Compact circular polarisation design for equilateral-triangular microstrip antenna with spur lines

A novel compact circular polarisation (CP) design for a single feed equilateral-triangular microstrip antenna with inserted spur lines at the patch edges is presented. It is found that, with increasing spur-line length, the resonant frequency of the triangular microstrip patch is significantly lowered. Also, by further adjusting the inserted spur lines to have a length ratio of ~0.96, the proposed design can achieve CP radiation at a much lowered operating frequency, resulting in compact triangular microstrip antennas with circular polarisation