As we have mentioned that if the time varying current density 
on the antenna is known, the radiated 
and 
fields can be determined. However, it is often advantageous to compute the radiated fields in an indirect manner, by introducing potential functions. We illustrate the procedure below.
In a region not containing free charges, for time harmonic case we can write Maxwell's equations as:
................................(7.1a)
.....................................(7.1b)
................................................(7.1c)
...............................................(7.1d)
From equations (7.1a) and (7.1b)
| Fundamentals of Antennas and Radiating systems |
In many practical antenna structures it is often possible to estimate the current distribution with sufficient accuracy to obtain good approximation of radiated fields. However, in order to calculate the impedance properties of an antenna, the current distribution is required to be known with higher accuracy. |