Design of a high performance wideband S-APAS architecture

The S-APAS (Scalable Multifunction Radio Frequency - Active Phased Array System) architecture has already been presented in previous papers [1] [2] [3]. The potential use of this architecture, in different versions and different operating bands, have been also analyzed on the basis of parallel technological developments [4] [5] [6] [7] [8]. However, the most challenging issue for the S-APAS architecture is a suitable design which allows this architecture to work at different operating frequencies and with wide instantaneous bandwidth, by using the same T/R modules and the same framework structure, while offering the best radio frequency performance at different frequencies. The main problems in defining such a wideband version of the S-APAS architecture are both in the technological aspects, i.e. producing T/R modules, with enough performance at frequencies of interest, and in system design, i.e. defining an array structure that is capable to provide high performance radio frequency figures while changing frequency, by means of a suitably reconfigurable beamforming and beamshaping. This paper tackles these problems, in order to assess feasibility of the wide band approach both in terms of technological capability and architectural feasibility. Regarding the first problem, the technological capabilities of the T/R components, in particular the GaN amplifier, are examined, starting from the wideband characteristics of the present generation of GaN components and analyzing the medium term improvements which have been planned in this area. With regard to the wideband architecture, a frequency tapered array design approach [9] is taken into consideration and its properties are analyzed, in order to evaluate the best configuration that is applicable to the S-APAS architecture.