On the Use of Multi-Tone for the Estimation andMeasurement of Noise Power Ratio inThird-Order Nonlinear System

Multi-tone signal is widely used to estimateand measure the nonlinear distortion in communicationsystem. A generalized formula for the estimation ofNoise power ratio (NPR) distortion in memoryless thirdordernonlinear system is presented in this paper. An accurateand low-cost NPR measurement setup with fewertones than traditionally used is also introduced in this paper.Accurate measurement of NPR distortion is achievedby averaging distortion power stimulated by multi-tone signalswith different random phases. Automatic measurementprocedure is developed to reduce the test time andapply the test setup for the production environment. Comparingthe measurement results between our method using60-tone and traditional technology using 10,000-tone,the NPR measurement error is only 0.23dB. The accuracyof the NPR estimation formula is verified using this testenvironment. The variance between estimation and measurementis below 1dB when the DUT is in the lightlynonlinear region.