Three active antenna systems have been synthesized for 14-spot European coverage in the down-link range 12.5-12.75 GHz: far-field multibeam antenna, a near-field multibeam antenna, and a direct radiating phased array. The block diagram for all the three antenna systems is shown, assuming that a single antenna is utilized for both transmission and reception. Through a set of diplexers, both receiver and transmitter modules use the shared feeds. The use of a single antenna for both transmission and reception has been shown to be attractive in terms of size and weight reduction. These features conflict, however, with the thermal and interconnecting issues that can arise in practical systems. The transmitter topology and complexity seem important points in the feasibility of the integration with the receiver. In particular, the number and allocation of the power amplifiers are quite critical.