Start-up automatic frequency control (AFC) method and apparatus
AssigneeInterDigital Technology Corporation
InventorAlpaslan Demir
Life of this patent
Estimating the term…
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 positive and negative 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).
Claims24
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 at a given frequency in a positive direction to produce a positively rotated phase of the stored sequence and in a negative direction to produce a negatively rotated phase of the stored sequence;
- correlating said received sequence with the positively rotated phase of the stored sequence to produce a positive phase correlation;
- correlating said received sequence with the negatively rotated phase of the stored sequence to produce a negative phase correlation;
- combining the positive and negative phase correlations to provide a frequency estimate;
- and
- filtering at least one frequency estimate to control the generation of a frequency by an oscillator.
A cell search method for a receiver, where the cell search processing includes processing of a received sequence to facilitate the determination of a frequency location of a received signal, the method comprising:
- conducting a periodic cell search to obtain a best base station during a given period by periodically:
- rotating a phase of a stored sequence at a given frequency in a positive direction to produce a positively rotated phase of the stored sequence and in a negative direction to produce a negatively rotated phase of the stored sequence;
- correlating said received sequence with the positively rotated phase of the stored sequence to produce a positive phase correlation;
- correlating said received sequence with the negatively rotated phase of the stored sequence to produce a negative phase correlation;
- and
- combining the positive and negative phase correlations to provide a frequency estimate;
- and
- filtering at least one frequency estimate to control the generation of a frequency by an oscillator.
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 at a given frequency in a positive and in a negative direction to produce positively and negatively rotated phases of the stored sequence;
- a positive phase correlator configured to correlate said received sequence with the positively rotated phase of the stored sequence to produce a positive phase correlation;
- a negative phase correlator configured to correlate said received sequence with the negatively rotated phase of the stored sequence to produce a negative phase correlation;
- and
- a combining component configured to combine positive and negative phase correlations produced by the correlators to produce a frequency estimate.
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;
- the frequency estimator including:
- a phase rotation component configured to rotate a phase of a stored sequence at a given frequency in a positive and in a negative direction to produce positively and negatively rotated phases of the stored sequence;
- a positive phase correlator configured to correlate said received sequence with the positively rotated phase of the stored sequence to produce a positive phase correlation;
- a negative phase correlator configured to correlate said received sequence with the negatively rotated phase of the stored sequence to produce a negative phase correlation;
- and
- a combining component configured to combine positive and negative phase correlations produced by the correlators to produce a frequency estimate;
- and
- the automatic frequency control including a sequence locator associated with the initial cell search processing component and configured to selectively produce received signal input for the frequency estimator.
Dependencies are inferred from the claim text.