Miniaturized Electron Paramagnetic Resonance (EPR) Spectrometer Based on a Fully-Integrated Full-Duplex Transceiver in Silicon
Doctor of Philosophy
Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR) phenomenon is based on the interaction of electromagnetic radiation with electron magnetic dipole moment in the presence of a DC magnetic field. It has a broad range of applications, including cancer detection and treatment, magnetic nanoparticle detection, biomedical sensing, and flow assurance in oil and gas industry. However, conventional EPR spectrometers are typically bulky, heavy, and expensive. Therefore, the utilization of EPR has long been restricted inside laboratories. In this dissertation, we address the deficiencies of conventional EPR spectrometers by integrating the entire electrical transceiver onto a single silicon chip. The resulting spectrometers are therefore small, light-weighted, and cost-effective. Specifically, three works will be presented in this dissertation. Firstly, we introduce the first continuous-wave (CW) absorption-power-based EPR spectrometer based on a single-chip transceiver. The transceiver has a tunable operation frequency from 885MHz to 979MHz. Utilizing a custom-built planar resonator, a EPR spectrometer is assembled and it successfully measures the EPR responses from a set of different samples, including DPPH powder, Fe2O3 nanoparticles, and Fe3O4 nanoparticles. During the operation of the first spectrometer, it is observed that the sensitivity of the system is limited by the transmitter self-interference signal. In order to mitigate this problem, we next introduce a single-chip transceiver with self-interference cancellation for EPR spectroscopy. The transceiver operates from 4.6GHz to 5.35GHz with a maximum transmitter output power of 22dBm. During the measurement, the self-interference cancellation circuit can cancel up to 38dB of self-interference signal. It improves the interference input-referred 1dB compression point from -25dBm to -8dBm, and increases the receiver gain by up to 15dB. Utilizing this transceiver, the EPR spectrometer sees a drastic improvement of 15dB in sensitivity even under a significantly lower isolation between the transmitter and the receiver. Moreover, for the first time, it enables a frequency-sweep method for the EPR measurement. In order to further improve the sensitivity of the EPR spectrometer, thirdly, we present a single-chip 3.8GHz-5.2GHz transceiver with an upgraded self-interference cancellation circuit, whose noise contribution to the receiver is significantly reduced. In the measurement, the receiver achieves a noise figure of 3.1dB/6.3dB at 10MHz/50kHz baseband frequencies when the transmitter and the cancellation circuit are off. The 1/f noise corner is 60kHz. When the transmitter and the cancellation circuit are turned on, at -10dBm interference power, the noise figure is 6.8dB/11.1dB at 10MHz/50kHz baseband frequencies. This is lower by 5.6dB/9.6dB at 10MHz/50kHz baseband frequencies compared to the noise figure with the cancellation circuit off at the same interference power. Utilizing this transceiver, the sensitivity of the EPR spectrometer is further improved by 10dB compared to the spectrometer in our second work.
Electron Paramagnetic Resonance; Transceiver; Silicon, Full-duplex