PAE improvement and compensation of small-signal gain drift due to temperature on power amplifiers through active biasing

摘要

Power millimetre-wave band transmitters are commonly formed by a chain of MESFET or HEMT GaAs MMIC power amplifiers. Under large-signal conditions the reverse gate output current, which appears at the gate port of those devices due to drain-gate breakdown mechanisms, causes a drop in the power amplifier's power added efficiency (PAE) figure, thus affecting the entire transmitter reliability. Additionally, it is desirable to obtain a stable performance from the transmitters for different ambient temperatures. In particular, millimetre-wave wireless systems, such as the local multipoint distribution system (LMDS), require constant small signal gain for a wide range of temperatures. In this paper, an active bias network is used to compensate for both effects. The performance of the active bias network is shown to be superior, in terms of the power amplifier's PAE and the compensation of the power amplifier's small signal gain drifts due to temperature, to a conventional resistive divider when used for biasing the power amplifier.