Adaptive digital predistortion technique for microwave power amplifiers

The proposed technique is based on the use of algorithms executed by a digital signal processing circuit. A third-order spline function is deduced for application as a signal generator which can provide a predistorted equivalent output for any value or input signal. Samples of the baseband complex equivalent of the signal at the input and output of the amplifier are entered into a lookup table to serve as data for interpolating such a function. This technique affords 45 dB reduction of intermodulation products and requires only a few input and output samples for good compensation of the distortion.