Analysis of Antenna Gain Enhancement with a New Planar Metamaterial Superstrate: an Effective Medium and a Fabry-Pérot Resonance Approach

摘要

We have compared gain enhancement behavior of patch and horn antennas from two different points of view: namely, effective medium analysis and a Fabry-Pérot cavity resonance approach. To examine how a near-zero refractive index (n) affects the performance of antennas, we designed a new planar metamaterial (MTM) superstrate, which can produce negative, zero, and positive values of n at around 2 GHz. We placed the MTM superstrate very close to the patch and horn antennas to see whether an n value that is effectively near zero can collimate antenna beams and increase antenna gain, which provided opposite gain behavior for the two antennas. To explain the dissimilar enhancement in the gain of the patch and horn antennas, we retrieved constitutive parameters from the proposed MTM superstrate and discussed the effect of various incidence angles upon the superstrate. In addition, to increase the gain further, we examined appropriate resonant heights between the antennas and the superstrate. Consequently, with the help of Fabry-Pérot cavity resonance, we obtained relatively high antenna gain. Moreover, the results of the prediction are in good agreement with the results of the measurement.