Direct Radiations of Surface Plasmon Polariton Waves by Gradient Groove Depth and Flaring Metal Structure

An efficient method to radiate surface plasmon polaritons (SPPs) directly using metallic corrugated strip with gradient grooves and flaring structure has been proposed, in which the gradient grooves are used to overcome the big mismatch of wavenumbers between SPP modes and radiated spatial waves while the flaring structure provides impedance matching in wide frequency band. Both numerical simulations and measurement results suggest good direct radiation performance of the proposed structure in a wide frequency band from 5 to 20 GHz, in which the measured radiation patterns show a high gain level of 9.9 dBi on average, and the average efficiency can achieve 92%. The proposed direct radiation structure is of great application values in communication systems and integrated circuits.