Adaptive MMIC Power amplifier for 3G and beyond mobile communications

Abstract

In this thesis, adaptive power amplifiers for the "intelligent" 3G and beyond mobile communications are proposed. Adaptive functions are defined to be a linearization, high-efficiencies, a stable operation at any environment, and a dual-band operation. The first three functions are implemented to the L-band mobile applications and the last one is implemented to the 2.4 GHz/5 GHz dual-band WLAN applications. First of all, a new adaptive on-chip linearizer, which maintains a constant base voltage of the power transistors by making a RF path in the bias circuit of which impedance is decreased with increasing input signal, improves 1dB gain compression point by 18.5 (20) dB and phase distortion by 6.1 (12.42)$^\circ$ for PCS (W-CDMA) band. PCS and W-CDMA dual-band InGaP/GaAs HBT MMIC power amplifier with single input and output, and no switch for band selection is embodied by implementing the adaptive linearizer and by designing the amplifier to have broadband characteristics. The dual band power amplifier exhibits an output power of 30 (28.5) dBm, PAE of 39.5 (36) %, and ACPR of -46 (-50) dBc at the output power of 28 (28) dBm under 3.4 V operation voltage for PCS (W-CDMA) applications. bias control circuit for a statistically high-efficient operation have been devised and implemented to a W-CDMA InGaP/GaAs HBT MMIC power amplifier. The on-chip bias current switching circuit supplies a quiescent current of 50 mA for a low power mode operation and 80 mA after a bias switching for a high power mode operation. The reduced quiescent current of 50 mA at the low power mode operation improves a PAE as much as 8.6 % at the output power of 20 dBm and 59.84 % under the output power of 0 dBm compared to that with high power mode operation only, resulting in an average power usage efficiency increase by 1.415 times. And the on-chip adaptive bias current control circuit, which improves efficiency at the low output power level and linearity at the high output power level sim...