Đang tải... (xem toàn văn)
Bài giảng Antennas
February 2005 Copyright 2005 All Rights Reserved 1Antennas (1 September, 2006) February 2005 Copyright 2005 All Rights Reserved 2● Explain the types of wireless LAN antennas and how/when to use them● Describe the various wireless LAN accessories and where they are usedObjectivesUpon completion of this chapter you will be able to: February 2005 Copyright 2005 All Rights Reserved 3 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 http://www.fab-corp.com February 2005 Copyright 2005 All Rights Reserved 4Omni-directional Antenna✔Mast mount omni✔ Blade omni✔ PC Card integrated omni✔Pillar mount omni✔Ground plane omni✔Ceiling mount (blister) omni http://www.fab-corp.com February 2005 Copyright 2005 All Rights Reserved 5 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 6Omni-directional Antenna Radiation Pattern February 2005 Copyright 2005 All Rights Reserved 7 Dipole/Omni AntennaOmni Ceiling Mount AntennaOmni Pillar Mount AntennaOmni Ceiling (Blister) Mount AntennaOmni Blade Antenna February 2005 Copyright 2005 All Rights Reserved 8Omni-directional UsageOmni Coverage● Used when coverage in all directions is required.● Typically in a ✔Pt-multipoint link✔warehouse✔hotspot✔Tradeshow✔Airport February 2005 Copyright 2005 All Rights Reserved 9Omni-directional Antennas2.4 Gz 10 dBi Omni-Directional Antenna2.4 Gz 5 dB Magnetic Mount Omni Antenna February 2005 Copyright 2005 All Rights Reserved 10Cantenna Waveguide Antennahttp://www.cantenna.com/ [...]... Connector RP-TNC Dimensions (H x W) 11.5 x 1.125 in. Mounting Mast mount—indoor/outdoor February 2005 Copyright 2005 All Rights Reserved 34 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... http://www.fab-corp.com February 2005 Copyright 2005 All Rights Reserved 39 Different Polarized Antennas Vertically Polarized Antenna Horizontally Polarized Antenna February 2005 Copyright 2005 All Rights Reserved 32 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...February 2005 Copyright 2005 All Rights Reserved 35 Multipath Fading Multipath Reception Distortion February 2005 Copyright 2005 All Rights Reserved 2 ● Explain the types of wireless LAN antennas and how/when to use them ● Describe the various wireless LAN accessories and where they are used Objectives Upon completion of this chapter you will be able to: February 2005 Copyright 2005... 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 1 Antennas (1 September, 2006) February 2005 Copyright 2005 All Rights Reserved 10 Cantenna Waveguide Antenna http://www.cantenna.com/ February 2005 Copyright 2005 All Rights Reserved 30 Fresnel Zone ✔ The . All Rights Reserved 1Antennas (1 September, 2006) February 2005 Copyright 2005 All Rights Reserved 2● Explain the types of wireless LAN antennas and how/when. http://www.fab-corp.com February 2005 Copyright 2005 All Rights Reserved 5 Omni-directional Antennas ●The omni-directional Dipole antenna is the most common WLAN antenna.✔