Gigabit QPSK Modulator.
01 January 1988
High-speed modulators which operate at gigabit transmission rates are an essential component in many high-capacity communication links. We describe a QPSK (quaternary phase shift keyed) modulator which is fabricated using a pair of beam-leaded Schottky diodes and appropriate high-pass and low-pass filters on a dielectric substrate. A modulator and demodulator were operated in cascade at a carrier frequency of 13 GHz. This circuit showed clean eye diagrams of the recovered data trains up to 1.5 Gbit/s with corresponding error rates of less than 10(-11). The modulator can be readily scaled to higher frequencies with a proportional increase of the information rate.