ANALYSIS OF A HIGH-GAIN FABRY-PEROT CAVITY ANTENNA WITH AN FSS SUPERSTRATE: EFFECTIVE MEDIUM APPROACH

A new approach to analyze the behavior of a Fabry-Perot cavity type high-gain antenna covered with a frequency selective surface (FSS) superstrate is presented. Using an image theory and effective constitutive parameter retrieval, properties of impedance and a refractive index of the entire cavity structure are investigated. Through the analysis, we show that our antenna inherently operates in the medium whose maximum magnitude of the refractive index is lower than '0.5'. In consequence, we demonstrate that the high-gain feature of the Fabry-Perot cavity antenna is not only due to satisfy a conventional cavity resonance condition, but also for a wave collimation effect of a metamaterial with the effectively low index of refraction. To show the collimation effect of the cavity, phase properties of a radiating wave with and without the FSS superstrate are examined. Moreover, the effect of the real and imaginary parts of the refractive index on behaviors of the antenna is also investigated by analyzing the derivative of a realized gain of the antenna within an impedance matched frequency band.