PROJECT REPORT ON ANTENNA DESIGN, SIMULATION AND FABRICATION
PROJECT REPORTONANTENNA DESIGN, SIMULATION ANDFABRICATIONThis project report is submitted to VNIT in partial fulfillment of therequirements for the degree of“Bachelor of Technology in Electronics and Communication”Under the guidance ofDr. A. S. GandhiSubmitted byPrasanna Ramachandran, T.S.Keshav, Laxmikant MinzVamsikrishna Parupalli and Shaibal ChakravartyDepartment of Electronics and Computer Science EngineeringVisvesvaraya National Institute of Technology(Deemed University)Nagpur – 4400112006-2007
DEPARTMENT OF ELECTRONICS ANDCOMPUTER SCIENCE ENGINEERINGVISVESVARAYA NATIONAL INSTITUTE OFTECHNOLOGY, NAGPURCERTIFICATEThis is to certify that Mr. Prasanna Ramachandran, Mr.T.S.Keshav, Mr. Laxmikant Minz, Mr. VamsikrishnaParupalli and Mr. Shaibal Chakravarty have carried out theirproject work on Antenna Design, Simulation and Fabrication inthe Electronics and Computer Science Department of VNIT,Nagpur during the year 2006-2007. Their work is approved forsubmission in partial fulfillment of the requirements for the degreeof “Bachelor of Technology”.Dr. O. G. KakdeHead of the DepartmentDept. of ECE, VNITDate:Dr. A.S. GandhiProject GuideDept. of ECE, VNIT
ACKNOWLEDGEMENTSWe would like to thank our Project Guide, Dr. A.S. Gandhi, for hiscontinuous support and encouragement. It was he who provided an aim anddirection to this project and constantly pushed us to work harder on it.We would also like to thank the Communication Lab in charge, Mr.Prashant Jaronde for providing us all hardware and software tools requiredfor completing this project. His assistance was invaluable.
ABSTRACTWireless technology is one of the main areas of research in the world ofcommunication systems today and a study of communication systems isincomplete without an understanding of the operation and fabrication ofantennas. This was the main reason for our selecting a project focusing onthis field.The field of antenna study is an extremely vast one, so, to grasp thefundamentals we used a two pronged approach by dividing ourselves intogroups.The first group focused on the fabrication and testing of a slotted waveguideomni directional antenna and a biquad directional antenna.The second group focused on the design and simulation of patch antennas(which are widely used in cell phones today) with an emphasis onoptimization of a 1.9 GHz rectangular probe fed patch antenna. A dual bandantenna and a microstrip fed patch antenna, used in the communication labwere also simulated.
ContentsChapter 1 - Introduction to Antennas11.1 Antenna Parameters11.2 Types of Antennas9Chapter 2 – Hardware Aspects – Fabrication and Testing of13RF Antennas2.1 Introduction132.2 Slotted Waveguide Antenna132.3 Biquad Antenna162.4 Testing of the Antennas20Chapter 3 – Software Aspects – Design and Simulation ofMicrostrip Patch Antennas263.1 Introduction263.2 Applications of Microstrip Patch Antennas283.3 Advantages and Disadvantages of Patch Antennas293.4 Feed Techniques293.5 Methods of Analysis343.6 Simulation Software – IE3D403.7 Design of a Simple Rectangular Patch Antenna41
3.8 Simulation of 1.9 GHz Patch Antenna433.9 Simulation of 5GHz Patch Antenna703.10 Simulation of Dual Band Patch Antennas74Chapter 4 – Conclusions and Scope for Improvement854.1 Conclusions854.2 Scope for Improvement85Appendix A - MATLAB Codes86Appendix B - Data on Equipment used for Antenna Analysis88References92
Chapter 1Introduction to AntennasOur project focuses on the hardware fabrication and software simulation of severalantennas. In order to completely understand the above it is necessary to start off byunderstanding various terms associated with antennas and the various types of antennas.This is what is covered in this introductory chapter.1.1 Antenna parametersAn antenna is an electrical conductor or system of conductorsTransmitter - Radiates electromagnetic energy into spaceReceiver - Collects electromagnetic energy from spaceThe IEEE definition of an antenna as given by Stutzman and Thiele is, “That part of atransmitting or receiving system that is designed to radiate or receive electromagneticwaves”. The major parameters associated with an antenna are defined in the followingsections.1.1.1 Antenna GainGain is a measure of the ability of the antenna to direct the input power into radiation in aparticular direction and is measured at the peak radiation intensity. Consider the powerdensity radiated by an isotropic antenna with input power P0 at a distance R which isgiven by S P0/4πR2. An isotropic antenna radiates equally in all directions, and itsradiated power density S is found by dividing the radiated power by the area of the sphere4πR2. An isotropic radiator is considered to be 100% efficient. The gain of an actualantenna increases the power density in the direction of the peak radiation:Equation 1.1Gain is achieved by directing the radiation away from other parts of the radiation sphere.In general, gain is defined as the gain-biased pattern of the antenna.1
Equation 1.21.1.2 Antenna EfficiencyThe surface integral of the radiation intensity over the radiation sphere divided by theinput power P0 is a measure of the relative power radiated by the antenna, or the antennaefficiency.Equation 1.3where Pr is the radiated power. Material losses in the antenna or reflected power due topoor impedance match reduce the radiated power.1.1.3 Effective AreaAntennas capture power from passing waves and deliver some of it to the terminals.Given the power density of the incident wave and the effective area of the antenna, thepower delivered to the terminals is the product.Equation 1.4For an aperture antenna such as a horn, parabolic reflector, or flat-plate array, effectivearea is physical area multiplied by aperture efficiency. In general, losses due to material,distribution, and mismatch reduce the ratio of the effective area to the physical area.Typical estimated aperture efficiency for a parabolic reflector is 55%. Even antennas withinfinitesimal physical areas, such as dipoles, have effective areas because they removepower from passing waves.1.1.4 DirectivityDirectivity is a measure of the concentration of radiation in the direction of themaximum.Equation 1.5Directivity and gain differ only by the efficiency, but directivity is easily estimated frompatterns. Gain—directivity times efficiency—must be measured. The average radiationintensity can be found from a surface integral over the2
radiation sphere of the radiation intensity divided by 4π, the area of the sphere insteradians:Equation 1.6This is the radiated power divided by the area of a unit sphere. The radiation intensityU(θ,φ) separates into a sum of co- and cross-polarization components:Both co- and cross-polarization directivities can be defined:Equation 1.7Directivity can also be defined for an arbitrary direction D(θ,φ) as radiation intensitydivided by the average radiation intensity, but when the coordinate angles are notspecified, we calculate directivity at Umax.1.1.5 Path LossWe combine the gain of the transmitting antenna with the effective area of the receivingantenna to determine delivered power and path loss. The power density at the receivingantenna is given by equation 1.2 and the received power is given by equation 1.4. Bycombining the two, we obtain the path loss as given below.Equation 1.8Antenna 1 transmits, and antenna 2 receives. If the materials in the antennas are linearand isotropic, the transmitting and receiving patterns are identical . When we considerantenna 2 as the transmitting antenna and antenna 1 as the receiving antenna, the pathloss isEquation 1.9We make quick evaluations of path loss for various units of distance R and for frequencyf in megahertz using the formula3
where KU depends on the length units as shown in table 1.1Table 1.11.1.6 Input ImpedanceThe input impedance of an antenna is defined as “the impedance presented by an antennaat its terminals or the ratio of the voltage to the current at the pair of terminals or the ratioof the appropriate components of the electric to magnetic fields at a point”. Hence theimpedance of the antenna can be written as given below.Equation 1.10where Zin is the antenna impedance at the terminalsRin is the antenna resistance at the terminalsXin is the antenna reactance at the terminalsThe imaginary part, Xin of the input impedance represents the power stored in the nearfield of the antenna. The resistive part, Rin of the input impedance consists of twocomponents, the radiation resistance Rr and the loss resistance RL. The power associatedwith the radiation resistance is the power actually radiated by the antenna, while thepower dissipated in the loss resistance is lost as heat in the antenna itself due to dielectricor conducting losses.4
1.1.7 Antenna FactorThe engineering community uses an antenna connected to a receiver such as a spectrumanalyzer, a network analyzer, or an RF voltmeter to measure field strength E. Most of thetime these devices have a load resistor ZL that matches the antenna impedance.The incident field strength Ei equals antenna factor AF times the received voltage Vrec.We relate this to the antenna effective height:Equation 1.11AF has units meter but is often given as dB(m ). Sometimes, antenna factor is referredto the open-circuit voltage and it would be one-half the value given by equation 1.11. Weassume that the antenna is aligned with the electric field; in other words, the antennapolarization is the electric field component measured: 1 1Equation 1.12This measurement may be corrupted by a poor impedance match to the receiver and anycable loss between the antenna and receiver that reduces the voltage and reduces thecalculated field strength.1.1.8 Return LossIt is a parameter which indicates the amount of power that is “lost” to the load and doesnot return as a reflection. Hence the RL is a parameter to indicate how well the matchingbetween the transmitter and antenna has taken place. Simply put it is the S11 of anantenna. A graph of s11 of an antenna vs frequency is called its return loss curve. Foroptimum working such a graph must show a dip at the operating frequency and have aminimum dB value at this frequency. This parameter was found to be of crucialimportance to our project as we sought to adjust the antenna dimensions for a fixedoperating frequency (say 1.9 GHz). A simple RL curve is shown in figure 1.1.5
Figure 1.1 – RL curve of an antenna1.19 Radiation PatternThe radiation pattern of an antenna is a plot of the far-field radiation properties of anantenna as a function of the spatial co-ordinates which are specified by the elevationangle (θ) and the azimuth angle (φ). More specifically it is a plot of the power radiatedfrom an antenna per unit solid angle which is nothing but the radiation intensity. It can beplotted as a 3D graph or as a 2D polar or Cartesian slice of this 3D graph. It is anextremely parameter as it shows the antenna’s directivity as well as gain at various pointsin space. It serves as the signature of an antenna and one look at it is often enough torealize the antenna that produced it.Because this parameter was so important to our software simulations we needed tounderstand it completely. For this purpose we obtained the 2D polar plots of radiationpatterns for a few antennas in our lab using a ScienTech antenna trainer kit shown infigure 1.2.6
Figure 1.2 – ScienTech Antenna Trainer KitThe transmitter of the kit was rotated through 360 degrees in 20 degree intervals and thereceived power was measured (in µV – converted to dB) by a receiver to plot theradiation patterns of a few antennas. A simple MATLAB code written by us to obtain the2D Polar Plots is given in Appendix A. The main disadvantage of this trainer kit is that itworks only at 750MHz. However, it helped us to visualize the radiation patterns of someantennas shown in the following pages.Figure 1.3 – 2D Polar Plot for a Yagi Antenna7
Figure 1.4 – 2D Polar Plot for a Helical AntennaFigure 1.5 – 2D Polar Plot for a Rhombus Patch AntennaA general 3D radiation pattern is also shown in figure 1.6Figure 1.6 – 3D Radiation Pattern for a rectangular patch8
1.20 BeamwidthBeamwidth of an antenna is easily determined from its 2D radiation pattern and is also avery important parameter. Beamwidth is the angular separation of the half-power pointsof the radiated pattern. The way in which beamwidth is determined is shown in figure1.7.Figure 1.7 – Determination of HPBW from radiation pattern1.2 Types of AntennasAntennas can be classified in several ways. One way is the frequency band of operation.Others include physical structure and electrical/electromagnetic design. Most simple,non-directional antennas are basic dipoles or monopoles. More complex, directionalantennas consist of arrays of elements, such as dipoles, or use one active and severalpassive elements, as in the Yagi antenna. New antenna technologies are being developedthat allow an antenna to rapidly change its pattern in response to changes in direction ofarrival of the received signal. These antennas and the supporting technology are calledadaptive or “smart” antennas and may be used for the higher frequency bands in thefuture. A few commonly used antennas are described in the following sections.1.2.1 Dipoles and MonopolesThe vertical dipole—or its electromagnetic equivalent, the monopole—could beconsidered one of the best antennas for LMR applications. It is omni directional (inazimuth) and, if it is a half-wavelength long, has a gain of 1.64 (or G 2.15 dBi) in thehorizontal plane. A center-fed, vertical dipole is illustrated in figure 1.8 (a). Although thisis a simple antenna, it can be difficult to mount on a mast or vehicle. The ideal verticalmonopole is illustrated in figure 1.8 (b). It is half a dipole placed in half space, with aperfectly conducting, infinite surface at the boundary.9
Figure 1.8 - The vertical dipole and its electromagnetic equivalent, the verticalmonopoleA monopole over an infinite ground plane is theoretically the same (identical gain,pattern, etc., in the half-space above the ground plane) as the dipole in free space. Inpractice, a ground plane cannot be infinite, but a ground plane with a radiusapproximately the same as the length of the active element, is an effective, practicalsolution. The flat surface of a vehicle’s trunk or roof can act as an adequate ground plane.Figure 1.9 shows typical monopole antennas for base-station and mobile applications.Figure 1.9 - Typical monopole antennas for (a) base-station applications and (b)mobile applications1.2.2 Corner ReflectorAn antenna comprised of one or more dipole elements in front of a corner reflector,called the corner-reflector antenna, is illustrated in figure 1.10.10
Figure 1.10 - Corner-reflector antennasThis antenna has moderately high gain, but its most important pattern feature is that theforward (main beam) gain is much higher than the gain in the opposite direction. This iscalled the front-to-back ratio and is evident from its radiation pattern shown in figure1.11.Figure 1.11 - A corner-reflector antenna horizontal-plane pattern1.2.3 Yagi AntennaAnother antenna design that uses passive elements is the Yagi antenna. This antenna,illustrated in figure 1.12, is inexpensive and effective. It can be constructed with one ormore (usually one or two) reflector elements and one or more (usually two or more)director elements. Figure 1.1.3 shows a Yagi antenna with one reflector, a folded-dipoleactive element, and seven directors, mounted for horizontal polarization.11
Figure 1.12 - The Yagi antenna — (a) three elements and (b) multipleelementsFigure 1.13 - A typical Yagi antennaFigure 1.14 is the typical radiation pattern obtained for a three element (one reflector, oneactive element, and one director) Yagi antenna. Generally, the more elements a Yagi has,the higher the gain, and the narrower the beamwidth. This antenna can be mounted tosupport either horizontal or vertical polarization and is often used for point-to-pointapplications, as between a base station and repeater-station sites.Figure 1.14 - A Yagi antenna horizontal plane pattern12
Chapter 2Hardware Aspects - Fabrication and Testing of RFAntennas2.1 IntroductionFor the project we constructed two RF antennas and tested them in our lab.The antennas that we constructed were: 1) Slotted Waveguide Antenna. (Omnidirectional)2) Biquad antenna. (Directional)Working central frequency of these antennas is 2.4GHz. 2.4GHz comes under theunlicensed wireless band usually used in WLAN.2.1.1 Significance of 2.4 GHzSince 1986, FCC rules have provided for unlicensed spread-spectrum operation in the915 MHz (902–928 MHz), 2.4 GHz (2400–2483.5 MHz), and 5.7 GHz (5725–5850MHz) bands. But a vast number of RF devices currently operate in the 2.4 GHz band(like microwave ovens, cordless telephones, medical devices etc.). Recently there hasbeen proliferation of "Wi-Fi" hotspots and wireless computers permitting undeterredinternet access by the public and RF identification (RFID) technology.2.2 Slotted Waveguide Antenna2.2.1 IntroductionSlotted waveguides are resonant antennas and have a relatively narrow operatingfrequency range. A slotted waveguide is a waveguide that is used as an antenna inmicrowave radar applications. Prior to its use in surface search radar, such systems used aparabolic segment reflector.A slotted waveguide has no reflector but emits directly through the slots. The spacing ofthe slots is critical and is a multiple of the wavelength used for transmission andreception. The antenna's vertical focus is usually enhanced by the application of amicrowave lens attached to the front of the antenna. As this, like the companion slottedwaveguide, is a one-dimensional device, it too may be made relatively cheaply ascompared to a parabolic reflector and feed horn. In a related application, so-called leakywaveguides are also used in the determination of railcar positions in certain rapid transitapplications. They are primarily used to determine the precise position of a train when itis being brought to a halt at a station, so that the doorway positions will align correctlywith queuing points on the platform or with a second set of safety doors should such beprovided.13
2.2.2 WorkingA waveguide is a very low loss transmission line. It allows propagation of signals to anumber of smaller antennas (slots). The signal is coupled into the waveguide with asimple coaxial probe and as it travels along the guide it traverses the slots. Each of theseslots allows a little of the energy to radiate. The slots are in a linear array pattern, and thetotal of all the radiated signals adds up to a very significant power gain over a small rangeof angles close to the horizon. In other words, the waveguide antenna transmits almost allof its energy at the horizon, usually exactly where we want it to go. Its exceptionaldirectivity in the elevation plane gives it quite high power gain. Additionally, unlikevertical co-linear antennas, the slotted waveguide transmits its energy using horizontalpolarization, the best type for distance transmission.2.2.3 ConstructionFigure – 2.1 – A Slotted Waveguide AntennaThe components we used to construct this antenna are given belowi) 1m RG-213U cable (coaxial cable)ii) N connectors (BNC-female)iii) Plastic casingEach sector of the antenna needs to be a 1/2 wavelength long multiplied by the velocityfactor of the cable. The velocity factor of RG-213 is 0.66. If a different cable (such asLMR-400) is used then the velocity factor of that cable needs to be determined and all thedimensions will need to be recalculated.V * C 0.66 * 2997924581/2 wavelength ------- ---------------------- 0.0405m 40.5mmEquation 2.12*F2 * 2441000000V Velocity Factor of RG213 0.66C Velocity of light 299792458 m/sF Frequency of Signal 2441000000 Hz (middle of the 2.4GHz range)14
The 1/4 wave element is n
The second group focused on the design and simulation of patch antennas (which are widely used in cell phones today) with an emphasis on optimization of a 1.9 GHz rectangular probe fed patch antenna. A dual band antenna and a microstrip fed patch antenna, used in the communication lab were also simulated.
Random Length Radiator Wire Antenna 6 6. Windom Antenna 6 7. Windom Antenna - Feed with coax cable 7 8. Quarter Wavelength Vertical Antenna 7 9. Folded Marconi Tee Antenna 8 10. Zeppelin Antenna 8 11. EWE Antenna 9 12. Dipole Antenna - Balun 9 13. Multiband Dipole Antenna 10 14. Inverted-Vee Antenna 10 15. Sloping Dipole Antenna 11 16. Vertical Dipole 12 17. Delta Fed Dipole Antenna 13 18. Bow .
Random Length Radiator Wire Antenna 6 6. Windom Antenna 6 7. Windom Antenna - Feed with coax cable 7 8. Quarter Wavelength Vertical Antenna 7 9. Folded Marconi Tee Antenna 8 10. Zeppelin Antenna 8 11. EWE Antenna 9 12. Dipole Antenna - Balun 9 13. Multiband Dipole Antenna 10 14. Inverted-Vee Antenna 10 15. Sloping Dipole Antenna 11 16. Vertical Dipole 12 17. Delta Fed Dipole Antenna 13 18. Bow .
Wire-Beam Antenna for 80m. 63 Dual-Band Sloper Antenna. 64 Inverted-V Beam Antenna for 30m. 65 ZL-Special Beam Antenna for 15m. 66 Half-Sloper Antenna for 160m . 67 Two-Bands Half Sloper for 80m - 40m. 68 Linear Loaded Sloper Antenna for 160m. 69 Super-Sloper Antenna. 70 Tower Pole as a Vertical Antenna for 80m. 71 Clothesline Antenna. 72 Wire Ground-Plane Antenna. 73 Inverted Delta Loop for .
Professional Wireless HA-8089 helical antenna – 470-900MHz Sennheiser A2003 UHF W/B Antenna Sennheiser A5000CP Antenna Sennheiser AD3700 Active Antenna Shure UA830WB UHF Active Antenna Booster Shure UA860/SWB omnidirectional antenna UHF Shure UA870-WB Active Antenna Shure UA874-WB Active Antenna Shure
headliner, down the A-pillar to the instrument panel. For antenna removal, see REMOVAL . For antenna installation, see INSTALLATION . OPERATION ANTENNA BODY AND CABLE The antenna body and cable connects the antenna mast to the radio. The radio antenna is an . 2008 Jeep
ANTENNA MODELING Antenna Modeling does not design your antenna, it only allows you to evaluate your design. ARRL - Antenna Modeling for Beginners 3961 by N0AX Arrl Antenna Modeling Course by L. B. Cebik (Both books have been discontinued but might be available as used books.) Note: The ARRL Antenna Book includes a free copy of EZNEC 47
2.4 TV Antenna Basics 13 2.5 Dipole Antenna 15 2.6 Planar Antennas 19 3 FRACTAL DIPOLE ANTENNA DESIGN 3.0 Introduction 21 3.1 Antenna Design Specifications 21 3.2 Design of the antenna using antenna design software 23 3.3 Simulation Using Computer Simulation Technology 27 3.3.1 SMA and Waveguide Port Connector 28
Antenna Array Also called an array antenna, antenna arrays are several antennas connected & arranged in a regular structure to form a single antenna. also Phased array antenna (PAA) is a multiple antenna system, in which, that the radiation pattern can be reinforced in a particular direction &
