A Measuring Technique of Amplifiers' Non-linear Characteristics with Digital Terrestrial Television Broadcasting Signals

Abstract

In dealing with digital terrestrial television broadcasting systems using OFDM, a spectrum measurement is usually used to check the extent of a transmitting amplifier's non-linearity effect. However, capturing both input and output signals and measuring the difference between them are necessary to identify the non-linear characteristics. A new technique to identify non-linear characteristics of an amplifier, which is assumed to follow the AM-AM / AM-PM conversion model, is described. Non-linear characteristics can be measured using this technique with only the output signal of an amplifier working during actual broadcasting. The process requires no special signals. An undistorted (input) signal is estimated using the conventional demodulating process. The characteristics of the two amplifiers were measured, and the results were compared with those of another identification technique. The characteristics derived from the two techniques were found to agree.