Adaptive linearizer and MMIC smart power amplifier for W-CDMA portable terminlas

Abstract

This thesis focuses on the two most important issues in MMIC power amplifier for portable terminals : the linearization and the overall power efficiency. A new idea linearizing the power amplifier has been demonstrated with two novel linearizer circuits, and a new dual chain amplifier has been devised for highly efficient smart function. These ideas have been demonstrated to InGaP/GaAs HBT MMICs with compact chip size. First of all, this paper proposes a new on-chip linearizer and its implementation to high linear monolithic microwave integrated circuit (MMIC) power amplifier for 1.95 GHz wide-band code division multiple-access (W-CDMA) system. The linearizer consists of InGaP/GaAs heterojunction bipolar transistor (HBT) active bias circuit and coupling component that coupled partial RF transmission power to base node of HBT of bias circuit. Two different approaches have been tried: one with the coupling component of constant transmission coefficient and the other is that of dynamic transmission coefficient. A linearizer having transmission coefficient corresponding to 0.8pF coupling capacitance has been designed as the optimum structure in consideration of linearity improvement and power consumption. To obtain dynamic transmission coefficient to input power, we devised reverse biased junction diode of which dynamic admittance to input power level functions adaptively to control the bias to the amplifier. The proposed linearizers have little insertion power loss, and more importantly, they consume no additional die area and DC power. The proposed linearizer using 0.8pF coupling capacitor (reverse biased diode) improved gain compression point by 18(19.7)dB and the phase distortion by $20^\circ$ compared with non-linearized amplifier. The fabricated HBT MMIC power amplifier with the integrated linearizer using 0.8pF coupling capacitor (reverse biased diode) exhibits a maximum output power of 28.7(30.3) dBm, a power gain of 27.5(27.5) dB, a power added efficienc...