For my final year undergraduate project i am designing an Antenna for Radar applications and following is a great article to understand the concept of the Balance transmission line and the Unbalanced transmission line.
http://www.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=6
Summary:
Balanced transmission line has parallel conductors which carries current which are equal in magnitude but opposite in direction. Which makes the overall electromagnetic fields the conductors induce
approximately cancel out. So the transmission lines which are balanced does not radiate any waves which makes them not a part of the antenna but a medium which assist in transferring the power back and forth of the antenna.
In contrast to the Balanced transmission line the unbalanced transmission line has parallel conductors which contains current which are not equal in magnitude. It makes the net induced electromagnetic flux non-zero making the transmission line a part of the antenna and it will radiate a portion of the power which is transmitted by the transmitter. Therefore the efficiency of the antenna will be less.
A coaxial cable's outer shield is typically connected to the ground, and if it is a solid ground connection then the voltage at the outer conductor will always be zero. That makes the center conductor carrying the net differential voltages which makes it an unbalanced transmission line.
To connect an unbalanced transmission line to a balanced system we need a component which is known as the balun. What balun does is that it converts an unbalanced circuit into a balanced circuit. Sometimes the balun is designed such a way that it acts as an impedance transformer.
Thank you.
No comments:
Post a Comment