Self-linearizing technique for L-band HBT power amplifier: effect of source impedance on phase distortion

L-band power amplifiers operating with high efficiency and high linearity at a single and low supply voltage are in strong demand for mobile communication systems. This paper presents a new self-linearizing technique for power heterojunction bipolar transistors (HBTs). Utilizing the nonlinear input conductance of the device itself and setting the source impedance to the self-linearizing impedance, the phase distortion and the adjacent channel leakage power (ACP) for /spl pi//4-shift QPSK modulated signal of our InGaP/GaAs power HBTs have been greatly improved. As a result, the HBT exhibited the ACP at 50 kHz offset frequency of -49.2 dBc with a power-added efficiency (PAE) of 56% at an output power (P/sub out/) of 31 dBm under a supply voltage of 35 V.