A Fast Settling Phase Modulator for Outphasing Transmitters in 65-nm CMOS

We present a phase modulator architecture with very fast settling time for use in high data-rate outphasing transmitters. The proposed design utilizes the phase-shifting capabilities of a resonant tank and the ability to separately control the circuit properties via its components. A prototype in 65-nm CMOS achieves 9 bits of effective resolution, with a fast settling time of less than five carrier cycles to within 1^°. The circuit is also tested as a standalone transmitter showing an error vector magnitude of less than 5% for 8-PSK modulation at maximum data rate of 240 Mb/s, meeting the Federal Communications Commission requirements for operation at the medical implant communication services band.