the incident and scattered fields in terms of radial and angular Mathieu functions.