Amplifier linearisation using RF feedback and feedforward techniques

The performance of feedback as a distortion reduction technique is highly dependent on the integrity of the feedback path. Any error or noise generated in this path is directly reflected into the output of the amplifier. Cartesian feedback requires a demodulator in the feedback loop and this is a potential source of linear errors, nonlinear errors, and noise. RF feedback with Cartesian compensation is proposed as a technique for overcoming these problems. In addition the RF nature of the input, feedback and error signals makes the system suitable for incorporating into a feedforward system to further improve the linearisation capability. Design equations and simulation results are given for such a system.