Vector modulator-based phase shifter with 810º control range for 43-Gbps optical transceivers

A vector-modulator-based phase shifter for 43-Gbps RZ-DQPSK optical transceivers was developed by using InP HBTs. The weighting of the vector paths is controlled by a novel pseudo-sine-cosine generator using folding circuit, which covers the phase-control range of 810° with only one control voltage. To reduce the process, voltage, and temperature (PVT) dependence, a PVT compensation circuit is newly proposed. The monolithic integrated phase shifter exhibits monotonic phase control and constant output amplitude of 360 ± 11 mV through the whole phase-control range for 21.5-GHz signal. Small phase variations lower than 40° were observed for ±5% power voltage and 25-80°C temperature variations. To our knowledge, this is the first voltage-controlled phase shifter with an over 720° phase-control range above 20 GHz reported to date.