Micowave and Millimeter Wave Technologies Modern UWB antennas and equipment Part 1 ppt

Two different techniques for Directive Ultra-Wideband Planar Antennas were presented throughout chapter 1: the operation of a novel bow-tie antenna with high front-to-back ratio and dire

Microwave and Millimeter Wave

Technologies: Modern UWB antennas and equipment

Microwave and Millimeter Wave

Technologies: Modern UWB antennas and equipment

Edited by Prof Igor Minin

In-Tech

intechweb.org

Published by In-Teh

In-Teh

Olajnica 19/2, 32000 Vukovar, Croatia

Abstracting and non-profit use of the material is permitted with credit to the 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 Publisher assumes no responsibility liability for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained inside After this work has been published by the In-Teh, authors have the right to republish it, in whole or part, in any publication of which they are an author or editor, and the make other personal use of the work

Technical Editor: Sonja Mujacic

Cover designed by Dino Smrekar

Microwave and Millimeter Wave Technologies:

Modern UWB antennas and equipment,

Edited by Prof Igor Minin

p cm

ISBN 978-953-7619-67-1

Preface

Novel generation wireless system is a packet switched wireless system with wide area coverage and high throughput It is designed to be cost effective and to provide high spectral efficiency The 4th wireless uses Orthogonal Frequency Division Multiplexing, Ultra Wide Radio Band and millimeter wireless and smart antenna Highly directive, planar UWB antennas are gaining more and more attention, as required in many novel and important applications With the release of the microwave and millimeter band, applications for short-range and high-bandwidth different new devices are primary research areas in UWB systems Two different techniques for Directive Ultra-Wideband Planar Antennas were presented throughout chapter 1: the operation of a novel bow-tie antenna with high front-to-back ratio and directivity and a differential planar UWB antenna characterized by higher gain (more than

11 dB around 7 GHz) with respect to conventional printed radiators has been demonstrated The chapter 2 is timely in reporting the aspects of the conventional and state-of-the-art antenna design in the UWB system For example, design methods of the conventional UWB antennas such as log-periodic dipole array are overviewed and the UWB antennas which are recently researched are introduced Also the principle and design methods to notch the particular frequency band in UWB antenna are summarized

As it well known microstrip patch antennas have problems of low bandwidths In the chapter

3 various ways to overcome this problem by using various matching techniques for numerous patch antenna array schemes is show

The recent progress in the development of UWB planar antenna technology has been reviewed and some types of UWB metal-plate monopole antennas, UWB printed monopole antennas and UWB printed slot antennas are described in the chapter 4

In the chapter 5 design and implementation of a practical reconfigurable communication system including an additive ultra wide band white Gaussian noise and delay lines in X-band from 6 to 12 GHz with other necessary microwave parts as the test bed are introduced Also design and implementation procedures of all microwave parts such as ultra wideband amplifiers, dividers, switches, drivers, gain controllers, generators, filters, delay components, bias tee, transitions and etcetera are discussed

Slot array antennas using rectangular waveguides were widely used based on their various important capabilities in microwave telecommunications In the chapter 6 detailed study of polarization agility achievement in Annular Waveguide Slot Antennas (AWSA) are presented

In an AWSA, the waveguide and the slots are all circularly oriented to fit the boundary

Far-field radiation pattern control has strong potential in smart antennas, wireless communications and radar Typical planned applications include multipath fading and interference mitigation, data rate and coverage enhancement, etc For implementing these functionalities, either switch beam or reconfigurable Half-Power Beam-Width (HPBW) antennas are required In the chapter 7, the authors present different antenna concepts to obtain reconfigurable radiation pattern capability in millimeter waves as follows: multibeam antennas are demonstrated based on Butler matrices at 24 and 60 GHz, and reconfigurable Half Power BeamWidth antennas are shown Also a new technique is presented to shape the radiation pattern of an antenna to achieve directive or sectorial beams In this case, the antenna design is based on an inhomogeneous lens fed by several sources

In the chapter 8 author investigate the ring loop antenna for the UHF digital terrestrial broadcasting A ring loop antenna is excited by a simple and low-cost feeder system The broadband input impedance and the high gain are obtained in the calculation and the measurement

During the past few decades, there has been growing interest in the use of microwave and millimeter wave radiometers for remote sensing of the earth The chapter 9 addresses the subject of antenna array design in aperture synthesis radiometers Also a novel antenna array

is described, which is a sparse antenna array with an offset parabolic cylinder reflector at millimeter wave band

As it well known the antenna is an important element of communication, remote sensing and radio-localization systems The measurement of the antenna radiation pattern characteristics allows to verify the conformity of the antenna The different antenna measurement techniques are reviewed in the chapter 10

The interpretation of the radiated EMI measurement is a very complex problem due to many disturbing influences affecting such a measurement The antenna brings into measurement additional errors, which increase measurement uncertainty These errors and their effect

on the entire uncertainty of the measurement are investigated in the chapter 11 in case of broadband Bilog antenna, a typical receiving antenna for radiated EMI measurement Over the past few years, a large number of pattern synthesis techniques of antenna arrays have been studied and developed In the chapter 12 authors study the influence of the sensor directivity into the array beampattern, in order to test if the effects on the array pattern must

be taken into consideration in design methods of pattern array synthesis, and other array design methods

In the chapter 13, a brief introduction of mm-wave RoF system is given and the optical techniques of generating mm-wave signals are presented Unlike the conventional discussions about mm-wave RoF systems focusing on the downlink only, the design of bidirectional mm-wave RoF systems are also considered

Rain-induced attenuation creates one of the most damaging effects of the atmosphere on the quality of radio communication systems, especially those operating above 10 GHz The chapter 14 presents results that have thus far been acquired from an integrated research campaign jointly carried out by researchers at Institut Teknologi Sepuluh Nopember, Indonesia and Kumamoto University, Japan The research is aimed at devising transmission strategies suitable for broadband wireless access in microwave and millimeter-wave bands, especially in tropical regions

High-precision and high-temporal global rainfall maps are very important for scientific studies for global water cycle and practical applications for water resources The purpose of the chapter 15 is to briefly describe the Global Satellite Mapping of Precipitation algorithm, provide examples of rainfall maps from microwave radiometers

Conventional metallic waveguides have several major advantages, including low propagation losses and high power transmissions in the microwave frequency range One disadvantage

of metallic waveguides is that the propagation frequency band is limited at frequencies above the cutoff frequency The chapter 16 introduces a system that uses a dual-frequency band waveguide Authors present the fundamental principles of this dual-frequency band waveguide in which a dual in-line dielectric array is installed It has been shown the electromagnetic waves were propagated in a waveguide with dual in-line dielectric rods made of LaAlO3 and without higher modes above the 2 cutoff frequencies

In the chapter 17 authors propose a design method of a voltage-controlled oscillator using on-chip coplanar waveguide (CPW) resonator thus replacing an LC-resonator at 5 GHz band

It has been shown the advantages of employing CPW resonator is the wide frequency-tuning range, and it also saves about 30% of chip size whereas the measured other performance of the proposed oscillators are comparable to that of an oscillator using LC resonator The design technique is applicable for higher frequencies

The microwave and millimeter wave broadband amplifier is importance for wideband wireless communications operating within microwave frequency range The chapter 18 provides the fundamental design concepts of broadband amplifier using the modern CMOS technology Various design techniques are introduced for achieving high performance microwave broadband amplifiers The main design considerations and current trends are also discussed

The chapter 19 illustrates the interferometric concept in quadrature down-conversion for communication and radar sensor applications

In the chapter 20 describe a new method for the analysis of passive waveguide components, composed of the cascade connection of planar junctions This new method extracts the main computations out of the frequency loop, thus reducing the overall CPU effort for solving the frequency-domain problem

The fundamental theory permitting the synthesis of the negative group delay cell is described

in details in the chapter 21 A time domain study based on a Gaussian wave pulse response, the physical meaning of this phenomenon at microwave wavelengths is also provided and

a new concept of frequency-independent active phase shifter used in recent applications are described

In the chapter 22, the authors summarize the design procedure of broadband MMIC high power amplifiers Some special considerations, as well as, experimental results are focused

on GaN technology

Historically magnetrons were one of the first devices used to build radar systems In the last chapter 23 it has been shown that the utilization of recent advances in magnetron manufacturing technology, the introduction of novel approaches in radar design as well as a vast progress in digital signal processing technique result in a solid overall performance of the magnetron based millimeter wavelengths radars

It is expected the book will attract more interest in microwave and millimeter wave technologies and simulate new ideas on this fascinating subject

Editor:

Prof Igor Minin

Novosibirsk State Technical University, Russia

Prof.minin@gmail.com

Directive Ultra-Wideband Planar Antennas 1

Directive Ultra-Wideband Planar Antennas

A.-D Capobianco, F.M Pigozzo, A Locatelli, D Modotto, C De Angelis, S Boscolo, F Sacchetto, M Midrio

x

Directive Ultra-Wideband Planar Antennas

A.-D Capobianco #1, F.M Pigozzo #2, A Locatelli *3, D Modotto *4, C De

Angelis *5, S Boscolo +6, F Sacchetto +7, M Midrio +8

#DEI, Università degli Studi di Padova

*DEA, Università degli Studi di Brescia

+DIEGM, Università degli Studi di Udine

Italy

1 Introduction

Since the acceptance of unlicensed use of the Ultra-Wideband (UWB) technology in the

range between 3.1 and 10.6 GHz in the USA (FCC, 2002) and more recently between 3.4 and

8.5 GHz in Europe (ETSI, 2008), the realization of low-cost UWB wireless systems is

considered a fundamental research goal both for military and commercial applications The

possible use and benefits of UWB technology are significant and among its potential

applications, high-resolution radar and short-range ultra-high speed data transmission are

very attractive In this scenario, design, fabrication and characterization of effective antennas

for UWB systems are challenging tasks with respect to the case of narrowband systems A

suitable UWB antenna should be capable of operating over an ultra-wide bandwidth

Therefore it is necessary to guarantee a good behavior of the antenna in the band of interest

in terms of impedance matching with the transmitter, radiation and time-domain properties

Moreover, recent UWB antenna development tends to focus on ultra-compact planar

antennas as they are more practical in terms of manufacturing, integration with the system

electronics board and form factor Typical configurations exhibit radiation patterns similar

to the traditional monopole/dipole antennas, i.e they behave as omnidirectional radiators

in the plane normal to the radiating element This feature is desirable in UWB devices which

do not have a fixed or a-priori defined orientation with respect to the environment and thus

when it is not necessary to favour any specific direction On the other hand, strongly

directive radiators are required for radar applications, especially when power,

low-interference and high-resolution devices are needed Directive UWB radiators are also

interesting towards several complementary goals, e.g to provide extra radio link gain to

single antenna transceivers, to mitigate the effects of multipath in the indoor UWB channel,

and, last but not least, to result in a high front-to-back ratio, which is desirable in many

applications such as in wireless body-area networks (WBAN)

In the past few years, several printed broadband monopole-like configurations have been

reported for UWB applications, but presently, very few efforts have been made to increase

their directionality This chapter intends to provide the reader with two different design

methodologies for increasing the directivity of planar UWB antennas In section 2, a novel

antenna layout will be presented, as the result of subsequent modifications of a native

1

2

omnidirectional radiator: the bow-tie antenna A high front-to-back ratio, low-profile design

will be developed by exploiting a planar reflector and studying ad-hoc optimizations of both

the antenna geometry and the feeding arrangement The final layout could be particularly

well-suited for point-to-point high data-rate UWB radio links around the 5.5 GHz center

frequency

In section 3, a different approach will be adopted: instead of backing an omnidirectional

printed wideband dipole, a structured ground plane will be employed with a two-element

array of disc monopoles The resulting highly directive UWB antenna is designed to be used

in combination with a single-chip radar transceiver operating between 6 and 8 GHz

(Cacciatori et al., 2007)

The reader will find a detailed step-by-step design procedure, along with experimental data

obtained through characterization of several prototypes in anechoic chamber

2 An UWB Bow-Tie Antenna with High Front-to-Back Ratio

2.1 Design Principles

As previously said in the introduction of this chapter, in the UWB communication

framework there are scenarios in which directivity is mandatory, for example when the

antenna has to be located in the corner of a room or against a wall to provide a sectoral radio

coverage from the transmitter (i.e an access point) to the receiver (i.e a set-top box)

Moreover, small dimensions and low-profile are desirable features for an easier integration

in the final device For all these reasons the RF engineer may start the antenna design with

the choice of the candidate wideband radiator along with its initial geometrical parameters

As directionality can be effectively achieved through the use of a planar reflector, the

wide-band, planar radiating element can be natively omnidirectional, such as the bow-tie antenna

In the following, a design methodology is presented, starting from the technical

specifications summarized in Table 1

flat reflector dimensions 100 x 70 mm2

laminate – reflector distance roughly 5 mm

Table 1 Technical specifications

The well known design guidelines for a bow-tie resonating at 5.5 GHz (Balanis, 2005) would

lead to a total length of 16 mm, a small value that may cause problems when connecting the

antenna to the feed-line whose dimensions are comparable with the radiator itself; this fact

imposes to enlarge the antenna, and thus to force it to operate at a higher order resonance

However, the laminate technical specifications limit the maximum size of the bow-tie As a

consequence, a good trade-off is the antenna layout shown in Fig 1 The latter will in turn

allow to save enough space to arrange the feeding/matching line on the same laminate It is

important to note that an antipodal configuration is preferable since the antenna will be fed

using a 50 Ohm SMA connector

Such an early model, mounted at a given distance above a planar reflector, can be studied and subsequently optimized through numerical simulations with CST Microwave Studio commercial software (CST, 2009)

0 200 400 600 800 1000

-400 -200 0 200 400 600

of interest, and the resonance approaches the desired center frequency of 5.5 GHz

Directive Ultra-Wideband Planar Antennas 3

omnidirectional radiator: the bow-tie antenna A high front-to-back ratio, low-profile design

will be developed by exploiting a planar reflector and studying ad-hoc optimizations of both

the antenna geometry and the feeding arrangement The final layout could be particularly

well-suited for point-to-point high data-rate UWB radio links around the 5.5 GHz center

frequency

In section 3, a different approach will be adopted: instead of backing an omnidirectional

printed wideband dipole, a structured ground plane will be employed with a two-element

array of disc monopoles The resulting highly directive UWB antenna is designed to be used

in combination with a single-chip radar transceiver operating between 6 and 8 GHz

(Cacciatori et al., 2007)

The reader will find a detailed step-by-step design procedure, along with experimental data

obtained through characterization of several prototypes in anechoic chamber

2 An UWB Bow-Tie Antenna with High Front-to-Back Ratio

2.1 Design Principles

As previously said in the introduction of this chapter, in the UWB communication

framework there are scenarios in which directivity is mandatory, for example when the

antenna has to be located in the corner of a room or against a wall to provide a sectoral radio

coverage from the transmitter (i.e an access point) to the receiver (i.e a set-top box)

Moreover, small dimensions and low-profile are desirable features for an easier integration

in the final device For all these reasons the RF engineer may start the antenna design with

the choice of the candidate wideband radiator along with its initial geometrical parameters

As directionality can be effectively achieved through the use of a planar reflector, the

wide-band, planar radiating element can be natively omnidirectional, such as the bow-tie antenna

In the following, a design methodology is presented, starting from the technical

specifications summarized in Table 1

flat reflector dimensions 100 x 70 mm2

laminate – reflector distance roughly 5 mm

Table 1 Technical specifications

The well known design guidelines for a bow-tie resonating at 5.5 GHz (Balanis, 2005) would

lead to a total length of 16 mm, a small value that may cause problems when connecting the

antenna to the feed-line whose dimensions are comparable with the radiator itself; this fact

imposes to enlarge the antenna, and thus to force it to operate at a higher order resonance

However, the laminate technical specifications limit the maximum size of the bow-tie As a

consequence, a good trade-off is the antenna layout shown in Fig 1 The latter will in turn

allow to save enough space to arrange the feeding/matching line on the same laminate It is

important to note that an antipodal configuration is preferable since the antenna will be fed

using a 50 Ohm SMA connector

Such an early model, mounted at a given distance above a planar reflector, can be studied and subsequently optimized through numerical simulations with CST Microwave Studio commercial software (CST, 2009)

0 200 400 600 800 1000

-400 -200 0 200 400 600

of interest, and the resonance approaches the desired center frequency of 5.5 GHz

Fig 4 (a) real part and (b) imaginary part of the input impedance versus frequency for

different positions of the feeding point: a = 0 mm (solid line), a = 5 mm (dashed line), a = 6

mm (dashed-dotted line), a= 7 mm (gray line)

The next step in the design procedure is to provide a feasible microstrip transmission line to

drive the signal up to the feeding points A transmission line with 200 Ohm intrinsic

impedance, a value which roughly coincides with the real part of the antenna input

impedance, may be designed by suitably choosing the stripes widths and spacing (see Fig

5(a)) Notice that, as in the case of many other planar transmission lines, the intrinsic

impedance decreases for increasing strip widths This in turn suggests that matching to a

conventional 50 Ohm connector can be obtained by suitably tapering the strip widths

Further refinements of the antenna resonance may be obtained by acting on the bow-tie tips,

i.e where the most intense currents flow For instance, we observed that if we truncate the

tip edges as shown in Fig 5(b), a slight increase of the resonant frequency takes place (see

Fig 6, where the reflection coefficient of the antenna with and without the tips is reported)

If the antenna with truncated tips is chosen, two ways of designing the transmission line

may be envisaged Indeed, the stripes may be bent upward or downward from the feeding

points The latter option (see Fig 7) is preferable, as a longer transmission line will in turn

result in a smoother tapered transition to the 50 Ohm connector

Fig 5 Selected feeding point position and stripes arrangement: (a) with and (b) without bow-tie tips

-40 -35 -30 -25 -20 -15 -10 -5 0

Fig 6 Reflection coefficient of the antenna with off-vertex feeding: solid line refers to design

of Fig 5(a), dashed line refers to design of Fig 5(b) In both cases, the reference impedance was set to 200 Ohm

Bending the stripes downward will also cause the transmission line to run through the tie truncated tips As we will show in section 2.3, if the spacing between the line stripes and

bow-the truncated tips is small enough, two radiating slots (Balanis, 2005) are created This will

provide an additional resonance that may be tuned to further increase the overall antenna bandwidth

2.2 Antenna Layout

Fig 8 shows the final antenna layout The laminate is a 50 x 30 x 1.575 mm3 Rogers RO4003C mounted above a 110 x 90 mm2 rectangular metal reflector (not depicted in the figure for sake of clarity) at a distance of 6 mm

The thickness of the copper is 35 µm everywhere A linear tapering of the feed-line ending with 3 mm width for the top layer and 8 mm width for the bottom layer provides the transition to the 50 Ohm SMA connector

Fig 4 (a) real part and (b) imaginary part of the input impedance versus frequency for

different positions of the feeding point: a = 0 mm (solid line), a = 5 mm (dashed line), a = 6

mm (dashed-dotted line), a= 7 mm (gray line)

The next step in the design procedure is to provide a feasible microstrip transmission line to

drive the signal up to the feeding points A transmission line with 200 Ohm intrinsic

impedance, a value which roughly coincides with the real part of the antenna input

impedance, may be designed by suitably choosing the stripes widths and spacing (see Fig

5(a)) Notice that, as in the case of many other planar transmission lines, the intrinsic

impedance decreases for increasing strip widths This in turn suggests that matching to a

conventional 50 Ohm connector can be obtained by suitably tapering the strip widths

Further refinements of the antenna resonance may be obtained by acting on the bow-tie tips,

i.e where the most intense currents flow For instance, we observed that if we truncate the

tip edges as shown in Fig 5(b), a slight increase of the resonant frequency takes place (see

Fig 6, where the reflection coefficient of the antenna with and without the tips is reported)

If the antenna with truncated tips is chosen, two ways of designing the transmission line

may be envisaged Indeed, the stripes may be bent upward or downward from the feeding

points The latter option (see Fig 7) is preferable, as a longer transmission line will in turn

result in a smoother tapered transition to the 50 Ohm connector

Fig 5 Selected feeding point position and stripes arrangement: (a) with and (b) without bow-tie tips

-40 -35 -30 -25 -20 -15 -10 -5 0

Fig 6 Reflection coefficient of the antenna with off-vertex feeding: solid line refers to design

of Fig 5(a), dashed line refers to design of Fig 5(b) In both cases, the reference impedance was set to 200 Ohm

Bending the stripes downward will also cause the transmission line to run through the tie truncated tips As we will show in section 2.3, if the spacing between the line stripes and

bow-the truncated tips is small enough, two radiating slots (Balanis, 2005) are created This will

provide an additional resonance that may be tuned to further increase the overall antenna bandwidth

2.2 Antenna Layout

Fig 8 shows the final antenna layout The laminate is a 50 x 30 x 1.575 mm3 Rogers RO4003C mounted above a 110 x 90 mm2 rectangular metal reflector (not depicted in the figure for sake of clarity) at a distance of 6 mm

The thickness of the copper is 35 µm everywhere A linear tapering of the feed-line ending with 3 mm width for the top layer and 8 mm width for the bottom layer provides the transition to the 50 Ohm SMA connector