A New Method for Measuring Distortion Using a Multitone Stimulus and Noncoherence

A new approach for measuring distortion based on dual-channel analysis of noncoherence between a stimulus and response is presented. This method is easy to implement, provides a continuous distortion curve against frequency, and can be used with a multitone stimulus, noise, or even music. Multitone is a desirable test signal for fast frequency response measurements and also for assessing system nonlinearities. However, conventional single-channel multitone measurements are challenging because the number of intermodulation tones grows rapidly with the number of stimulus tones and makes it difficult to separate harmonics from intermodulation products. By using dual-channel measurement techniques, only well-known, standard signal processing techniques are used, resulting in simplicity, accuracy, and repeatability.