A method is described that, according to one exemplary embodiment, involves the following: generating a first radio frequency (RF) signal by a first RF oscillator and a second RF signal by a second RF oscillator, mixing the first RF signal and the second RF signal by a mixer to generate a mixer output signal, digitizing the mixer output signal to generate a digitized signal, and calculating an estimate for a power spectral density of the mixer output signal from the digitized signal. Based on the estimate for the power spectral density of the mixer output signal, an estimate for a noise power spectral density characterizing the noise contained in the first and the second RF signals is calculated.