Design and analysis of annular ring-based RIS and its use in dual-band patch antenna miniaturization for wireless applications

摘要

This paper proposes the design of a Reactive Impedance Surface (RIS) which comprises a 5 x 5 array of grounded unit cells. The unit cells have annular ring structures on their top surfaces. A detailed analysis of the unit cell leading to its impedance characteristic is presented and validated with simulated results. The RIS exhibits inductive impedance below 4.92 GHz. Next, the RIS is used as the ground of a dual-band patch antenna instead of a metallic ground for the purpose of miniaturization. As a result, the lower resonant frequency of the antenna is lowered from 3.36 to 2.4 GHz exhibiting 28.6% miniaturization. The higher resonant frequency is decreased from 4.77 to 3.43 GHz exhibiting 28.1% miniaturization. The theory of antenna miniaturization using RIS is also discussed. The lower and higher resonant frequencies of the miniaturized antenna correspond to the WiFi and WiMAX frequencies, respectively. The gain and efficiency at these two frequencies are significant and radiation patterns are stable with low cross-polarization level. Hence, the proposed structure can be used for practical wireless applications.