Design TeamJarret LavalleeCorey Davis

WiFi Basics•Wireless adapters transmit

frequencies of 2.4 GHz and 5 GHz.

•The higher the frequency, the more data they can hold and transmit.

•The two most common networking standards are 802.11g and 802.11b

•We are going to be using 802.11g. It sends up to 54 megabits per second and uses OFDM which is more efficient at encoding than CCK

How WiFi Waves are Transmitted and

Received•WiFi waves are transmitted by means of oscillating electromagnetic fields which pass through space.

•These waves are picked up and received by antennas in some type of receiver.

•The distance the waves can travel depends on the strength of the transmitter.

WiFi Diagram

Antennas• The two most commonly used antennas are

narrow beam antennas and reflector antennas.

• The main characteristics of an antenna are its gain and half power beamwidth.

•Gain is measured by how much of the input power is concentrated in any given direction.

•Half power beamwidth is the angular separation between the half power points on the antenna radiation pattern, where the gain is one half the maximum value.

Narrow Beam

Antenna

Reflector Antenna

Antenna Designs

•There are two different antenna designs

•The Cassegrain design uses a convex subreflector and a hyperboloidal surface.

•The Gregorian design uses a concave design with a ellipsodial surface.

Gain and Half Power Beamwidth

In Short•“The gain of an antenna is

determined by the intended area of coverage. The gain at a given wavelength is achieved by appropriately choosing the size of the antenna. The gain may also be expressed in terms of the half power beamwidth.”

WiFi Antennas

• Omni-directional• Significant gain at 360º around• Can be small and portable

WiFi Antennas

Cont.• Directional• Large gain at small angle.• Bulkier than Omni-directional

Collinear Dipole Design

• Based on Coax Design

• Alternating lengths of wire intensify the pattern of the wave, ~6 dB gain

• Advantages:-Simple Design-Cheap and readily available materials

• Disadvantages:-Difficult to build-Not enough gain

Cantenna Directional Antenna

Use the shape of a can to reflect waves to focused point ~10 dB gain.

•Advantages:-Simple Design-Cheap and readily available parts-Good amount of Gain•Disadvantages-Directional-Limited by shape of the can

Biquad and Double Biquad Directional

• Use the shape of the bow tie and reflector plate to intensify signal gain. Biquad ~11 dB and Double Biquad ~12 dB

• Advantages:-High gain-Customizable

• Disadvantages-Difficult to assemble-Directional-Parts not readily available

Satellite Dishes

•Directional Antennas can be mounted on a satellite dish

•Gives significantly more gain

•Focuses waves at the focus point

•Also directional

•~22 dB Gain

•Best Design?

•Cost-Effective

•Simple

•Durable

•Significant Gain

Best Design

Satellite Dish Mounted Cantenna

• Satellite dishes are readily available and cheap

• Most durable set up

• Great gain ~ 24 dB

• Easy to assemble

• Highly customizable

• Most cost Effective design