Patent ID: 7324024

Claim:
A high frequency compensator configured to compensate high frequency component of a digital audio signal comprising: a down-sampler configured to perform ½ down-sampling for the digital audio signal; an up-sampler configured to perform double up-sampling for an output signal of the down-sampler; and a digital low-pass filter configured to filter an output signal of the up-sampler, and to output the filtered digital audio signal, wherein coefficients of the digital low-pass filter are calculated by using a signal decompression system model, the signal decompression system model including: an analog/digital converter configured to convert an original analog audio signal having a limited band into a digital signal; an infinite impulse response filter configured to perform oversampling for the digital signal; a digital/analog converter configured to convert the digital signal oversampled by the infinite impulse response filter into an analog signal; and a subtracter configured to calculate an error signal between the analog signal and the original analog audio signal, wherein coefficients of the infinite impulse response filter are calculated by Sampled-data H-Infinity control theory so as to decrease the error signal, and the coefficients of the digital low-pass filter are obtained from the calculated coefficients of the infinite impulse response filter.