BROAD-BAND ACTIVE MICROSTRIP ANTENNA DESIGN WITH THE SIMPLIFIED REAL FREQUENCY TECHNIQUE

This paper deals with the design of broadband active microstrip antenn as where the amplifier is integrated with the radiator, Theoretically sound definitions for gain and noise figure of the active antenna are introduced, and their relationships with the definitions for the compo sing circuit and radiator parts are explained. A sequential design pro cedure is presented that allows the straightforward and optimal design of transmitting and receiving antennas with multiple active stages, t aking into account input and output matching, the gain-versus-frequenc y curve as well as the noise performance. The theoretical concepts are illustrated with two examples: one of a transmitting active antenna a nd one of a receiving antenna, The former one is a two-stage design th at achieves nearly 25% of bandwidth with regard to gain and matching a nd 24 dB gain improvement as compared to the matched passive antenna. The second one is a receiving antenna (one stage) with a measured nois e figure of 1.2 dB in a bandwidth of over 17% and a gain improvement o f 11.9 dB over the corresponding passive antenna, Finally co- and cros s-polar radiation patterns in E- and H-plane prove that the antennas a lso have favorable radiation characteristics in a wide bandwidth (at l east 18%).