The Globalstar system breakthroughs in efficiency in microwave andsignal processing technology

摘要

The Globalstar system will employ active phased array antennas andenergy management in combination with CDMA technology to achieveunprecedented power efficiency for satellite communications. Activephased array antennas incorporate multibeam functionality in very smallspace. Such phased array antennas depend upon the use of highlyefficient and uniform MMIC amplifiers that were not previouslyavailable. MMIC amplifiers coupled directly to each radiating elementresult in very high G/T and EIRP for the size of the antenna aperturesand power capacity and noise figures of the amplifiers. As a result,unprecedented dc to RF power efficiency is achieved in the transmitdirection and from input flux density to C/N in the receive phasedarrays. The Qualcomm CDMA waveform employed in the User Terminals(handsets) and Gateways to the terrestrial networks (PSTNs), spreads theRF energy evenly over the allotted spectrum, as seen by the userantennas, optimizing power handling (signal fidelity) in the MMICamplifiers. This CDMA implementation originally developed forterrestrial cellular and PCS works particularly well in a system thatemploys a constellation of low earth orbiting (LEO) satellites