System and method for time-of-flight determination using categorization of both code and phase in received signal

In a receiver, an apparatus for detecting an earliest arrival time among one or more component signals of a received signal, the received signal having embedded therein a probe signal, the probe signal being a periodic signal that repeatedly encodes a pseudo-random (PRN) code, each period of the probe signal being of a predetermined duration, the received signal having a duration exceeding two or more times the predetermined duration, the apparatus comprising:

• (i) an analog-to-digital circuit that divides the received signal into sections and samples each section of the received signal into samples of two sample types, the sample types being in-phase samples and quadrature samples;
• (ii) a category assignment circuit which categorizes each section of the received signal to one of a plurality of categories, based on both an estimated delay and an estimated doppler frequency experienced in transit by the received signal, including one or more transition-encompassing categories, wherein each transition-encompassing category represents a section of the probe signal that includes a signal transition;
• (iii) an accumulator that accumulates the sections of the received signal assigned to the transition-encompassing categories separately by both their assigned categories and their sample types;
• and
• (v) a processor circuit that (a) detects one of the signal transitions in the accumulated sections of in-phase samples, (b) detects a time of arrival of a peak value in the corresponding accumulated sections of quadrature samples, wherein the time of arrival precedes the signal transition, and (c) outputs the time of arrival to be the detected earliest arrival time.