Frequency offset estimating apparatus and estimating method thereof

1. A frequency offset estimating method, implemented in a signal receiver, comprising steps of:

generating a nth power signal by raising a received signal to nth power; and

analyzing a spectrum of the nth power signal to obtain a frequency offset, comprising:

calculating the spectrum of the nth power signal, comprising:

selecting a plurality of segments from the nth power signal in a time domain;

transforming the plurality of segments into a frequency domain and calculating power of the plurality of segments; and

summing up the power of the plurality of segments to obtain the spectrum of the nth power signal;

locating a frequency value with a maximum power from the spectrum; and

obtaining the frequency offset according to the frequency value;

wherein each of the plurality of segments comprises a plurality of consecutive sampling points in the nth power signal.

2. The method as claimed in claim 1 , wherein n is a multiple of 2.

3. The method as claimed in claim 1 , wherein lengths of the plurality of segments are same.

4. The method as claimed in claim 1 , wherein the step of obtaining the frequency offset according to the frequency value comprises a step of:

adjusting the frequency value according to a scaling factor to obtain the frequency offset.

5. The method as claimed in claim 1 , being applied to a Digital Video Broadcasting (DVB) system, for estimating the frequency offset of the received signal of the DVB system.

6. A frequency offset estimating apparatus, comprising:

an nth power computing module, for generating a nth power signal by raising a received signal to nth power; and

a spectrum analyzing module, coupled to the nth power computing module, for analyzing a spectrum of the nth power signal to obtain a frequency offset, comprising:

a spectrum calculating unit, for calculating the spectrum of the nth power signal, comprising:

a selecting unit, for selecting a plurality of segments from the nth power signal in a time domain;

a transforming unit, coupled to the selecting unit, for transforming the plurality of segments to a frequency domain and calculating power of the plurality of segments; and

a summing unit, coupled to the transforming unit, for summing up the power of the plurality of segments to obtain the spectrum of the nth power signal;

a comparing unit, coupled to the spectrum calculating unit, for locating a frequency value with maximum power from the spectrum; and

a processing unit, coupled to the comparing unit, for obtaining the frequency offset according to the frequency value;

wherein the selecting unit selects a plurality of consecutive sampling points from the nth power signal in each of the plurality of segments.

7. The frequency offset estimating apparatus as claimed in claim 6 , wherein n is a multiple of 2.

8. The frequency offset estimating apparatus as claimed in claim 6 , wherein lengths of the plurality of segments are the same.

9. The frequency offset estimating apparatus as claimed in claim 6 , wherein the processing unit adjusts the frequency value according to a scaling factor to obtain the frequency offset.

10. The frequency offset estimating apparatus as claimed in claim 6 , being applied to a receiver of a Digital Video Broadcasting (DVB) system, for estimating the frequency offset of the received signal.

11. The frequency offset estimating apparatus as claimed in claim 10 , wherein the frequency offset estimating apparatus is turned on when the receiver operates in a frequency compensation mode; and the frequency offset estimating apparatus is turned off when the receiver operates in a normal operation mode.