PURPOSE: To improve the modulating accuracy of a vector modulator and expand the modulating function of the modulator by performing arbitrary nonlinear processing by suppressing the amplitude fluctuation of component outputs to be modulated by using a phase modulator for the modulation of vector component signals. CONSTITUTION: In a vector modulating system 20, phase modulators 22a and 22b are used instead of amplitude modulators and the 90 deg.-phase shift network of the modulator is exchanged with a phase shift network 24 which generates an arbitrary phase shift. In the system 20, therefore, component phase modulated signals Va and Vb on lines 26 and 28 have fixed amplitudes, but the combined output signal outputted to a line 30 from an addition network 32 can have both amplitude and phase modulation. Therefore, vector modulation can be performed over a wide range.
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