This paper addresses the problem of cochannel interference (CCI) generated in a mixed cell architecture in microcellular systems. In this type of microcellular systems in which both microcells and macrocells coexist in the same geographical urban area, the base station antennas mounted on the rooftops of buildings to cover wide circular radio zones suffer severe CCI from the surrounding low base stations. A dielectric-loaded slotted-cylinder antenna (DSCA) is applied to horizontally polarized omnidirectional array antennas in a height-diversity configuration with the high gain of 8&#x2009;dBi, which is comparable to that of a collinear antenna, to reduce the CCI. The measurements conducted in a suburban area clarify the reduction in the CCI for three techniques. The beam-tilt technique reduces the CCI level by approximately 10&#x2009;dB for both collinear antennas and the DSCA array antennas. The use of horizontal polarization reduces the CCI level by approximately 13&#x2009;dB for the DSCA array antennas with and without beam tilt. The combination of the beam tilt and horizontal polarization or the DSCA array antennas with beam tilt significantly reduces the CCI level by approximately 23&#x2009;dB.

Shuta Uwano

Atsuya Ando

Tomohiro Seki

Yasushi Takatori

Takefumi Hiraguri

Experimental Investigations of Cochannel Interference Reduction Effect at High Elevation Base Station Using Beam Tilt and Orthogonal Polarization

Two examples of microwave devices, fed by a coplanar waveguide and realized on a thin substrate (or without such a substrate), are employed to investigate the influence of devices&#x2019; curvatures and the proximity of different materials on their parameters. To perform the tests, a broadband antenna and a low-pass filter are chosen. A feeding coplanar waveguide is realized on a dielectric material brick attached to an SMA connector and the main device structure is placed in the air or on a thin substrate. The utilization of a thin substrate or its removal from the structure gives rise to the possibility of placing the devices on curved surfaces. The investigated devices are redesigned and manufactured. The antenna has a total size of 46&#x2009;mm &#xd7; 44&#x2009;mm and covers a frequency range of 2.4&#x2013;35&#x2009;GHz which gives a 174&#x25; fractional bandwidth. The filter has a total size of 50&#x2009;mm &#xd7; 80&#x2009;mm and its bandwidth has a cutoff frequency of 3.4&#x2009;GHz. The obtained results are verified by measurements and good agreement is achieved.

Rafal Lech

Wojciech Marynowski

Adam Kusiek

Jerzy Mazur

Coplanar Waveguide-Fed Broadband Microwave Devices with (or without) a Thin Dielectric Substrate for Use in Flexible Electronic Systems

This work investigates fade dynamics of satellite communication systems in equatorial heavy rain region based on a one year of Ku-band propagation measurement campaign carried out in Universiti Teknologi Malaysia (UTM), Johor, Malaysia. First order statistics of rain attenuation are deduced and the results are found to be in good agreement with those obtained from other beacon measurements gathered within the same area (Kuala Lumpur). Moreover, the fade duration and slope statistics of the satellite signal variations are also carefully derived and subsequently compared with the ITU-R recommendation model. Such information is useful for the system operator and radio communication engineer for the design of appropriate fade mitigation techniques as well as the quality of service that could be offered to the user (according to the time interval for a typical day). Further evaluation on the performances of several ITU-R models in the heavy rain region are needed based on the measurement database available of this climatic region.

Siat Ling Jong

Michele D&#x2019;Amico

Jafri Din

Hong Yin Lam

Analysis of Fade Dynamic at Ku-Band in Malaysia

Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of &#x3bb; or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than &#x2212;10&#x2009;dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric properties to determine and compare the propagation constants and quarter-wave thickness. The quarter-wave thickness for the tire dust was 3&#x2009;mm less than that of the rice husk material, but we preferred the rice-husk material. This preference was based on the fact that our goal was to achieve minimum backward reflections, and the rice-husk material, with its low dielectric constant, high loss factor, large attenuation per unit length, and ease of fabrication, provided a better opportunity to achieve that goal. The performance of the absorbers was found to be better (lower) than &#x2212;20&#x2009;dB, and comparison of the results proved that the hollow design with 58&#x25; less weight was a good alternative to the use of solid absorbers.

Muhammad Nadeem Iqbal

Mohd. Fareq Malek

Yeng Seng Lee

Liyana Zahid

Muhammad Shafiq Mezan

A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

A planar printed dipole antenna with reflectors and directors, able to steer its radiation pattern in different directions, is proposed for telecommunication applications. Starting from a dual-beam printed dipole antenna achieved by combining two elementary dipoles back to back, and by loading four PIN diodes, three modes of reconfigurable radiation patterns are achieved at the frequency 2.56&#x2009;GHz thanks to switches states. A prototype of the structure was realized and characterized; an efficiency of 75&#x25; is obtained. Simulation and measured results of the results are presented and discussed.

Imen Ben Trad

Jean Marie Floc&#x2019;h

Hatem Rmili

M&#x2019;hamed Drissi

Fethi Choubani

A Planar Reconfigurable Radiation Pattern Dipole Antenna with Reflectors and Directors for Wireless Communication Applications

Four different models are applied to effectively describe a geometrically simple dielectric-composite slab. The corresponding model parameters, when the oblique incidence is taken into account, are retrieved based on the transmission and reflection data and compensated with the nonmagnetic assumption. The scattering parameters of each model with derived parameters for various angles of incidence are then analytically calculated using the forward propagation matrix method and compared with the simulated scattering parameters from the real composite slab. According to these comparisons, it is shown that spatial dispersion makes it challenging to achieve angle-independent parameters for the applied four models. Moreover, when a stratified model is employed to describe the composite slab of our interest under oblique incidence, the boundary layers need to be anisotropic.

Jiaran Qi

Jinghui Qiu

Chongzhi Han

Homogenization Models for a Simple Dielectric-Composite Slab upon Oblique Incidence

This paper deals with the possibility of adopting microwave imaging to continuously monitor a patient after the onset of a brain stroke, with the aim to follow the evolution of the disease, promptly counteract its uncontrolled growth, and possibly support decisions in the clinical treatment. In such a framework, the assessed techniques for brain stroke diagnosis are indeed not suitable to pursue this goal. Conversely, microwave imaging can provide a diagnostic tool able to follow up the disease&#x2019;s evolution, while relying on a relatively low cost and portable apparatus. The proposed imaging procedure is based on a differential approach which requires the processing of scattered field data measured at different time instants. By means of a numerical analysis dealing with synthetic data generated for realistic anthropomorphic phantoms, we address some crucial issues for the method&#x2019;s effectiveness. In particular, we discuss the role of patient-specific information and the effect of inaccuracies in the measurement procedure, such as an incorrect positioning of the probes between two different examinations. The observed results show that the proposed technique is indeed feasible, even when a simple, nonspecific model of the head is exploited and is robust against the above mentioned inaccuracies.

R. Scapaticci

O. M. Bucci

I. Catapano

L. Crocco

Differential Microwave Imaging for Brain Stroke Followup

Electromagnetic bandgap structures are considered a viable solution for the problem of switching noise in printed circuit boards and packages. Less attention, however, has been given to whether or not the introduction of EBGs affects the EMI potential of the circuit to couple unwanted energy to neighboring layers or interconnects. In this paper, we show that the bandgap of EBG structures, as generated using the Brillouin diagram, does not necessarily correspond to the suppression bandwidth typically generated using S-parameters. We show that the reactive near fields radiating from openings within the EBG layers can be substantial and are present in the entire frequency band including propagating and nonpropagating mode regions. These fields decay fast with distance; however, they can couple significant energy to adjacent layers and to signal lines. The findings are validated using full-wave three-dimensional numerical simulation. Based on this work, design guidelines for EBG structures can be drawn to insure not only suppression of switching noise but also minimization of EMI and insuring signal integrity.

Baharak Mohajer-Iravani

Omar M. Ramahi

On the Suppression Band and Bandgap of Planar Electromagnetic Bandgap Structures

About this journal

International Journal of Antennas and Propagation publishes research on the design, analysis, and applications of antennas, along with studies related to the propagation of electromagnetic waves through space, air, and other media.

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Chief Editor, Professor Koziel, engages in research focused on surrogate-based modeling and optimization including space mapping technology for engineering design at Reykjavik University.

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International Journal of Antennas and Propagation - Table of contents 2014

International Journal of Antennas and Propagation | Hindawi

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International Journal of Antennas and Propagation publishes research on the design, analysis, and applications of antennas, along with studies related to the propagation of electromagnetic waves through space, air, and other media.

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International Journal of Antennas and Propagation

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International Journal of Antennas and Propagation