Highly efficient broadband transmission system

A highly efficient 8x4 amplitude-phase shift keying (8x4 APSK) modulation satellite broadband communication system that features a compact two-beam spatial superposition that improves the usage efficiency of the frequency resources and energy is presented. The system incorporates an eight phase-shift keying (8PSK) modulator, a quadrature phase-shift keying (QPSK) modulator, and multiple high power amplifiers (HPAs) that operate in their nonlinear region at a high level of efficiency. Their output signals are spatially combined using a specially tailored antenna array to produce a new 8x4 APSK signal. The performance of the new 32APSK system using this scheme was investigated. The system had a better bit error rate (BER) performance than a conventional 32APSK system when operated in the HPA nonlinear high efficiency region. Theoretical transmission analysis showed the acceptable spatial superposition errors. An antenna array system suitable for combining the two beams is presented. An antenna array study demonstrated that the acceptable errors were attained with the proposed circular array system over a +/5 degree angle and this range is wide enough to cover satellite communication service areas. The HPA power consumption was reduced about 50% compared with that of the conventional system. Thus, the proposed compact system is feasible and will enable broadband transmission while using the available amount of energy and bandwidth more efficiently.