Precise phase and frequency measurement using all digital dual mixer time difference technique

A new technique for precise phase and frequency measurement is described in this paper. A primary frequency standard, namely, Cs atomic fountain has already been developed at CSIR-NPL. Six commercial Cs atomic beam clocks along with an H-Maser are continuously inter-compared and constitute a stable time scale. H-Maser frequency is being evaluated with respect to the Cs fountain on regular basis. For evaluating the frequencies of these different frequency sources precisely, a stable, low noise and very accurate frequency measurement instrument is required. All digital implementation of dual mixer time difference technique is a step towards more precise measurement and evaluation of frequencies and will provide better stability estimation of timescale, microwave and optical (under development) standards at NPL India.