Microstrip-fed crossed-slot array antenna

A microstrip-fed crossed-slot array antenna having a circular polarisation is developed. First, a single crossed-slot antenna, that can radiate a circularly polarised wave in the broadside direction, is designed and its coupling level to the microstrip line is analysed. Based on this result, an eight-element crossed-slot array is designed and its characteristics are experimentally investigated at 12 GHz band. The return loss of -17 dB is obtained at the design frequency of 11.85 GHz, and the axial ratio of less than 3 dB is achieved over the fractional bandwidth of 5%.