Patent ID: 8144762

Claim:
A band extending apparatus comprising: a first generating device for generating a baseband signal by up-sampling an input signal and then transmitting it through a low-pass filter; a second generating device for generating a high-frequency signal, which is a signal component corresponding to the input signal and which is a signal component on a higher-frequency side than the input signal, by extracting a signal component on a higher-frequency side of a signal which is obtained by squaring a band limited signal, the band limited signal is a signal component with a predetermined band of the baseband signal; and a third generating device for generating an output signal by adding the high-frequency signal to the baseband signal, said second generating device further comprises: a Fourier transforming device for generating a Fourier transform signal by performing a Fourier transform process on the baseband signal; a determining device for determining a frequency at which a signal level of the Fourier transform signal is suddenly dropped, as an upper-end frequency; a changing device for changing a level of the Fourier transform signal so as to maintain a level of a signal component with a band defined in accordance with the upper-end frequency, of the Fourier transform signal, and to zero a level of a signal component other than the signal component with the band defined in accordance with the upper-end frequency, of the Fourier transform signal; and an inverse Fourier transforming device for generating an inverse Fourier transform signal by performing an inverse Fourier transform process on the Fourier transform signal in which the level is changed by the changing device, and said second generating device generates the high-frequency signal, with using the inverse Fourier transform signal as the band limited signal.