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- 1. RF Antenna (RT-RFA)
- 2. RT-RFA <ul><li>© Copyright 2001 Global Wireless Education Consortium </li></ul><ul><li>All rights reserved. This module, comprising presentation slides with notes, exercises, projects and Instructor Guide, may not be duplicated in any way without the express written permission of the Global Wireless Education Consortium. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial training materials or for-profit education programs, books, databases, or any kind of software without the written permission of the Global Wireless Education Consortium. Making copies of this module, or any portion, for any purpose other than your own, is a violation of United States copyright laws. </li></ul><ul><li>Trademarked names appear throughout this module. All trademarked names have been used with the permission of their owners . </li></ul>
- 3. RT-RFA <ul><li>Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039. </li></ul><ul><li>GWEC EDUCATION PARTNERS: This material is subject to the legal License Agreement signed by your institution. Please refer to this License Agreement for restrictions of use. </li></ul>
- 4. Table of Contents <ul><li>Overview 5 </li></ul><ul><li>Learning Objectives 6 </li></ul><ul><li>Antennas as Part of All Communications Systems 7 </li></ul><ul><li>Fundamental Antenna Characteristics 12 </li></ul><ul><li>Antenna Radiation Patterns 19 </li></ul><ul><li>Antenna Types 27 </li></ul><ul><li>Antenna Configuration Requirements 49 </li></ul><ul><li>Signal Coverage Problems 56 </li></ul><ul><li>Advanced System Antennas 63 </li></ul><ul><li>Antenna Covers and Support Structures 71 </li></ul><ul><li>Contributors 76 </li></ul>
- 5. Overview <ul><li>How antennas transmit and receive signals </li></ul><ul><li>Fundamental characteristics of antennas </li></ul><ul><li>Types and features of antennas </li></ul><ul><li>Signal coverage problems and how to overcome them </li></ul><ul><li>How to perform return loss measurement and antenna gain measurement </li></ul>
- 6. Learning Objectives <ul><li>Explain how an antenna transmits and receives signals </li></ul><ul><li>Explain fundamental characteristics of antennas including radiated power, antenna gain, beam width, and front-back ratio </li></ul><ul><li>Describe features of different types of antennas </li></ul><ul><ul><li>Describe the different types of radiation patterns </li></ul></ul><ul><li>Explain why and how to measure impedance </li></ul><ul><li>Explain strategies to address signal coverage problems </li></ul><ul><ul><li>Explain antenna diversity and isolation strategies </li></ul></ul><ul><li>Perform a return loss measurement on an antenna </li></ul><ul><li>Perform an antenna gain measurement </li></ul>
- 7. Antennas as Part of All Communications Systems
- 8. Antenna System Components <ul><li>Transmit antenna </li></ul><ul><li>Receive antenna </li></ul><ul><li>Duplexer </li></ul><ul><li>Multicoupler </li></ul><ul><li>Combiner </li></ul><ul><li>Isolator </li></ul><ul><li>Tuning cavities </li></ul><ul><li>Cabling </li></ul>
- 9. Antenna Operation <ul><li>Antenna - a series of metal wires, rods, or other shapes </li></ul><ul><ul><li>Transmits when an electric current of radio frequency passes through it </li></ul></ul><ul><li>Current generates electromagnetic field around antenna </li></ul><ul><li>Electromagnetic field moves outward from antenna </li></ul><ul><li>At receiver antenna, does same thing in reverse </li></ul><ul><li>Tuned to a particular radio wavelength (λ) </li></ul><ul><ul><li>Simple fraction or multiple of that length: λ/2, λ/4, etc. </li></ul></ul><ul><ul><li>Most common length is one-half a wavelength, or λ/2 </li></ul></ul>
- 10. Antennas, Frequency, and Wavelength <ul><li>Resonant length changes with frequency and wavelength of electric signal </li></ul><ul><ul><li>The higher the frequency, the shorter the wavelength, and the shorter the required antenna </li></ul></ul><ul><ul><li>The lower the frequency, the longer the wavelength, and the longer the required antenna </li></ul></ul><ul><li>Cellular band antenna </li></ul><ul><ul><li>Wavelength for cellular telephone transmission is about 0.33 m </li></ul></ul><ul><ul><li>Length of a cellular antenna should be 0.165 m (λ/2) </li></ul></ul>
- 11. Assorted Facts <ul><li>Antenna Radiation Pattern </li></ul><ul><ul><li>Same radiation pattern and gain for transmit and receive antenna </li></ul></ul><ul><li>Transceiver </li></ul><ul><ul><li>Transmitter and receiver electronics housed in a single box </li></ul></ul><ul><ul><li>Generally use a single antenna for both </li></ul></ul><ul><li>Impedance Match </li></ul><ul><ul><li>Coaxial cable must be terminated with characteristic impedance for maximum power to be passed to antenna </li></ul></ul><ul><ul><li>If not, reflections will reduce power passed to antenna and cause protection circuitry in transmitter to reduce its output power </li></ul></ul><ul><li>RF Transmission Planning </li></ul><ul><ul><li>Optimizes signal strength received by base station and mobile station regardless of their positions in the network </li></ul></ul><ul><ul><li>Choice and configuration of antenna system plays an important role </li></ul></ul>
- 12. Fundamental Antenna Characteristics
- 13. Radiated Power <ul><li>Mean power received at any large distance is calculated by the Friis free-space equation: </li></ul><ul><ul><li>P t = transmitted power </li></ul></ul><ul><ul><li>P r (d) = received power, a function of transmitter-receiver distance </li></ul></ul><ul><ul><li>G t = transmitter antenna gain </li></ul></ul><ul><ul><li>G r = receiver antenna gain </li></ul></ul><ul><ul><li>d = transmitter-receiver separation in meters </li></ul></ul><ul><ul><li>L = miscellaneous loss factor for loss not related to propagation </li></ul></ul><ul><ul><ul><li>L = 1 means no loss </li></ul></ul></ul><ul><ul><ul><li>L > 1 means loss </li></ul></ul></ul><ul><ul><li>λ = wavelength in meters </li></ul></ul>
- 14. Antenna Bandwidth <ul><li>Range of frequencies radiated where lowest and highest frequencies have radiated power that is 3 dB less than the radiated power at frequency with maximum power, f(max) </li></ul><ul><ul><li>Upper frequency, f(up), is frequency above f(max) where power is 3 dB lower than f(max) </li></ul></ul><ul><ul><li>Lower frequency, f(low), is frequency below f(max) where power is 3 dB lower than f(max) </li></ul></ul><ul><li>As a percent, B(p), of center frequency, f(ctr) </li></ul>
- 15. Antenna Gain <ul><li>Ratio of antenna’s maximum radiation intensity to maximum radiation intensity from a reference antenna with same input power </li></ul><ul><ul><li>dBi – If reference antenna is i sotropic source of 100% efficiency </li></ul></ul><ul><ul><li>dBd – If reference antenna is simple dipole of typical efficiency </li></ul></ul><ul><ul><ul><li>Gdip (gain with respect to dipole antenna) is 2.15 dB less than Gi (gain with respect to isotropic antenna) </li></ul></ul></ul><ul><li>Antenna gain, G ant , is a function of wavelength </li></ul><ul><li>A e = Effective antenna area </li></ul>
- 16. Antenna Beam Width <ul><li>Antenna achieves gain by concentrating its radiation pattern in a certain direction </li></ul><ul><ul><li>The greater the gain, the narrower the beam width </li></ul></ul><ul><li>Beam width is width of radiated pattern where signal strength is one-half that of maximum signal strength </li></ul><ul><ul><li>At this point, signal is 3 dB less than that of the maximum </li></ul></ul><ul><ul><li>Angle between left and right points that are 3 dB down from maximum is beam angle or beam width </li></ul></ul><ul><li>For unidirectional antennas, resulting major lobe of radiation pattern has a certain width </li></ul><ul><ul><li>Common beam widths for cellular antennas: 60º, 90º, and 120º. </li></ul></ul>
- 17. Antenna Front-Back Ratio <ul><li>Measure of antenna’s ability to focus radiated power in intended direction successfully </li></ul><ul><ul><li>And not interfere with other antennas behind it </li></ul></ul><ul><li>Referred to as f-b ratio or f/b ratio </li></ul><ul><li>Ratio of radiated power in intended direction to radiated power in opposite direction </li></ul><ul><li>Ratio of the two gains is the f/b ratio: </li></ul>
- 18. Frequency Re-Use <ul><li>Same frequencies used </li></ul><ul><li>repeatedly in all </li></ul><ul><li>directions </li></ul><ul><li>Ability to radiate power in </li></ul><ul><li>desired direction is </li></ul><ul><li>critical </li></ul>
- 19. Antenna Radiation Patterns
- 20. Isotropic Radiation Pattern <ul><li>Characteristics </li></ul><ul><ul><li>Completely non-directional antenna </li></ul></ul><ul><ul><li>Radiates and receives equally well in all directions </li></ul></ul><ul><ul><li>Theoretical point source or receiver </li></ul></ul><ul><ul><li>Radiation pattern is spherical </li></ul></ul><ul><li>Exists only as a mathematical concept </li></ul><ul><ul><li>There is no preferential radiation in one direction </li></ul></ul><ul><li>Used as a reference to specify gain of a practical antenna </li></ul>
- 21. Omnidirectional Radiation Pattern Horizontal Pattern Vertical Pattern
- 22. Unidirectional Radiation Pattern Horizontal Pattern Vertical Pattern
- 23. Radiated Power Compared
- 24. Properties of Unidirectional Antennas <ul><li>Provide increased gain in a limited direction </li></ul><ul><li>Multiply use of separate channels by virtue of enabling sectorization </li></ul><ul><li>Do not overcome major disadvantages of omnidirectional antennas such as co-channel interference </li></ul>
- 25. Antenna Polarization <ul><li>Polarization is an important property of a radio wave </li></ul><ul><li>Radio waves have magnetic field H & electrical field E </li></ul><ul><li>Orientation of electrical field determines polarization </li></ul><ul><ul><li>If electrical field is vertical, radio wave is polarized vertically </li></ul></ul><ul><ul><li>If electrical field is horizontal, radio wave is polarized horizontally </li></ul></ul><ul><li>Antenna of receiver should be oriented in same direction as polarization of transmitter antenna </li></ul><ul><li>Mobile antennas should be in the same orientation for best reception </li></ul><ul><ul><li>This is not always possible with hand-held phones </li></ul></ul>
- 26. Voltage Standing Wave Ratio (VSWR) <ul><li>Ratio of maximum voltage to minimum voltage of standing wave along transmission line </li></ul><ul><li>Measure of impedance match between antenna and transmission line or coaxial cable </li></ul><ul><ul><li>The closer VSWR is to one, the greater </li></ul></ul><ul><ul><li> the efficiency of electrical power transfer </li></ul></ul><ul><li>Formula </li></ul><ul><li>Pr = Power, reflected </li></ul><ul><li>Pi = Power, incident </li></ul>
- 27. Antenna Types
- 28. Radiation Pattern of Half-wave Dipole Antenna 3-D view Vertical section Horizontal section
- 29. Omnidirectional Antennas Omnidirectional antenna Hertz antenna 1
- 30. Marconi Antenna
- 31. Omnidirectional Antenna Limitations <ul><li>Radiates and receives equally well in all directions in the horizontal plane </li></ul><ul><ul><li>Signal power spread uniformly and only small percentage of radiated power reaches receiver </li></ul></ul><ul><li>Receiving antenna receives signals equally well from all directions in horizontal plane </li></ul><ul><ul><li>For mobile transmitter to be distinguished, it must be stronger than other signals and the background noise </li></ul></ul><ul><li>Limited bandwidth efficiency </li></ul><ul><li>Very limited re-use of frequencies in adjoining areas </li></ul>
- 32. Radiating Coaxial Cable Antenna Radiating Coaxial Cable Antenna Radiating Cable Radiation Pattern RF in from transmitter RF out (terminated)
- 33. Multi-antenna System Examples <ul><li>Pair of directional antennas mounted in different directions </li></ul><ul><ul><li>Radiation patterns point in opposite directions </li></ul></ul><ul><li>Series of antennas around a given building </li></ul><ul><ul><li>Used when omnidirectional antennas would not be effective </li></ul></ul><ul><li>Series of antennas located on the side of a building </li></ul><ul><ul><li>Minimizes interference with other receivers </li></ul></ul>
- 34. Panel Antennas
- 35. Unidirectional Antennas <ul><li>Referred to as beam antennas </li></ul><ul><li>Focus beams in one direction </li></ul><ul><li>Concentrate radiated power into a beam while minimizing emission in other directions </li></ul><ul><li>Classifications: </li></ul><ul><ul><li>Linear </li></ul></ul><ul><ul><li>Logarithmic </li></ul></ul><ul><ul><li>Parasitic </li></ul></ul><ul><li>Broadband antenna </li></ul>
- 36. Unidirectional Antennas <ul><li>Traveling-wave Wire Antenna </li></ul><ul><li>Folded Dipole Antenna </li></ul><ul><li>Turnstile Antenna </li></ul><ul><li>Loop Antenna </li></ul><ul><li>Rhombic Antenna </li></ul><ul><li>Yagi-Uda Antenna </li></ul><ul><li>Log Periodic Antenna </li></ul><ul><li>Mobile Antenna </li></ul><ul><li>Sector Antenna </li></ul>
- 37. Traveling-wave Wire Antenna Reflected wave Dipole antenna Incident wave Resonant wave of wavelength antenna Reflected wave Incident wave Antenna Traveling wave for non-simple antenna
- 38. Folded Dipole Antenna Beam Driven element length = Reflector length 2 + 5% Radiation pattern Folded dipole antenna
- 39. Turnstile Antenna Turnstile antenna Radiation pattern
- 40. Loop Antenna Loop antenna Radiation pattern in horizontal plane
- 41. Rhombic Antenna L L L L 800 Preferred direction of radiation L L L L 800
- 42. Rhombic Antenna Radiation Pattern
- 43. Yagi-Uda Antenna Yagi-Uda Antenna Director Driven element Reflector
- 44. Yagi-Uda Antenna
- 45. Log Periodic Antenna <ul><li>All elements driven by transmitter </li></ul><ul><li>All elements driven but not active at same frequency </li></ul><ul><li>Has broad frequency response </li></ul><ul><li>Operates on more than one frequency </li></ul>
- 46. Mobile Antennas: Collinear Gain Antenna <ul><li>Low-gain antenna </li></ul><ul><li>Two types </li></ul><ul><ul><li>- Through-the-glass </li></ul></ul><ul><ul><li>Standard mount </li></ul></ul><ul><li>Have upper and lower portion </li></ul><ul><li>separated by phase matching coil </li></ul>
- 47. Sector Antennas 3-sector cell 6-sector cell
- 48. Sector Antennas Realistic antenna coverage in 6-sector cell Antenna overlap in 6-sector cell
- 49. Antenna Configuration Requirements
- 50. Antenna Configuration Requirements <ul><li>Antenna separation </li></ul><ul><li>Diversity </li></ul><ul><li>Isolation </li></ul><ul><li>Interference </li></ul><ul><li>Radiation patterns not distorted by obstacles or reflections </li></ul>
- 51. Space Diversity
- 52. Polarization Diversity
- 53. Isolation <ul><li>Needed to avoid distortion due to intermodulation </li></ul><ul><li>Need to fulfill these isolation values </li></ul><ul><ul><li>TX – RX isolation > 30 dB </li></ul></ul><ul><ul><li>TX – TX isolation > 30 dB </li></ul></ul><ul><li>Horizontal physical separation requirements </li></ul><ul><ul><li>30 dB isolation: 11.5 λ </li></ul></ul><ul><ul><li>800 MHz: 10 feet </li></ul></ul><ul><ul><li>1900 MHz: 6 feet </li></ul></ul><ul><li>Vertical separation requirement for antenna is 0.2 meter </li></ul>
- 54. Antenna Downtilt Beam of vertically- mounted antenna Beam of vertically-mounted- antenna with tilted beam
- 55. Antenna Height <ul><li>Reducing antenna height by 50% will reduce average received signal by 6 dB </li></ul><ul><li>Repositioning transmit and/or receive antenna can help maintain system balance </li></ul>
- 56. Signal Coverage Problems
- 57. Signal Coverage Problems <ul><li>Design problems </li></ul><ul><li>Maintenance problems </li></ul><ul><li>System maturation </li></ul><ul><li>Site location and geometry </li></ul><ul><li>Shadows in pattern </li></ul><ul><li>Nulls in pattern </li></ul><ul><li>Intermodulation, co-channel, and adjacent channel interference problems </li></ul>
- 58. Resolving Signal Coverage Problems <ul><li>Reduce antenna height </li></ul><ul><li>Downtilt the antenna </li></ul><ul><li>Use higher or lower gain antenna </li></ul><ul><li>Use antenna with wider or narrower horizontal or vertical beam width </li></ul>
- 59. Return Loss of an Antenna <ul><li>Power difference between incident and reflected wave in transmission line feeding the antenna </li></ul><ul><li>3 dB return loss means reflected power is half of incident power </li></ul>
- 60. Interference Multipath condition
- 61. Interference Rayleigh fading
- 62. Co-Channel Interference
- 63. Advanced System Antennas
- 64. Advanced Antenna Systems <ul><li>Are expensive </li></ul><ul><li>Increase cell coverage and capacity without building additional sites </li></ul><ul><li>Examples </li></ul><ul><ul><li>Multi-beam antenna systems </li></ul></ul><ul><ul><li>Smart antenna systems </li></ul></ul>
- 65. Multi-Beam Antennas Standard cell divided into 18 microsectors
- 66. Smart Antenna Systems Fixed Beam Strategy Adaptive Beam Strategy
- 67. Smart Antenna Systems <ul><li>Time division duplex (TDD) communication systems transmit and receive on same frequency </li></ul><ul><li>Frequency division duplex (FDD) transmit and receive on separate frequencies </li></ul><ul><li>Capacity for frequency reuse is greater than a standard cell system </li></ul><ul><li>Power needed for radio beam is less than for fixed beam strategy </li></ul><ul><li>Use code division multiple access method to balance the traffic load </li></ul>
- 68. Traffic Load Balancing Smart Antenna Systems Cell with unbalanced load Cell with balanced load
- 69. Handling Capacity of Smart Antenna Systems
- 70. Switched Beam versus Adaptive Array Systems <ul><li>Factors to consider </li></ul><ul><ul><li>Interference suppression </li></ul></ul><ul><ul><li>Range and coverage </li></ul></ul><ul><ul><li>Spatial division multiple access (SDMA) </li></ul></ul><ul><ul><ul><li>Enables wireless system to efficiently use available frequencies where customers are located </li></ul></ul></ul><ul><ul><ul><li>Creates a sector for each receiver while maximizing signal strength at receiver and minimizing interference </li></ul></ul></ul><ul><ul><ul><li>Uses multiple antennas to combine signals in space at location of receiver </li></ul></ul></ul>
- 71. Antenna Covers and Support Structures
- 72. Antenna Covers and Support Structures <ul><li>Antenna covers </li></ul><ul><ul><li>Protect antenna element from weather </li></ul></ul><ul><ul><li>Make antenna more aesthetically pleasing </li></ul></ul><ul><li>Types of support structures </li></ul><ul><ul><li>Self-supporting towers </li></ul></ul><ul><ul><li>Guyed towers </li></ul></ul><ul><ul><li>Monopole </li></ul></ul><ul><ul><li>Camouflaged towers </li></ul></ul><ul><ul><li>Existing structures </li></ul></ul>
- 73. Antenna Support Structures <ul><li>Self-supporting towers </li></ul><ul><ul><li>Large 3-D framework of galvanized girders </li></ul></ul><ul><ul><li>Antenna may be placed at top or any level of tower based on transmission requirements </li></ul></ul><ul><li>Guyed towers </li></ul><ul><ul><li>Made of crisscrossing steel girders </li></ul></ul><ul><ul><li>Held in place by guy wires that form a 15 degree vertical angle </li></ul></ul><ul><ul><li>Antenna may be placed at top or any level of tower based on transmission requirements </li></ul></ul>
- 74. Antenna Support Structures Monopole with 3-sector head <ul><li>Requires less land area </li></ul><ul><li>and is more aesthetically </li></ul><ul><li>pleasing than other structures </li></ul><ul><li>Antenna placement depends </li></ul><ul><li>on transmission requirements </li></ul>
- 75. Antenna Support Structures <ul><li>Camouflaged towers </li></ul><ul><li>Existing support structure </li></ul><ul><ul><li>Buildings </li></ul></ul><ul><ul><li>Water towers </li></ul></ul><ul><ul><li>Electric towers </li></ul></ul><ul><ul><li>Light pole </li></ul></ul><ul><ul><li>Highway signs </li></ul></ul><ul><li>FAA identifies special lighting and/or safety requirement </li></ul><ul><li>FCC specifies power allowed based on various factors </li></ul><ul><ul><li>Terrain </li></ul></ul><ul><ul><li>Frequencies used </li></ul></ul><ul><ul><li>Other radio uses in the area </li></ul></ul>
- 76. Industry Contributors <ul><li>AT&T Wireless ( http://www.attwireless.com ) </li></ul><ul><li>Ericsson ( http://www.ericsson.com ) </li></ul><ul><li>LCC International, Inc. ( http://www.lcc.com ) </li></ul><ul><li>Motorola ( http://www.motorola.com ) </li></ul><ul><li>Nortel Networks ( http://www.nortel.com ) </li></ul><ul><li>Northeast Center for Telecommunications Technologies( http://nctt.org/index2.htm ) </li></ul><ul><li>RF Globalnet ( http://www.rfglobalnet.com ) </li></ul>The following companies provided materials and resource support for this module:
- 77. Industry Contributors, cont. <ul><li>Space 2000 ( http://www.cdmaonline.com ) </li></ul><ul><li>Telcordia Technologies, Inc ( http://www.telcordia.com ) </li></ul><ul><li>Verizon ( http://www.verizon.com ) </li></ul>The following companies provided materials and resource support for this module:
- 78. Individual Contributors <ul><li>The following individuals and their organization or institution provided materials, resources, and development input for this module: </li></ul><ul><li>Dr. Chaouki Abdallah </li></ul><ul><ul><li>University of New Mexico </li></ul></ul><ul><ul><li>http://www.unm.edu </li></ul></ul><ul><li>Dr. Jamil Ahmed </li></ul><ul><ul><li>British Columbia Institute of Technology </li></ul></ul><ul><ul><li>http://www. bcit.ca </li></ul></ul><ul><li>Dr. John Baldwin </li></ul><ul><ul><li>South Central Technical College </li></ul></ul><ul><ul><li>http://Jbaldwin@means.net </li></ul></ul>
- 79. Individual Contributors, cont. <ul><li>Dr. Derrek Dunn </li></ul><ul><ul><li>North Carolina A&T State University </li></ul></ul><ul><ul><li>http://www. ncat . edu </li></ul></ul><ul><li>Mr. Robert Elms </li></ul><ul><ul><li>ACRE Engineering Services </li></ul></ul><ul><ul><li>http:// Rielms @ myexcel .com </li></ul></ul><ul><li>Mr. Stuart D. MacPherson </li></ul><ul><ul><li>Durban Institute of Technology </li></ul></ul><ul><li>Dr. James Masi </li></ul><ul><ul><li>Springfield Technical Community College </li></ul></ul><ul><ul><li>http://www.stcc.mass.edu/nsindex.asp </li></ul></ul>
- 80. Individual Contributors, cont. <ul><li>Ms. Annette Muga </li></ul><ul><ul><li>Ericsson </li></ul></ul><ul><ul><li>http://www.ericsson.com </li></ul></ul><ul><li>Dr. Dave Voltmer </li></ul><ul><ul><li>Rose-Hulman Institute of Technology </li></ul></ul><ul><ul><li>http:// www.rose-hulman.edu </li></ul></ul>

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