Characterization of Planar Ring-shaped Array Antenna Fed by Differentially Proximity Coupling Method

This paper presents the characterization of an array antenna composed of 2×5 ring-shaped patch elements arranged in a planar manner. Each radiating patch element is differentially fed by a proximity coupling method at the opposite sides. This method aims to produce symmetrical radiation pattern with proper impedance matching and adequate impedance bandwidth. The proposed array antenna is fabricated using two layers of FR4 epoxy dielectric substrate with the total dimension of 0.805λ
o
× 0.417λ
o
× 0.014λ
o
. From the experimental characterization, the result shows that the proposed array antenna operated at the center frequency of 1.275 GHz with the –10 dB impedance bandwidth of 27 MHz. Moreover, the fabricated array antenna produced a symmetrical radiation pattern with the front-to-back ratio of 6.41 dB, in which this result is comparable to the simulated one with the front-to-back ratio of 10.45 dB.