THD and SNR tests using the simplified Volterra series with adaptive algorithms

A test technique for the total harmonic distortion (THD) and signal to noise ratio (SNR) is proposed. A modified Volterra series using harmonics in place of powers of the sinusoidal input is used to model the nonlinear characteristic of the device under test (DUT). The least-mean square (LMS) adaptive algorithm is used to identify the DUT model. While maintaining comparable accuracy this technique provides a more flexible test procedure than conventional methods, in terms of the frequency resolution, the number of samples, and the sampling rate. It outperforms conventional methods when there is a bin energy leakage, which occurs in a non-coherent system. It requires a lower number of data points, as a result, less data acquisition time is needed and test time is reduced. In addition, it is real-time computing while other conventional methods post-process blocks of data.