Device and method for handling carrier frequency offset

1. A communication device, comprising:

a receiving circuit, receiving a first plurality of time-domain signals;

a computing circuit, coupled to the receiving circuit, performing a J th power operation according to the first plurality of time-domain signals to respectively generate a first plurality of computed signals;

a transforming circuit, coupled to the computing circuit, transforming the first plurality of computed signals to a first plurality of frequency-domain signals according to a time-frequency transformation;

a control circuit, coupled to the transforming circuit, performing an absolute value operation on the first plurality of frequency-domain signals to generate a first plurality of output signals;

a selecting circuit, coupled to the control circuit, selecting a maximum output signal satisfying a check condition from the first plurality of output signals; and

a frequency estimating circuit, coupled to the selecting circuit, estimating a carrier frequency offset according to the maximum output signal to obtain an estimated carrier frequency offset,

wherein the communication device is configured to apply the estimated carrier frequency offset to compensate for phase distortion of the plurality of time-domain signals.

2. The communication device according to claim 1 , wherein when the first plurality of output signals do not include the maximum output signal satisfying the check condition, the communication performs operations of:

the receiving circuit receiving a second plurality of time-domain signals;

the computing circuit performing the J th power operation according to the second plurality of time-domain signals to a second plurality of computed signals;

the transforming circuit transforming the second plurality of computed signals to a second plurality of frequency-domain signals according to the time-frequency transformation;

the control circuit performing the absolute value operation on the second plurality of frequency-domain signals to generate a second plurality of output signals; and

the selecting circuit correspondingly adding the first plurality of output signals and the second plurality of output signals to generate a plurality of auxiliary signals, selecting the maximum output signal from the plurality of auxiliary signals, and determining whether the maximum output signal satisfies the check condition.

3. The communication device according to claim 1 , wherein the selecting circuit sequentially selects the maximum output signal from a plurality of sets of output signals of the first plurality of output signals using a window according to a sliding window method, and checks whether the maximum output signal satisfies the check condition.

4. The communication device according to claim 3 , wherein one set of output signals of the plurality of sets of output signals satisfies the check condition according to an equation:

f ({ Z k } k=1,k≠sub _ max M )+ Z sub _ max <G*Z sub _ max ;

where {Z k } k=1 M is the set of output signals, M is a size of the window, f(⋅) is a function, sub_max is an index of a maximum output signal of the set of output signals, and G is a positive real number.

5. The communication device according to claim 4 , wherein the function is an equation:

f ({ Z k } k=1,k≠sub _ max M )=Σ k=1,k≠sub _ max M Z k .

6. The communication device according to claim 1 , wherein the time-frequency transformation comprises a fast Fourier transform (FFT).

7. The communication device according to claim 1 , wherein the J th power operation is a 4 th power operation.

8. The communication device according to claim 1 , wherein the maximum output signal has a maximum amplitude satisfying the check condition.

9. A method for handling carrier frequency offset, comprising:

receiving a first plurality of time-domain signals by a receiving circuit;

performing a J th power operation according to the first plurality of time-domain signals to respectively generate a first plurality of computed signals by a computing circuit;

transforming the first plurality of computed signals to a first plurality of frequency-domain signals according to a time-frequency transformation by a transforming circuit;

performing an absolute value operation on the first plurality of frequency-domain signals to generate a first plurality of output signals by a control circuit;

selecting a maximum output signal satisfying a check condition from the first plurality of output signals by a selecting circuit;

estimating a carrier frequency offset according to the maximum output signal by a frequency estimating circuit to obtain an estimated carrier frequency offset; and

applying the estimated carrier frequency offset to compensate for phase distortion of the plurality of time-domain signals.

10. The method according to claim 9 , wherein when the first plurality of output signals do not include the maximum output signal satisfying the check condition, the method further comprises:

receiving a second plurality of time-domain signals by the receiving circuit;

performing the J th power operation according to the second plurality of time-domain signals to respectively generate a second plurality of computed signals by the computing circuit;

transforming the second plurality of computed signals to a second plurality of frequency-domain signals according to the time-frequency transformation by the transforming circuit;

performing the absolute value operation on the second plurality of frequency-domain signals to generate a second plurality of output signals by the control circuit; and

correspondingly adding the first plurality of output signals and the second plurality of output signals to generate a plurality of auxiliary signals, and selecting the maximum output signal satisfying the check condition from the plurality of auxiliary signals by the selecting circuit.

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

sequentially selecting the maximum output signal from a plurality of sets of output signals of the first plurality of output signals using a window according to a sliding window method, and checking whether the maximum output signal satisfies the check condition by the selecting circuit.

12. The method according to claim 11 , wherein one set of output signals of the plurality of sets of output signals satisfies the check condition according to an equation:

f ({ Z k } k=1,k≠sub _ max M ) + Z sub _ max <G*Z sub —max ;

where {Z k } k=1 M is the set of output signals, M is a size of the window, f(⋅) is a function, sub_max is an index of a maximum output signal of the set of output signals, and G is a positive real number.

13. The method according to claim 12 , wherein the function is an equation:

f ({ Z k } k=1,k≠sub _ max M )=Σ k=1,k≠sub _ max M Z k .

14. The method according to claim 9 , wherein the time-frequency transformation comprises a fast Fourier transform (FFT).

15. The method according to claim 9 , wherein the J th power operation is a 4 th power operation.

16. The method according to claim 9 , wherein the maximum output signal has a maximum amplitude satisfying the check condition.