DIGITAL LINEARIZER FOR RF AMPLIFIERS

Broadcast technology is at the beginning of a new era. It is character ized by the intensive use of the most advanced digital modulations for mats (8VSB, QAM, OFDM) in combination with high power RF amplifiers. T o date the linearity required for these digital formats has only been accomplished in cumbersome low efficiency class A amplifier or even mo re cumbersome feed-forward systems. A potentially more efficient and c ost effective approach is the combination of non linear power amplifie rs and a predistortion technique capable of compensating for the non l inear amplifiers. Digital predistortion will provide a highly linear o utput and improved efficiency. Itelco has developed a digital adaptive base band predistorter to provide for improved performance and cost. The technique is independent of the modulation type, the output freque ncy, or the signal bandwidth. Furthermore the capability of automatic adaptive predistortion to compensate for the environment (temperature, power supply variations, aging,and even operation during replacement of a Faulty module) is highly desirable.