A Novel Optimization Method for Nonlinear Bessel-Fourier PA Model Using an Adjusted Instantaneous Voltage Transfer Characteristic

A novel technique for improving the accuracy of low order Bessel-Fourier (BF) envelope behavioural model of nonlinear power amplifiers (PA) is presented. This technique is based on a special extrapolation of a hypothetical instantaneous voltage transfer (IVT) characteristic derived from a high order accurate BF envelope behavioural model. The extrapolation is optimized `manually´ to reduce the number of coefficients required for an accurate Fourier series model of the IVT, and from this a new `optimized´ BF envelope model which has improved accuracy is then derived. The model construction has been realized in a five-step algorithm. Using various figures of merit, such as average error (AE), normalized mean square error (NMSE), and adjacent channel error power ratio (ACEPR), the performances of low order classical BF model and optimized BF model of an LDMOS PA are compared in their modeling accuracy against measured data when the LDMOS PA is amplifying a 3G WCDMA signal.