Abstract: A pulsed electron spin resonance spectrometer is provided with a first microwave oscillator for generating measuring signals of a high microwave frequency of about 80 GHz or above. A second microwave oscillator generates auxiliary signals at a lower microwave frequency of about 12 GHz or below. A first mixer generates mixed signals by mixing a measuring signal with an auxiliary signal. A pulse shaping channel generates pulsed mixed signals having a pulse length sufficient for carrying out pulsed electron spin resonance experiments. Moreover, a measuring resonator is provided to which the pulsed mixed signals are applied. A second mixer generates an output signals of a lower microwave frequency by mixing the mixed signal outputted from the measuring resonator with a signal being derived from the first microwave oscillator. A pulse shaping channel is switched between the second microwave oscillator and the first mixer.