Digital phase discrimination based on frequency sampling

摘要

The present invention provides a simple all digital method and apparatus ( fig. 4 ) for determining the phase of a first clock signal (Fs) relative to a second clock signal (Fs). The first clock signal (Fs) may be a digital approximation of a periodic analog signal such as an RF signal. A sampling technique is employed that produces a stream of digital bits (X) containing relative phase information. From the stream of digital data bits is formed a digital word indicative of the relative phase ( fig. 11A ). The digital word may be formed using a digital filter ( fig. 13 ). Advantageously, an extensive body of digital filtering techniques applicable to Sigma-Delta (sometimes referred to as Delta-Sigma) A/D converters ( fig. 1 ) may be applied directly to he digital stream (X). By using an appropriately chosen weighting function, high accuracy may be obtained.