Browsing by Author "Yang, Xuebei"
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Item Ambipolar electronics(2010) Yang, Xuebei; Mohanram, KartikAmbipolar conduction, characterized by a superposition of electron and hole currents, has been observed in many next-generation devices including carbon nanotube, graphene, silicon nanowire, and organic transistors. This paper describes exciting new design opportunities in both analog and digital domains, all of which are inspired by the ability to control ambipolarity during circuit operation. We illustrate this with (i) a single-transistor polarity controllable amplifier, which can greatly simplify communication circuits and (ii) polarity controllable ambipolar logic gates, which are highly expressive yet compact compared to conventional CMOS.Item Electron paramagnetic resonance (EPR) systems and methods for flow assurance and logging(2021-12-14) Babakhani, Aydin; Yang, Xuebei; Rice University; United States Patent and Trademark OfficeAn Electron Paramagnetic resonance (EPR) system and method allows the measurement paramagnetic characteristics of materials in real-time, such as heavy oil, hydrocarbons, asphaltenes, heptane, vanadium, resins, drilling fluid, mud, wax deposits or the like. The EPR systems and methods discussed herein are low cost, small and light weight, making them usable in flow-assurance or logging applications. The EPR sensor is capable of measuring paramagnetic properties of materials from a distance of several inches. In some embodiments, a window will be used to separate the EPR sensor from the materials in a pipeline or wellbore. Since the sensor does need to be in direct contact with the materials, it can operate at a lower temperature or pressure. In other embodiments, the EPR sensor may be placed in the materials.Item Electron paramagnetic resonance (EPR) systems with active cancellation(2020-05-26) Babakhani, Aydin; Yang, Xuebei; Rice University; United States Patent and Trademark OfficeAn active cancellation system may be utilized to cancel interference, such as from transmitter leakage or self-interference in a transceiver of an electron paramagnetic resonance (EPR) spectrometer. The active cancellation system may be inserted between the transmitter and receiver. The active cancellation system may receive the output of the transmitter, and generate a cancellation signal with the same amplitude, but phase shifted relative to the self-interference signal. The cancellation system may include an attenuator/amplitude tuner, buffer, VQ generator, and phase shifter.Item Electron spin resonance for medical imaging(2018-01-02) Yang, Xuebei; Chen, Charles; Seifi, Payam; Babakhani, Aydin; Rice University; United States Patent and Trademark OfficeA method includes generating, from an integrated oscillator circuit, an oscillating output signal and generating, by an integrated power amplifier (PA) circuit, an amplified oscillating output signal based on the oscillating output signal. The method further includes receiving, by integrated receiver amplifier circuit, an electron spin resonance (ESR) signal from biological samples that include a magnetic species and generating, by the integrated receiver amplifier circuit, an amplified ESR signal based on the received ESR signal. The method further includes receiving, by the integrated receiver amplifier circuit, an electron spin resonance (ESR) signal from magnetic nanoparticles that are loaded with drugs or attached to human cells.Item EPR systems for flow assurance and logging(2019-09-10) Babakhani, Aydin; Yang, Xuebei; Rice University; United States Patent and Trademark OfficeAn Electron Paramagnetic resonance (EPR) system and method allows the measurement paramagnetic characteristics of materials in real-time, such as heavy oil, hydrocarbons, asphaltenes, heptane, vanadium, resins, drilling fluid, mud, wax deposits or the like. The EPR systems and methods discussed herein are low cost, small and light weight, making them usable in flow-assurance or logging applications. The EPR sensor is capable of measuring paramagnetic properties of materials from a distance of several inches. In some embodiments, a window will be used to separate the EPR sensor from the materials in a pipeline or wellbore. Since the sensor does need to be in direct contact with the materials, it can operate at a lower temperature or pressure. In other embodiments, the EPR sensor may be placed in the materials.Item Graphene Ambipolar Multiplier Phase Detector(IEEE, 2011-10) Yang, Xuebei; Liu, Guanxiong; Rostami, Masoud; Balandin, Alexander A.; Mohanram, KartikWe report the experimental demonstration of a multiplier phase detector implemented with a single top-gated graphene transistor. Ambipolar current conduction in graphene transistors enables simplification of the design of the multiplier phase detector and reduces its complexity in comparison to phase detectors based on conventional unipolar transistors. Fabrication of top-gated graphene transistors is essential to achieve the higher gain necessary to demonstrate phase detection. We report a phase detector gain of −7 mV/rad in this letter. An analysis of key technological parameters of the graphene transistor, including series resistance, top-gate insulator thickness, and output resistance, indicates that the phase detector gain can be improved by as much as two orders of magnitude.Item Intergrated electron spin resonance spectrometer(2017-06-27) Yang, Xuebei; Chen, Charles; Seifi, Payam; Babakhani, Aydin; Rice University; United States Patent and Trademark OfficeAn integrated electron spin resonance (ESR) circuit chip includes a chip substrate, a transmitter circuit, and a receiver circuit. The transmitter circuit and receiver circuit are disposed on the chip substrate. The transmitter circuit includes an oscillator circuit configured to generate an oscillating output signal and a power amplifier (PA) circuit configured to generate an amplified oscillating output signal based on the oscillating output signal. The receiver circuit receives an ESR signal from an ESR probe. The receiver circuit includes a receiver amplifier circuit configured to generate an amplified ESR signal based on the received ESR signal, a mixer circuit configured to receive the amplified ESR signal and to down-convert the amplified ESR signal to a baseband signal, and a baseband amplifier circuit configured to generate an amplified baseband signal based on the baseband signal. An integrated electron spin resonance (ESR) circuit chip includes a chip substrate, a transmitter circuit, and a receiver circuit. The transmitter circuit and receiver circuit are disposed on the chip substrate. The transmitter circuit includes an oscillator circuit configured to generate an oscillating output signal and a power amplifier (PA) circuit configured to generate an amplified oscillating output signal based on the oscillating output signal. The receiver circuit receives an ESR signal from an ESR probe. The receiver circuit includes a receiver amplifier circuit configured to generate an amplified ESR signal based on the received ESR signal, a mixer circuit configured to receive the amplified ESR signal and to down-convert the amplified ESR signal to a baseband signal, and a baseband amplifier circuit configured to generate an amplified baseband signal based on the baseband signal.Item Miniaturized Electron Paramagnetic Resonance (EPR) Spectrometer Based on a Fully-Integrated Full-Duplex Transceiver in Silicon(2016-03-16) Yang, Xuebei; Babakhani, AydinElectron 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.Item Semi-analytical model for carbon nanotube and graphene nanoribbon transistors(2010) Yang, Xuebei; Mohanram, KartikCarbon nanotubes and graphene provide high carrier mobility for ballistic transport, high carrier velocity for fast switching, and excellent mechanical and thermal conductivity. As a result, they are widely considered as next generation candidate materials for nanoelectronics. In this thesis, I first propose a physics-based semi-analytical model for Schottky-barrier (SB) carbon nanotube (CNT) and graphene nanoribbon (GNR) transistors. The model reduces the computational complexity in the two critical but time-consuming steps, namely the calculation of the tunneling probability and the self-consistent evaluation of the surface potential in the transistor channel. Since SB-type CNT and GNR transistors exhibit ambipolar conduction that is not preferable in digital applications, I further propose a semi-analytical model for the double-gate transistor structure that is able to control the ambipolar conduction in-field. Future directions, including the modeling of new CNT and GNR devices and novel circuits based on the in-field controllability of ambipolar conduction, will also be described.