Monday, July 20, 2020

TRAVELING WAVE ANTENNA

TRAVELING WAVE ANTENNA

              In radio and telecommunication, traveling wave antenna is a class of antenna that uses traveling wave on guiding structure as the main radiating mechanism.

                                           

DEFINITION :
            The antenna in which standing waves does not exist along the length of the antenna is called traveling wave antenna. It is a non- resonant  type ( aperiodic antenna) antenna which can be used over much broader frequencies.
     • It is a directional antenna in which traveling wave of electromagnetic oscillations is propagated along its geometric axis.
     • These antennas are made either with discrete radiators or in the form of continuous radiators.
     • Common types of traveling wave antenna are
           1. Beverage antenna
           2. Rhombic antenna
    •  This two types of antennas are used in transmitting and receiving installations for all            wavelengths of the radio band.

TYPES :
       In general, two types of traveling wave antenna are there
             1.SLOW WAVE STRUCTURE
             2.FAST WAVE STRUCTURE 

1.SLOW WAVE STRUCTURE :
            Slow wave structure is also known as the surface wave antenna where the phase velocity of the wave is smaller than the velocity of light in free space. The radiation for this type of antenna occurs typically from the feed and terminate regions.  There is an optimum length for this antenna depending upon the desired location of the main beam.

2.FAST WAVE STRUCTURE  :
            Fast wave structure is also known as the leaky wave antenna where the phase velocity of wave is greater than the velocity of light in free space. This structure radiates all its power within the fields in the direction of wave travels.

EXAMPLES OF TRAVELING WAVE ANTENNAS ARE :

      • The Helical antenna
      • The yagi-uda antenna
      • The spiral antenna

                            

Some of the linear wire antennas are the dominant type of traveling wave antenna. Recently, a new simple analytical and technical design of meanderline antenna has been developed which enables reduction of antenna length in traveling wave structure.

ADVANTAGES: 
     • This antennas are distinguished from other antennas by the presence of traveling wave and by the propagation of power in a single direction.
     • Since they are non- resonant type ,they often have wider bandwidth than the resonant antennas.
     • This antennas are simple and easy to construct.
     • Input impedance is high for this antenna.

APPLICATIONS :
    This antennas are used in various fields like
      • Commercial applications
      • RF communication
      • Microwave communication
      • Light aircraft
      • Military appliances
      • Long closed places like tunnels.

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