Patent ID: 7876169

Claim:
A modulating circuit, comprising: a stereo signal generation part which synthesizes a sum signal of an L-channel signal and an R-channel signal, a difference signal of the L-channel signal and the R-channel signal, and a pilot signal, and outputs its result as a stereo composite signal; a first quadrature modulation part which divides the stereo composite signal into an in-phase signal and a quadrature signal having a phase orthogonal to the phase of the in-phase signal and performs a quadrature modulation by performing frequency conversion of the in-phase and quadrature signals using a first frequency; and a second quadrature modulation part which performs a quadrature modulation by performing frequency conversion of the in-phase and quadrature signals, which are generated by the first quadrature modulation part, by using in-phase and quadrature carriers which have a second frequency which is higher than the first frequency, and whose phases are shifted by 90 degrees with respect to each other.