Antennas

Polarization

• Vertical
• Horizontal
• Circular
• Point-to-point - antennas must have the same polarization

Radiation Patterns

• Radiation pattern chart -  describes the signal sent by an antenna
• There are two fields that antennas radiate their power
• E-Plane
  • The elevation plane, or elevation chart - side view
  • Composes the electric field vector
• H-Plane
• The horizontal plane, or azimuth chart - top view
• Composes the magnetic field vector

RF Math

• Watt - energy measurement represents one Joule per second
• Decibel - logarithmic unit used to express the ratio between two values
• dBm- compare the relative power between two signal expressed in mW
○ 0dB = same power as measured
○ 3dB = Twice the power
○ 10dB = 10X the power
○ -3dB = Half the power
○ -10dB = 1/10 of the power

                -dBm = 10*Log10(mW)
                 mW = 10(dBm/10) 

Radio Frequency (RF) Fundamentals

Frequency - how fast a cycle repast itself
Wavelength - how wide is one cycle
Amplitude - related directly with power
Hertz (Hz) - how often a wave repeats per second

Low frequency travels further than higher frequency because it is less affected by the air

RSSI - Received Signal Strength Indicator
• Closer to zero better
• Negative value measured in dBm

Wireless Network and Topology

Types

• WAMP -Wireless personal area networks 
  ○ Range up to 30feet
  ○ 802.15standard
  ○ Low power , easy to use, low cost. 
  ○ E.g. Bluetooth
  
• WLAN - Wireless local area networks
  ○ Range about 300 feet
  ○ More power consumption
  
• WMAN - Wireless metropolitan area network
  ○ Range-city or suburb
  ○ Most of the time uses licensed frequencies
  ○ E.g.WiMAX
  
• WWAN - Wireless wide-area network
  ○ Very large distance coverage
  ○ Uses licensed frequencies
  ○ GSM is the most common in the world. CDMA, int he US and Japan 
  ○ E.g. Mobile phones network