Spectrally pure excitation signals: only a dream?

For accurate testing of a nonlinear device-under-test (DUT), the spectral purity of the input signal is utterly important. This paper describes a method to create very pure signals, such as sine waves, dual-tones or multi-tones, using only power measurements. The signals are generated with an arbitrary waveform generator (AWG). Any unwanted spectral line is removed, independent of its exact origin. This allows to apply the correct signal to the DUT, even if the signal source is not perfect or is followed by filters or amplifiers with a small non-linear distortion. Measurements are used to demonstrate the capabilities of the method.