Spectrally pure excitation signals: Only a dream?

Multi-tone excitation signals become increasingly important for test and measurement purposes. However, the signal sources used to create such multitone signals are not perfect and often create unwanted spectral contributions. This paper presents a method to create spectrally pure signals, such as two-tones or multitones, using signal sources based on arbitrary waveform generators (AWG). Only amplitude information is needed, so that a spectrum analyzer can be used to perform all necessary measurements. Unwanted spectral lines are suppressed, independent of their exact origin. This allows to apply a testsignal with the correct spectral content to the device under test, even if the signal source is not perfect or external disturbances are present. Measurements on an RF amplifier show the capabilities of the method.