# US 7,412,013 B2 · Start-up automatic frequency control (AFC) method and apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,412,013 B2 - Document ID: US7412013B2 - Status: Granted - Kind: B2 - Application number: 11/754,013 - Filed: 2007-05-25 - Published: 2007-10-04 - Granted: 2008-08-12 - Earliest claimed: 2002-07-31 - Assignees: InterDigital Technology Corporation - Inventors: Alpaslan Demir - Web page: https://patentgrep.com/patent/US7412013B2 ## CPC - H04B 1/14: Automatic detuning arrangements - H04B 1/708: Parallel implementation - H04J 11/0069: {Cell search, i.e. determining cell identity [cell-ID] (design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655)} - H04L 27/0014: {Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657)} - H03J 2200/02: Algorithm used as input for AFC action alignment receiver - H04B 1/70735: {Code identification (H04B1/7083 takes precedence)} - H04L 2027/0024: {at the receiver end} - H04L 2027/0065: {Frequency error detectors (H04L2027/0067 takes precedence)} - H04L 2027/0091: {Continuous signals} - H04B: TRANSMISSION - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H03J: TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS ## 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). ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The method of claim 1 wherein the stored sequence is a primary synchronization code sequence. ### Claim 3 (depends on 1) The method of claim 1 further comprising repeating the rotating, correlating and combining a given number of times to produce a series of frequency estimates. ### Claim 4 (depends on 3) The method of claim 3 wherein the rotating, correlating and combining are preferably repeated twenty-four (24) times. ### Claim 5 (depends on 1) The method of claim 1 wherein a received input power level of the received signal is adjusted prior to the rotating, correlating and combining. ### Claim 6 (depends on 5) The method of claim 5 wherein the received signal is digitized after adjustment of the power level. ### Claim 7 (depends on 5) The method of claim 5 wherein the power level is set employing open loop gain control. ### Claim 8 (depends on 1) The method of claim 1 wherein the initial cell search processing includes obtaining a primary synchronization code. ### Claim 9 (depends on 8) The method of claim 8 further comprising employing the primary synchronization code to extract a secondary synchronization code from the received signal. ### Claim 10 (depends on 9) The method of claim 9 wherein the primary synchronization code and secondary synchronization code are utilized to extract a midamble portion from the received input. ### Claim 11 (depends on 10) The method of claim 10 wherein a midamble having a highest energy is selected from the extracted midamble portion. ### Claim 12 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. ### Claim 13 (depends on 1) The method of claim 1 wherein the frequency is numerically controlled. ### Claim 14 (depends on 1) The method of claim 1 wherein the frequency is voltage controlled. ### Claim 15 (depends on 1) The method of claim 1 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 and N≧1. ### Claim 16 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. ### Claim 17 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. ### Claim 18 (depends on 17) The wireless communication device of claim 17 wherein the frequency estimator includes an early frequency estimator component configured to produce a frequency estimate based on an early version of said received sequence, a punctual frequency estimator component configured to produce a frequency estimate based on a punctual version of said received sequence, a late frequency estimator component configured to produce a frequency estimate based on a late early version of said received sequence and a summer configured to sum the frequency estimates produced by the frequency estimator components. ### Claim 19 (depends on 16) The wireless communication device of claim 16 wherein the frequency estimator is configured to use is a primary synchronization code as the received sequence. ### Claim 20 (depends on 16) The wireless communication device of claim 16 wherein the filtering component is configured to selectively integrate frequency estimates responsive to an initial or steady state conditions of a cell search process and the oscillator comprises one of a voltage controlled oscillator (VCO) and numeric controlled oscillator (NCO). ### Claim 21 (depends on 20) The wireless communication device of claim 20 wherein the filtering component is a Proportional integral (PI) filter. ### Claim 22 (depends on 20) The wireless communication device of claim 20 wherein the filtering component is a digital filter having a delay element of 1/(1−z−1). ### Claim 23 (depends on 16) A user equipment comprising the wireless communication device of claim 16. ### Claim 24 (depends on 17) A user equipment comprising the wireless communication device of claim 17.