×

Automatic frequency control under low signal-to-noise conditions

  • US 8,548,033 B2
  • Filed: 12/20/2011
  • Issued: 10/01/2013
  • Est. Priority Date: 12/23/2010
  • Status: Expired due to Fees
First Claim
Patent Images

1. A method for determining a carrier frequency offset and a corresponding sample-to-sample phase shift present in a sampled digital signal from a radio of a wireless transceiver, said method comprising the steps of:

  • dividing a carrier frequency offset (CFO) range to be covered into a plurality of intervals;

    creating from a received signal as many parallel derived streams as there are intervals and pre-compensating (“

    back rotating”

    ) signals received by the sample-to-sample phase shift corresponding to a midpoint of a particular one of the plurality of intervals;

    computing magnitude and phase resulting from a correlation of an expected preamble pattern period waveform with a preamble segment of each derived stream in parallel;

    selecting a largest resulting magnitude value(s) to zoom in on an actual CFO present in an input stream of the signals received;

    repeating a search for a shorter interval centered on a CFO value located in a first run, if needed, in order to improve accuracy in the presence of noise and provided there is still input preamble left to work on; and

    determining an actual CFO from the CFO values belonging to the selected interval and the result of the corresponding computed correlation phase.

View all claims
  • 7 Assignments
Timeline View
Assignment View
    ×
    ×