In: Physics
I need fast for my Courseworks, need al least 4 hours after i post this question.
1. Explain About Linear Antenna And Surface Antenna and gives some examples!
2. What is Major Direction and Null Direction of EM Waves Radiation
Thank you for your answer! I'll appreciate it. Need answer for both of question
Linear antennas are considered to be those antennas that imply the use of electrically thin conductors (wavelength>>conductor diameter.
Electric current flows over the conductor surface.inorder to calculate fields in these antennas, conductor are modelled as if they are current lines with no diameter.
Example-loop antennas,Helix, Helix axial radiation mode.
Surface antenna is atype of radio antenna with a low profile,which can be mounted on a flat surface.it consist of a flat rectangular sheet or a patch of metal,mounted over a larger sheet of metal called ground plane.
Ex-planar inverted f antenna (PIFA),printed monopole antenna.
2.Null is a direction in an antennas radiation pattern where the antenna radiates almost no radio waves,so the far field strength is a local minimum.Null occurs because of an antenna radiates radio waves of different phase.
Major direction of em wave radiation is the direction in a most of the radiation travels .generally the radiated waves are in same phase.