One curve-fit method for the evaluation of the total distortion of sinusoidal signal

With the requirement of measurement and the development of electronic technology, the index of distortion measurement technique has a larger increase. How to improve the measurement accuracy and extend the frequency domain is becoming more and more important. The current method of sine waveform distortion measurement is reviewed and the total distortion measurement technique for the sine waveform, which is based on curve-fit method, is discussed in this paper. Aiming to solve the problem that it is difficult to obtain the parameters in curve-fit method, a new method and its complete procedure are developed by using the Hilbert-Huang transform (HHT) and the ergodicity method to obtain the parameters of base wave curve and to evaluate the total distortion. Unlike classical three- or four-parameter sine-wave fitting procedure, this method avoids selecting initial value of the parameters and working out the nonlinear equations. The feasibility and effectiveness of this method and procedure were verified through a group of simulation results, with a signal at the frequency of 1 MHz.