Abstract: A vector modulator that sums outputs of a plurality of quadrature-phase-shift-key (QPSK) modulator elements, each controlled by two digital input signals and a single local oscillator. The local oscillator provides a periodic sinusoidal output signal, and the modulator elements process the periodic sinusoidal output signal and the digital input signals. The state of the respective digital input signals determines which of four phase states are present at the output of the QPSK modulator. A plurality of summing devices are coupled to outputs of the modulator elements, and one summing device provides an analog constellation output signal of the vector modulator. A plurality of attenuators are provided for amplitude weighting output signals from the plurality of modulator elements.