Demodulating apparatus and demodulating method

A demodulating apparatus having time synchronizing signal generator means for receiving a digital orthogonal frequency division multiplex modulated signal in which an information signal modulates a plurality of carriers having respective frequency components in an orthogonal relationship with each other and each frame of which is comprised of a null symbol, a synchronization symbol and a plurality of subsequent symbols and for generating a time synchronizing signal synchronized with a symbol forming each of said frames of said digital orthogonal frequency division multiplex modulated signal, frame synchronizing signal generator means for generating a frame synchronizing signal synchronized with each frame of said digital orthogonal frequency division multiplex modulated signal, and fast Fourier transform means for receiving said digital orthogonal frequency division multiplex modulated signal, said frame synchronizing signal, and said time synchronizing signal and for fast Fourier transforming said digital orthogonal frequency division multiplex modulated signal to thereby produce a demodulated signal information signal, in which a window signal used in said fast Fourier transform means for said synchronization symbol and said plurality of subsequent symbols is based on the frame synchronizing signal, comprising:

• correlation detector means for detecting a correlation between a guard section of said symbol of said digital orthogonal frequency division multiplex modulated signal and a section having a correlation with the guard section in an effective symbol of that symbol;
• section integrator means for section integrating a detected output of said correlation detector means with respect to said guard section;
• peak detector means for detecting a peak of a triangular wave signal output from said section integrator means;
• and
• frame timing signal producing means for producing a frame timing signal of a predetermined frame of each of said frames based on a peak value detected signal from said peak detector means,
• wherein said frame synchronizing signal generator means is synchronized by said frame timing signal from said frame timing signal producing means.

A demodulating method in which, based on a digital orthogonal frequency division multiplex modulated signal in which an information signal modulates a plurality of carriers having respective frequency components in an orthogonal relationship with each other, a time synchronizing signal synchronized with a symbol forming each frame of said digital orthogonal frequency division multiplex modulated signal is generated, a frame synchronizing signal synchronized with each frame of said digital orthogonal frequency division multiplex modulated signal is generated, and said digital orthogonal frequency division multiplex modulated signal is fast Fourier transformed by using said frame synchronizing signal and said time synchronizing signal into a demodulated signal information signal, comprising the steps of:

• detecting a correlation between a guard section of a symbol of said digital orthogonal frequency division multiplex modulated signal and a section having a correlation with the guard section in an effective symbol of that symbol;
• section-integrating the correlation detecting output with respect to the guard section;
• detecting a peak of a triangular wave signal output from the section integrating step;
• generating a frame timing signal of a predetermined frame of each of said frames based on the peak detected in said detecting step;
• and
• making the frame synchronizing signal synchronized by the generated frame timing signal.

A demodulating method in which a time synchronizing signal synchronized with a symbol forming each frame of a digital orthogonal frequency division multiplex modulated signal is generated, based on a digital frequency orthogonal division multiplex modulates signal in which an information signal modulates a plurality of carriers having respective frequency components in an orthogonal relationship with each other and each frame of which is comprised of a null symbol, a synchronization symbol, and a plurality of subsequent symbols, a frame synchronizing signal synchronized with each frame of said digital orthogonal frequency division multiplex modulated signal is generated, and the digital orthogonal frequency division multiplex modulated signal is fast Fourier transformed by using said frame synchronizing signal and said time synchronizing signal, whereby a window signal used in said fast Fourier transform for said synchronization symbol and said plurality of subsequent symbols is based on said frame synchronizing signal, comprising the steps of:

• detecting a correlation between a guard section of said symbol of said digital orthogonal frequency division multiplex modulated signal and a section having a correlation with said guard section in an effective symbol of said symbol;
• section integrating the correlation detecting output with respect to the guard section;
• detecting a peak of a triangular wave signal output from the section integrating step;
• generating a frame timing signal of a predetermined frame of each of said respective frames based on said peak detected in said detecting step;
• and
• making said frame synchronizing signal synchronized by said frame timing signal output from the step of generating.