Development of a beam-forming matrix using MMICs for multibeam active phased arrays

In recent years, traffic capacity of communications satellites has been increased by the introduction of frequency reuse through polarization and spatial isolation of antenna beams. Therefore, recent satellite payload designs have required the use of high-gain antennas capable of producing multiple spot beams. Active phased-array antennas using gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) offer the ability to simultaneously form multiple beams, while providing the additional advantages of power sharing among beams, and flexibility of independent beam reconfigurability and steerability. In addition, by forming narrow beams, higher effective isotropic radiated power (EIRP) can be achieved, making communication with small earth stations possible, and reducing the overall service cost. A critical element in the realization of active phased-array antennas is the beam-forming matrix (BFM), which provides beam shaping and steering. This paper presents the design of a highly integrated, modular, Ku-band BFM, which is relatively easy to assemble with the antenna array. Test results for the fully assembled BFM over the 11- to 13-GHz frequency range demonstrate uniform performance for all phase shifter states and transmission paths within the BFM. The BFM has been assembled with a 24-element high-power army and has been used to successfully generate four independently steerable simultaneous beams.<>