A planar leaky-wave antenna (LWA) with flexible circular polarization (CP) characteristic is proposed in this paper, which is promising for satellite communication applications. A novel fan-blade shape slot is utilized to achieve left-or right-handed circular polarizations by manipulating the wave propagating directions in the waveguide. Moreover, a two-LWA array is further investigated to obtain dual CPs in both the backward and forward scanning. In addition, the proposed LWA overcomes the open stopband, which is a problem frequently plaguing LWAs. As a result, the proposed LWA scans continuously from backward to forward. An example LWA is designed in the Ka band using the substrate integrated waveguide (SIW) technique with coaxial connector feedings. The main radiation beam steers continuously from-45°to 45°in dual CPs when the operating frequency varies between 28 and 37.3 GHz. A prototype has been fabricated and tested to demonstrate the design idea and application scenario.