A CMOS Wireless Synchronization and Control System for Sensor Modules in MRI Scanners

Abstract

Monitoring motion in a magnetic resonance imaging (MRI) environment safely and reliably requires placing wireless nuclear magnetic resonance (NMR) sensors in the bore. This paper proposes an integrated circuit capable of achieving phase synchronization and creating triggering events for such sensors. It relies on the transmission of a Radio Frequency (RF) tone with amplitude modulation (AM). A variable-gain amplifier (VGA) compensates for the path loss of the broadcasted RF signal in the scanner room. A divider-less bang-bang phase-locked loop (BB-PLL) based on a digitally controlled crystal oscillator (DCXO) achieves phase lock with a sub-picosecond integrated jitter. Lastly, an envelope detector processes the two-level amplitude-shift keying (ASK) AM on the RF signal to control subsequent sensors. The overall system is integrated into a 65nm CMOS process and exhibits a power consumption of 5.2mW in an area smaller than 1.5mm2 with a sensitivity of −57 dBm.