A radar sensor includes a mixer configured to receive an radio frequency (RF) input signal to down-convert the RF input signal into a base-band or intermediate frequency (IF) band, an analog-to-digital converter (ADC), and a signal processing chain coupled between the mixer and the ADC. The radar sensor further includes an oscillator circuit that is configured to generate a test signal. The ADC is coupled to an output of the signal processing chain, and is configured to generate a digital signal by digitizing an output signal of the signal processing chain, the output signal being derived from the test signal. The radar sensor further includes a digital signal processing circuit coupled to the ADC downstream thereof, the digital signal processing circuit being configured to perform a spectral analysis on frequency values of the digital signal.