Rectangular patch Antenna

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Thesis of miniaturization of patch antenna using DGS

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  • my husband was searching for VA 21-22 several days ago and came across a website that has a lot of fillable forms . If others are wanting VA 21-22 as well , here's a http://goo.gl/sX6VOP.
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  • Hi sir,iam doing a project in this topic.Your thesis will helpfull to me. please send me a copy of this to my mail.....fetiyang@gmail.com....thank you
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  • Hi Sulaim, please give me the citation details of this thesis (author(s), dept. and university where it has been submitted and year). I will refer to this work in my M. Tech. thesis.
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  • ass. hi sir, my last project about this topic. and i think your thesis will helpfull to me. please send me a copy of this to my mail.
    husnul.khatim@gmail.com

    thanks a lot.
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  • its very useful to me thanks
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Rectangular patch Antenna

  1. 1. CHAPTER 1 INTRODUCTION This chapter consists of a brief introduction to my project including problemstatement, objectives, scope of work and outline of my thesis. This chapter highlightedthe important of the project and the arrangement of this thesis.1.1 INTRODUCTION Antenna is one of the important elements in the RF system for receiving ortransmitting signals from and into the air as medium. Without proper design of theantenna, the signal generated by the RF system will not be transmitted and no signal canbe detected at the receiver. Antenna design is an active field in communication for futuredevelopment. Many types of antenna have been designed to suit with most devices. Oneof the types of antenna is the microstrip patch antenna (MPA). The microstrip antennahas been said to be the most innovative area in the antenna engineering with its lowmaterial cost and easy to fabricate which the process can be made inside universities orresearch institute. The idea of microstrip antenna was first presented in year 1950β€Ÿs but itonly got serious attention in the 1970β€Ÿs [1]. 1
  2. 2. Due to MPA advantages such as low profile and the capability to be fabricated usinglithographic technology, antenna developers and researchers can come out with a noveldesign of antenna which will reduce the cost of its development. Through printed circuittechnology, the antenna can be fabricated in mass volume which contributes to costreduction.MPA are planar antennas used in wireless links and other microwave applications. It usesconductive strips and patches formed on the top surface of a thin dielectric substrateseparating them from a conductive layer on the bottom surface which is the ground forthe antenna. A patch is typically wider than a strip and its shape and dimension areimportant features of the antenna. MPA are probably the most widely used antennastoday due to their advantages such as light weight, low volume, low cost, compatibilit ywith integrated circuits and easy installation on the rigid surface. Furthermore, they canbe easily designed to operate in dual-band, multi-band application, dual or circularpolarization. They are important in many commercial applications [7]. They areextremely compatible for embedded antennas in handheld wireless devices such ascellular phones, pagers etc. These low profile antennas are also useful in aircraft,satellites and missile applications, where size, weight, cost, ease of installation, andaerodynamic profile are strict constraints [8].MPA with inset feed has been studied extensively over the past two decades because ofits advantages. However, length of MPA is comparable to half wavelength with singleresonant frequency with bandwidth around 2%. Moreover, some applications of the MPAin communication systems required smaller antenna size in order to meet theminiaturization requirements. So, significant advances in the design of compact MPAhave been presented over the last years.Many methods are used to reduce the size of MPA like using planar inverted F antennastructure (PIFA) or using substrate with high dielectric constant [9]. Defected GroundStructure (DGS) is one of the methods to reduce the antenna size.DGS is relatively a new area of research and application associated with printed circuitand antennas. The evolution of DGS is from the electron band gap (EBG) structure [10]. 2
  3. 3. The substrate with DGS must be designed so that it becoming metamaterial. The substratewith DGS is considered as metamaterial substrate when both relative permittivity, Ξ΅r andpermeability, Β΅r are negative. The invented metamaterial antenna will have comparable performance and smaller sizeto conventional one. The substrate that I used was RO3003. The metamaterial antennabehaves as if it were much larger than it really is.By designing the antenna with the DGS makes possible to reduce the size for a particularfrequency as compared to the antenna without the DGS. MPA inherently has narrowbandwidth and bandwidth enhancement is usually demanded for practical applications, sofor extending the bandwidth, DGS approaches can also be utilized.1.2 PROBLEM STATEMENT In the microstrip antenna application, one of the problem is to reduce its size whilehaving considerable performance. Moreover, the propagating of surface wave will reducethe efficiency of the antenna. This is due to the increment of the side and back radiation.When this happen, the front lobe or main lobe will decrease which lead to reduction ingain.1.3 OBJECTIVES OF THE PROJECT Conventional antenna follows the right-hand rule which determine howelectromagnetic wave behaves. This antenna radiates at frequency of half wavelength ofthe patch length while metamaterial antenna able to omit this rule. Metamaterial antennaable to radiates while having smaller size of antenna. Moreover, metamaterial offers analternative solution to widen the antenna applications using the left-hand rule. Theunique properties of metamaterial enable the enhancement of the conventional antenna,thus open more opportunities for better antenna design. This project will emphasize onobtaining the metamaterial using DGS with optimized parameters of negative indexbehaviour in which both permittivity and permeability co-exist simultaneously in therequired frequency region. 3
  4. 4. The main objectives of this project are: i) To prove the concept of metamaterial. ii) To reduce the size of rectangular patch antenna by implementing metamaterial as substrate. iii) To compare the performance of DGS and conventional antenna.1.4 SCOPE OF WORK This project focuses on the development of two miniaturized rectangular patchantenna using DGSs that functions at 4.7 GHz and 2.4GHz. The scope of the project willincludes the study of metamaterial having both negative permittivity and permeability.Then, produce the metamaterial substrate by using DGS. The work includes the designingof DGS that will change RO3003 substrate into metamaterial. These substrates are thentested through simulation using NRW method to find the metamaterial functionalfrequency. Then, both conventional and DGS antennas are designed to resonate at theobtained frequency. The parameter of conventional rectangular patch antenna is based onformula [11] and [12] while DGS patch antennas size are tuned to work at the desirefrequency. All simulation for conventional and DGS antennas had been done in CSTMWS. Thus, the size and performance of conventional and DGS antenna are compared.Fabrication was made to verify the simulation results.1.5 ORGANIZATION OF THE THESISThis thesis consists of six chapters and the overview of all the chapters are as follows:Chapter 1: This chapter provides a brief introduction on the background, the objectives ofthe project and scope of work involved in accomplishing the project. 4
  5. 5. Chapter 2: Literature review of fundamental of antenna properties, equation ofconventional rectangular patch antenna, metamaterial and defected ground structure(DGS) are described in this chapter. This chapter focuses on fundamentals and theories ofmetamaterial and how itβ€Ÿs able to reduce antenna size.Chapter 3: This chapter gives an overview of the antenna design methodology,simulation, fabrication and testing (measurement) procedures.Chapter 4: This chapter describes the simulation and measurement results obtained fromthis project, including description and discussion.Chapter 5: A final conclusion is made in chapter 5 based on the outcome of the project,followed by the recommendations for the future work.1.6 SUMMARY Understanding of metamaterial is the most important topic in this project to developminiaturized antenna. By obtaining metamaterial substrate will introduce β€žleft handedβ€Ÿregion. The size reduction is due to the antenna radiates or resonates at lower frequency.Moreover, conventional antenna radiates at frequency of half wavelength of patch lengthwhile metamaterial antenna omit this rule. The metamaterial substrates are realized usingDGS. DGS is used to alter the electrical properties of RO3003 so that both permittivityand permeability becoming negative. 5
  6. 6. CHAPTER 2 LITERATURE REVIEW This chapter consists of explanation to antenna fundamentals, microstrip patchantenna (MPA), metamaterial, negative refractive index and defected ground structure(DGS).2.1 INTRODUCTION Antenna is a device used for radiating and receiving an electromagnetic wave infree space [13]. The antenna works as an interface between transmission lines and freespace. Antenna is designed for certain frequency band. Beyond the operating band, theantenna rejects the signal. Therefore, we might look at the antenna as a band pass filterand a transducer. There are many different types of antennas.The isotropic point source radiator is one of the basic theoretical antenna which isconsidered as a radiation reference for other antennas. In reality such antenna cannotexist. The isotropic point source radiator radiates equally in all direction in free space.Antennasβ€Ÿ gains are measured with reference to an isotropic radiator and are rated indecibels with respect to an isotropic radiator (dBi). Antennas can be categorized into 9types which are [7]: 6
  7. 7. i. Active integrated antennas ii. Antenna arrays (including smart antennas) iii. Dielectric antennas (such as dielectric resonant antennas) iv. Microstrip antennas (such as patches) v. Lens antennas (sphere) vi. Wire antennas (such as dipoles and loops) vii. Aperture antennas (such as pyramidal horns) viii. Reflector antennas (such as parabolic dish antennas) ix. Leaky wave antennas2.2 ANTENNA PROPERTIES This part describes the performance of antenna, definitions of its various parameters.Some of the parameters are interrelated and not at all of them need to be specified forcomplete description of the antenna performance. 2.2.1 Polarization Polarization is the direction of wave transmitted (radiated) by the antenna. It is aproperty of an electromagnetic wave describing the time varying direction and relativemagnitude of the electric field vector. Polarization may be classified as linear, circular, orelliptical as shown in Figure 2.1. Polarization shows the orientation of the electric fieldvector component of the electromagnetic field. In line-of-sight communications it isimportant that transmitting and receiving antennas have the same polarization (horizontal,vertical or circular). In non-line-of-sight the received signal undergoes multiplereflections which change the wave polarization randomly. 7
  8. 8. Linear Elliptical Circular E = electrical field vector Figure 2.1: Types of antenna polarization [2] 2.2.2 Radiation pattern An antenna radiation pattern is defined as a mathematical function or a graphicalrepresentation of the radiation properties of the antenna as a function of spacecoordinates. In most cases, the radiation pattern is determined in the far-field region andis represented as a function of the directional coordinates. Radiation properties includepower flux density, radiation intensity, field strength, directivity phase or polarization.Radiation pattern provides information which describes how an antenna directs theenergy it radiates and it is determined in the far field region. The information can bepresented in the form of a polar plot for both horizontal (azimuth) and vertical as figure2.2. 8
  9. 9. Figure 2.2: Polar radiation pattern [3] Figure 2.3 shows radiation pattern in 3D. The radiation pattern could be divided into:i. Main lobes This is the radiation lobe containing the direction of maximum radiation.ii. Side lobes These are the minor lobes adjacent to the main lobe and are separated by various nulls. Side lobes are generally the largest among the minor lobes.iii. Back Lobes This is the minor lobe diametrically opposite the main lobe. 9
  10. 10. First null beamwidth Major lobe Half power beamwidth (HPBW) Minor lobes Side lobe Back lobe Minor lobes Figure: 2.3 Radiation pattern [3]. 2.2.3 Half Power Beam width (HPBW)The half power beam width is defined as the angle between the two directions in whichthe radiation intensity is one half the maximum value of the beam. The term beam widthdescribe the 3dB beam width as shown in Figure 2.4.The beam width of the antenna is a very important figure-of-merit, and it often used to asa trade off between it and the side lobe level. By controlling the width of the beam, thegain of antenna can be increased or decreased. By narrowing the beam width, the gainwill increase and it is also creating sectors at the same time [14]. 10
  11. 11. Figure 2.4: Rectangular plot of radiation pattern [2]. 2.2.4 Antenna Gain Antenna gain is a measure of directivity properties and the efficiency of the antenna.It is defined as the ratio of the radiation intensity in the peak intensity direction to theintensity that would be obtained if the power accepted by the antenna were radiatedisotropically. The gain is similar to directivity except the efficiency is taken into account.Antenna gain is measured in dBi. The gain of the antenna can be described as how far thesignal can travel through the distance. When the antenna has a higher gain it does notincrease the power but the shape of the radiation field will lengthen the distance of thepropagated wave. The higher the gain, the farther the wave will travel concentrating itsoutput wave more tightly [15]. The gain of an antenna will equal to its directivity if theantenna is 100% efficient. Normally there are two types of reference antenna can be usedto determine the antenna gain. Firstly is the isotropic antenna where the gain is given indBi and secondly is the half wave dipole antenna given in dBd. I will be using only dBias a reference. 11
  12. 12. 2.2.5 Voltage Standing Wave Ratio (VSWR) Voltage Standing Wave Ratio is the ratio of the maximum to minimum voltage on theantenna feeding line. Standing wave happen when the matching is not perfect which thepower put into antenna is reflected back and not radiated. For perfectly impedancematched antenna the VSWR is 1:1. VWSR causes return loss or loss of forward energythrough a system. 2.2.6 Bandwidth The bandwidth of an antenna means the range of frequencies that the antenna canoperate. The bandwidth of an antenna is defined as the range of frequencies within whichthe performance of the antenna, with respect to some characteristics, conforms to aspecified standard [16]. In other words, there is no unique characterization of thebandwidth and the specifications are set to meet the needs of each particular application.There are different definitions for antenna bandwidth standard. I considered thebandwidth at -10 dB at the lower and upper centre frequency from the return loss versusfrequency graph as shown in figure 2.5. Figure 2.5: Graph return loss versus frequency [4]Return loss is a measure of reflection from an antenna. 0 dB means that all the power isreflected; hence the matching is not good. -10dB means that 10% of incident power isreflected; meaning 90% of the power is accepted by the antenna. So, having -10dB as abandwidth reference is an assumption that 10% of the energy loss. 12
  13. 13. Referring to figure 2.5, the value of bandwidth can be calculated in the form ofpercentage as formula (1) below: 𝑓2 βˆ’π‘“1 π΅π‘Žπ‘›π‘‘π‘€π‘–π‘‘π‘‘π‘• = π‘₯ 100% (1) 𝑓2 +𝑓12.3 MICROSTRIP ANTENNA 2.3.1 Overview of Microstrip Antenna A microstrip antenna consists of conducting patch and a ground plane separated bydielectric substrate. This concept was undeveloped until the revolution in electroniccircuit miniaturization and large-scale integration in 1970. The early work of Munson onmicrostrip antennas for use as a low profile flush mounted antennas on rockets andmissiles showed that this was a practical concept for use in many antenna systemproblems. Various mathematical models were developed for this antenna and itsapplications were extended to many other fields. The number of papers, articles publishedin the journals for the last ten years. The microstrip antennas are the present day antennadesignerβ€Ÿs choice. Low dielectric constant substrates are generally preferred formaximum radiation. The conducting patch can take any shape but rectangular andcircular configurations are the most commonly used configuration. A microstrip antennais characterized by its length, width, input impedance, gain and radiation patterns.Various parameters, related calculation and feeding technique will be discussed furtherthrough this chapter. The length of the antenna is about half wavelength of its operationalfrequency. The length of the patch is very critical and important that result to thefrequency radiated. 2.3.2 Surface wave effect The surface wave gives effect of reduction to the amplitude of the input signalbefore propagate through the air. Additionally, surface waves also introduce spuriouscoupling between different circuit or antenna elements. This effect severely degrades theperformance of microstrip filters because the parasitic interaction reduces the isolation inthe stop bands. Surface waves reaching the outer boundaries of an open microstripstructure are reflected and diffracted by the edges. The diffracted waves provide an 13
  14. 14. additional contribution to radiation which degrading the antenna pattern by raising theside lobe and the cross polarization levels. Surface wave effects are mostly negative, forcircuits and for antennas, so their excitation should be suppressed if possible. 2.3.3 Microstrip lineMicrostrip line is a conductor of width W printed on a thin grounded dielectric substrateof thickness h and relative permittivity, πœ€ π‘Ÿ . Microstrip line is used as a feeding techniquefor inset feed. Moreover, the electrical properties which are the permittivity andpermeability can also be achieve using this method. The diagram of the microstrip line isshown in figure 2.6. Figure 2.6: Microstrip line with width W and thickness h.The effective dielectric constant of a microstrip line is given by [9] as equation (2): πœ€ π‘Ÿ +1 πœ€ π‘Ÿ βˆ’1 12𝑕 βˆ’1 πœ€ 𝑒𝑓𝑓 = + (1 + )2 (2) 2 2 π‘ŠThe value of characteristic impedance used mostly 50Ω and 75 Ω. The value that I amusing is 50 Ω transmission line. 14
  15. 15. The characteristic impedance, Zo can be calculated as: 60 8𝑕 𝑀 𝑀 ln + π‘“π‘œπ‘Ÿ ≀1 πœ€ 𝑒𝑓𝑓 𝑀 4𝑕 𝑕 π‘π‘œ = (3) 120 πœ‹ 𝑀 𝑀 𝑀 [ + 1.393 + 0.667 ln + 1.444 ] π‘“π‘œπ‘Ÿ β‰₯1 πœ€ 𝑒𝑓𝑓 𝑕 𝑕 𝑕 2.3.4 Rectangular patch antenna design The figure 2.7 shows the microstrip diagram of rectangular shape of microstrip patchantenna and the equivalent circuit. The arrows show how the wave flows through thepatch and the ground plane [11]. Figure 2.7: Microstrip diagram and equivalent circuit [4].The conventional patch antenna equations were taken from [11] and [12]. The equationto realize the conventional rectangular patch antennas are shown as below: βˆ’1 𝑐 πœ€ π‘Ÿ +1 2 π‘Š= (4) 2𝑓 π‘Ÿ 2Where W is the patch antenna width, π‘“π‘Ÿ is the operational frequency and Ξ΅r is the substratepermittivity. 15
  16. 16. Another point to note is that the EM fields are not contained entirely within themicrostrip patch but propagate outside of the patch as well. This phenomena result tofringing effect. Two parallel plates of microstrip and ground will form a capacitor; theelectric field does not end abruptly at the edge of the plates. There is some field outsidethat plates that curves from one to the other. This causes the real capacitance to be largerthan what I calculate using the ideal formula. Thus I will have larger capacitancecompare to ideal equation. While considering the fringing effect the effective length andthe effective permittivity will change. Figure 2.8 shows that EM field are not containedentirely within the microstrip patch. Figure 2.8: EM fields around the microstrip line [5]. c L= βˆ’ 2βˆ†l (5) 2f r Ξ΅effWhere L is the patch antenna length and c is speed of EM wave in vacuum which equal to3x108m/s. 𝑀 πœ€ 𝑒𝑓𝑓 +0.3 𝑕 +0.264 βˆ†π‘™ = 0.412𝑕 𝑀 (6) πœ€ 𝑒𝑓𝑓 βˆ’0.258 +0.8 𝑕The substrate length and width dimensions are calculated as equation (7) and (8): 16
  17. 17. π‘Šπ‘  = π‘Š + 6𝑕 (7) 𝐿 𝑠 = 𝐿 + 6𝑕 (8)Where Ws is the substrate width and Ls is the substrate length 2.3.5 Feeding Techniques Antenna feeding technique can generally divide into two categories which arecontacting and non-contacting. The four most popular feed techniques used in patchantenna are the microstrip line, coaxial probe (both contacting schemes), aperturecoupling and proximity coupling (both non-contacting). 2.3.5.1 Microstrip Line Feed Microstrip line feed is a feeding method where a conducting strip is connected tothe patch directly from the edge as shown in figure 2.9. The microstrip line is etched onthe same substrate surface which gives advantage of having planar structure. The methodis easy to fabricate because it only need a single layer substrate and no hole. Microstrip feed Patch Substrate Ground plane Figure 2.9: Microstrip line feed [5]. 17
  18. 18. Another point to note is that microstrip line feed need an inset cut in the patch. Thepurpose of the inset cut in the patch is to match the impedance of the feed line to thepatch without the need for any additional matching element. This is achieved by properlycontrolling the inset position. Hence this is an easy feeding scheme, since it provides easeof fabrication and simplicity in modelling as well as impedance matching.This feeding method will be used in my antenna design. The simplified calculation forthe length of the inset cut shown by equation (9): (9)where:l = the inset cut lengthΞ΅r = Permittivity of the dielectricL = Length of the microstrip patch 2.3.5.2 Coaxial feed The Coaxial feed is a very common technique used for feeding Microstrip patchantennas. As seen from Figure 2.10, the inner conductor of the coaxial connector extendsthrough the dielectric and is soldered to the radiating patch, while the outer conductor isconnected to the ground plane. 18
  19. 19. Substrate Patch (a) Substrate Coaxial Ground plane connector (b)Figure 2.10 Rectangular patch antenna structure with coaxial feed: (a) Top view (b) side view [5].The benefit of this feeding method is that the connector can be put at any location withinthe patch to match the impedance. Moreover, this feed method is easy to fabricate andhas low spurious radiation. However, there is some disadvantage. When dealing withthicker substrate the inductance increase could effect to the matching problem. 19
  20. 20. 2.3.5.3 Aperture Coupled Feed Patch Aperture slot Microstrip line Substrate 1 Ground plane Substrate 2 Figure 2.11: Diagram of aperture coupled feed [5]. The coupling aperture is usually centred under the patch, leading to lower cross-polarization due to symmetry of the configuration. The amount of coupling from thefeed line to the patch is determined by the shape, size and location of the aperture. Sincethe ground plane separates the patch and the feed line, spurious radiation is minimized.Generally, a high dielectric material is used for bottom substrate and a thick, lowdielectric constant material is used for the top substrate to optimize radiation from thepatch [18]. The major disadvantage of this feeding technique is that it is difficult tofabricate due to multiple layers, which also increases the antenna thickness. This feedingscheme also provides narrow bandwidth. 2.3.4.3 Proximity Coupled FeedThis type of feed technique is more less the same as aperture couple feed except that themicrostrip line is optimized to get the best matching. The main advantage of this feedtechnique is that it eliminates spurious feed radiation and provides high bandwidth [18].Matching can be achieved by controlling the length of the feed line and the width-to-lineratio of the patch. The main disadvantage of this method is using double layer substrateand needs proper alignment which is tedious in fabrication process. 20
  21. 21. Patch Microstrip line Substrate 1 Substrate 2 Figure 2.12: Proximity Coupled feed [5]2.4 METAMATERIAL 2.4.1 Metamaterial theory Metamaterial define as artificial effective electromagnetic structures with unusualproperties not readily found in nature. However, β€žunusualβ€Ÿ is generally meant to implymaterial properties which have been hardly explored before the turn of 20 th century, inparticular negative refractive index [19].Metamaterial is a material having negative relative permittivity and permeability. Thesetwo properties determine how a material will interact with electromagnetic radiation.When both permittivity and permeability are simultaneously negative, itβ€Ÿs then having anegative refractive index (NRI) or left-handed material (LHM). This relationship isshown by the following Maxwellβ€Ÿs equation for refractive index: 𝑛 = Β± πœ‡πœ€ (8)Maxwellβ€Ÿs equation tells us how the electromagnetic wave behaves which contain bothelectric and magnetic field. Figure 2.13 shows the electric and magnetic field whichpropagates in perpendicular to each other. The field directions in a plane wave also form 21
  22. 22. right angles with respect to their direction of travel (the propagation direction). When anelectromagnetic wave enters in a material, the fields of the wave interact with theelectrons and other charges of the atoms and molecules that compose the material,causing them to move about. For example, this interaction alters the motion of the wave-changing its speed or wavelength. Electric field Electric field Propagation direction Magnetic field Figure 2.13: Electromagnetic wave [6]Knowing that the permittivity and permeability are the only material properties thatrelevant in changing the wave behaviour, thus changing or tuning this value gives higherdegree of freedom in designing an antenna.Another point to notes is that only when both permittivity and permeability are positiveand negative is useful in antenna design as shown is figure 2.14. Single negative regionwhich is region II and IV impede the signal. Region I is where the permittivity andpermeability are both positive. This region is most explored. This is where most ofmaterial behaves. However, region III is less explored. This is where the matamaterialexist. Materials that exist and behave in this region are not readily available in nature. Atthe intersection (point A) it is the zero refractive index (n) diagrams. 22
  23. 23. Figure 2.14: Permittivity-permeability(Ξ΅-ΞΌ) diagram which shows the material classifications [14]. 2.4.2 Behaviour of wave An electromagnetic wave can be depicted as a sinusoidal varying function that travelsto the right or to the left as a function of time. Figure 2.15 shows that the wave travelsinto the material having positive refractive index from n1 to n2. The speed of the wavedecreases as the refractive index of the mataterial increase. S O U R C E n1 n2>n1 Figure 2.15: Wave incidents on a positive index material [6]. 23
  24. 24. When the refractive index is negative, the speed of the wave, given by c/n is negative andthe wave travels backwards toward the source as shown in Figure 2.16. Therefore, inleft-handed metamaterial, wave propagates in the opposite direction to the energy flows. S O U R C E n1 n2>-n1 Figure 2.16: Wave incidents on a negative index material [6]. 2.4.3 Refraction and Snells Law One of the most important fundamental theories that govern the optical effect orbending of light between two material is the refraction. Refraction is a basic theorybehind lenses and other optical element that focus, changing direction and manipulateslight. The principle and theory applicable for other wave as well such as RF signal.Highly sophisticated and complex optical devices are developed by carefully shapingmaterials so that light is refracted in desired ways. Every material, including air, has anindex-of-refraction (or refractive index). When an electromagnetic wave travels from amaterial with refractive index n1 to another material with refractive index n2 the change inits trajectory can be determined from the ratio of refractive indices n2/n1 by the use ofSnells Law shown in equation (9). 𝑛1 sin πœƒ1 = 𝑛2 π‘ π‘–π‘›πœƒ2 (9)The Snellβ€Ÿs law is also applicable for left-handed material with the same refraction anglewith respect to normal line except in different direction as shown in figure 2.17. These 24
  25. 25. figures show how travelling waves from free space entering right-handed (havingpositive-index of refraction) and left-handed (having negative-index of refraction)material. Positive-index material Negative-index material Figure 2.17: Incident wave travelling through positive-index and negative-index material.In addition, figure 2.18 and 2.19 show how the spreading patterns of the waves onentering and exiting the conventional and LHM material respectively. For conventionalmaterial, the refracted waves are spreading away after entering and exiting the medium.For LHM, the waves are refracted in such a way as to produce a focus inside the materialand then another just outside. The radiation pattern is more a beamlike, which leads tothe creation of highly directional antennas and also may allow more antennas to be placedin closely packed space. 25
  26. 26. Vacuum Conventional material Figure 2.18: Refracted rays in conventional material [6].Vacuum Conventional material Figure 2.19: Refracted rays in Left-handed material [6]. 26
  27. 27. 2.4.4 Metamaterial structures There are four basic structures that had been discussed in literatures to realizemetamaterial substrates as in figure 2.20. Combining the electric dipole and magneticdipole structure can result to metamaterial substrate. The summary of the different elements used for metamaterial synthesis shows infigure 2.20. Each one of the element can be considered as either electric or magneticdipole. Split-ring resonators (SRRs) and slot lines can be considered as magnetic dipolewhile metal wire lines and complementary split-ring resonator (CSRRs) are regarded aselectric dipole. (a) (b) (c) (d)Figure 2.20: Structure used for metamaterial synthesis (a) SRRs , (b) metal wire lines, (c) CSRRs, (d) slot linesMetamaterial substrates are synthesized by combining electric and magnetic dipoleelements. These structures are able to realize metamaterial if properly aligned.Specifically, there are four combination methods as listed below [19]: β€’ SRR and Wire dipole: This is the widely used combination structure. 27
  28. 28. β€’ SRR and CSRR: This structure does no gain much popularity because the arrangement is difficult. β€’ Slot dipole and wire dipole: The mushroom as figure 2.21a structures falls in this category. β€’ Slot dipole and CSRR: The structure as shown in figure 2.21b. This structure had been used for wideband filter applications (a) (b) Figure 2.21: Metamaterial structure (a) Mushroom structure, (b) Planar CRLH structure 2.4.5 Nicholson Ross Weir (NRW)NRW is a tool or method converting scattering parameter from the simulation ormeasurement into electrical properties which are permittivity, Ξ΅r and permeability, Β΅r.In the NRW algorithm, the reflection coefficient is Ξ“ = πœ’ Β± Ο‡2 βˆ’ 1 (10)Where, 2 2 𝑠11 βˆ’π‘ 21 +1 πœ’= (11) 2𝑠11 28
  29. 29. As a step to acquire the correct root, X is must be in the form of S-parameter, themagnitude of the reflection coefficient, must be less than one. The following stage is tocalculate the transmission coefficient of the metamaterial. S 11 +S 21 βˆ’Ξ“ Ξ€= (12) 1βˆ’(S 11 +S 21 )Ξ“ 1 1 ln = ln + 𝑗(πœƒ 𝑇 + 2πœ‹π‘›) (13) 𝑇 𝑇Where 𝐿 𝑛= (14) πœ†π‘”Where𝑛 = π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘Ÿπ‘œπ‘œπ‘‘πΏ = π‘šπ‘Žπ‘‘π‘’π‘Ÿπ‘–π‘Žπ‘™ 𝑙𝑒𝑛𝑔𝑑𝑕 𝑖𝑛 π‘π‘šπœ† 𝑔 = π‘€π‘Žπ‘£π‘’π‘™π‘’π‘›π‘”π‘‘π‘• 𝑖𝑛 π‘π‘šπœƒ 𝑇 = π‘π‘•π‘Žπ‘ π‘’ π‘œπ‘“ π‘‘π‘Ÿπ‘Žπ‘›π‘ π‘šπ‘–π‘ π‘–π‘œπ‘› π‘π‘œπ‘’π‘“π‘“π‘–π‘π‘–π‘’π‘›π‘‘ 𝑖𝑛 π‘Ÿπ‘Žπ‘‘π‘–π‘Žπ‘›we define: 1 1 1 2 =- [ ln⁑ )]2 ( (15) Ξ› 2πœ‹πΏ Ξ€Then we can solve for the permeability using 1+Ξ“ πœ‡π‘Ÿ = 1 1 (16) (1βˆ’Ξ“)Ξ› βˆ’ πœ†2 πœ†2 0 𝑐Where πœ†0 is the free space wavelength and πœ† 𝑐 is the cutoff wavelength. The permittivity is given by πœ†2 1 1 1 πœ€π‘Ÿ = 0 [ πœ† 2 βˆ’ [2πœ‹πΏ ln ]2 ] (17) πœ‡π‘Ÿ 𝑐 Ξ€ 29
  30. 30. 2.5 RELATION BETWEEN DGS, EBG AND METAMATERIALThe concept of DGS arises from the studies of Photonic Band Gap (PBG) structure whichdealing with manipulating light wave. PBG is known as Electron Band Gap (EBG) inelectromagnetic application. They are actually artificial periodic structures that can givemetamaterial behavior. These structures would have periodic arrangement of metallic, π‘›πœ† 𝑔dielectric or metalodielectric bodies with a lattice period 𝑝 = , Ξ» being the guide 2wavelength. In 1999, a group of researchers further simplified the geometry anddiscarded the periodic nature of pattern. They simply use a unit cell of dumbbell shape tothe same response as EBG which known as β€žDefected Ground Structureβ€Ÿ (DGS).Therefore, a DGS is regarded as a simplified variant of EBG on a ground plane [23].Thus DGS can be described as a unit cell EBG or an EBG with limited number of cells.The DGS slots are resonant in nature. The presence of DGS can realize metamaterialsubstrate.Figure 2.23 shows different geometries that have been explored with the aim of achievingimproved performance in term of stopband and passbands, compactness, and ease ofdesign [23]. 30
  31. 31. (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l) (n) (o) (p) (q) (r) (s) (t)Figure 2.23 : Different DGS geometries : (a) dumbbell-shape (b) Spiral-shaped (c) H-shaped (d) U-shaped (e) arrow head dumbbell (f) concentric ring shaped (g) split-ring resonators (h)interdigital (i) cross-shaped (j) circular head dumbbell (k) square heads connected with U slots (l)open loop dumbbell (m) fractal (n)half-circle (o) V-shaped (q) meander lines (r) U-head dumbbell (s) double equilateral U (t) square slots connected with narrow slot at edge.DGS has been widely used in the development of miniaturized antennas. In, our design,DGS is a defect etched in the ground plane that can give metamaterial behavior inreducing the antenna size. DGS is basically used in microstrip antenna design fordifferent applications such as antenna size reduction, cross polarization reduction, mutualcoupling reduction in antenna arrays, harmonic suppression etc. DGS are widely used inmicrowave devices to make the system compact and effective [21]. 31
  32. 32. CHAPTER 3 METHODOLOGY3.1 METHODOLOGY OVERVIEW This chapter consists of the design methodology used for this project whichincludes the description on the selected DGS structures, conventional and DGS antennasimulation and fabrication process. The methodology of this project starts byunderstanding of the microstrip antenna technology. This includes the properties study ofthe antenna such as operating frequency, radiation pattern, and antenna gain. The relatedliterature reviews are carried out from reference books and IEEE publish paper. Thesimulation has been done by using Computer Simulation Technology Microwave Studio(CST MWS). To meet the theoretical expectation, the design is being optimizedaccordingly. The methodology described here is illustrated in Figure 3.1. The simulationsperformed also have limitation. The fabrication process is started after the optimizationresult from the simulation. 32
  33. 33. 3.2 FLOW CHART OF DESIGN METHODOLOGY The implementation of this project includes two main parts which are softwaredesign and hardware design. The approaches of the project design are represented in theflow chart in figure 1. The software simulation includes the designing of conventionalantennas and DGS metamaterial antennas. CST Microwave Studio software is used forantenna simulation. The designing of DGS antennas are implemented by finding themetamaterial response of the substrate having both permittivity, Ξ΅r and permeability, Β΅rnegative. The bottom copper of Rogers3003 must critically shape for these purposes. Start Design possible metamaterial structure NO CST simulation Metamaterial structure used Optimize antennas design Antenna fabricate Measurement Data analysis End Figure 3.1: Flow chart of antenna design. 33
  34. 34. 3.3 DGS STRUCTURES Before designing the antenna with DGS substrate, two DGS structures weredesigned first. The target parameter is for the substrate to behave as metamaterial at 4.75GHz and 2.45 GHz. The characteristics parameters of the substrate are described in theTable 3.1. RO3003 has good permittivity accuracy with deviations of only 0.04 mm. Thesubstrate thickness is 0.5 mm. The loss tangent is a parameter of a dielectric material thatquantifies its inherent dissipation of electromagnetic energy. This substrate has lowtangent loss which is 0.0013. Lower tangent loss means lower signal loss. Thus thesubstrate is suitable for antenna design. Table 3.1: Characteristic parameter of substrate (RO3003) Characteristics Values Permittivity, Ξ΅r 3.00 Β± 0.04 Permeability, Β΅r 1.00 Loss tangen, tan 𝛿 0.0013 Thickness, h 0.5 mm Copper cladding, t 0.035 mmThe DGSs are designed to resonate at 2.4 GHz and 4.7 GHz. These structures are designedbased on [4]. Two DGS structures have been designed. The first design (a) is the circularrings and the second design (b) is the split rings. Structure (b) is a modification made from(a) so that the substrate behaves as metamaterial at 2.45 GHz. 34
  35. 35. DGS Copper (a) (b) Figure 3.2: Bottom view of DGS structures: (a) circular rings behave as metamaterial at 4.75 GHz, (b) split rings behave as metamaterial at 2.45 GHz.3.4 INVESTIGATION OF METAMATERIAL SUBSTRATE The designing of DGS antennas are implemented by finding the metamaterialresponse of the substrate having both permittivity, Ξ΅r and permeability, Β΅r negative atdesired frequency. The bottom copper of Rogers 3003 must be critically shaped for thispurpose.The transmission line method is selected for analysis purposes as shown in figure 3.3.The substrate two-port S-parameter was extracted using this technique in simulation. TheNRW method act as a converter to obtain the permittivity, Ξ΅r and permeability,Β΅r of thematerial. The transmission line technique has been introduced by Zijie lu [19]. 50 Ξ© line DGS structure Figure 3.3.Transmission line method [17]. 35
  36. 36. As mention before the value of permittivity and permeability of the substrate can bechanged, influenced by introducing DGS. The location of negative permittivity, Ξ΅r andpermeability, Β΅r were observed base on NRW calculation. Microsoft Excel was used tomake calculation faster. Optimization was done so that the substrate becomesmetamaterial at desired frequency. In figure 3.4 the blue line represents the permittivity, Ξ΅r value and the red linerepresents permeability, Β΅r value. Figure shows that for circular rings structure havingboth permittivity and permeability becoming negative at 4.7 GHz frequency band.Therefore, we can realize that this substrate operate as metamaterial at 4.7 GHz.Moreover, this substrate also operates as metamaterial at higher frequency. As we can seeat 9.6 GHz, both electrical properties are negative. 4.75 GHz Ξ΅r= -154 Β΅r= -0.000818 Figure 3.4: Relative permittivity, Ξ΅r and permeability, Β΅r value versus frequencies for substrate with circular rings DGS 36
  37. 37. In figure 3.5 the blue line represents the permittivity, Ξ΅r value and the red linerepresents permeability, Β΅r value. Figure shows that for circular rings structure havingboth permittivity, Ξ΅r and permeability, Β΅r becoming negative at 2.4 GHz frequency band.Therefore, we can realize that this substrate operate as metamaterial at 2.4 GHz.Moreover, this substrate also operates as metamaterial at higher frequency. As we can seeat 9.6 GHz, both electrical properties are negative. 2.45 GHz Ξ΅r= -132 Β΅r= -0.000461 Figure 3.5: Permittivity, Ξ΅r and permeability, Β΅r value versus frequencies for substrate with slip rings DGS. Final physical parameters of both substrates are shown as in figure 3.6. Thesesubstrate structures had been tuned to get the metamaterial functional at desiredfrequencies. Figure 3.6 shows two rings with inner radii of 5 mm and 6 mm. Both ofrings have 0.5mm width operate with (a) 4.7 GHz and (b) 2.45 GHz. The rings have 1.29mm gap. The slip rings structure is a modification made from double rings so that thesubstrate behaves as metamaterial at 2.45 GHz. The 1.29 mm gap increase the copperarea thus increases the total capacitance value. 37
  38. 38. 17.9 17.5 1.29 20.0 20.0 (a) (b) Figure 3.6: Designed metamaterial substrates dimension (mm) (a) double rings and (b) slip ring physical parameter.3.5 ANTENNA DESIGN This part discusses the process of designing the rectangular patch and DGSantenna. Antenna design process also includes optimization, fabrication and measurementprocess. 3.5.1 Designing rectangular patch antenna The simulation of conventional antenna is designed for the purpose of comparison toDGS one. Two conventional MPA antennas were designed at 4.75 GHz and 2.4 GHzrespectively. The conventional patch antenna equations were taken from [10] and [11] asmention previously in chapter 2. The objectives of the antenna design are described in the Table 3.2. The antennadesign should have the value of return loss less than negative 10dB at the operationalfrequency. The antenna considered to radiate as return loss is less than negative 10dB.Specifically, the return loss should be as low as possible to reduce the matchingimpedance. Moreover, the design antenna should have linear polarization. 38
  39. 39. Table 3.2: Characteristics goals of conventional rectangular patch antenna Frequency of operation 4.7 GHz and 2.4 GHz Return loss (dB) <-10dB Feeding method Microstrip line Polarization Linear Base on simulation each of conventional rectangular patch antennas are able tooperate at 4.75 GHz and 2.4 GHz respectively. The dimension is as shown in figure 3.7aand 3.7b. The simulation template used was β€žAntenna (mobile phone)β€Ÿ which have thefollowing default settings as table 3.3. The setting units of mm and GHz in simulation aredue the ease of simulation. The boundaries of simulation are set to free space for alldirection. These settings are used to calculate the farfield radiation pattern so that theantenna surrounding set as open space. Table 3.3 Settings for CST MWSMeasurement unit length mmMeasurement unit frequency GHzBoundaries Free space 25.6 21.3 3.9 21.3 17.9 6.1 (a) 39
  40. 40. 47.2 43.5 39.0 4.3 35.0 11.0 (b) Figure 3.7 Top view dimensions (mm) of conventional rectangular patch antenna : (a) 4.7 GHz antenna (b) 2.4 GHz antenna The simulation was done from 1GHz to 10 GHz. All the calculation of EM fieldwas done using β€žtransient solverβ€Ÿ with default settings. The optimization was done so thatthe antennas having lowest reflection coefficient at the desired frequency. The length ofthe inset cut were tune to get the result. Figure 3.8a shows return loss of 4.7 GHz conventional patch antenna havingdifferent inset cut length. Changing the length of inset cut will change the impedancevalue. Different values of inset cut length are observed for the purpose of optimization.Having short inset length such 3.0 mm the return loss is negative 5.1 dB and with deeperinset length of 6.5 mm the return loss become negative 16.1 dB. The best inset length is6.1 mm with return loss of negative 28.0 dB. Figure 3.8b shows return loss of 2.4 GHz conventional patch antenna havingdifferent inset cut length. Having inset length of 11.4 mm the return loss become negative18.3 dB. The best inset length is 11 mm with return loss of negative 21.7 dB. Thus it canbe understood that if the inset cut is far from the matching impedance the return loss willincrease. 40
  41. 41. : -5.1 : -5.5 : -0.8 -17.0 : -5.5 : : -5.5 -23.4 : : -5.5 -28.0 : -16.1 (a) : -21.7 : -21.6 : -21.0 : -19.7 : - : -18.3 5.5 (b)Figure 3.8: Result of return loss simulation on variations inset cut length for conventional rectangular patch antenna: (a) 4.7 GHz antenna (b) 2.4 GHz antenna 41
  42. 42. Table 3.4 summarized the physical parameters that change the antennaperformance. By increasing or decreasing the inset cut, patch width or length the designantenna is able to achieve the desired frequency and performance. The correct length of inset feed will have the lowest reflection coefficient. Shorteror longer inset cut will increase the reflection coefficient. Reducing the antenna width will increase the antenna resonance frequency.Increasing the length will reduce the resonance frequency. Excessive reduction orincrement will increase reflection coefficient. Reducing the length will increase the antenna resonance frequency. Increasing thelength will reduce the resonance frequency. Antenna resonates mainly due to antennalength which is half wave length of the operational frequency. Thus the length of patchlength affects the resonance frequency more than the patch width. Table 3.4 Antenna Design OptimizationDesign Parameters CommentInset cut length Need specific length. Longer or shorter increase the reflection coefficient.Antenna Width Reduce width = increase resonance frequency. Increase width = reduce the resonance frequency.Antenna Length Reduce length = increase the antenna resonance frequency. Increase length = reduce the resonance frequency. 42
  43. 43. 3.5.2 Designing rectangular patch antenna with DGS The metamaterial antennas were designed using two DGS substrates that werediscussed before. The two rings structure used to implement metamaterial antenna thatoperates at 4.75 GHz and the slip rings at 2.45 GHz. Figure 3.9 shows diagram of DGSantenna. Rectangular patch RO3003 Substrate Defected ground structure Figure 3.9: 3D view structure DGS antenna.Then, the patch size including the length, width was tuned so that the antenna operates atthe desired frequency. Moreover, the inset cut was also tuned to obtain the best matchingimpedance.3.6 FABRICATION PROCESSThe fabrication process involves 5 steps which are: ο‚· Generate mask on transparency film ο‚· Photo exposure process ο‚· Etching in developer solution ο‚· Etching in Ferric Chloride ο‚· Soldering the probe.Each of the listed process will be explained further below. 43
  44. 44. 3.6.1 Generate mask on transparency film First step is to transfer the antennas top and bottom layer structure into .DXF formatthat is compatible with Auto-Computer Added Drawing (AutoCAD) and print it onto thetransparency film. 3.6.2 Photo exposure process Second step is the Ultraviolet exposure process. It is done to transfer the image of thecircuit pattern with a film in a UV exposure machine onto to the photo resist laminatedboard. 3.6.3 Etching in developer solution The third step is to ensure the pattern will be fully developed, during the developingprocess. The photo resist developer solution was used to wash away the exposed resist.Then the solution was removed by spray wash. In this process, water was added withSodium Hydroxide (NaOH). 3.6.4 Etching in Ferric Chloride Fourth step is the etching in ferric chloride. It will remove the unwanted copper areaand this process was followed by the removal of the solution by water. 3.6.5 Soldering the probe The second process in the fabrication is the soldering process. This process onlycan be done after the etching process has finish. In this process, a port and a solder willbe used. The soldering process actually is to connect the port to the antenna. After that,the feeder will be soldered together with the antenna. 1mm SMA connector was solderedto the microstrip antenna. 44
  45. 45. 3.7 MEASUREMENTS The measurement is done to investigate the performance of the fabricated antenna.The return loss and the radiation pattern are analyzed and investigated. From the returnloss, we also can observe the transmission loss and bandwidth. Then, the measurementwill be compared to the simulation. The return loss was measured using Vector NetworkAnalyzer (VNA). The equipment was calibrated before taking any measurements. One-port scattering parameter for both conventional and DGS antenna were measured. Then,all the measurement data was stored. The radiation patterns were measured in anechoic chamber room. Anechoic chamberare guarded with absorbers located around the walls. The absorbers are used to absorb theunwanted signal to reduce the reflected signal. It can increase the efficiency of themeasurement process. The equipments were divided into two sections. The first sectionconsist of the horn antenna and VNA, the second section consist of a spectrum analyzer,a positioner and a rotator. The first section is the transmitter part and the second section is the receiving part.The antenna under test (AUT) will be placed at the rotator. The positioner will control therotator to rotate the tested antenna from 0 degrees to 360 degrees. The received signal ofthe antenna will be measured by the spectrum analyzer at different angle in the term ofsignal to noise ratio. This measurement is done to see the radiation pattern of the antenna.To use these device, the experience user is needed to guide inexperience user to use thesedevice because it can make hazardous effect by higher frequency and quite expensive. Figure 3.10 shows all the connection of the devices for anechoic chamber. The VNAis connected to reference antenna (horn antenna). The rotator are connected to theantenna under test (AUT). From that the measurement value decision can be madewhether the value is same from the expected requirement. 45
  46. 46. Antenna under test (AUT)Horn antenna Rotator VNA Spectrum analyzer Figure 3.10: Anechoic chamber 46
  47. 47. CHAPTER 4 RESULT AND DISCUSSION4.1 INTRODUCTION In Chapter 3, metamaterial substrate and microstrip patch antenna had beendesigned. The method and procedures in designing metamaterial structure and microstrippatch antenna had been elaborated extensively in chapter 3. This chapter presents theresults and findings of both 4.75 GHz and 2.45 GHz antennas.4.2 4.75 GHZ ANTENNAS This part presents the simulation and measurement of 4.75 GHz antenna. Bothconventional and DGS antenna had been build. This part also consists of comparisonbetween conventional and DGS antenna performance in term of return loss, bandwidthand radiation pattern. 4.2.1 Antenna parameters The simulation result shows that metamaterial antenna can reduce the of rectangularpatch antenna. The antenna with circular rings DGS can reduce the size up to 34.3% asshown in figure 4.1. This antenna operates at 4.75 GHz. 47
  48. 48. 25.6 21.3 19.0 2.9 21.3 3.9 17.9 17.5 13.6 7.1 6.1 20.0 (a) (b)Figure 4.1: Top view dimension of the of 4.7 GHz antennas (a) conventional (b) metamaterial antenna with circular rings DGS. 4.2.2 Simulation: Return loss comparison between conventional and DGS Figure 4.2: Comparison of return loss simulation data of conventional antenna and DGS metamaterial antenna. 48
  49. 49. Figure 4.2 describes the return loss 𝑆11 response of metamaterial microstripantenna compared to return loss 𝑆11 response of conventional antenna. Noticed that therectangular patch antenna with DGS gives better return loss which is -35.6dB comparedto the simulated result of patch antenna without DGS which is just -25.7dB. Theoperating frequency of the DGS antenna is between 4.65 GHz to 4.74 GHz. Thebandwidth of DGS antenna is 96 MHz which is greater than conventional antenna whichis just 50.8 MHz. Notice that DGS antenna increase the bandwidth by 89%. 4.2.3 Simulation: Radiation pattern of 4.75 GHz antennasFigure 4.3 (a) and 4.3 (b) shows the 3D radiation pattern for the conventional antenna andDGS metamaterial antenna at 4.7 GHz. The simulated gain for the DGS metamaterialantenna is 3.5 dBi as for the conventional antenna the simulated gain is 4.41 dBi. Thisshows that DGS antenna have considerable gain as compared to conventional one. Figure 4.3 (c) and (d) show the polar plot for the conventional antenna and DGSmetamaterial antenna. The beam main lobe direction for conventional antenna is 4 degreewith beam width 102.5 degree. The beam main lobe direction for DGS antenna is 5degree with beam width 95.4 degree. (a) (b) 49
  50. 50. Figure 4.3 : 4.7 GHz radiation pattern (a) 3D conventional antenna (b) 3D Antenna with DGS (c) Polar plot Conventional Antenna (d) Polar plot of DGS Antenna.Table 4.1 describes all data obtained from simulation in CST Microwave Studio. Thedirectivity of DGS metamaterial antenna is 4.28 dBi slightly less than directivity ofconventional antenna that has 6.3 dBi of directivity change is due to the introduction ofDGS. Based on the data analyzed, it can be concluded that the performance of both theantenna through simulation more less the same. Table 4.1: Comparison Between 4.7GHz Conventional and DGS Antenna Parameter 4.7GHz 4.7GHz conventional DGS antenna antenna Return loss,dB -25.7 -35.6 Bandwidth, 50.7 97.2 MHz Gain, dBi 4.41 3.5 Directivity, 6.3 4.28 dBi Size, mm2 545.28 358 Total 64.4 83.6 Efficiency, % 50
  51. 51. 4.2.4 Comparison between simulation and measurement Figure 4.4 shows the size comparison between conventional, DGS antenna and 50cent Malaysian coin. These antennas operate at 4.7 GHz. These antennas are connectedwith SMA connector. The smaller antenna is the 4.7 GHz metamaterial antenna. Themetamaterial antenna has a DGS structure at the ground. (a) (b) Figure 4.4:Size comparison of fabricated 4.7 GHz antenna(a) front view (b) bottom viewThe simulation results indicate that the metamaterial structure has an effect to theconventional patch antenna by shifting the frequency regions to different value as well asaffecting the S11 parameters. As far as current simulations performed, it is shown thatthe metamaterial structure will be able to reduce the size of the patch antenna. Figure 4.5 shows comparison between measurement and simulation result of 4.7GHz conventional antenna. The measurement shows negative 15.5 dB return loss whichis higher compared to the simulation with negative 25.7 dB. The fabricated antennaoperates at 4.7 GHz which is in good agreement with simulation. Figure 4.6 shows comparison between measurement and simulation result of 4.7GHz DGS antenna. The measurement result shows negative 15.6 dB return loss which ishigher compared to the simulation with negative 25.7 dB. The fabricated antennaoperates at 4.7 GHz which is in good agreement with simulation. It can be concluded thatthe build antenna has a lower performance compared to simulation. 51
  52. 52. Figure 4.5: Graph simulation and measurement of 4.7 GHz conventional antenna versus frequency.Figure 4.6: Graph simulation and measurement of 4.7 GHz DGS antenna versus frequency. 52
  53. 53. 4.2.5 Comparison of conventional and DGS antenna Figure 4.7 shows the comparison of 4.7 GHz DGS and conventional antenna thatI have fabricated and measured. Figure 4.2 describes the return loss 𝑆11 response ofmetamaterial microstrip antenna compared to return loss 𝑆11 response of conventionalantenna. Notice that the rectangular patch antenna with DGS having comparable returnloss which is -15.6dB. Figure 4.7: Graph comparing between 4.7 GHz conventional and DGS antennas. It can be concluded from the S11 comparison graphs that the resonant frequencyhas shifted in the magnitude from the designed frequency for most of the designs. Theroot cause of the shift is could be due to the patch and substrate dimension that varies infabrication process. 53
  54. 54. 4.2.6 Radiation pattern measurements The antenna radiation patter was measured inside the anechoic chamber. The setupof the experiment in measuring the radiation pattern is described chapter 3. Figure 4.8shows the measured radiation pattern, of the DGS metamaterial antenna and conventionalantenna resonating at 4.7GHz. For the conventional antenna radiation pattern themaximum power received is –45.18 dBm as for the DGS metamaterial antenna decreaseto -44.16 dBm . 0 350 360 2 10 20 340 30 330 0 40 320 -2 50 310 -4 60 300 -6 70 -8 290 80 -10 280 90 dBm conventional -12 270 100 260 110 250 120 240 130 230 140 220 150 210 160 200 190 180 170 (a) 54
  55. 55. 0 350 360 2 10 20 340 30 330 0 40 320 -2 50 310 -4 60 300 -6 70 -8 290 80 -10 280 90 dBm DGS -12 270 100 260 110 250 120 240 130 230 140 220 150 210 160 200 190 180 170 (b) Figure 4.8: Measurement radiation pattern (a) conventional antenna.(b) Antenna with DGS4.3 2.4 GHZ ANTENNAS This part presents the simulation and measurement of 2.4 GHz antenna. Bothconventional and DGS antenna had been build. This part also consists of comparisonbetween conventional and DGS antenna performance in term of return loss, bandwidthand radiation pattern. 4.3.1 Antenna parameters The simulation result shows that metamaterial antenna can reduce the of rectangularpatch antenna. The antenna with slip rings DGS can reduce the size up to 80% as shownin figure 4.9. This antenna operates at 2.4 GHz. 55
  56. 56. 47.2 43.5 39.0 16.0 4.3 35.0 17.5 14.8 11.0 20.0 (a) (b) Figure 4.9: Top view dimension (mm) of the of 2.4 GHz antennas (a) conventional (b) metamaterial antenna with slips rings DGS 4.3.2 Simulation: return loss comparison between conventional and DGSFigure 4.10: Comparison of return loss simulation data of conventional antenna and DGS metamaterial antenna Figure 4.10 describes the return loss 𝑆11 response of metamaterial microstripantenna compared to return loss 𝑆11 response of conventional antenna. Noticed that theDGS antenna return loss is -24 dB compared to the simulated result of patch antennawithout DGS which is just -22 dB. The operating frequency of the DGS antenna is 56
  57. 57. between 2.452 GHz to 2.468 GHz. The bandwidth of DGS antenna is 15 MHz which issmaller than conventional antenna which is 21.6 MHz Notice that 2.4GHz DGS antennahave to compensate bandwidth by 30.56%. 4.3.3 Simulation: Radiation pattern of 2.4 GHz antenna Figure 4.11 (a) and 4.11 (b) show the 3D radiation pattern for the conventionalantenna and DGS metamaterial antenna at 2.4 GHz. The simulated gain for the DGSmetamaterial antenna is 4.48 dBi as for the conventional antenna the simulateddirectivity is 5.96 dBi . Figure 4.11 (c) and (d) show the polar plot for the conventional antenna and DGSmetamaterial antenna. The beam main lobe direction for conventional antenna is 2 degreewith beam width 100.2 degree. The beam main lobe direction for DGS antenna is 5degree with beam width 102.3 degree. (a) (b) 57
  58. 58. (c) (d) Figure 4.11: 2.4 GHz antenna radiation pattern (a) 3D Conventional antenna (b) Antenna with DGS (c) Polar plot Conventional Antenna (d) Polar plot of DGS Antenna. Table 4.2 describes all data obtained from simulation in CST Microwave Studio. Thedirectivity of DGS metamaterial antenna is 4.48 dBi slightly less than directivity ofconventional antenna that has 5.96 dBi of directivity due to the introduction of DGS.Based on the data analyzed, it can be concluded that the performance of both the antennathrough simulation more less the same. Table 4.2: Comparison Between 2.4GHz Conventional and DGS Antenna Parameter 2.4GHz 2.4GHz conventional DGS antenna antenna Return loss -22.2 -24.1 Bandwidth, MHz 22.7 15.2 Gain, dBi 1.88 -10.9 Directivity, dBi 5.96 4.48 Size, mm2 1840.8 350 Total efficiency,% 38.8 2.9 58
  59. 59. 4.2.4 Comparison between simulation and measurement Figure 4.12 shows the size comparison between conventional, DGS antenna and 50cent Malaysian coin. The smaller antenna is the metamaterial antenna. These antennasoperate at 2.4 GHz. These antennas are connected with SMA connector. Figure 4.12: Size comparison of fabricated 2.4 GHz antennaThe simulation results indicate that the metamaterial structure has an effect to theconventional patch antenna by shifting the frequency regions to different value as well asaffecting the S11 parameters. As far as current simulations performed, it is shown thatthe metamaterial structure will be able to reduce the size of the patch antenna. Figure 4.13 shows comparison between measurement and simulation result of2.4 GHz conventional antenna. The measurement shows negative 15.0 dB return losswhich is higher compared to the simulation with negative 22.2 dB. The fabricatedantenna operates at 2.6 GHz. Noticed that the fabricated antenna operates at higherfrequency. Figure 4.14 shows comparison between measurement and simulation result of2.4 GHz DGS antenna. The measurement result shows negative 16.2 dB return losswhich is higher compared to the simulation with negative 24.4 dB. The fabricatedantenna operates at 2.4 GHz which is in good agreement with simulation. It can beconcluded that the build antenna has a lower performance compared to simulation. 59
  60. 60. Figure 4.13: Graph simulation and measurement of 2.4 GHz conventional antenna versus frequency.Figure 4.14: Graph simulation and measurement of 2.4 GHz DGS antenna versus frequency. 60
  61. 61. 4.2.5 Comparison of conventional and DGS antenna Figure 4.15 shows the comparison of 2.4 GHz DGS and conventional antenna thatI have fabricated and measured. Figure 4.15 describes the return loss 𝑆11 response ofmetamaterial microstrip antenna compared to return loss 𝑆11 response of conventionalantenna. Notice that the rectangular patch antenna with DGS having comparable returnloss which is -15.6dB. The DGS antenna operates at lower frequency compared toconventional one. Figure 4.15: Graph comparing between 2.4 GHz conventional and DGS antenna. 4.2.6 Radiation pattern measurements The antenna radiation patter was measured inside the anechoic chamber. The setupof the experiment in measuring the radiation pattern is described chapter 3 Figure 4.16 shows the measured radiation pattern, of the DGS metamaterialantenna and conventional antenna resonating at 4.7GHz. For the conventional antennaradiation pattern the power received is –35.38 dBm as for the DGS metamaterial antennadecrease to -45.43 dBm . 61
  62. 62. 0 350 360 2 10 20 340 30 330 0 40 320 -2 50 310 -4 60 300 -6 70 -8 290 80 -10 280 90 dBm conventional -12 270 100 260 110 250 120 240 130 230 140 220 150 210 160 200 190 180 170 (a) 0 350 360 0 10 20 340 -2 30 330 -4 40 320 -6 50 310 -8 60 -10 300 70 -12 290 -14 80 -16 280 90 dBm DGS -18 270 100 260 110 250 120 240 130 230 140 220 150 210 160 200 190 180 170 (b)Figure 4.16: Measurement of radiation pattern (a) 2.4 GHz conventional antenna (b) 2.4GHz antenna with DGS. 62
  63. 63. 2.4 CONCLUSION Based on the data, the dimension of a microstrip patch antenna operating at 4.7GHz had been successfully reduced up to 34 % of the original dimension while havinglarger bandwidth. Moreover, 2.4 GHz metamaterial antenna is able to reduce the size upto 80% but having poor performance. I noticed that the reflection coefficient reduced andshift in all measurements. This is due to the poor matching which related to theintroduction of SMA connector, soldering and accuracy of etching process. However,overall the measurements values are comparable to the simulation result. 63
  64. 64. CHAPTER 5 CONCLUSION AND FUTURE IMPROVEMENTS5.1 CONCLUSIONS The goals of this project is to design two miniaturized rectangular patch antenna thatoperate at 4.75 GHz and 2.4GHz frequencies using metamaterial substrate. The antennasfabricated expected of having comparable or better performance to the conventional one.The conventional microstrip antenna was designed as a reference with a microstrip line asa feed.The S11 (input return loss) plot for microstrip antennas have a magnitude of much lessthat –10dB at the operating frequency which means that the matching impedance isachieve.It is proved that the microstrip antenna with metamaterial substrate can improves the sizeof the antenna. Moreover, this project proves that DGS can be implemented to alter theelectrical properties.As an overall conclusion, all the planned works and the objectives of this project havebeen successfully implemented and achieved, even though the performance of the 64
  65. 65. antenna designed do not shows a big different after integrated with DGS structures. But,the improvement of the antenna size and bandwidth still can be noticed.5.2 SUGGESTION FOR FUTURE WORKSIn term of DGS structure, the design can be further improve in terms of basic parameterssuch as type of substrate, dielectric constant, the thickness of the substrate. From thisproject , we can design the DGS structure for different frequency of operation. Moreover,investigation into designing the microstrip antenna with different patch shapes and sizesare vital. In term of DGS structure, the design can be further improveThe DGS structure also can be applied in the array antenna. This array antenna can befurther classified according to the different thickness of the substrate and the variousvalue of dielectric constant.In addition the slip rings structure DGS should be further study for filter application. Inthe future different structure of DGS should be design in order to improve theperformance of the microwave devices. 65
  66. 66. REFERENCE[1] Pozar, D.M. Microstrip antennas. Proceedings of the IEEE. Volume 80, Issue 1, Jan. 1992 Page(s):79 – 91.[2] M.I.A. Khaliah, β€œ Electromagnetic Band Gap (EBG) for Microstrip Antenna Design”, Master of Engineering (Electrical –Electronic Telecommunication), Faculty of Electrical Engineering, Universiti Teknologi Malaysia 2007.[3] Ahmed A. Kishk, β€œFundamentals of Antennas”, Center of Electromagnetic System Research (CEDAR), Department of Electrical Engineering, University of Mississippi.[4] R, M. Kamal, β€œ Electromagnetic Band Gap (EBG) Structure in Microwave Device Design”, Jabatan Kejuruteraan Radio, Fakulti Kejuruteraan Elektrik, Universiti Teknologi Malaysia 2008.[5] C.V.V. Reddy, β€œDesign of Linear Polarized Rectanglar Microstrip Patch Antenna Using IEED/PSO”, Department of Electronics and Communication Engineering, National Institute of Technology Rourkela 2009.[6] H, Suria, β€œ Antenna with Metamaterial Design”,Faculty of Electrical Engineering, Universiti Teknologi Malaysia 2007.[7] J. Q. Howell, β€œMicrostrip Antennas,” in Dig. Int. Symp. Antennas Propogat. Soc., Williamsburg, VA, Dec. 1972, pp. 177-180[8] Nashaat, D.; Elsadek, H.A.; Abdallah, E.; Elhenawy, H.; Iskander, M.F.; , "Multiband and miniaturized inset feed microstrip patch antenna using multiple spiral-shaped defect ground structure (DGS)," Antennas and Propagation Society International Symposium, 2009. APSURSI 09. IEEE , vol., no., pp.1-4, 1-5 June 2009[9] Debatosh Guha, β€œMicrostrip and printed antennas, new trends technique and application,” John Wiley & Sons, New York, 2010[10] Matin, M.A. β€œA Design Rule for Inset-fed Rectangular Microstrip Patch Antenna,”. 66
  67. 67. [11] David M. Pozar, "Input impedance and mutual coupling of rectangular microstrip antennas," IEEE Transactions on Antennas & Propagation, Vol. AP-30, November 1982, pp. 1191-1196.[12] IEEE standard definitions of terms for antennas. IEEE Std 145-1993 21 June 1993[13] Balanis, C.A. Antenna Theory: Analysis and Design. 2nd Ed. New York: John Wiley and Sons. 1997.[14] J. Q. Howell, β€œMicrostrip Antennas,” in Dig. Int. Symp. Antennas Propogat. Soc., Williamsburg, VA, Dec. 1972, pp. 177-180[15] C. A. Balanis, β€œAntenna Theory, Analysis and Design,” John Wiley & Sons, New York, 2008[16] James, J. R., and P. S. Hall (Eds), Handbook of Microstrip Antennas, Peter Pereginus, London, UK, 1989.[17] S K Behera, β€œNovel Tuned Rectangular Patch Antenna As a Load for Phase Power Combining” Ph.D Thesis, Jadavpur University, Kolkata.[18] Microstrip and printed antennas, new trends technique and application[19] Zijie Lu, β€œTwo-Port Transmission Line Technique for Dielectric Property Characterization of PolymerElectrolyte Membranes,” J. Phys. Chem. B , 2009[20] J. Garcia, J. Bonache, I. Gil, F. Martin, M. Castillo, and J. Martel, β€œMiniaturized microstrip and CPW filters using coupled metamaterial resonators,” IEEE Trans. Microwave Theory Tech., vol. 54, no. 6, pp. 2628–2635, June 2006.[21] H. S. Rajeshwar Lal Dua, Neha Gambhir, "2.45 GHz Microstrip Patch Antenna with Defected Ground Structure for Bluetooth," International Journal of Soft Computing and Wang, Weijen, β€œ Directive antenna using metamaterial substrates,” Open Educational Resources (OER).[22] K.A. Carver and J.A. Mink, "Microstrip antenna technology," IEEE Transactions on Antennas & Propagation, Vol. 29, January 1981, pp. 2-24.[23] N. F. Salam, "Metamaterial Antenna with Dual Concentric Square Defected Ground " Bachelor of Engineering (Hons). in Electrical, Fakulti Kejuruteraan Elektrik, Universiti Teknologi MARA 2012. 67
  68. 68. [24] H. Pues and A. Van De Capelle, "Accurate transmission line model for the rectangular microstrip antenna," IEEE Proceedings on Microwaves, Optics & Antennas, Vol. 134, 1984, pp. 334βˆ’340.[25] David M. Pozar, "Input impedance and mutual coupling of rectangular microstrip antennas," IEEE Transactions on Antennas & Propagation, Vol. AP-30, November 1982, pp. 1191-1196.[26] Lorena I. Basilio, Michael A.Khayat, Jeffery Williams, and Stuart A. Long, "The Dependence of the Input Impedance on Feed Position of Probe and Microstrip Line βˆ’ Fed patch Antennas," IEEE Transactions on Antennas & Propagation, Vol. 49, January 2001, pp. 45-47.[27] Rahmat-Samii, Y.; , "Metamaterials in Antenna Applications: Classifications, Designs and Applications," Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on , vol., no., pp. 1- 4, March 6-8, 2006 68
  69. 69. APPENDICES ο‚· Roogers 3000 datasheet Series High Frequency Laminated ο‚· GPR antenna Bandwidth 69

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