A method for optimization of a frequency spectrum includes the following steps: sampling a time domain signal to obtain an initial sampling signal based upon a first subset of sample points; transforming the initial sampling signal to a frequency domain signal; determining a frequency parameter and an amplitude parameter for each of harmonic components of the frequency domain signal; establishing a leakage energy equation and a graduation shifting quantity; determining an optimum number of sample points that will result in minimum leakage energy; obtaining an adjusted sampling signal based on a second subset of the sample points, wherein the number of the sample points in the second subset is equal to the optimum number; and transforming the adjusted sampling signal to an optimized frequency domain signal having harmonic components associated with graduations of an optimized frequency spectrum, wherein the graduations are calculated based upon the graduation shifting quantity.