Directivity Enhancement of Microstrip Antenna using SL-FSS for Wireless Power Transfer

In this study, a rectangular microstrip patch antenna at frequency of 2.4 GHz was designed for WPT applications. To improve the directivity of the antenna, we applied the technique of adding a square-loop frequency selective surface (SL-FSS) placed near the antenna with an air bandgap. The SL-FSS is made of a 4X3 periodic structure using a ring unit cell located perpendicular to the main lobe of the antenna. Based on the measurement results, the use of SL-FSS at a distance of 30 mm has increased the directivity to 6.6 dBi. Similarly, the gain value has become 5.66 dB, the VSWR is 1.4, and S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> is −15.57 dB. Furthermore, the antenna configurations with and without SL-FSS have the same radiation pattern, making it very useful for improving efficiency in WPT.