Spoof surface plasmon polariton‐fed circularly polarized leaky‐wave antenna with suppressed side‐lobe levels

Abstract

A wide-angle scanning circularly polarized (CP) leaky-wave antenna (LWA) with suppressed side-lobe levels (SLLs) is proposed, which can be a good candidate for future radar and wireless communication systems. The LWA consists of 12 cross slotted elliptical patch elements, which are fed by a microstrip spoof surface plasmon polariton (SSPP) line. Two fundamental modes of the patch array with two orthogonal polarizations can be excited by the electromagnetic coupling between the array and the SSPP line. By optimizing the elliptical eccentricity e and etching cross slots on the elliptical patch array, a 90° phase difference is introduced, and then, the CP radiation is realized. A tapered aperture field distribution is also realized by adjusting coupling intensities between the patch elements and the SSPP line, which is beneficial to reduce the SLLs. The electrical size of the LWA is 1.29λ0 × 6.02λ0 × 0.08λ0, where λ0 is air wavelength at 12.9 GHz (broadside direction). Both the simulated and measured results indicate that the CP operating band is 12.0 to 15.0 GHz. The proposed CP LWA scans continuously from −14° to 38°. In the whole operating band, the axial ratios are less than 3 dB, and the SLLs are less than −20 dB as well.