TH82002A - Dual-band automatic frequency control for wireless communication - Google Patents

Abstract

The DC60 describes a method for achieving frequency control using dual-band automatic frequency control (AFC). A dual-band AFC includes an inner band, which corrects short-duration frequency variations (e.g., due to the Doppler effect), and an outer band, which corrects long-duration frequency variations (e.g., due to component consent tolerances and temperature variations). In one design, a first inner band is implemented for frequency control of the first system (e.g., a broadcasting system), a second inner band is implemented for frequency control of the second system (e.g., a cellular system), and at least one outer band is implemented for correcting the reference frequency used to receive the first and second systems. Each inner band estimates and corrects frequency errors in the input signals for the co-acquiring systems and may allow, when receiving the systems, the reference frequency to be used for frequency downshifting, sampling, and/or other purposes. The method for achieving frequency control using dual-band automatic frequency control (AFC) is described. A dual-band AFC includes an inner band, which corrects for short-duration frequency variations (e.g., due to the Doppler effect), and an outer band, which corrects for long-duration frequency variations (e.g., due to component consent tolerances and temperature variations). In one design, a first inner band is effective for frequency control of the first system (e.g., a broadcasting system), a second inner band is effective for frequency control of the second system (e.g., a cellular system), and at least one outer band is effective for correcting the reference frequency used to receive the first and second systems. Each inner band approximates and corrects frequency errors in the input signal for the co-acquiring system and may allow, when receiving, the reference frequency to be used for frequency downshifting, sampling, and/or other purposes.

Claims (58)

1. An instrument comprising at least one processor configured to perform frequency control to achieve results for the first communication system with the first inner band, to perform frequency control for the second communication system with the second inner band, and to adjust the reference frequency with the outer band. The reference frequency is used to receive the first and second communication systems, and memory connected to at least one processor. 2. The instrument of Claim 1 shall be structured as a processor with at least one processor to estimate and correct the frequency error in the first input signal for the first communication system with the first inner band, and to estimate and correct the frequency error in the second input signal for the second communication system with the second inner band. 3. The instrument of Claim 1 shall be configured with at least one processor to estimate and correct frequency errors between the reference frequency and the frequencies of the first and second communication systems with the outer band. 4. The instrument of Claim 1, which provides at least one processor to make the first and second outer bands effective for the first and second communication systems, respectively; to update the first and second outer bands with the first and second inner bands, respectively; and to select either the first or second outer band as the outer band with the corrected reference frequency. 5. The instrument of claim paragraph 4, which provides for the configuration of at least one processor to allow access to the first inner ring and the first outer ring when receiving only the first communication system, and to allow access to the first and second inner rings and the second outer ring when receiving the first and second communication systems. 6. Instruments of Claim 1, whereby at least one processor is configured to update the outer ring with the first inner ring, or the second inner ring, or both the first and second inner rings. 7. Instruments of Claim 1, where the first communication system is a broadcasting system and the second communication system is a cellular system. 8. Instruments of Claim 1 whereby the first and second communication systems will utilize two different types of radio technology. 9. Instruments of Claim 1, where the first communication system is a broadcasting system utilizing orthogonal frequency division multiplexing (OFDM), and where the second communication system is a code-divided multiple access (CDMA) system. 10. Instruments of Claim 1, using a reference frequency for the downshifting of signals received from the first and second communication systems. 11. Instruments of Claim 1, using a reference frequency for sampling signals for the first and second communication systems. 12. Instrumentation of Claim 1, whereby the reference frequency is further used to receive the Satellite Positioning System. 13. A processor configured to achieve frequency control for the first communication system with the first inner band, to achieve frequency control for the second communication system with the second inner band, and to correct the reference frequency with the outer band. The reference frequency is used to receive the first and second communication systems. 14. The processor of claim 13 and thereafter configures to update the outer band with the first inner band when the first communication system is selected to correct the reference frequency and to update the outer band with the second inner band when the second communication system is selected to correct the reference frequency. 15. The processor of claim 13 and thereafter configures to allow passage to the first inner circle when receiving the first communication system and to allow passage to the second inner circle when receiving the second communication system. 16. The procedure comprises the implementation of frequency control to achieve results for the second communication system with the inner band of the first, the implementation of frequency control to achieve results for the second communication system with the inner band of the second, and the correction of the reference frequency with the outer band. The reference frequency is used to receive the first and second communication systems. 17. The method of claim 16, which includes the updating of the outer band with the first inner band when the first communication system is selected to correct the reference frequency, and the updating of the outer band with the second inner band when the second communication system is selected to correct the reference frequency. 18. The method of claim 16, which includes opening the first inner circle when receiving the first communication system and opening the second inner circle when receiving the second communication system. 19. An instrument comprising a path for achieving frequency control for the first communication system with the first inner band, a path for achieving frequency control for the second communication system with the second inner band, and a path for correcting the reference frequency with the outer band. The reference frequency is used to receive the first and second communication systems. 20. The instrument of claim 19, which includes the path for updating the outer band with the first inner band when the first communication system is selected to correct the reference frequency, and the path for updating the outer band with the second inner band when the second communication system is selected to correct the reference frequency. 21. The instruments of claim 19, which include the means for opening the first inner circle when receiving the first communication system, and the means for opening the second inner circle when receiving the second communication system. 22. A computer-readable medium encodes a computer program to perform frequency control to achieve results for the first communication system with the first inner band, performs frequency control to achieve results for the second communication system with the second inner band, and adjusts the reference frequency with the outer band. The reference frequency is then used to receive the first and second communication systems. 23. An instrument comprising at least one processor configured to estimate and correct frequency errors for the first communication system with the inner band, and to estimate and correct frequency errors in the outer band. A reference frequency is used to receive the first and second communication systems, and memory connected to at least one processor. 24. The instruments of claim 23 shall, in which the inner band shall consist of a phase rotor to correct the frequency error in the input sample for the first communication system and provide an output sample; a first frequency error estimator to obtain a frequency error estimate using the output sample as the basis; and a band filter to filter out the frequency error estimate and provide an inner band output signal indicating the frequency error for the first communication system and to correct the frequency error in the input sample. 25. Instrument of Claim 24, where the first frequency error estimator obtains a frequency error estimate for each received OFDM symbol by performing a circular prefix correlation of the received OFDM symbols. 26. The instrument of claim 24 where the inner loop is further incorporated with a second frequency error estimator configured to obtain the initial frequency error estimation using the input sample as the basis, and where the loop filter is initially determined with the initial frequency error estimation. 27. The instrument of claim 26, where the second frequency error is estimated, obtains the initial frequency error estimate by performing periodic sequence correlation on the signal received from the first communication system. 28. Instruments of claim 26 where the second frequency error estimator is operated once when the inner loop is first opened, and where the first frequency error estimator is operated when the inner loop is first opened, and where the first frequency error estimator is operated when the inner loop is first opened. 29. The instrumentation of claim 24, whereby the inner circle shall include a frequency lock detector configured to determine whether frequency locking has been achieved for the first communication system. 30. The instrumentation of claim 23 shall be such that the outer band shall consist of a module one to calculate the average frequency error from the band and a band filter to filter out the average frequency error and provide an outer band output signal to be used to correct the frequency error to a reference frequency. 31. Instrumentation of claim 30, whereby the outer loop is further incorporated with a second module to limit the input signal for the loop filter. 32. Instrumentation of claim 31 where the outer band can be operated in either the acquisition or tracking manner, and where the second module restricts the input signal for the band filter to within the first range in the acquisition manner and to within the second range in the tracking manner, with the second range being smaller than the first range. 33. Instruments of Claim 30 where the outer circle can be executed in either the Acquisition or Tracking method, and where the circle filter uses the first gain in the Acquisition method and the second gain in the Tracking method, with the second gain being smaller than the first gain. 34. Instruments of Claim 23, where the first communication system is a broadcast system and the second communication system is a cellular system. 35. A processor configured to estimate and correct frequency errors for the first communication system using the inner band, and to estimate and correct frequency errors at the reference frequency using the outer band. The reference frequency is used to receive the first and second communication systems. 36. The processor of claim 35, whereby the inner band shall include a phase rotor to correct the frequency error in the input sample for the first communication system, and shall provide an output sample, a first frequency error estimator to obtain a frequency error estimate using the output sample as the basis, and a band filter to filter the frequency error estimate, and shall provide an inner band output signal indicating the frequency error for the first communication system and to correct the frequency error in the input sample. 37. The processor of claim 35, where the outer band comprises a module to calculate the average frequency error from the inner band and a band filter to filter out the average frequency error and provide an outer band output signal used to correct the frequency error to a reference frequency. 38. A method comprising the estimation and error correction of the frequency for the first communication system using the inner band, and the estimation and error correction of the frequency at the reference frequency using the outer band. The reference frequency is used to receive the first and second communication systems. 39. The procedure for claiming Article 38, whereby the estimation and correction of frequency errors for the first communication system shall consist of: correcting the frequency errors in the input sample for the first communication system to obtain the output sample; obtaining a frequency error estimate using the output sample as the basis; and filtering the frequency error estimate to obtain the inner band output signal, which indicates the frequency error for the first communication system and is used to correct the frequency error in the input sample. 40. The procedure for claiming Article 38, whereby the estimation and correction of frequency errors at the reference frequency shall include the calculation of the average frequency error from the inner band and the filtering of the average frequency error to obtain the outer band output signal, which is used to correct the frequency errors at the reference frequency. 41. An instrument comprising a method for estimating and correcting frequency errors for the first communication system using the inner band, and a method for estimating and correcting frequency errors at the reference frequency using the outer band. The reference frequency is used to receive the first and second communication systems. 42. Instruments of Claim 41, whereby the means for estimating and correcting frequency errors for the first communication system shall consist of: a means for correcting the frequency error in the input sample for the first communication system to obtain the output sample; a means for obtaining frequency error estimates using the output sample as the basis; and a means for filtering the frequency error estimates to obtain the inner band output signal, which indicates the frequency error for the first communication system and is used to correct the frequency error in the input sample. 43. The instruments of claim 41, where the means for estimating and correcting frequency errors in the reference frequency, shall include a means for calculating the average frequency error from the inner band and a means for filtering the average frequency error to obtain an outer band output signal which is used to correct the frequency errors in the reference frequency. 44. A computer-readable medium that is encoded by a computer program to estimate and correct frequency errors for the first communication system using the inner band, and to estimate and correct frequency errors at a reference frequency using the outer band. The reference frequency is used to receive the first and second communication systems. 45. An instrument comprising at least one processor configured to receive data in burst form, to update the inner band at each interval between data bursts, estimating the inner band and correcting the frequency error in the data burst, and to update the outer band at each outer band update interval, estimating the outer band and correcting the frequency error in the reference frequency used to receive the data burst, and memory connected to at least one processor. 46. Instruments of Claim 45, where each data burst contains at least one OFDM symbol, and where at least one processor is configured to update the inner circle with each OFDM symbol received. 47. Instruments of claim 45 where at least one processor is configured to update the outer loop at the end of each data burst. 48. The instrument of claim 45 is that at least one processor is configured to initiate execution before each data burst and to pause execution between data bursts. 49. A processor configured to receive data in burst format adjusts the inner band to the correct frequency during each data burst adjustment. During each inner band adjustment, the inner band estimates and corrects frequency errors at the reference frequency used to receive the data burst. Similarly, during each outer band adjustment, the outer band estimates and corrects frequency errors at the reference frequency used to receive the data burst. 50. The processor of claim 49 and its subsequent configurations updates the inner circle with each OFDM symbol received in each data burst. 51. The processor of claim 49 and its subsequent configurations updates the outer loop to the end of each data burst. 52. The method comprises burst reception, inner band updating at intervals between data bursts, inner band estimation and frequency error correction at each data burst, and outer band updating at each outer band updating interval, estimating the outer band and correcting the frequency error at the reference frequency used to receive the data bursts. 53. The method of claim 52, where the inner circle update shall include updating the inner circle with each OFDM symbol received in each data burst. 54. The method of claim 52, where the outer circle update includes the outer circle update at the end of each data burst. 55. The instrument comprises a method for receiving burst data, a method for inner band updating during each inner band update interval between data bursts, inner band estimation and frequency error correction in data bursts, and a method for outer band updating during each outer band update interval, outer band estimation and frequency error correction at the reference frequency used to receive data bursts. 56. The instrumentation of claim 55, whereby the method for updating the inner circle shall consist of the method for updating the inner circle with each OFDM symbol received in each data burst. 57. The instrumentation of claim 55, whereby the outer circle updating path shall include the outer circle updating path at the end of each data burst. 58. A computer-readable medium encoded by a computer program to update the inner band to the correct value during each data burst, estimating the inner band and correcting frequency errors in each data burst, and updating the outer band during each outer band update, estimating the outer band and correcting frequency errors at the reference frequency used to receive the data burst.