A novel single layer, dual-polarization reflectarray is proposed to operate at transmit (30 GHz) and receive (20 GHz) frequencies for Ka-band terminal antennas. The proposed reflectarray antenna is based on a unit cell with several resonant elements of adjustable length printed on the same side of a conductor backed substrate. Crossed dipoles and truncated rectangular rings are used to adjust the phase at 30 GHz, while cross-shaped loops are used for the phasing at 20 GHz. The adjustment of phase in each element is made by varying the resonant length of the printed elements. An 18-cm reflectarray antenna with separate feeds for 20 GHz and 30 GHz has been designed and analyzed. The simulated results show satisfactory focused beams with a gain of 30.6 dBi at 20 GHz and 33.7 dBi at 30 GHz.