Effects of digital baseband predistortion on linearized transmitter design

Digital baseband predistortion is an effective approach to linearize a power amplifier (PA). In practice, the predistortion performance is affected greatly by the error of the other components in a transmitter. However, there are a few papers discussing such problems at present. Taking the example of orthogonal frequency division multiplexing (OFDM) signals, we analyze the predistorted spectral characteristic by means of convolution operation. Although the predistorter (PD) results in spectrum spread, unlike the PA, its intermodulation products (IMP) are beneficial to the transmitter. In order to feed the IMP to the PA losslessly, the sampling rate of the source signal must be improved, and the bandwidth of the bandpass filter must be increased. Theoretical analysis and simulation results show that, for the digital baseband predistortion method, the source sampling rate and the bandpass filter bandwidth are quite important, and should be properly designed to achieve better linearization performance.