Calculation of Small Antennas Quality Factor Using FDTD Method

The complexity in the evaluation of the radiation quality factor Q of small antenna lies in the calculation of the stored energy. Previous authors proposed several analytical expressions for simple antennas to obtain the Q, which is of practical importance because of its relationship to the antenna bandwidth. This letter presents a general numerical method to calculate the Q using finite-difference time-domain (FDTD) method giving us accurate results and can be applied to complex antennas. Examples of a linear dipole antenna, a loop antenna and an inverted L-shaped antenna along with their results are presented and compared to analytical results of the literature.