In-line, unbalanced amplifier, predistortion circuit

摘要

A plurality of amplifiers are connected in cascade to form an in-line predistortion circuit. The amplifiers are unbalanced in that each amplifier stage in the circuit has two DC voltage rails which are independently controlled to provide different, i.e. offset, DC voltage levels to the unbalanced amplifiers. This unbalance in the amplifiers generates predistortion in a signal which can be used to cancel the inherent distortion caused by a non-linear device which subsequently processes or transmits the predistorted signal. Control of the DC voltage offset in at least one of the amplifier stages is necessary to match the predistortion to the inherent distortion being corrected. A tilt circuit can be used in cascade with the plurality of amplifiers (in front of the RF amplifiers) to compensate the amplitude change caused by the unbalanced RF amplifiers. Either side of the DC voltage can be changed in order to correct for either sublinear or superlinear laser diode curves.