The transmitter synthesizes amplitude and phase components and calibrates a delay mismatch between amplitude and phase components with high accuracy at high speed. The transmitter has: a digital-to-analog converter (DAC) and a low-pass filter (LPF) in its amplitude-signal path; and a phase modulator operable to convert up a phase component into an RF component in its phase-signal path. In an operation of delay calibration, a test input signal is supplied to a delay-calibrating unit in the amplitude-signal path, and the delay-calibrating unit provides a test input signal to DAC. Then, LPF generates a test output signal. The delay-calibrating unit detects a delay of the test output signal relative to the test input signal, calibrates an amplitude signal delay in a range from the input of the delay-calibrating unit to the output of LPF, reduces the difference between amplitude and phase signal delays of the phase modulator in the phase-signal path.