Low Profile Dual Spiral-Loop Antenna over Electromagnetic Band-gap Ground Plane for Circular Polarization

Electromagnetic band-gap (EBG) structures exhibit unique electromagnetic properties that have led to a wide range of applications in antenna and propagation fields [1], [2]. There are two major advantages associated with EBG ground planes. First, such structures exhibit the possibility of creating a perfect magnetic conductor (PMC) because of their in-phase reflection phase characteristics. This feature can cause efficient radiation for antennas laid adjacent to the EBG ground plane [3]. Second, these structures forbid the propagation of electromagnetic waves in a certain frequency band. Therefore, they can be used to block surface waves that usually corrupt antenna performance [4]. There have been efforts for designing low profile antennas with circular polarization using a mushroom-like EBG surface. A monopole curl antenna [5] and a square spiral antenna above a mushroom-like EBG surface [6] have been studied for circular polarization. In this paper, a low profile circular polarized antenna is designed using an EBG ground plane. The investigated antenna shows 8% axial ratio bandwidth (≤ 3 dB) and 7.8% return loss bandwidth (≤ -10 dB) with centre frequency of 2.4 GHz. In comparison with PEC ground plane, the total thickness of the structure is reduced 60%.