DVB-T Power Amplifiers Modelling and Compensation

Digital video broadcasting terrestrial (DVB-T) signals, used in digital terrestrial television (DTT) networks in Europe, can have a very high crest factor of around 13 dB. Consequently broadcast power amplifiers need to be as linear as possible to avoid spectral regrowth interfering with adjacent channels. The first solution is to use a class A amplifier which is of course very linear but has a poor efficiency. The second solution is to replace the class A amplifier by a class AB amplifier with a predistorter to improve its linearity. LDMOS class AB amplifiers are being more often used for this application. To simulate such a system including an amplifier, the first step is often to model the amplifier. A great number of models have been proposed but they are generally just applicable to one kind of amplifier. We will compare them to the memoryless Abuelma´atti model based on Bessel expansion series for in-phase and quadrature parts of the signal. Then a digital predistorter using look up tables of gain and phase is described and applied to the modelled amplifier