A method for determining phase noise in a periodically modulated signal is described. The modulated signal is processed to generate a processed signal from the modulated signal. At least an approximate period of a modulation of the modulated signal is determined from the processed signal. The type of modulation of the modulated signal is determined from the processed signal. The modulated signal is demodulated based on the determined period and the determined type of modulation to generate a demodulated signal, and the phase noise is determined from the demodulated signal. Moreover, a measurement device is described.