A practical second-order delta-sigma frequency-to-digital converter

Digital phase-locked loops (DPLLs) that operate in an analogous fashion to delta-sigma (ΔΣ) modulator A/D converters have been recently proposed. Although they offer certain advantages over conventional DPLLs, their direct implementation requires components that are difficult to realize without high-precision analog circuitry. This paper presents an alternate mechanization approach that gives rise to systems that have the same theoretical performance as those presented previously but consist of easily implemented components such as analog integrators, digital flip-flops, and digital counters