Signal transmitting apparatus and signal receiving apparatus using orthogonal frequency division multiplexing

A signal receiving apparatus using orthogonal frequency division multiplexing, comprising:

• first means for reproducing a pilot signal from a multi-value QAM modulation signal by angle demodulation;
• second means for converting a frequency of the reproduced pilot signal to change the reproduced pilot signal into a clock signal;
• and
• a fast Fourier transform circuit for converting the multi-value QAM modulation signal into a digital information signal;
• wherein the fast Fourier transform circuit is driven by the clock signal generated by the second means.

A signal transmitting apparatus using orthogonal frequency division multiplexing, comprising:

• an inverse fast Fourier transform circuit for converting a digital information signal into a first multi-value QAM modulation signal;
• a guard interval setting circuit for periodically generating a guard interval signal equal to a time segment of the first multi-value QAM modulation signal, and inserting the guard interval signal into the first multi-value QAM modulation signal to convert the first multi-value QAM modulation signal into a second multi-value QAM modulation signal;
• and
• a clock signal generating circuit for generating a first clock signal which drives the inverse fast Fourier transform circuit, and generating a second clock signal which drives the guard interval setting circuit;
• wherein the inverse fast Fourier transform circuit comprises means for setting a given-order carrier as a reference carrier, wherein the given-order carrier corresponding to a given integer times approximately its half wavelength is present in a guard interval occupied by the guard interval signal in the second multi-value QAM modulation signal, and wherein the inverse fast Fourier transform circuit comprises means for changing a phase of the reference carrier for every symbol interval by an amount corresponding to a given odd number times its quarter wavelength.