Minimum ACPR “sweet-spot“ using statistical power distribution function

During the linearity optimization, the ACPR improvement is quite different from the inter-modulation third-order distortion ratio (IM3R) improvement, but there exist some relation between ACPR and IM3R To correlate the IM3R and ACPR, we propose the statistical probability density function (PDF) method to predict the relation between the ACPR improvement and the IM3R improvement for weekly nonlinear amplifiers. There is a 10 dB difference between measured ACPR and IM3R near sweet spot region, however, through our modification process, only 2-3 dB difference between our theoretical prediction and measured ACPR exist. Two of the modulation signals, W-CDMA and QPSK, have been proved that the prediction of ACPR from two-tone IM3R can be much closed to the measured one as long as the modified PDF term is utilized.