Antennas, Base and Mobile Stations -11.Mobile Station Transmission Power Amplifier
The role of the transmission power amplifier is to amplify high frequency signals to the required power level. Transmission power amplifiers are now built on MMICs using GaAs-FET devices instead of Si technology, and the operating voltage has been reduced from 12 volts for vehicle-mounted equipment to 3 volts, which is equivalent to the output of one lithium-ion battery cell.
Analog and digital portable telephones use saturation and linear amplifiers, respectively. Through our development of HRA and HMRA circuit configuration technologies, which improve the conversion efficiency of the saturation amplifier, NTT DOCOMO has been successful in eliminating the problem of F-class amplifiers in which losses are increased during high power output. As a result, the power conversion efficiency has been improved as much as 60%, and this figure is expected to rise to 90% for saturation amplifiers and over 60% for linear amplifiers in the near future. This technology substantially contributes to the excellent efficiency of the Digital Mova system.
Transmission Power Amplifier Technology