Low-profile circularly polarized antenna exploiting fabry-perot resonator principle

Abstract

We designed a patch antenna surrounded by a mushroom-like electromagnetic band-gap (EBG) structure and completed it by a partially reflective surface (PRS). EBG suppresses surface waves and creates the bottom wall of the Fabry-Perot (FP) resonator. PRS plays the role of a planar lens and forms the top wall of the FP resonator. The novel PRS consists of a two-layer grid exhibiting inductive and capacitive (LC) behavior which allows us to obtain a reflection phase between -180o and +180o. Thanks to this PRS, we can control the height of the cavity in the range from λ/2 to λ/300. Obtained results show that the FP resonator antenna enables us to achieve a low profile and a high-gain. The patch is excited by a microstrip transmission line via the crossslot aperture generating the circular polarization. Functionality of the described concept of the FP antenna was verified at 10GHz. The antenna gain was 15 dBi, the impedance bandwidth 2.3% for |S11| < -10dB, and the axial ratio bandwidth 0.6% for AR < 3.0dB. Hence, the antenna is suitable for narrowband applications. Computer simulations show that the microwave FP antenna can be simply redesigned to serve as a source of circularly polarized terahertz waves.