A polar coordinate modulation circuit, a polar coordinate modulation method, an integrated circuit, and a radio transmitting apparatus wherein the path delay difference between a phase signal and an amplitude signal can be compensated for with high precision in a polar coordinate modulation system, while the increase of the circuit scale being suppressed. A delay amount determining part (102) stores, as table data, the delay amount information, which is based on the step response characteristic of a power amplifying part (105), for the amplitude values of amplitude signals and for transmission level information (S1). In this way, the delay adjustment is performed with an amplitude signal and transmission level information (S1) used as reference signals, whereby the path delay difference between the amplitude signal and the phase signal can be compensated for with high precision, while the increase of the circuit scale being suppressed.
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