主权项 |
1. A method of Digital Pre Distortion (DPD) comprising the steps of:
modeling the non linear behavior of a power amplifier by using Volterra Kernel series with memory effects:y[n]=∑lwlUl(x[n]) where: y[n] is the power amplifier output at sampling time n, x[n] is PA input at sampling time n; Ul(x[n]) is general Volterra kernel with memory effects expressed in apolynomial form; and wl is a corresponding coefficient; searching for the dominant Volterra Kernel with the minimum residue error by letting x[n] be the first new build orthogonal base e1[n]=x[n]
Step 1, calculating a residual error of using e1[n] to model y[n] as follows:y_error[n]1=y[n]-〈y[n],e1[n]〉〈e1[n],e1[n]〉e1[n] where: <x,y> denotes x and y cross-correlation,
Step 2, building an innovation base for each of the Volterra Kernels versus e1(n) as follows:{Ul(x[n]}innovation=Ul(x[n])-〈Ul(x[n]),e1[N]〉〈e1[N],e1[N]〉e1[N],l=2,3,4… Step 3, calculating the residual error of using each innovation base and selecting an innovative base with the minimum residual error as the new orthogonal base e2[n], putting the corresponding Volterra kernel into a candidate list for the next update of the Volterra kernels set for the DPD engine as follows:y_error[n]1l=y_error[n]1-〈y_error[n]1,{Ul(x[n]}innovation〉〈{Ul(x[n]}innovation,{Ul(x[n]}innovation〉{Ul(x[n]}innovation,l-2,3,4,5…e2[n]={Uk(x[n]}innovation,k=min{〈y_error[n]1l,y_error[n]1l〉}y_error[n]2=y_error[n]1k where: Volterra Kernels Candidate is {Ul, Uk} and Uk is removed from search candidate list, andrepeating step 1, step 2 and step 3 to generate a new orthogonal base list [e1, e2, e3 . . . ] and a dominant Volterra Kernel candidates list [Ul, Uk . . . ]; and continuously updating the digital pre distortion process with the optimal Volterra Kernel set. |