A low-Q resonant tank phase modulator for outphasing transmitters

A new design concept is proposed for a phase modulator for outphasing transmitter architectures, utilizing 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 12 bits of resolution, with a fast settling time of less than five carrier cycles to within 1°. The circuit is also tested as a stand-alone transmitter showing an EVM of less than 5% for 8-PSK modulation at maximum data rate, meeting the FCC requirements for operation at the medical implant communication services (MICS) band.