Copyright 2005 All Rights Reserved

Name: Copyright 2005 All Rights Reserved
Uploaded: 2017-11-30T15:46:57+00:00
Duration: PTM29S27
Channel: Jordan Simpson
Description: Copyright 2005 All Rights Reserved

Objectives Upon completion of this chapter you will be able to: Explain the types of wireless LAN antennas and how/when to use them Describe the various wireless LAN accessories and where they are used February 2005 Copyright 2005 All Rights Reserved

External Antenna Classifications
Omni-directional Antenna Mast mount omni Pillar mount omni Ground plane omni Ceiling mount omni Highly- directional Antenna Parabolic dish Grid antenna Semi-directional antenna Patch Antenna Panel Antenna Sectorized antenna Yagi Antenna 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Omni-directional Antenna Mast mount omni Blade omni PC Card integrated omni Pillar mount omni Ground plane omni Ceiling mount (blister) omni 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Omni-directional Antennas
The omni-directional Dipole antenna is the most common WLAN antenna. The radiating element is about 1 inch long for 2.4 Ghz and even shorter for the 5 Ghz frequency. As the wavelength becomes higher the antenna becomes shorter. It radiates energy equally around the antenna axis- 360 degrees. However it dos not radiate along the length of the antenna hence the radiation pattern is in the shape of a doughnut. Anything radiating in all directions equally (the sun) is called and isotropic radiator. The gain of an antenna is referenced to an isotropic Radiator. The higher the gain the more horizontally squeezed the doughnut. February 2005 Copyright 2005 All Rights Reserved

5.2 dBi Omni-directional Antenna Contd Frequency Range GHz VSWR Less than 2:1, 1.5:1 Nominal Gain 5.2dBi Polarization Vertical Azimuth 3dB BW Omnidirectional 360 degrees Elevations Plan (3dB BW) 50 degrees Antenna Connector RP-TNC Dimensions (H x W) 11.5 x in. Mounting Mast mount—indoor/outdoor February 2005 Copyright 2005 All Rights Reserved

Semi-directional antenna Patch Antenna Panel Antenna Sectorized antenna Yagi Antenna 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Semi-directional antenna Semi-directional antenna radiate in a cylindrical coverage pattern Used for: Connecting buildings A long corridor in the corner of a large indoor space rail yards, retail stores Manufacturing facilities Golf Courses, etc They are most often used for short distances (2-3 miles) to bridge two buildings. 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Patch Antenna Contd Frequency Range GHz VSWR 2:1 Max, 1.5:1 Nominal Gain 8.5dBi Polarization Vertical Azimuth 3dB BW 60 degrees Elevations 3dB BW 55 degrees Antenna Connector RP-TNC Dimensions (H x W x D) 4.88 x 4.88 x .6 in. Mounting Wall Mount February 2005 Copyright 2005 All Rights Reserved

2.4 Gz 13.5 dBi Radome Yagi Frequency Range GHz VSWR Less than 2:1, 1.5:1 Nominal Gain 13.5dBi Front to Back Ratio Greater than 30 dB Polarization Vertical Azimuth 3dB BW 30 degrees Elevations 3dB BW 25 degrees Antenna Connector RP-TNC Dimensions (H x W) 18 x 3 in. Wind Rating 110 MPH Mounting Mast/Wall Mount February 2005 Copyright 2005 All Rights Reserved

Semi-directional Antenna Radiation Pattern Directional Yagi Antenna Side Lobe Main lobe Beamwidth Back Lobe Beamwidth is calculated by measuring the number of degrees off-axis where the beam drops to -1/2 its strength at the zero-degree position. February 2005 Copyright 2005 All Rights Reserved

Highly- Directional Antenna Parabolic dish Grid antenna 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Highly-directional antenna Highly-directional antenna radiate in a cylindrical coverage pattern that is highly flattened. Not used for communicating with clients. Used for Pt-to-Pt communication links Blast through obstructions Must be accurately aligned. They are most often used for long distances (35 miles) for pt-to-pt communication. 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

2.4 Ghz 21 dBi Parabolic Dish Antenna
February 2005 Copyright 2005 All Rights Reserved

2.4 Ghz 21 dBi Parabolic Dish Antenna
Frequency Range GHz VSWR Less than 1.8:1, 15:1 Nominal Power 5 watts Gain 21dBi Front to Back Ratio Greater than 25 dB Maximum Side Lobe -17 dB Polarization Vertical Azimuth 3dB BW 12.4 degrees Elevation 3dB BW Antenna Connector RP-TNC Dimensions (H x W) 24 x 15.5 in. Wind Rating 110 MPH Mounting Mast Mount February 2005 Copyright 2005 All Rights Reserved

2.4 Gz 19 dBi Reflector Grid Antenna Grid Dish Parabolic Antenna (2400 to 2485 MHz Operation) 15dBi, 19dBi and 24dBi models Rugged and Weatherproof Ultra Low Wind Loading and Low Visual Impact Vertical or Horizontal Polarization 2.4GHz Wireless LAN Applications • Point to Point Backhaul 802.11b and g Wireless • Client Antennas February 2005 Copyright 2005 All Rights Reserved

Line of sight L i n e o f S g h t The RF Line of Sight (LOS) is an apparent straight line between the transmitter and receiver. It is apparent because of changes in RF direction due to refraction, diffraction and reflection. RF LOS is affected by blockage of the Fresnel Zone. February 2005 Copyright 2005 All Rights Reserved

Fresnel Zone L i n e o f S g h t The Fresnel Zone occupies a series of concentric circles around the RF LOS. Objects in the Fresnel Zone can diffract or reflect the RF wave away from receiver thereby changing the RF LOS. The formula to calculate the "60 percent unobstructed radius" is: d/4f r = 43.3 x Typically 20%-40% Fresnel Zone blockage introduces little or no interference. Attempt to Design the link with 0% blockage. If this is not possible then allow no more than 20% blockage of the Fresnel Zone. February 2005 Copyright 2005 All Rights Reserved

Line of sight There are several options to establish or improve the line of sight: Raise the antenna mounting point on the existing structure Build a new structure, i.e. radio tower, which is tall enough to mount the antenna Increase the height of an existing tower Locate a different mounting point, i.e. building or tower, for the antenna Cut down problem trees February 2005 Copyright 2005 All Rights Reserved

Earth Bulge L i n e o f S i g h t The earth's horizon can obstruct the Fresnel Zone if the distance between antennas is greater than 7 miles. The formula for calculating the additional antenna height needed to correct for the communication links greater than 7 miles is: H=D2/8 The formula for calculating the minimum antenna height for communication links over 7 miles is: D2/8 D/4F) + H = (43.3 x February 2005 Copyright 2005 All Rights Reserved

Diverse Antennas 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Diverse Antennas Diverse antennas are used to overcome multipath distortion (multipath fading). This uses two antennas separated by at least one wavelength. Multipath distortion occurs at the receiver when the wavelength travels multipaths from the transmitter to the receiver. The reflected wave travels farther than the desired wave arriving later in time. The reflected wave travels farther and loses more RF energy than the direct wave. The signal will lose energy when reflected. 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Multipath Fading Multipath Reception 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. Distortion February 2005 Copyright 2005 All Rights Reserved

Diverse Antenna Switch Diverse antennas include two antennas that are connected to an RF switch which in turn is connected to the receiver. The receiver switches between antennas sampling the preamble. It then selects the best antenna for receiving the signal. The transmitter then uses the same signal for transmission. 1. The first mobile telephone systems began n 1946 in St Louis Mo. The cost was approximately $2500. 2. The first Mobile radio was in 1921and was employed by the Detroit police department. February 2005 Copyright 2005 All Rights Reserved

Antenna Concepts Antenna's have four fundamental concepts: Polarization: The orientation of the Electric component of the electro-magnetic field. Gain: A measure of the increase in power. Direction: The shape of the radiated transmission pattern. Free Space Path Loss: RF signal loss due to transmission distance. February 2005 Copyright 2005 All Rights Reserved

Polarization The Radio wave is made up of an oscillating electro-magnetic field composed of two planes: H-Plane: The Magnetic plane is created perpendicular to the antenna. E-Plane: The Electric plane is created parallel to the antenna and defines the orientation of the radio waves radiated from the antenna. Vertical polarization has the E-Plane perpendicular to the earth. Most WLAN antennas are vertically polarized. Horizontal Polarization has the E-Plan horizontal to the earth. H-Plane Antenna E-Plane February 2005 Copyright 2005 All Rights Reserved

Gain and Direction Gain is the increase in energy that an antenna appears to add to the RF Signal. An antenna has passive gain – they do not increase the power input to them. Real antennas reshape the radiation pattern by simply redirecting the energy through reflection – think of a flashlight that has the ability to change its beamwidth. It provides more energy in one direction and less in another. As the Antenna gain increases the angle of radiation decreases: This provides greater coverage distance but Less coverage angle February 2005 Copyright 2005 All Rights Reserved

Beamwidth Contd Directional Antenna Horizontal Beamwidth V e r t i c a l B m w d h Narrowing or focusing antenna beams increase or decrease the antenna's gain – dBi. The beamwidth is composed of a vertical and a horizontal element. February 2005 Copyright 2005 All Rights Reserved

Gain and Direction Contd Basic Antenna gain is rated in comparison to an Isotropic radiator. An isotropic radiator is a theoretical construct that radiates equally in all direction simultaneously. The Antenna's gain is measured in dBi – decibels relative to an Isotropic radiator. The dBi rating is used to compare the power level of a given antenna to the theoretical isotropic radiator. For example, an isotropic radiator has a gain of 0 dBi whereas a dipole is rated at 2.14 dBi. February 2005 Copyright 2005 All Rights Reserved

Free Space loss Free Space loss is the loss incurred by an RF signal as it travels over distance. The signal disperses (broadens) over distance. The power decrease is inversely proportional to the distance traveled and proportional to the signal wavelength. The 6dB rule states A 6dB increase in EIRP doubles the range. A 6dB decrease in EIRP cuts the range in half. February 2005 Copyright 2005 All Rights Reserved

Copyright 2005 All Rights Reserved

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