Leaky wave antennas based on spoof SPP along metallic wire with gradient radial grooves

Abstract

In this paper, we propose a kind of leaky-wave antenna based on spoof surface plasmon polaritons (SPP) along the metallic wire with gradient radial grooves. Coaxial wire, supporting traditional guided waves, is used to feed the proposed structure. The conversion between coaxial wire and SPP waveguide is achieved by the flaring outer conductor of the coaxial wire and gradient radially corrugated inner conductor, which can match the momentum and impedance of the two kinds of transmission lines. The fact that any surface wave can be converted to a leaky wave if a periodic perturbation is introduced along the guiding structure is the foothold of this particular design. Thus the periodic gradient radial grooves are introduced to bring periodic perturbation to the propagation of the surface wave. Then the surface wave can be converted to radiating modes, resulting in the leakage of the energy during transmission. The simulated results show that the proposed structure can support leaky-wave modes in a wide frequency band of 3–7 GHz. The total scanning angle can reach 118.3° from backward to forward directions with an average gain of 9.29 dBi. Both endfire and broadside directions of the proposed leaky-wave antenna can be reached by the scanning beam during the operating band. To the best knowledge of the authors, this is the first time to realize such a wide scanning angle by the leaky-wave antenna based on spoof SPP. The wide operation band, wide scanning angle, and simple structure make the proposed antenna promising in the future wireless and satellite communication systems. This work fulfills one of the applications of SPP waveguides.