A 2 V 100 MHz CMOS vector modulator

For digital wireless communications, precise phase and amplitude control in carrier modulation is essential to achieve efficient spectrum utilization. In contrast to the conventional I-Q vector modulator, this phase-amplitude vector modulation method can generate a high intermediate-frequency (IF) modulated carrier. A high IF carrier mitigates the design specifications for the radiofrequency (RF) front-end of a heterodyne radio transceiver. This type of modulation is especially suitable for circuit realization of constant-envelope phase modulation schemes that do not require amplitude modulation, such as the Gaussian filtered minimum shift keying (GMSK). The authors present a modulator chip implementing this technique. This chip uses a standard 0.6 /spl mu/m single-poly, double-metal digital CMOS process, and operates with a single 2 V supply.