High-efficiency power amplifier using dynamic power-supply voltage for CDMA applications

Efficiency and linearity of the microwave power amplifier are critical elem ents for mobile communication systems, This paper discusses improvements in system efficiency that are obtainable when a de-de converter is used to co nvert available battery voltage to an optimal supply voltage for the output RF amplifier. A boost de-de converter with an operating frequency of 10 MH z is demonstrated using GaAs heterojunction bipolar transistors. Advantages of 10-MHz switching frequency and associated loss mechanisms are described . For modulation formats with time-varying envelope, such as CDMA, the prob ability of power usage is described. Gains in power efficiency and battery lifetime are calculated. An envelope detector circuit with a fast feedback loop regulator is discussed. Effects of varying supply voltage with respect to distortion are examined along with methods to increase system linearity .