Increasing Radiation Efficiency Using Antenna Shape Optimization Approach

From the characteristic mode point of view of electrically small antennas, radiation efficiency normally decreases significantly if multiple modes are well excited. Among all these well-excited modes, the one with the lowest modal radiation efficiency determines how much actual radiation efficiency is guaranteed. Based on this idea, this letter proposes a method for improving antenna efficiency using shape optimization approach. The optimized shape can give rise to a high efficiency and an implied high gain after being excited using a single port whose location is easily selected by observing characteristic-mode current distributions.