Abstract:

Considering the strong memory effects of the broadband power amplifier, a feedforward cross memory polynomial model is proposed. This model consists of two loops. One is used as a signal cancellation loop which adopts memory polynomial to model dynamic linear memory effect in-band. And the other is used as a distortion injection loop, which adopts memory time signals cross item memory to model spectrum spread behavior out-of-band. In order to overcome the numerical instability problem of the least-square method, a conjugate gradient method is used to identify the model coefficients. The ADS envelope simulation method is adopted to obtain accurate complex envelop data of power amplifier input and output signals. This method eliminates the effects of noise and measurement error on the identification of model parameters effectively. The model performance is analyzed and evaluated sufficiently based on the obtained complex envelop data. The experimental results show that the proposed model can achieve good approximation capability for the nonlinear dynamic characteristics of the broadband power amplifier, especially the spectrum spread behavior out-of-band. Approximation precision is improved almost 10 dB compared with the common methods.