A Gate to Linearity? Gate Bias Modulation for Power Amplifiers: Gregor Lasser

Journal article, 2026

Gate bias modulation is an linearity enhancement technique for power amplifiers (PAs). While its potency was already practically demonstrated in 1979, its use in high power telecommunication and radar transmitters is still not mainstream, at least for compound semiconductor technologies that will be the focus of this article. While digital predistortion (DPD) has its undeniable merits in terms of accuracy and seamless integration before the digital to analog conversion of high power telecommunication transmitters, it faces limitations for extremely wide bandwidths, long-term memory effects, and very large MIMO transmitters where individual DPD for hundreds of amplifiers becomes prohibitive from a complexity and power consumption perspective. After explaining the fundamentals of gate bias modulation, this article presents a brief historical summary before revealing how multi-stage amplifiers can be linearized completely in terms of gain and phase distortions. The compensation of trapping related memory effects in GaN will be discussed next, both as a hardware technique to reduce memory effects to a minimum for efficient DPD linearization, and as a way how to remove the gain collapse for drain modulated GaN PAs. The use of gate modulation on the auxiliary amplifier of a Doherty PAs allows for a flatter gain characteristic as will be discussed before finally addressing GaAs PAs for frequencies up to 114GHz, where gate modulation not only improves linearity but also efficiency and achieved output power.