Payload nonlinearity effects on the Globalstar forward link

Forthcoming satellite personal communication networks (S-PCN) like Globalstar are going to use bent-pipe transponders and active phased-array antenna in conjunction with code division multiple access (CDMA). Efficient payload operations require one to operate the on-board power amplifiers close to their saturated power whereby distortion effects can not be neglected. The paper presents the impact of solid-state amplifiers on the Globalstar forward link multiplex for two possible payload configurations namely single PA per beam and active phased-array on-board antennas. It turns out that the conventional noise power ratio intermodulation figure fails to accurately predict the end-to-end system performance. Multi-beam active-phased array is shown to provide superior performance compared to a system employing a single amplifier per antenna beam