Essam A. Hashish

Low-SAR, Miniaturized Printed Antenna for Mobile, ISM, and WLAN Services

Recently, the mobile handsets support both the mobile and wireless LAN services. Thus, our target is to introduce a new antenna that supports both services. The antenna operates for most of the mobile applications such as the GSM 850, GSM 900, DCS 1800, PCS 1900, UMTS 2100, and most of the LTE bands, especially the low-frequency LTE 700 band. The antenna also supports the WiMAX, wireless local area network (WLAN), and the Industrial, Scientific, and Medical (ISM) bands. The antenna not only has a compact size, but also it supports a low specific absorption rate (SAR) radiation at all the operating frequencies. It consists of a monopole, a meander line, and an electromagnetic band-gap (EBG) structure. In order to cover the low frequency bands, a meander line is utilized due to its compact size, but unfortunately it is a narrowband antenna that is difficult to cover both LTE700 and GSM 900 bands. The solution stems from the use of an EBG structure that widens the band to cover the two low frequency bands and to reduce the maximum SAR. The higher frequency bands are supported by both the monopole and the meander line since they acts as traveling-wave antennas at the high frequency bands. The antenna meets three challenging parameters: the compact size, the multiband operation including the low frequency bands, and the low SAR radiation. Good agreement is found between the experimental and the simulated results.

Novel Reconfigurable Defected Ground Structure Resonator on Coplanar Waveguide

A novel reconfigurable defected ground structure (DGS) resonator fabricated on coplanar waveguide (CPW) technology is presented. The resonator is endowed with an original design which enables the generation of multiple transmission zeros at arbitrary frequencies. The chosen design is indeed based on a slot defect created on the lateral ground planes of the CPW with the double advantage to allow a simple reconfiguration, by means of surface mounted (or fabricated) components, and a very compact solution, by exploiting the transversal dimension of the coplanar wave transmission line (CPW-TL). Four different states of the diodes configuration are investigated, where in each state multiple transmission zeros are produced in the frequency range from 1 GHz to 11 GHz. The equivalent circuit of each state is obtained using a conventional circuit parameter extraction method. Moreover, the slotline design equations are used to identify the transmission zeros and validated using the magnetic field distribution inside the slot. In this work, the reconfigurability is first proven by means of short bridges mounted in specific locations. These bridges are then replaced by PIN diodes. Simulated and measured results are in good agreement.

Optimum negative response of a coincident‐loop electromagnetic system above a polarizable half‐space

The loop radius of the coincident-loop system above a polarizable half-space has a significant effect on the magnitude of the negative response and its time of occurrence. Computations are made to study this phenomenon for various values of the electrical parameters of the ground, which is described by a Cole-Cole model. An optimum loop radius is found to exist, which leads to the largest peak of the negative response. It is found that for values of the frequency parameter (c) larger than 0.5, the largest peak of the negative response occurs at a time nearly equal to the Cole-Cole time constant. Empirical formulas are deduced relating both the optimum loop radius and the largest peak of the negative response to the electrical parameters of the polarizable half-space. The above phenomena may be used as a simple and effective guide for the detection of a polarizable target and estimating its electrical parameters.

Design of a Compact UWB Planar Antenna with Band-Notch Characterization

A compact ultra-wideband (UWB) antenna with band-notch characteristic of size 28 mm times 29 mm is proposed. This antenna is designed to cover the Federal Communication Commission (FCC) bandwidth for UWB applications (3.1-10.6 GHz) and have a notch- filtering at the IEEE 802.1 Ia frequency band (5.15-5.825 GHz). This notch-filter effect is obtained by introducing a resonant U-shaped slot at this frequency. The design parameters and the performance of the proposed antenna are analyzed by using different techniques to assure the validity of the simulated results. Comparison between measurements and simulation is also presented.

DESIGN OF A PERFECT ELECTROMAGNETIC CONDUCTOR (PEMC) BOUNDARY BY USING PERIODIC PATCHES

Perfect electromagnetic conductor (PEMC) is a novel concept in electromagnetic flelds of interesting properties and many potential applications. This paper introduces a new technique to design an artiflcial surface that has equivalent PEMC properties. The proposed PEMC boundary is based on a periodic structure composed of two conducting patches on a grounded dielectric slab. One of them is embedded inside the substrate and the other lies on the surface of the substrate. A conducting via is used to connect the two patches. In the resulting PEMC boundary, the polarization of the re∞ected wave is controlled by the tilting angle between the two patches.

Electromagnetic Scattering From a Buried Cylinder Using a Multiple Reflection Approach: TM Case

A simple, fast, and accurate analytical method is introduced to obtain the EM scattered fields due to an infinite circular cylinder buried in a homogeneous dielectric half-space, illuminated by a normally incident transverse magnetic (TM) plane wave. The method is applied to perfect electric conducting (PEC) and dielectric cylinders of complex permittivity with the host dielectric medium being lossy or lossless. The accuracy of this method is verified using a finite-difference time-domain code (FDTD) on a wide frequency range and the results are presented discussing the range of validity of this approach.

A novel reconfigurable DGS cell for multi-stopband filter on CPW technology

A novel defected ground structure cell was presented. The cell was built on coplanar waveguide technology. Two diodes in each side of the ground planes allow us to switch the filter between different passbands. Simulated and measured responses were presented showing very good agreement. An electromagnetic explanation of the structure based on slot transmission line was also presented. The cell shows very promising features for the implementation of small and efficiently reconfigurable building block for filters. The very narrow stopbands in the responses may be enhanced by putting more cells in cascade. This work is a first step toward implementation of a silicon integrated reconfigurable filter using MEMS switches in place of diodes.

Quasi Self-Complementary UWB Notched Microstrip Antenna for USB Application

UWB antenna is a crucial part of any UWB system required for indoor application. In this paper, a novel design is presented, which relies on self-complementary structure. The structure is fed by a microstrip line, where a triangular notch is embedded in the ground plane. The design in this paper yields a UWB bandwidth that extends from 2.86.0{40.0GHz. To ensure coexistence of UWB with WLAN applications (5.15{5.825GHz) with minimal interference, a frequency notch is introduced using two parasitic U-shaped elements embracing the microstrip feeding line that resonates in the vicinity of the band notch frequency band. The proposed design was subject to parametric study to reach optimum parameters. The flnal design was fabricated using photolithographic technique and the measured results showed very good agreement with simulated ones.

Fractal quasi-self complimentary miniaturized UWB antenna

A miniature Ultra-wideband (UWB) quasi self-complementary antenna with Koch fractal boundary for ultra-wideband is presented. The proposed antenna has a total size of 16 mm × 13 mm × 1.5 mm that enables embedding in various portable devices with wide impedance bandwidth covering the range from 3.3-13.5 GHz with return loss better than -10dB. It also exhibits a much-reduced ground plane effect compared to the stand-alone design. Omnidirectional radiation patterns with appreciable gain across the operating band can be obtained.

Novel compact circular N-shaped patch antenna for 5.2 GHz wireless communications

This paper presents compact circular N-shaped antenna which is designed for wireless LAN (IEEE 802.11a) and other wireless communication systems using the 5.15-5.35 GHz frequency range. The reduction in its size is achieved by perturbing the surface current path on the edge of a circular patch antenna by two triangular slots which will form the N- shape. The proposed antenna is designed and fabricated on two-layered (air, Duriod 5880) and has equivalent performance with about 62% reduction in size with respect to the conventional circular antenna on Duriod 5880. The maximum measured bandwidth is approximately 240 MHz or 4.6%, which meets the requirements of WLAN (5.15-5.35 GHz) systems. A comprehensive parametric study has been carried out to understand the effect of various dimensional parameters and to optimize the performance of the antenna.