26-12-2012, 11:12 AM
Antenna Aperture
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The concept of aperture is most simply introduced by considering a Rx antenna. Suppose that the Rx antenna a Rectangular horn immerged on the field of Uniform Plane Wave.
Antenna terminal Impedance
Consider the antenna simply is circuit element that must be properly matched to the rest of the network for efficient power transfer.
The I/p or terminal Impedance of an antenna is complicated function of frequency
At a single frequency it is represented by a resistance and capacitance
A better approximation applicable to linear antenna involves with a distributed N/W; such as a Txline.
For length of antenna less than length, the input impedance can be represented over a narrow band of frequency by R and c in series R= Radiation Resistance and C= capacitive reactance.
For length of antenna greater than length, the I/P inductive and would be represented R in Series with L.