Start-up automatic frequency control (AFC) method and apparatus
AssigneeInterDigital Technology Corporation
InventorAlpaslan Demir
Life of this patent
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Abstract
A method and apparatus for use in connection with wireless communication to adjust the frequency of an oscillator to synchronize with a received signal by correlating a synchronization code channel with training sequences to estimate relative offsets which are employed to estimate an error, which is then filtered. The filtered output preferably provides a voltage controlling a voltage controlled oscillator (VCO). The same technique may be employed to control a numeric controlled oscillator (NCO).
Claims22
A start-up automatic frequency control method used during initial cell search processing by a receiver, where the initial cell search processing includes processing of a received sequence to facilitate the determination of a frequency location of a received signal, the method comprising:
- rotating a phase of a stored sequence to produce a first version of the stored sequence having a rotated phase;
- correlating the received sequence with the first version of the stored sequence to produce a first phase correlation;
- correlating the received sequence with a second version of the stored sequence that has a different rotated phase than the first version to produce a second phase correlation;
- combining the first and second phase correlations to provide a frequency estimate;
- and
- filtering at least one frequency estimate to control the generation of a frequency by an oscillator;
- wherein the processing to facilitate the determination of a frequency location of a received signal is repeated every N frames where N is an integer greater than 0.
A wireless communication device comprising:
- an automatic frequency control having an oscillator configured to produce an adjusted frequency during initial cell search and an associated initial cell search processing component configured to process a received sequence to facilitate the determination of a frequency location of a received signal;
- the automatic frequency control having a frequency estimator configured to produce at least one frequency estimate and a filtering component configured to produce a signal to adjust the frequency produced by the oscillator;
- and
- the frequency estimator including:
- a phase rotation component configured to rotate a phase of a stored sequence to produce a first version of the stored sequence having a rotated phase;
- a first phase correlator configured to correlate said received sequence with the first version of the stored sequence to produce a first phase correlation;
- a second phase correlator configured to correlate said received sequence with a second version of the stored sequence that has a different rotated phase than the first version to produce a second phase correlation;
- and
- a combining component configured to combine first and second phase correlations produced by the correlators to produce a frequency estimate.
Dependencies are inferred from the claim text.