In this paper we have extended the concept of a travelling wave fed circularly polarized antenna [1,2], to provide an active antenna with the capability to switch between right and left hand polarization. The antenna was fabricated in a multilayer format using a newly available polymer material, with PIN diodes to perform the switching function. Measured data at 15GHz showed a good return loss in both states, with well behaved radiation characteristics. The design technique offers potential for further development to provide an integrated antenna with high functionality.