Use of a digital PLL in an ESR heterodyne spectrometer

Describes the transformation of a homodyne spectrometer into a heterodyne spectrometer by the use of a digital phase frequency comparator. The local oscillator is a low-power reflex klystron whose offset frequency in relation to the main klystron is maintained constant at 30 MHz. The phase frequency comparator works in the phase range mod -2 pi , +2 pi mod and no adjustment is required to effect the frequency locking of the local oscillator.