A GaAs MMIC Digital Phase Modulator

The paper introduces a GaAs MMIC digital phase modulator based on a lumped quadrature hybrid. The quadrature coupler is implemented using two interleaved spiral inductors in a transformer-like configuration. The phase control is obtained electronically tuning two L-C resonators that load the coupled ports. The resulting phase modulator exhibits a continuous phase-shift capability of nearly 230°. The modulator can be digitally driven providing a 0°-180° or 0°-90° phase-shift, with constant insertion loss. Theoretical and experimental results are discussed.