A Digital Filter Design at Auxiliary Receiver for Optimal Pre-Distortion Performance

The design specifications for the digital filter of the auxiliary receiver at digital pre-distortion designs used for the RF power amplifiers are optimized and explored. It is observed from the simulations that the passband of FIR filter should be from DC to 0.625BW of the baseband signal when the IF sampling method and the digital down converter are used in the auxiliary receiver implementation. When the pass frequency of digital filter is moved from 0.5BW to 0.625BW, some performance improvement is obtained. Further extension of the filter passband will not provide any performance improvement even if it increases the implementation cost. The stopband of digital filter is determined by the ADC DC offset that must be filtered out after the digital mixing stage for the optimal digital pre-distortion performance.