Patent ID: 8626809

Claim:
A method for performing digital up-down conversion for a frequency conversion in a mobile communication system using plural frequency conversion, the method comprising: Infinite Impulse Response (IIR)-filtering an input signal by a magnitude response IIR filter having a filter coefficient calculated according to a Levinson polynomial, wherein the filter coefficient of the magnitude response IIR filter has a same magnitude response as in Finite Impulse Response (FIR) filtering and secures stability of the magnitude response IIR filter; and receiving, from the magnitude response IIR filter, the IIR filtered signal, and performing IIR filtering by a phase compensation IIR filter having a filter coefficient compensating for a non-linear phase to a linear phase, wherein IIR-filtering the input signal comprises: receiving a magnitude response of the input signal filtered by an FIR filter and calculating an impulse response signal using an Inverse Fast-Fourier Transform (IFFT); determining an order of the magnitude response IIR filter and calculating an autocorrelation sequence of the calculated impulse response signal; calculating a Levinson polynomial using the calculated autocorrelation sequence and checking security of stability according to the calculated Levinson polynomial; and determining the stable filter coefficient of the magnitude response IIR filter according to the Levinson polynomial when the security of stability is achieved.