A predistorter for a polar transmitter, using look-up tables and interpolation, and possessing a simple training procedure.

摘要

An amplitude predistorter for an EDGE polar RF transmitter comprises a look-up table 205 containing a small set of input-output values defining a piecewise linear model of the amplitude response of the amplifier (105, figure 1). The two input-output value pairs defining the segment in which the input amplitude lies are fed from the LUT 205 to a linear interpolator 204. A phase correction look-up table may be provided also (figure 4). The precorrection unit 201 provides scaling and offset to match the input signal range to the available amplifier output range. The contents of the look-up tables may be determined relatively promptly and without iteration during a training mode, using a low-bandwidth Cartesian receiver (106, figure 1). The LUT 205 may contain a bitmap denoting whether each segment end point is above or below the input to the LUT. The priority encoder 203 operates on the bitmap output to select a segment.