Data sampler for digital frequency/phase determination
View Patent ↗A digital circuit and method for forming number streams for frequency and/or phase comparison of digital or digitized signals, referred to herein as clock signals, where typically one of the clock signals is a known clock signal and another of the clock signal is an unknown clock signal. The unknown clock signal may be derived, for example, from a communications signal. The rate of the unknown clock signal may exceed the rate of the known clock signal. In an exemplary embodiment, an “alias” value (e.g., an integer 1, 2, 3, etc.) is applied to the circuit as an indication of the expected frequency range of the unknown clock signal. The number stream is formed accordingly.
1. A circuit for comparing an unknown first clock signal and a known second clock signal, the circuit comprising:
an input section, clocked by the unknown first clock signal, that produces a slower first clock signal;
a plurality of logic chains, wherein a first logic chain of said plurality of logic chains comprises:
a first logic unit clocked by the unknown first clock signal and storing the slower first clock signal;
two or more logic units, coupled to the first logic unit, that are clocked by the known second clock signal;
an edge detector, coupled to the last of the two or more logic units and the second to last of the two or more logic units, that detects an edge transition;
wherein each of the plurality of logic chains, other than said first logic chain, comprises:
a first logic unit clocked by the unknown first clock signal and storing an output signal from the first logic unit of the preceding logic chain;
two or more logic units, coupled to the first logic unit, that are clocked by the known second clock signal; and
an edge detector, coupled to the last of the two or more logic units and the second to last of the two or more logic units, that detects an edge transition;
an alias-detection circuit, coupled to the edge detectors, that determines a logic to be output in accordance with an alias value and the known second clock.