Apparatus and method for estimating carrier frequency offset
An apparatus for estimating carrier frequency offset includes an M th -power circuit, a spectrum generating circuit, a spectrum adjusting circuit, a peak frequency determining circuit and a frequency offset determining circuit. The M th -power circuit performs an M th -power calculation on an input signal to generate an M th -power calculation result. The spectrum generating circuit generates a spectrum according to the M th -power calculation result. The spectrum adjusting circuit identifies a partial energy peak value in a partial frequency range from the spectrum, and increases the partial energy peak value to be higher than any other energy in the spectrum to generate an adjusted spectrum. The peak frequency determining circuit identifies a peak frequency having a maximum energy peak value from the adjusted spectrum. The frequency offset determining circuit determines an estimated carrier frequency offset result according to the peak frequency.
1. An apparatus for estimating carrier frequency offset (CFO), comprising:
an M th -power calculation circuit for performing an M th -power calculation on an input signal to generate an M th -power calculation result, where M is an integer greater than 1 and is associated with a modulation scheme of the input signal;
a spectrum generating circuit for generating a spectrum according to the M th -power calculation result;
a spectrum adjusting circuit for increasing a partial energy peak value in a partial frequency range in the spectrum to generate an adjusted spectrum, wherein the partial frequency range is −½T to ½T and T represents a symbol duration of the input signal;
a peak frequency determining circuit for identifying a peak frequency from the adjusted spectrum, wherein the peak frequency has a maximum peak energy in the adjusted spectrum; and
a frequency offset determining circuit for generating an estimated CFO result.
2. The apparatus according to claim 1 , wherein the spectrum adjusting circuit comprises:
a search circuit for identifying the partial energy peak value in the partial frequency range from the spectrum, identifying a corresponding partial peak frequency according to the partial energy peak value, and identifying energies corresponding to a plurality of frequencies that are spaced by integral multiples of 1/T from the partial peak frequency as a plurality of energy increments;
an addition circuit for adding the energy increments and the partial energy peak value to generate an adjusted energy; and
an adjusting circuit, adjusting the spectrum according to the partial peak frequency and the adjusted energy to generate the adjusted spectrum, wherein the partial peak frequency corresponds to the adjusted energy in the adjusted spectrum.
3. The apparatus according to claim 1 , wherein the spectrum adjusting circuit comprises:
a search circuit for identifying the partial energy peak value in the partial frequency range from the spectrum, and identifying a corresponding partial peak frequency according to the partial energy peak value;
an addition circuit for adding a predetermined energy increment and the partial energy peak value to generate an adjusted energy; and
an adjusting circuit for adjusting the spectrum according to the partial peak frequency and the adjusted energy to generate the adjusted spectrum, wherein the partial peak frequency corresponds to the adjusted energy in the adjusted spectrum.
4. A method for estimating carrier frequency offset (CFO), comprising:
performing an M th -power calculation on an input signal to generate an M th -power calculation result, where M is an integer greater than 1 and is associated with a modulation scheme of the input signal;
generating a spectrum according to the M th -power calculation result;
identifying a partial energy peak value in a partial frequency range from the spectrum, wherein the partial frequency range is −½T to ½T and T represents a symbol duration of the input signal;
increasing the partial energy peak value to generate an adjusted spectrum;
identifying a peak frequency from the adjusted spectrum, wherein the peak frequency has a maximum energy peak value in the adjusted spectrum; and
determining an estimated CFO result according to the peak frequency.
5. The method according to claim 4 , wherein the step of increasing the partial energy peak value to generate the adjusted spectrum comprises:
identifying a corresponding partial peak frequency according to the partial energy peak value;
identifying energies corresponding to a plurality of frequencies that are spaced by integral multiples of 1/T from the partial peak frequency as a plurality of energy increments;
adding the energy increments and the partial energy peak value to generate an adjusted energy; and
adjusting the spectrum according to the partial peak frequency and the adjusted energy to generate the adjusted spectrum, wherein the partial peak frequency corresponds to the adjusted energy in the adjusted spectrum.
6. The method according to claim 4 , wherein the step of adjusting the partial energy peak value to generate the adjusted spectrum comprises:
identifying a corresponding partial peak frequency according to the partial energy peak value;
adding a predetermined energy increment and the partial energy peak value to generate an adjusted energy; and
adjusting the spectrum according to the partial peak frequency and the adjusted energy to generate the adjusted spectrum, wherein the partial peak frequency corresponds to the adjusted energy in the adjusted spectrum.