Compact, wideband antennas enabled by interdigitated capacitor-loaded metasurfaces

In this paper, a class of integrated metasurface (MS)-based planar antennas are proposed, which are fed by monopoles operating below their fundamental modes. Various interdigitated capacitor (IC) loading schemes for a metallic sheet backed MS are investigated, which provide footprint miniaturization and bandwidth enhancement. A linearly polarized (LP) MS-based antenna, loaded by ICs, provides a 15% impedance bandwidth and a gain higher than 6.67 dBi. The radiation mechanism and resonant frequency dependence were revealed via a dispersion analysis, which serves to explain the working principle of the proposed antenna. Next, a miniaturized antenna with doubly loaded ICs was introduced, achieving an impedance bandwidth of 10%, a gain above 6 dBi, and a more than 30% footprint reduction. A more advanced compact, circularly polarized (CP) MS-based antenna with a compact footprint, and improved 3-dB axial ratio (AR) bandwidth were also presented, by introducing triangular IC and diagonal slot loadings to the MS. It is demonstrated that this antenna achieves an impedance bandwidth of 16%, a gain above 5.5 dBi, and an AR < 3dB bandwidth of 10%. Three antenna prototypes were fabricated and measured, with good correspondence between the experimental results and simulation predictions, confirming the proposed design methodologies. These compact and well-performing MS-based antennas have promising potential for applications in modern wideband wireless systems.