Low sampling rate digital predistortion of power amplifier assisted by bandpass RF filter

In this paper, a low sampling rate digital predistortion of power amplifier assisted by bandpass RF filter is demonstrated. Owing to RF filter integrated after power amplifier, the spectral regrowth of output signals is restricted into a limited bandwidth, which alleviates the burden of ADC sampling rate efficiently. By adopting a band-limited memory polynomial(BLMP) model, the bandwidth of every product terms in memory polynomial model is controlled with a low-pass FIR filter. A GaN Doherty power amplifier excited by a 40 MHz 2-carrier LTE-A Signal is employed to validate this approach. With 2 times over-sampling, a 70 MHz band-pass RF filter and a 35 MHz low-pass FIR filter, the output ACPR is successfully improved from -34.9 dBc to -46.0 dBc with a sampling rate of only 92.16 Msps. The experiment result shows that this approach works much better than the traditional methodologies based on memory polynomial(MP) in the situation of wideband application.