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A Diamond Quantum Magnetometer Based on a Chip-Integrated 4-Way Transmitter in 130-nm SiGe BiCMOS
Solid-state magnetometers based on color centers in diamond are emerging as one of the leading quantum sensors due to their outstanding room-temperature properties, such as high sensitivity and calibration-free long-term stability. However, their integration into compact systems is still an active area of research. To tackle this challenge, in this paper, we present a quantum magnetometer based on negatively charged nitrogen-vacancy (NV) centers using a custom-designed, chip-integrated 4-way transmitter. In combination with a custom-designed microcoil array, the 4-way transmitter delivers microwave magnetic fields up to 226 µT for carrier frequencies around 7 GHz with a conversion gain of ≥32 dB to NV centers. The local oscillator (LO) signal required to drive the on-chip quadrature upconversion mixer is generated by a custom-designed quadrature PLL, which provides a 22% tuning range between 6.4 and 8 GHz, and a low phase noise of -122 dBc/Hz at 1 MHz offset from a 7 GHz carrier, to enable broadband, low-noise magnetometry. To verify the excellent performance of the integrated electronics, we have embedded them into a widefield diamond magnetometer using off-chip scanning optics, achieving a state-of-the-art AC-magnetic field limit of detection of 300 pT/Hz1/2.