Wide-Angle Spoof Surface Plasmon Polariton Leaky-Wave Antenna Exploiting Prefractal Structures With Backfire to Nearly Endfire Scanning

Abstract

This letter presents a single-layer, wide-angle, low-cost frequency beam scanning leaky-wave antenna (LWA) based on spoof surface plasmon polaritons (SSPPs). Here, two rows of Sierpinski prefractal parasitic patches are placed near an ultrathin planar SSPP waveguide, which can achieve continuous backfire to nearly endfire beam scanning with increasing frequency. The overall width of the proposed antenna is only 0.75 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{\text{0}}$</tex-math></inline-formula> (with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{\text{0}}$</tex-math></inline-formula> being the wavelength of the lowest operating frequency). This SSPP LWA provides high-performance backfire and broadside radiations due to applying prefractal units. Simulated results show that the proposed SSPP LWA achieves a wide scanning range from −90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> to +58 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> within the frequency range of 3–8 GHz. The average gain and radiation efficiency of the antenna are 10.9 dBi and 88%, respectively. An antenna prototype is fabricated and measured. The measured results agree reasonably well with the simulated ones.