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WiFi Antennas

WiFi Antennas Reid Palmeira EE496 WiFi Specification IEEE 802.11b Uses 2.4 GHz frequency band Up to 11 Mbps Has fallback data rates to 5.5, 2 and 1 Mbps Uses only Direct Sequence Spread Spectrum Approx. 200 ft. clear line of sight range 14 total channels, 11 channels (in US) Designs

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WiFi Antennas

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  1. WiFi Antennas Reid Palmeira EE496

  2. WiFi Specification • IEEE 802.11b • Uses 2.4 GHz frequency band • Up to 11 Mbps • Has fallback data rates to 5.5, 2 and 1 Mbps • Uses only Direct Sequence Spread Spectrum • Approx. 200 ft. clear line of sight range • 14 total channels, 11 channels (in US)

  3. Designs • Pringles can • Effective directional antenna • Cantenna • More effective • Parabolic dish • Much more effective • Significantly improved SNR • Limits the useful range of WiFi

  4. Legality Disclaimer • Illegal by FCC regulations • You can only attach an FCC approval antenna to a WiFi card or base station • Only commercial antennas are approved • Enforcement provisions are minimal

  5. Design Considerations • Effectiveness • SNR improvement • Signal range improvement • Size • Portability • Storage • Cost and Build Time • Realistic use • Accessibility • Legality • If the FCC comes knocking, be French: run away!

  6. Pringles

  7. Design • N-Connector and pigtail from the reflector (the can) to the AP or to the WiFi card • Mount the injector to the side of the reflector • Parts must be checked to make sure matching errors don’t occur – for example standard coax cable from something like a TV will absorb the entire signal very quickly. • The longer the reflector (the can) the more directional and less omni-directional the antenna becomes

  8. Benefits of can type booster antenna • Improved SNR and performance • Increase in effective range of WiFi • Cost is much less than commercial antenna with similar performance • Build and testing times are small

  9. Parabolic Antenna

  10. Design of Parabolic • Shaped wire mesh bent over a parabolic frame to form a miniature grid antenna • Mesh material should be such that • Attached to the AP • Focal length varies proportionally with the size of the mesh dish - scalability

  11. Benefits of parabolic design • Increased security, since signal degrades behind the parabola • Minimal parts and build time • Significant reduction of interference • Less parts and no N-connectors, pigtails or cables means no matching problems or transmission line worries • No modification of any WiFi cards or modification to parts of the AP

  12. Testing with Network Stumbler Green is signal Red is noise

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