The effect of source impedance on linearity in InGaP/GaAs power HBTs

Abstract
L-band power amplifiers operating with high efficiency and linearity at a single, low supply voltage are in strong demand in mobile communication systems. This paper reports the effect of source impedance on the phase distortion and the adjacent channel power (ACP) for a /spl pi//4-shift QPSK modulated signal in the InGaP/GaAs power heterojunction bipolar transistors (HBTs). Our results show that the phase distortion and the ACP of our HBTs are improved by adding a positive reactance to a gain-matched source impedance. The ACP for a 50 kHz offset is -49.2 dBc with a power-added efficiency (PAE) of 56% at a output power (P/sub out/) of 31 dBm under a supply voltage of 3.5 V.

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