A novel generalized low-frequency signal-injection method for multistage amplifier linearization

This paper presents for the first time the investigation of multistage amplifier linearization based on the generalized low-frequency signal-injection technique. Difference-frequency signals, generated by a predistortion circuit, are fed to the biasing circuitry of a multistage amplifier for third-order intermodulation-distortion cancellation. The reason that two-stage injection shows better linearization performance than the single-stage injection case is analytically derived. Furthermore, issues on the optimum operating condition, gain error, and bandwidth limitation are also addressed. For demonstration, the measured performance of an experimental system using both the two-tone and digitally modulated test signals are shown.