Open-Loop Digital Baseband Predistortion Based on Polynomials

As for model-based approaches, the polynomial model is a favorite choice due to its simplicity and ease of implementation. In this paper, an odd-order series of magnitude and phase angle form are derived from polynomial model of HPA nonlinearity. In-band distortion can be eliminated by alleviating odd-order terms of the series. Different from conventional feedback predistortion, we use human-computer interface to cancel the odd-order terms that need no feedback loop, i.e. open-loop digital baseband predistortion. Results from both Matlab simulation and small power test show that the open-loop predistortion method can effectively compensate for amplitude and phase nonlinearity and suppress the in-band distortion.