1. CCRI J. Bernardini Antenna Basics Module 3 Jerry Bernardini Community College of Rhode Island

2. Presentation Reference Material CWNA Certified Wireless Network Administration Official Study Guide (PWO-104), David Coleman, David Westcott, 2009, Chapter-4 The California Regional Consortium for Engineering Advances in Technological Education (CREATE) project Cisco Wireless technology Wireless Communications, Roy Blake, Chap-8 http://martybugs.net/ 7/14/2015 Wireless Networking J. Bernardini 2

3. CCRI J. Bernardini Antenna Principles A theoretical isotropic antenna has a perfect 360º vertical and horizontal beamwidth The Isotropic antenna the a reference for all antennas (dBi) Antennas are symmetrical: A receiving antenna has the same characteristics as a transmitter Antennas have gain in particular directions Direction other than the main intended radiation pattern, are typically related to the main lobe gain

4. How Antennas Work CCRI J. Bernardini Half Wave Dipole Antenna

5. Antenna Signals CCRI J. Bernardini Access Point Cable Antenna Electromagnetic Wave

6. Half-Dipole Radiation Pattern CCRI J. Bernardini

7. Different Antennas CCRI J. Bernardini

8. Key Antenna Terms Plane-H =Azimuth Chart –(Top-down view) Plane-E=Elevation Chart –(Side- view) Lobes Directional Omnidirectional Beamwidth Bandwidth Polarization (Vertical/Horizontal) ) Diversity VSWR Antenna Accessories

9. Antenna Gains CCRI J. Bernardini

10. Antenna Characteristics Main beam is the region around the direction of maximum radiation The main beam is centered at 90 degrees Sidelobes are smaller beams that are away from the main beam. Radiate in directions other than the main beam and can never be completely eliminated. Half Power Beamwidth (HPBW) is the angular separation in which the magnitude of the radiation pattern decrease by 50% (or -3 dB) from the peak of the main beam. Null to Null Beamwidth. the angular separation from which the magnitude of the radiation pattern decreases to zero (negative infinity dB) away from the main beam. CCRI J. Bernardini

11. H-Plane-Azimuth (Top-Down View) CCRI J. Bernardini 0o0o 270 o 90 o 180 o Beamwidth -3dB

12. Beamwidths CCRI J. Bernardini 0 dB -3dB

13. Polar Pattern Analysis CCRI J. Bernardini 50 o Beam

14. Dipole H and E Planes CCRI J. Bernardini

15. 5.8 dBi Omnidirectional Antenna, CCRI J. Bernardini

16. Typical Dipole Antenna Beam Pattern Starting from an Isotropic antenna energy lobes are ‘pushed in’ from the top and bottom Higher gain –Smaller vertical beamwidth –Larger horizontal lobe Typical dipole pattern

17. CCRI J. Bernardini 2.4 GHz Omni-Directional Antennas 2 dBi Dipole "Standard Rubber Duck"

18. Rubber Ducky Antenna Construction CCRI J. Bernardini Thin wire whip protruding from the top of the metal casing is approx 26mm Metal casing is a "decoupler", and is typically used to tune the antenna, by moving the decoupler up and down to vary the VSWR. Length of the metal casing is approx 24mm, with a total length of 50mm. Each half of the dipole is a 1/4 wavelength, with the length corrected based on the velocity of the coax being used. Assuming a centre frequency for 802.11b of 2.441GHz, a 1/4 wavelength in free space is 30.7mm.

19. CCRI J. Bernardini High Gain Omni-Directionals More coverage area in a circular pattern Energy level directly above or below the antenna will become lower

20. CCRI J. Bernardini 2.4 GHz Omni-Directional Antennas 5.2 dBi Mast Mount Vertical

21. CCRI J. Bernardini 2.4 GHz Omni-Directional Antennas 5.2 dBi Pillar Mount Diversity

22. CCRI J. Bernardini 2.4 GHz Diversity Omni-Directional Antennas 2 dBi Diversity Omni-Directional Ceiling Mount

23. CCRI J. Bernardini 2.4 GHz Omni-Directional Antennas 12 dBi Omni-Directional (Outdoor only)

24. CCRI J. Bernardini 2.4 GHz Diversity Antennas 6.5 dBi Diversity Patch Wall Mount – 55 degree

25. CCRI J. Bernardini 2.4 GHz Directional Antennas (cont.) 6 dBi Patch Antenna – 65 degree

26. CCRI J. Bernardini 2.4 GHz Directional Antennas (cont.) 8.5 dBi Patch Antenna – 60 degree

27. CCRI J. Bernardini 2.4 GHz 13.5 dBi Yagi Antenna – 25 degree Beamwidth

28. CCRI J. Bernardini 2.4 GHz Directional Antennas (cont.) 21 dBi Parabolic Dish Antenna – 12 degree

29. Antenna Polarization CCRI J. Bernardini E-Plane is parallel to the antenna H-Plane is perpendicular to the antenna Horizontal Polarization – the Electric field is parallel to the ground Vertical Polarization – the Electric field is perpendicular to the ground

30. CCRI J. Bernardini FCC Rules 2.4 GHz EIRP Point-to-Multipoint –FCC allows increasing the gain of an antenna/cable system if the transmitter power is reduced below 30 dBm in a 1:1 ratio –Reduce Transmit Power below maximum of 30 dBm by 1 dBm and increase antenna/cable system gain by 1dBi Point-to-Point –Maximum of 36 dBm EIRP –Installations – 30 dBm maximum transmitter power with 6 dBi in gain attributed to antenna and cable combination FCC allows exceeding the 36 dBm EIRP in Point-to-Point installations using the 3:1 rule –Reduce Transmit Power below maximum of 30 dBm by 1 dBm and increase antenna/cable system gain by 3 dBi

31. Voltage Standing Wave Ratio (VSWR ) A measure of the change in impedance to an AC signal. Ratio of the Maximum Voltage to Minimum Voltage in an RF system. Typical Values: 1.1 : 1 to 1.5 :1 (1:1 Ideal system; impossible to obtain) Measure of the amount of energy sent to the antenna that reflects back to the transmitter. Too large a VSWR will reflect too much energy back to the transmitter and damage the transmitter Output of Transmitter must match Cable, which matches Antenna impedance Return Loss – Ratio of Reflected voltage to Transmitter voltage in dB. Ideally this should be small CCRI J. Bernardini

32. VSWR Table CCRI J. Bernardini TRANS.RETURNTRANS.POWER VSWR LOSS TRANS.REFL. :1[dB] [%] 1.000,00∞01000 1.201.5820.830.03699.170.83 1.302.2817.690.07598.301.70 1.503.5213.980.17796.004.00 1.805.1110.880.3791.848.16 2.006.029.540.51288.9011.10 4.0012.004.441.9464.0036.00 5.0014.003.522.5555.6044.40 6.0015.602.923.149.0051.00 10.0020.001.744.8133.1066.90

33. Impedance Matching Effects CCRI J. Bernardini When the impedances are matched –Half of the source power is delivered to the load and half is dissipated within the (equivalent) generator as heat For receiving antenna, half the power captured is lost as heat in the antenna elements, the other part being reradiated (scattered) back into space When the antenna impedance is not matched to the transmitter output impedance (or to the receiver input impedance) or to the transmission line between them, impedance-matching devices must be used for maximum power transfer. -impedance-matching devices are used They are usually narrow-band Transmission lines often have significant losses

34. Antenna Diversity Receiver selects the stronger antenna signal compensating for multipath Frame by frame antenna sampling to determine strongest signal Transmitting occurs on the previous strong-signal antenna =Transmit Diversity Not all access points have Trasmitter Diversity CCRI J. Bernardini

35. Multiple-Input Multiple-Output (MIMO) A sophisticated form of antenna diversity Multipath signals are Space Time Coding (STC) processed to improve receiver performance IEEE 802.11n employs MIMO Not specified with 802.11a, b,g CCRI J. Bernardini

36. Antenna Path Considerations Radio line of sight Height of Earth bulge Fresnel Zone Radius Height of Obstacles

37. CCRI J. Bernardini Line of Sight The following obstructions might obscure a visual link: – Topographic features, such as mountains – Curvature of the Earth – Buildings and other man-made objects – Trees

38. CCRI J. Bernardini Longer Distances Line of Sight disappears at 6 miles (9.7 Km) due to the earth curve

39. CCRI J. Bernardini Fresnel Zone Theoretically there is an infinite number of Fresnel zones. For communications the first Fresnel zone is important You must know the diameter or radius of the first Fresnel zone

40. Fresnel Zone Radius CCRI J. Bernardini Radius of the first Fresnel zone should be calculated Obstruction of the first zone will reduce communications Objects must not encroach more than 40 percent of the first zone max radius Design for a max of 20%

41. CCRI J. Bernardini Improving Fresnel Effect Raise the antenna New structure Existing structure Different mounting point Remove trees

42. CCRI J. Bernardini Total Distance Fresnel @ 60% (Value “F”) Earth Curvature (Value “C”) Antenna Height (Value “H”) Site to Site Fresnel Zone Antenna Height –Fresnel zone consideration –Line-of-Sight over 25 miles (40 Km) hard to implement

43. CCRI J. Bernardini Antenna Alignment Line of Sight

44. CCRI J. Bernardini Antenna Installation Towers and antennas may require permits and must meet local regulations

45. Grounding Antenna towers must be ground to protect from lightning CCRI J. Bernardini Antenna Grounding Rods (6 ft r

46. CCRI J. Bernardini 5 GHz Integrated Antenna Innovative 5 GHz Combo Antenna: –Wall Mount: Fold antenna flat against access point housing for 6 dBi gain patch antenna –Ceiling Mount: Fold antenna out at a 90° angle for 5 dBi gain omni antenna In 5 dBi omni position In 6 dBi patch position

47. CCRI J. Bernardini 2.4 GHz Accessories

48. CCRI J. Bernardini RP-TNC Connectors

49. CCRI J. Bernardini Lightning Arrestor

50. CCRI J. Bernardini Lightning Arrestor Designed to protect LAN devices from static electricity and lightning surges that travel on coax transmission lines RP-TNC connectors used on all Cisco Antennas To Antenna Ground Wire From RF Device Lug Lockwasher Nut