Quantization analysis and design of a digital predistortion linearizer for RF power amplifiers

Optimum table spacing in predistorting amplifier linearizers

“…The derivatives of the complex gains and are important. Because it occurs frequently, we also define (5) Note that .…”

“…No interpolation is assumed in this analysis, so the resulting complex gain is piecewise constant. We assume that adaptation algorithms [1]- [5] make each table entry optimum in the sense of (3) at the midpoint of its range.…”

“…A powerful type of linearizer is the digital predistorter (PD) [1]- [5], which incorporates a lookup table (LUT) containing a representation of the inverse characteristic of the amplifier. The cascade of PD and PA is almost perfectly linear.…”

“…Reported work has the entries equispaced in power [1], [2], [4], because of its computational simplicity, or equispaced in amplitude [3], [5], because it frequently provides greater IM reduction. Most authors [1], [3]- [5] also note that nonuniform spacing, in which table entries are more closely spaced where the amplifier characteristics vary sharply, would provide better performance.…”

“…Most authors [1], [3]- [5] also note that nonuniform spacing, in which table entries are more closely spaced where the amplifier characteristics vary sharply, would provide better performance. Beyond this observation, however, there has been no progress to date on nonuniform spacing.…”