Antenna Clearance, an Index Factor for Electrical Size of Small Antennas

This paper presented the definition for the antenna clearance using the ratio of input impedance variation caused by the disturbance conducting wire. The clearance was discussed for 2D plane in this paper. The 3D distributions are necessary to estimate an electrical volume of the antenna which is occupied for the stable antenna resonance. The antenna volume is a key index factor to compare different shaped antennas in the view point of miniaturization. The antenna clearance definition provides an optimum method for small antenna design. Provided a restricted space for the antenna is given in advance, we could design an optimum antenna geometry taking into account of antenna near fields. A theoretical approach to define the antenna clearance is also an important issue and is left for future problem.