Surface-Wave Minimization Using Spherical Wave Expansion

This letter presents a method for reducing antenna-excited surface waves in mobile devices. Surface waves are canceled either by actively injecting compensating surface waves in opposite phase, or passively creating reactive conditions from which scattered, secondary surface waves cancel the primary waves. We use spherical wave expansion to calculate the amplitudes and phases of the canceling surface waves and show also how reactive loading near the antenna can launch these canceling waves. We verify the proposed method with simulations. Reduced surface waves result in a smoother radiation pattern and significantly increased gain.