Analysis, Design, and Fabrication of a High-Gain Low-Profile Metasurface Antenna Using Direct Feeding of Sievenpiper s HIS

HISs have recently shown the ability to support leaky waves, and to excite plasmonic and HIS resonance frequency modes for use as an antenna. In this paper, we analyzed, designed, and fabricated a TMA by directly feeding edge-located HIS cells through a microstrip feeding network. In contrast to other metasurface antennas that necessitate an external antenna to excite metasurfaces, our approach is inspired by the TMA design methodology that directly feeds the HIS cells rather than using it as a reflector. We developed a circuit model for the proposed structure and compared the results with those obtained from full-wave simulations. In addition, our further objective was to simplify the structure based on the working principle of the proposed antenna. This objective was achieved by converting square patches into parallel strip lines, leading to an aperture efficiency of 0.77. This simplification also creates additional space to explore various resonant patterns on the top surface and the feeding network on the bottom surface of the TMA. Full-wave simulation results indicate that, despite the compact dimensions of the proposed array with 64 electrically small patch resonators (1.84{\lambda}*1.84{\lambda}*0.032{\lambda}, where{\lambda}is the free space wavelength at 6.0 GHz), it achieves a realized gain, HPBW of about 15.1 dBi and 28{\deg} respectively at 6 GHz. Finally, we constructed a prototype and conducted measurements to validate the design. Measured results demonstrate good agreement with simulation ones with a gain of about 13.5 (+-0.5) dBi and a HPBW of 27{\deg} at 6 GHz. The proposed TMA is scaled to fit within the required dimensions for smart handheld devices at higher frequencies, while maintaining high gain capability. The design s scalability, single-feed, and compact footprint make it optimal for diverse wireless communication systems, such as car to car communications.

Metasurface Energy Harvesters: State-of-the-Art Designs and Their Potential for Energy Sustainable Reconfigurable Intelligent Surfaces

Metasurface Energy Harvesters (MEHs) have emerged as a prominent enabler of highly efficient Radio Frequency (RF) energy harvesters. This survey delves into the fundamentals of the MEH technology, providing a comprehensive overview of their working principle, unit cell designs and prototypes over various frequency bands, as well as state-of-the art modes of operation. Inspired by the recent academic and industrial interest on Reconfigurable Intelligent Surfaces (RISs)for the upcoming sixth-Generation (6G) of wireless networks, we study the interplay between this technology and MEHs aiming for energy sustainable RISs power by metasurface-based RF energy harvesting. We present a novel hybrid unit cell design capable of simultaneous energy harvesting and 1-bit tunable reflection whose dual-functional response is validated via full-wave simulations. Then, we conduct a comparative collection of real-world measurements for ambient RF power levels and power consumption budgets of reflective RISs to unveil the potential for a self-sustainable RIS via ambient RF energy harvesting. The paper is concluded with an elaborative discussion on open design challenges and future research directions for MEHs and energy sustainable hybrid RISs.