Tuesday, September 13, 2011

Introduction to Antenna

  • An antenna is an electrical conductor or system of conductors
             * Transmission - radiates electromagnetic energy into space
             * Reception - collects electromagnetic energy from space
  • In two-way communication, the same antenna can be used for transmission and reception


Antenna Definition

   An  antenna  is  a  circuit  element that  provides  a  transition  form  a guided wave on a transmission line to  a  free  space  wave  and  it provides  for  the  collection  of electromagnetic energy.

  In  transmit  systems  the  RF  signal  is generated,  amplified,  modulated  and applied to the antenna.

   In receive systems the antenna collects electromagnetic  waves  that  are “cutting”  through the  antenna  and induce  alternating  currents  that  are used by the receiver.

Polarization


   Polarization  is  the  direction  of  the  electric field and is the same as the physical attitude of the antenna.
 
          - A  vertical  antenna  will  transmit  a  vertically polarized wave.

  The  receive  and  transmit  antennas  need  to possess the same polarization.

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