When a crank line (CL) antenna is excited from its left and right input ports, it radiates right- and left-hand circular polarization (CP) wave beams, respectively. Each beam direction is determined by the radiation cell dimensions. For the use of a dual CP wave element, the directions of the two beams must be the same. Also, the left input port must be electrically isolated from the right input port, and vice versa. This paper presents the radiation characteristics of the CL antenna as a dual CP wave element; first, the cells are optimized to radiate a broadside CP wave beam, and the axial ratio in the broadside direction is discussed. Secondly, the frequency responses of the gain, axial ratio, and input port isolation for the optimized CL antenna are evaluated.