Tuesday, 31 December 2013

Antenna Wave Propagation

Antenna Wave Propagation

      1.      A communication system always involves a Spectrum or Band of Frequencies
      2.      Modulation may be defined as a process by which any characteristics of a wave is varied as a function
      3.      To radiate or receive electromagnetic waves an Antenna is required
4.      The boundary sphere between antenna region and free space region appears as opaque
5.      Electric field intensity is defined as the force on Unit Test Charge
6.      Lord Kelvin devised a method known as the IMAGE METHOD
7.      Magnetostatics can also be named as the Static Magnetic Current or Steady Electric Field Current
8.      The magnetic flux tubes are Continuous
9.      A Helical Soil or Solenoid is usually used to produce a magnetic field
10.  Fraday’s law gives the e.m.f induced in a closed circuit due to change of magnetic flux
11.  The electromagnetic equations derived earlier are Maxwell’s equation
12.  A homogeneous medium is that medium in which the quantities are constant
13.  The energy radiated in a particular direction by an antenna is measured interms of FIELD STRENGTH
14.  Different parts of radiation pattern referred to as LOBES
15.  Gain is closely associated with Directivity
16.  Directive gain depend entirely on the distribution of Radiative Power in Space
17.  Antenna band width is a measure of directivity of an antenna
18.  An antenna array is said to be Linear
19.  Broad side array is also known as Broad Side Couplet
20.  The minor lobes just adjacent to the main lobe are called Side Lobes
21.  The technique used in reduction of side lobe are called as Tapering
22.  The vertical radiator may be either Vertical Wire or Metallic Mast
23.  Electrically short antennas are generally used as Vertical Grounded Antennas
24.  Beverage or wave antenna is a non-resonant antenna
25.  There are two methods of exciting a tower antenna known as Series Excitation and Shunt Excitation
26.  The field distribution in vertical plane of a vertical grounded radiator depends upon the Height
27.  The V Antenna is an extension of long wire antennas
28.  V Antenna provides Multi Band Operation
29.  Resonant or Tuned Antenna considered in the HF band
30.  The Rhombic Antenna is based on the principle of Travelling Wave Radiator
31.  Rhombic arrays is one that is used for receiving purposes only in Multiple-Unit-Steerable Antenna
32.  Travelling Wave or Aperiodic Antenna are those antennas in which there is no Reflected Anteena
33.  A Radio Direction Finder is used to find determine of arrival of a radio signal
34.  The term Direction Finder has a special sense and general sense

35.  The radiation efficiency of closed loop antenna is low for transmission purposes\


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