Demodulating circuit, demodulating method, and receiving system

A method, implemented in a demodulating circuit, comprising:

• generating a plurality of carrier signals by fast Fourier transforming a received signal;
• extracting a first signal modulated in accordance with a first modulation method and a second signal modulated in accordance with a second modulation method from the plurality of carrier signals;
• inverse Fourier transforming transmission path characteristic values including a first transmission path characteristic value obtained based on the first signal, and a second transmission path characteristic value obtained based on the second signal;
• and
• controlling a position of a fast Fourier transform window based on the inverse Fourier transformed transmission path characteristic values.

A receiving system, comprising:

• a tuner which receives a signal and outputs an intermediate frequency signal;
• a demodulating circuit which receives the IF signal and outputs a digital signal;
• a decoder which receives the digital signal and generating an output signal;
• a control circuit which controls the demodulating circuit and the decoder;
• and
• an output circuit which outputs the output signal, wherein the demodulating circuit includes:
• a fast Fourier transform circuit which fast Fourier transforms a received signal and outputs a plurality of carrier signals;
• an output selecting circuit which selects at least two signals from the plurality of carrier signals, the at least two signals including a first signal modulated in accordance with a first modulation method and a second signal modulated in accordance with a second modulation method;
• an inverse fast Fourier transform circuit which inverse Fourier transforms transmission path characteristic values including a first transmission path characteristic value obtained based on the first signal and a second transmission path characteristic value obtained based on the second signal;
• and
• a FFT window control circuit which controls a position of an FFT window based on the inverse Fourier transformed transmission path characteristic values.