Abstract

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~|) 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~|, 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~| measurements in CMOS NV magnetometry. The proposed MWG is implemented in 180 nm CMOS technology and simulations were done to validate the proposed design. Post-layout simulation results show that the proposed MWG achieves a minimum sweep-step size of 50 kHz, which can be used to sense |B~|<0.9μT and exhibits a phase noise of −114.5 dBc/Hz at an offset of 1 MHz near 2.87 GHz center frequency.

Abstract

Increasing demands of wearable health monitoring seek dedicated spectrum for short range wireless communication of biosignals, for which frequency band near 400 MHz has been utilized recently. While using the dedicated spectrum, biosignal communication must not cause any out of band radiations and interference, for which there is a strong need to develop spur- free, low phase noise and energy efficient wireless transmitters (TX). In this research, for the first time we present design and implementation of a reference-spur-free, low phase noise, sub-mW dual modulation mode (frequency shift keying (FSK) and on-off keying (OOK)) 400 MHz TX for wearable health monitoring, where RF synthesis depends solely on an extremely low phase noise oscillator, which uses a 400 MHz surface acoustic wave resonator and does not include any power hungry, spur- generating frequency multiplier or phase/frequency lock loop. The proposed TX has been designed and fabricated in 180 nm CMOS technology. Measurement results show that the energy efficiencies of the proposed TX in FSK and OOK mode are 1.8 nJ/bit at 250 kb/s and 0.23 nJ/bit at 2 Mb/s, respectively. To prove the utility of the proposed TX, biosignal communication is also demonstrated with the help of a commercial receiver in actual operating scenarios, where the measured bit error rate in FSK mode was < 10−5 for range of 2 m. Index Terms—Health-monitoring, wearable, spur-free, trans- mitter, FSK, OOK, 400 MHz, MedRadio

Abstract

Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or acoustic resonators is quite a concern for oscillator performance, specially at mmWave frequencies. This small coefficient is the manifestation of the small ratio of motional capacitance to static capacitance in the resonators. This work provides a general solution to overcome the problem of relatively high static capacitance at mmWave frequencies and presents analysis and design techniques for achieving extremely low phase noise and a very high figureof-merit (FoM) in an on-chip MEMS resonator based mmWave oscillator. The proposed analysis and techniques are validated with design and simulation of a 30 GHz oscillator with MEMS resonator having quality factor of 10,000 in 14 nm GF technology. Post layout simulation results show that it achieves a phase noise of −132 dBc/Hz and FoM of 217 dBc/Hz at offset of 1 MHz.

Abstract

Increasing demands of wearable health monitoring seek dedicated spectrum for short range wireless communication of biosignals, for which frequency band near 400 MHz has been utilized recently. While using the dedicated spectrum, biosignal communication must not cause any out of band radiations and interference, for which there is a strong need to develop spurfree, low phase noise and energy efficient wireless transmitters (TX). In this research, for the first time we present design and implementation of a reference-spur-free, low phase noise, sub-mW dual modulation mode (frequency shift keying (FSK) and on-off keying (OOK)) 400 MHz TX for wearable health monitoring, where RF synthesis depends solely on an extremely low phase noise oscillator, which uses a 400 MHz surface acoustic wave resonator and does not include any power hungry, spurgenerating frequency multiplier or phase/frequency lock loop. The proposed TX has been designed and fabricated in 180 nm CMOS technology. Measurement results show that the energy efficiencies of the proposed TX in FSK and OOK mode are 1.8 nJ/bit at 250 kb/s and 0.23 nJ/bit at 2 Mb/s, respectively. To prove the utility of the proposed TX, biosignal communication is also demonstrated with the help of a commercial receiver in actual operating scenarios, where the measured bit error rate in FSK mode was < 10−5 for range of 2 m. Index Terms—Health-monitoring, wearable, spur-free, transmitter, FSK, OOK, 400 MHz, MedRadio

Abstract

This work presents the design of a low phase noise LC oscillator (LCO) for a phase locked loop (PLL)-free receiver (RX), which is used for wireless sensor nodes based healthcare applications. A detailed analysis of phase noise of free running LCO has been presented under the influence of offchip components, which are very often inevitable in biomedical radios. Based on the analysis, a low power cross coupled LCO has been optimally designed for Medical Device Radiocommunication (MedRadio) band, which is a recommended communication band for biomedical applications. The proposed LCO has been fabricated in 180 nm CMOS technology. Measurement results show that the LCO consumes 140 μW power from 1.8 V supply and exhibits a phase noise of -103 dBc/Hz at an offset of 300 kHz, which closely matches with the post layout simulation results. Measurement results also show that the proposed …