A microstrip line traveling-wave antenna has been designed, analyzed, and verified experimentally. The antenna demonstrated a broad input impedance bandwidth with a radiation efficiency dependent upon the height above the ground plane. The broadside circularly polarized radiation pattern was obtained by geometrically shaping the microstrip line. The experimental measurements show pattern bandwidths of 10 to 16 percent with input impedance bandwidths greater than 20 percent. The axial ratio is less than 3 dB within the operating bandwidths.