Patent ID: 7570721
Filing Date: 2009-08-04
Classification: G01R,H03D

Abstract:
1. A method of determining a relationship between an input signal frequency and a reference signal frequency, the reference frequency having a first period, the method comprising: deriving from the reference signal a plurality of internal reference signals, each of the internal reference signals characterized with each of the internal reference signals being temporally offset from one another and occurring within the first period; providing each of the plurality of internal reference signals to a level detection circuit; based upon a characteristic of any of the plurality of internal reference signals, sampling, with the level detection circuit, a plurality of signal levels of the input signal within the first period; providing an output of the level detection circuit to a time alignment circuit, the time alignment circuit being configured to produce an output which is a time-aligned version of the output of the level detection circuit; storing a value indicative of each of the sampled levels taken in the first period; storing one value indicative of a sampled level of the input signal from a previous period; correlating the sampled levels from the first period amongst themselves; correlating the one value indicative of a sampled level from the first period with the value indicative of a sampled level from the previous period; and deriving a relationship between the input signal frequency and the reference signal frequency based in part on: a) the step of correlating the sampled signal levels from the first period; and b) the step of correlating the one value indicative of the sampled level from the first period with the value indicative of the sampled level from the previous period.