Granted Patent B2

US 8,995,585 · App. 12/670,397 · Granted Mar 31, 2015

Abstract

Claims (54)

1. A carrier recovery device comprising:

a coarse estimator,

a fine estimator,

a switch to select an estimator output, and

a sweeper configured to sweep an input data carrier frequency offset within a certain range, the sweeper comprising a plurality of parallel scanners, each scanner including a pre-rotator and a detector, each pre-rotator configured to use a respective pre-defined frequency value to rotate data inputted into said pre-rotator, each detector configured to calculate a detected value based on an output of a corresponding pre-rotator;

wherein the coarse estimator receives, as input, a pseudo random noise signal and is arranged to estimate a residual frequency offset by using a correlation of the pseudo random noise;

wherein the fine estimator receives, as input, estimated channel information distinct from the pseudo random noise signal, and is arranged to estimate the residual frequency offset by using the estimated channel information;

wherein the switch is controlled to select data outputted out of the coarse estimator, the fine estimator or the sweeper as the estimator output.

2. The device according to claim 1 , wherein the sweeper further comprises an output of one of the scanners which is closest to a real frequency offset.

3. The device according to claim 1 , wherein a detector of each scanner to calculate an amplitude of a slide accumulated value of the rotated data.

4. The device according to claim 1 , wherein the coarse frequency estimator is arranged to estimate a coarse frequency offset by squaring a signal from at least one of a rotator and a selector when the pseudo random noise sequence has different phase in different frames.

5. The device according to claim 4 , wherein the coarse frequency estimator is arranged to filter squared signal to decrease the effect of noise.

6. The device according to claim 5 , wherein the fine estimator is arranged to estimate the fine frequency offset by using an estimated channel information to estimate the residual frequency offset.

7. The device according to claim 6 , wherein the fine frequency estimator comprises

a storage to store a pre-frame's estimated channel information,

a first selector to select an estimated channel's path whose amplitude is larger than a threshold,

a second selector to select the pre-frame's estimated channel's path with same selected position in present one,

a correlator to correlate the selected channel information outputted out of selectors with each other,

a filter to calculate a common phase difference in two consecutive estimated channel information, and

a phase detector to extract a phase difference and to get the residual frequency offset.

8. A carrier recovery method for pseudo random noise based systems, the method comprising:

sweeping, using a sweeper, an input data carrier frequency offset within a certain range, wherein the sweeper includes a plurality of parallel scanners, and the sweeping includes:

rotating data inputted into each scanner using a respective pre-defined frequency value, and

calculating a detected value based on the rotating performed for each scanner;

estimating, using a coarse estimator, a residual frequency offset by inputting a pseudo random noise signal and using a correlation of the pseudo random noise;

estimating, using a fine estimator, the residual frequency offset by inputting estimated channel information signal distinct from the pseudo random noise signal and using the estimated channel information; and

selecting an estimator output, using a switch to select data outputted from the sweeper, the coarse estimator, and the fine estimator as the estimator output.

9. The method of claim 8 , wherein the method further comprises:

selecting a scanner output which is closest to a real frequency offset.

10. The method according to claim 9 , further comprising:

calculating an amplitude of a slide accumulated value of the rotated data.

11. The method of claim 10 further comprising:

estimating a coarse frequency offset using the coarse frequency estimator by squaring a signal from a rotator when the pseudo random noise sequence has a different phase in different frames.

12. The method of claim 11 wherein the coarse frequency estimator is arranged to filter the squared signal to decrease an effect of noise.

13. The method of claim 12 wherein the fine estimator is arranged to estimate a fine frequency offset by using the estimated channel information to estimate the residual frequency offset.

14. The method according to claim 12 further comprising:

storing a pre-frame's estimated channel information in a storage in the fine frequency estimator;

selecting an estimated channel's path whose amplitude is larger than a threshold using a first selector in the fine frequency estimator;

selecting the pre-frame's estimated channel's path with same selected position in present one using a second selector in the fine frequency estimator;

correlating the selected channel information outputted out of selectors with each other using a correlator in the fine frequency estimator;

calculating a common phase difference in two consecutive estimated channels using a filter in the fine frequency estimator; and

extracting a phase difference to receive the residual frequency offset using a phase detector.

15. The method of claim 14 further comprising:

calculating, using the sweeper, a sweeper input data carrier frequency within a certain range;

estimating a residual frequency offset within the coarse estimator by inputting a pseudo random noise signal and using a correlation of the pseudo random noise;

estimating the residual frequency offset in the fine estimator by inputting an estimated channel information signal distinct from the pseudo random noise signal and using the estimated channel information; and

switching between steps based on the residual frequency offset's amount outputted out of the coarse estimator, the fine estimator or the sweeper as the estimator output.

16. A computer program product, comprising a non-transitory computer usable medium having a computer readable program code embodied therein, said computer readable program code adapted to be executed to implement a method for carrier recovery, the method comprising:

sweeping, using a sweeper, an input data carrier frequency offset within a certain range wherein the sweeper includes a plurality of parallel scanners, and the sweeping includes:

rotating data inputted into each scanner using a respective pre-defined frequency value, and

calculating a detected value based on the rotating performed for each scanner;

estimating, using a coarse estimator, a residual frequency offset by inputting a pseudo random noise signal and using a correlation of the pseudo random noise;

estimating, using a fine estimator, the residual frequency offset by inputting an estimated channel information signal distinct from the pseudo random noise signal and using the estimated channel information; and

selecting an estimator output, using a switch to select data outputted from the sweeper, the coarse estimator, and the fine estimator as the estimator output.

Assignments (6)