Method and apparatus for detecting a preamble in a received radio signal

摘要

A method for detecting a preamble in a received radio signal includes demodulating the radio signal based on a carrier derived from a local timing source to provide a digital signal including a sequence of bits oscillating at approximately a modulated data rate. A bit width of each successive bit of the digital signal is determined. If a pair of consecutive bit widths has a combined width within a threshold, the bit pair is indicated as potentially belonging to a preamble. If a threshold number of potential preamble bit pairs in a sequence of bit pairs within a given window is detected, the sequence of bit pairs is indicated as potentially belonging to a preamble. A measure of bit widths of at least some bits within a sequence of preamble bit pairs can be provided and a frequency of the local timing source can be adjusted according to the measure.

主权项

1. A method for detecting a preamble in a received radio signal, the method comprising:
demodulating the received radio signal based on a carrier derived from a local timing source to provide a digital signal comprising a sequence of bits oscillating at approximately a modulated data rate; determining a bit width of each successive bit of said digital signal; responsive to a pair of consecutive bit widths having a combined width within a threshold value, indicating a bit pair as potentially belonging to the preamble; responsive to detecting a threshold number of potential preamble bit pairs in a sequence of bit pairs within a given window, indicating said sequence of bit pairs as potentially belonging to the preamble; determining a statistical characteristic of at least some of said sequence of bit pairs potentially belonging to the preamble, including determining if a variance of bit widths of the sequence of bit pairs is less than a second threshold amount; and responsive to said statistical characteristic meeting a predefined criterion, confirming that said sequence of bit pairs belongs to the preamble.