Sometimes phase correction does not increase directivity of electromagnetic bandgap resonator antennas - a case study

Phase correction has been used to demonstrate increase in directivity of conventional electromagnetic bandgap resonator antennas (ERAs) [1-3]. The ERA considered as a base antenna for previously reported PCS designs has a gain of 12.5 dBi and poor electric near-field phase uniformity. That antenna comprises of an all-dielectric partially reflecting surface (PRS) having a reflection coefficient of ~0.6. A PCS when used with such an ERA increases its peak directivity by ~9dB, by tremendously improving its near-field phase uniformity. In this paper an ERA having a highly reflective printed PRS (reflection coefficient more than 0.9) is considered. It has a better electric near-field phase uniformity and is highly directive, with a directivity of 24 dBi. The principle of phase correction has been applied to further improve phase uniformity and peak directivity of this ERA. However, the peak directivity, with the PCS dropped and side lobe levels are increased. A preliminary investigation reveals that poor near-field amplitude distribution is the reason for deteriorated far-field performance.