An Active Cuber Circuit for Power Amplifier Analog Predistortion

This work deals with an active balanced cuber-circuit that can be used as IM3 generator in analog predistortion systems for mean power amplifiers. Such a circuit exploits the odd non-linear characteristic of a B-class push-pull amplifier and, compared with conventional diode designs, shows an improved third-order generation. A laboratory prototype of the cuber has been realized and inserted in a predistortion system and, as a next step, a pre-industrialized predistorter prototype has been realized using the active-cuber block: the whole system seems to be flexible enough to be used for the IM3 linearization of PAs. From experimental results obtained from a target 6W power amplifier we found that more than 8 dB of correction can be achieved in a fractional bandwidth of about 10%.