Design of 2.87 GHz Frequency Synthesizer with Programmable Sweep for Diamond Color Defect based CMOS Quantum Sensing Applications.

Recently, diamond color defect based quantum sensing applications such as nitrogen-vacancy (NV) center magnetometry have emerged in CMOS technology, which use optically detected magnetic resonance (ODMR) for sensing magnetic field strengths (|(B) over tilde|) from different environmental physical quantities. For ODMR based sensing, CMOS quantum sensors seek an onchip 2.87 GHz microwave (MW) signal generator. Moreover, in order to sense smaller |(B) over tilde|, these CMOS quantum sensors also require that MW signal should be swept with sufficiently small step-size near 2.87 GHz. In this work, we present a fractional-N synthesizer based 2.87 GHz MW-generator (MWG) with an extremely small programmable sweep step-size for improved sensitivity of |(B) over tilde| measurements in CMOS NV magnetometry. The proposed MWG is implemented in 180 nm CMOS technology and simulations were done to validate the proposed design. Postlayout simulation results show that the proposed MWG achieves a minimum sweep-step size of 50 kHz, which can be used to sense |(B) over tilde| < 0:9 mu T and exhibits a phase noise of -114.5 dBc/Hz at an offset of 1 MHz near 2.87 GHz center frequency.