Microstrip Antennas Part 1 docx

Lacava Analysis into Proximity-Coupled Microstrip Antenna on Dielectric Lens 155 Lawrence Mall Methods to Design Microstrip Antennas for Modern Applications 173 K... Zammit Electrically

MICROSTRIP ANTENNAS

Edited by Nasimuddin

All chapters are Open Access articles distributed under the Creative Commons

Non Commercial Share Alike Attribution 3.0 license, which permits to copy,

distribute, transmit, and adapt the work in any medium, so long as the original

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have the right to republish it, in whole or part, in any publication of which they

are the author, and to make other personal use of the work Any republication,

referencing or personal use of the work must explicitly identify the original source.Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher No responsibility is accepted for the accuracy of information contained in the published articles The publisher

assumes no responsibility for any damage or injury to persons or property arising out

of the use of any materials, instructions, methods or ideas contained in the book

Publishing Process Manager Katarina Lovrecic

Technical Editor Teodora Smiljanic

Cover Designer Martina Sirotic

Image Copyright 2010 Used under license from Shutterstock.com

First published March, 2011

Printed in India

A free online edition of this book is available at www.intechopen.com

Additional hard copies can be obtained from orders@intechweb.org

Microstrip Antennas, Edited by Nasimuddin

p cm

ISBN 978-953-307-247-0

free online editions of InTech

Books and Journals can be found at

www.intechopen.com

D C Nascimento and J C da S Lacava

Analysis of a Rectangular Microstrip Antenna

Tian Yu-Bo and Xie Zhi-Bin

Microstrip Antennas Conformed onto Spherical Surfaces 83

Daniel B Ferreira and J C da S Lacava

Mathematical Modeling of Spherical Microstrip Antennas and Applications 109

Nikolaos L Tsitsas and Constantinos A Valagiannopoulos

Cavity-Backed Cylindrical Wraparound Antennas 131

O M C Pereira-Filho, T B Ventura, C G Rego,

A F Tinoco-S., and J C da S Lacava

Analysis into Proximity-Coupled Microstrip Antenna on Dielectric Lens 155

Lawrence Mall

Methods to Design Microstrip Antennas for Modern Applications 173

K SiakavaraContents

Fractal-Shaped Reconfigurable Antennas 237

Ali Ramadan, Mohammed Al-Husseini, Karim Y Kabalan and Ali El-Hajj

A Microstrip Antenna Shape Grammar 251

Adrian Muscat and Joseph A Zammit

Electrically Small Microstrip Antennas Targeting Miniaturized Satellites: the CubeSat Paradigm 273

Constantine Kakoyiannis and Philip Constantinou

Circularly Polarized Microstrip Antennas with Proximity Coupled Feed for Circularly Polarized Synthetic Aperture Radar 317

Merna Baharuddin and Josaphat Tetuko Sri Sumantyo

Circularly Polarized Slotted/Slit-Microstrip Patch Antennas 341

Nasimuddin, Zhi-Ning Chen and Xianming Qing

Microstrip Antenna Arrays 361

Albert Sabban

Microstrip Antennas for Indoor Wireless Dynamic Environments 385

Mohamed Elhefnawy and Widad Ismail

DBDP SAR Microstrip Array Technology 433

Shun-Shi Zhong

Microwave Properties of Dielectric Materials 453

JS Mandeep and Loke Ngai Kin

Hybrid Microstrip Antennas 473

Alexandre Perron, Tayeb A Denidni and Abdel R Sebak

Integration of 60-GHz Microstrip Antennas with CMOS Chip 491

Gordana Klaric Felic and Efstratios Skafidas

A Practical Guide to 3D Electromagnetic Software Tools 507

Guy A E Vandenbosch and Alexander Vasylchenko

The microstrip antennas are low-profi le, low weight, ease of fabrication, conformable

to planar and non-planar surfaces and mechanically robust In the last 40 years, the microstrip antenna has been developed for many communication systems such as ra-dars, sensors, wireless, satellite, broadcasting, ultra-wideband, radio frequency iden-tifi cations (RFIDs), reader devices etc The progress in modern wireless communica-tion systems has increased dramatically the demand for microstrip antennas, capable

to be embedded in portable, handheld devices such RFID handheld reader, devices which provide a wireless network Recently, demands of these devices with smaller

in size and therefore antennas required smaller and light weight especially at the low microwave frequency range The microstrip antennas can be designed in very small size with lower gain and bandwidth For portable and handheld devices, gain and bandwidth of the antenna is not so important However antenna meets some gain with desired bandwidth constraint For millimeter wave applications, the antenna has to be high gain with broadband impedance bandwidth

In this book some recent advances in the microstrip antennas are presented while lighting the theoretical and practical design techniques for various wireless system applications The microstrip antennas on various available substrate materials such as artifi cial material, uni-axial and ferrite are analyzed and designed for reconfi gurable, dual and tunable applications The small microstrip antennas can be designed using artifi cial materials Various shaped radiators are also studied for compact antenna size and circular polarization radiation The circularly polarized microstrip antennas with diff erent feeding system and various shaped slott ed microstrip patch radiators is also studied and compared for compact size and broadband applications The microstrip antennas are also considered as a sensor for detection of materials properties Finally, the microstrip antennas for millimeter-wave applications are also covered in this book New emerging wireless systems that operate at millimeter wave frequencies, such as high data rate 60-GHz transceivers for wireless personal area networks (WPAN), use integrated antennas Therefore, antennas for these systems are commonly implement-

high-ed on in-package solutions The integration of antenna-in-package is also coverhigh-ed by using wire bonding or fl ip-chip bonding interconnections Lastly, the 3D electromag-netic soft ware tools for microstrip antennas designing is demonstrated for helping the microstrip antenna designers The proposed microstrip antennas book is useful for students, researchers and microstrip antenna design engineers

The microstrip antennas book covers diff erent types of the microstrip antennas and rays The book chapters are from experts/scientists in the area of the microstrip antennas

ar-and applied electromagnetics First book chapter begins introduction of the microstrip antennas with low-cost probe-fed microstrip antenna design methods Analysis of the rectangular microstrip antennas on uni-axial and artifi cial material substrates are pre-sented in chapters 2 and 3, respectively A particle-swarm-optimization based selective neural network ensemble and its application to modeling resonant frequency of the microstrip antenna are described in chapter 4 Chapters 5-8 present analysis of the microstrip antennas on the spherical surfaces, cylindrical wraparound, and dielectric lens Various shapes with slott ed/slit microstrip antennas are presented in chapters 9-17 for various wireless system applications such as multiband, reconfi gurable antennas, compact microstrip antennas and circularly polarized microstrip antennas etc These chapters are also presented in comparison with slott ed/slit microstrp antennas based

on fi xed overall antenna size In chapters 18-19, the microstrip antennas are proposed for detection of material properties The hybrid microstrip antennas and integration

of the microstrip antennas with CMOS Chip for millimeter applications are described

in chapters 2021 The last book chapter is a practical guide to 3D electromagnetic soft ware tools for analysis of the planar antennas and this helps reader with general guide-lines for antenna design using the 3D electromagnetic soft ware tools

-Nasimuddin

Institute for Infocomm Research

Singapore

1

Design of Low-Cost Probe-Fed

Microstrip Antennas

D C Nascimento and J C da S Lacava

Technological Institute of Aeronautics

Brazil

1 Introduction

The concept of microstrip radiators, introduced by Deschamps in 1953, remained dormant until the 1970s when low-profile antennas were required for an emerging generation of missiles (James & Hall, 1989; Garg et al., 2001; Volakis, 2007) Since then, but mainly over the last three decades, the international antenna community has devoted much effort to theoretical and experimental research on this kind of radiator (Lee & Chen, 1997) Currently, low-loss RF laminates are used in their fabrication and many of their inherent limitations have been overcome (Garg et al., 2001) On the other hand, low-cost solutions are in demand now that both market and technology are ready for mass production (Gardelli et al., 2004) Recently, the design of single-fed circularly-polarized (CP) microstrip antennas manufactured with FR4 substrate was reported (Niroojazi & Azarmanesh, 2004) Unfortunately, the use of low-cost FR4 as the substrate introduces some additional complexity on the antenna design This is due to the inaccuracy of the FR4 relative permittivity and its high loss tangent (around 0.02) Variations in the FR4 electrical permittivity can shift the operating frequency and the high loss tangent dramatically affects the antenna axial ratio and gain, resulting in poor radiation efficiency To increase the efficiency, microstrip antenna on moderately thick substrate must be designed However, the technique used to compensate for the probe inductance, when the patch is fed by a coaxial probe (a known practical way to feed microstrip antennas), still relies on the designer’s expertise For instance, a series capacitor, which may be constructed in several ways, has been utilized to neutralize this inductance (Hall, 1987; Alexander, 1989; Dahele et al., 1989; Vandenbosch & Van de Capelle, 1994; Nascimento et al., 2006), or the probe geometry has been modified (Haskins & Dahele, 1998; Teng et al., 2001; Chang & Wong, 2001; Tzeng et al., 2005) Unfortunately, due to their complexity, many such techniques are not suitable when the antennas are series-produced in an assembly line

To overcome some of the abovementioned issues, two efficient techniques for designing low-cost probe-fed microstrip antennas are proposed Using only their intrinsic characteristics, linearly- and circularly-polarized microstrip antennas can now be designed without the need for any external matching network Limitations of the proposed approach will also be discussed The chapter is organized as follows: Section 2 covers the design of linearly-polarized microstrip antennas; results obtained with the new approach are compared with those using the standard design technique Circularly-polarized antennas

Microstrip Antennas

2

are addressed in Section 3 and experimental results are shown in Section 4 Other

applications using the new design approach are presented in Section 5, and finally in Section

6, conclusions are drawn from the obtained results

2 Linearly-polarized microstrip antennas

The typical geometry of a rectangular-patch linearly-polarized (LP) microstrip antenna is

shown in Fig 1, where a denotes the patch length, b the radiating edge width, p the probe

position along the x-axis, and h the substrate thickness The patch is printed on a finite

rectangular substrate of dimensions (L by W) in order to avoid the excitation of surface

waves, and the antenna is directly fed by a 50-Ω SMA connector The analysis carried out in

this section is focused on this particular radiator

a

b h

plane Ground

point Feed

x

patch r Rectangula

L

W

(a)

plane Ground

connector SMA

patch r Rectangula

(b) Fig 1 Linearly-polarized probe-fed microstrip antenna: (a) top view – (b) side view

2.1 Radiation efficiency

The radiation efficiency is defined as the ratio of the total power radiated (P r) by an antenna

to the net power accepted (P in) by the antenna from the connected transmitter (IEEE Std 145,

1993) Since the antenna under consideration has its dielectric truncated, the cavity model,

although originally developed for the analysis of electrically thin microstrip antennas, can

be used for estimating the efficiency behavior For the microstrip antenna shown in Fig 1,

the geometry of its equivalent cavity, neglecting the fringe effect, is given in Fig 2 Under

the condition h << a < b, the electric field of the TMmn resonant mode excited within the

cavity is expressed by

mn z

V E

where V mn / h denotes the electric field intensity on the magnetic walls

In case of linearly-polarized antenna excited in the fundamental TM10 mode, the dielectric

(P d ) and metallic (P m) losses can be calculated by means of equations (2) and (3),

respectively

Design of Low-Cost Probe-Fed Microstrip Antennas 3

2

d d

2

2 0

h

ε εμ

where εr is the substrate relative permittivity, σdits electric conductivity,JGs the surface

electric current density on the metallic walls, R s the surface resistance, and ε0 and μ0 are the

electric permittivity and magnetic permeability of free space, respectively

h

a b

p x

y

wallsElectricwall

Magnetic

Fig 2 Geometry of the antenna equivalent cavity

The radiated power can be obtained by computing

where η0 denotes the free-space intrinsic impedance and Eθ and Eφ are the components of

the far electric field radiated by the antenna, evaluated using Huygens’s magnetic current

source approach (Lumini et al., 1999)

Neglecting the surface wave losses, since the antenna has its dielectric truncated, the

radiation efficiency can be estimated by the following expression

Using equations (1) – (5), the radiation efficiency of LP antennas, designed to operate at

1.575 GHz in the fundamental TM10 mode, were calculated, and the results are shown in Fig

3 In Fig 3(a), the radiation efficiency curves of a 1.524-mm thick LP antenna are plotted as a

function of the dielectric loss tangent, with the substrate relative permittivity as a parameter

In Fig 3(b), graphics of radiation efficiency are presented, for the case of a rectangular patch

printed on the FR4 laminate (εr = 4.2), as a function of the substrate thickness, with the loss

tangent as a parameter These graphics, although obtained from the cavity model, make

visible the behavior of the radiation efficiency of these microstrip antennas Thus, if low-cost

materials are used in the antenna manufacture, then moderately thick substrates must be

adopted for good radiation efficiency In the case of commercial FR4 laminates (εr = 4.2 and

tan δ = 0.02), a radiation efficiency close to 70% can be obtained if a 6.5 mm thick antenna is

designed

tanδ = 0.000 tanδ = 0.002 tanδ = 0.006 tanδ = 0.010 tanδ = 0.020 tanδ = 0.030

2.2 Rectangular patch: standard design

According to the standard procedure (James & Hall, 1989; Garg et al., 2001; Volakis, 2007)

for designing a LP patch in the fundamental mode TM10, the operating frequency is set up at

the maximum input resistance point Following this procedure and using the commercial

software HFSS (HFSS, 2010) for optimizing the radiator dimensions, a rectangular antenna

consisting of a h = 6.6 mm moderately thick (to obtain good radiation efficiency), FR4

(εr = 4.2 and tan δ = 0.02) substrate, fed by a 1.3-mm diameter coaxial probe, was designed to

operate at 2 GHz Utilizing a rectangular ground plane (L = 90 mm; W = 100 mm), the

following optimal dimensions were obtained: a = 31.25 mm, b = 40.6 mm and p = 10.4 mm

Results for the input impedance and the reflection coefficient magnitude (⎪Γ⎪) are shown in

Fig 4(a) and (b) respectively As expected, the radiation efficiency is 77.9% and the

directivity is 7 dB at the operating frequency

(a)

1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20 -8

-7 -6 -5 -4 -3 -2 -1 0

It can be seen from Fig 4(a) that the maximum input resistance occurs per design at the

operating frequency (2 GHz) As a result, the antenna input impedance is highly inductive

(Z in = 50 + j59 Ω, at 2 GHz) and can not be perfectly matched to a 50-Ω SMA connector (i e

⎪Γ⎪ = −6 dB, Fig 4(b)) without an external network Nowadays, this behavior is well known