System design and technology development for an EHF beam-hopped satellite downlink

The paper describes, in the context of future EHF satellite communications systems, the essential issues in the design of a 20 GHz beam-hopped downlink to be used in conjunction with a 44 GHz FDM uplink and a multichannel demodulating and multiplexing satellite. Several beam-hopping systems are examined from the point of view of their ability to generate a narrow beam, and switch its direction at a high rate. Phased-array systems with an electronically focused antenna and beam-array systems with optical focusing are compared in terms of performance, power requirements, and complexity. Other factors, such as the technologies used for antenna power amplification (GaAs FETs versus IMPATT diodes) and beam control (PIN-diode switches versus ferrite switches) strongly influence the design of such systems. Several of the system design issues and current hardware development efforts at MIT Lincoln Laboratory for such a downlink are described.