A single-feed circular polarized (CP) rectangular microstrip antenna (MPA) is proposed. Capacitive disk coupling feed is used in the design. By connecting a resistor load to another capacitive disk at the opposite position, CP radiation over a wide frequency range is realized. Experimental results show that the fabricated antenna has an impedance bandwidth (S11 return loss) of 78.7% and a 3-dB axial ratio (AR) bandwidth of 27.5%. The peak gain level is about 6.8 dB. As a result, this antenna can be used in occasions when wide AR CP performance is desired.