Power efficient MMIC power amplifiers for W-CDMA/PCS dual band and 5 GHz WLAN applications

Abstract

The major research issue in this thesis is on the efficiency improvement of the power amplifiers while satisfying the linearity requirements for the mobile communications and wireless LAN terminals applications. The InGaP/GaAs HBT was implemented as the basic building block for the monolithic microwave integrated circuit (MMIC) power amplifier, because the InGaP/GaAs HBT is the most reliable device structure for high power operation and the HBT supports higher power density than any other RF devices. Both the smart function for W-CDMA/PCS power amplifiers and optimum quiescent current for high linear 5 GHz WLAN power amplifiers are devised with novel active bias circuits including a bias control circuit and on-chip linearizer and implemented to the MMICs using the InGaP/GaAs HBTs. This thesis proposes a new integrated bias control circuit for the smart function and realizes an InGaP/GaAs HBT MMIC power amplifier satisfying both W-CDMA and PCS specifications for improved overall power efficiency. A factor of 1.7 improvement was achieved in average power usage efficiency by applying different quiescent currents according to the required output power levels below and above 16dBm. The implemented W-CDMA/PCS dual band MMIC power amplifier presents 8.8/8.2% power-added efficiency (PAE) and -39/-49 dBc adjacent channel (leakage) power ratio (ACLR/ACPR) at the low power mode of 16dBm while 39.4/36.1% PAE and -33/-46dBc ACLR/ACPR at the 28 dBm high power mode. In addition, a 5 GHz linear InGaP/GaAs HBT MMIC power amplifier for wireless LAN applications is realized. The three-stage power amplifier operates with 103 mA - low quiescent current of Class AB mode using active bias circuit under a single supply of +3.3V. A total current of 196(194)mA is consumed with an output power of 18dBm and PAE of 9.7% at 5.25(5.15)GHz. The power amplifier exhibits a power gain of 19.6 (17.8/18.5) dB, 1-dB compression point ($P_(1)$dB) of 26(25/25)dBm, and PAE of 27.8(25.4/20)% at 5.2...