Biography
Enrollment Date: 2015
Graduation Date：2018
Degree：M.S.
Defense Date：2018.05.23
Advisors：Xinpeng Xing
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Study of Low-power Transmitter and Local Oscillator Generation Circuit
Abstract:
In recent years, with more concern on health and the rapid development of the semiconductor technique, wireless capsule endoscopy systems have been applied more and more in clinical practice. The capsule endoscope is required to work inside the human body for 5-6 hours, with limited battery capacity. So the low-power design of the wireless transmitter, which consumes most energy of the system, becomes one important design bottleneck. Besides, the data rate of the transmitter determines the frame rate and the resolution of the images transmitted by the wireless endoscope system, and directly affects the quality of a practice.
This thesis studies and designs a low-power transmitter for wireless capsule endoscope system. The transmitter architecture is based on the principle of injection locking and Class-E power amplifier. The QPSK modulation and up frequency conversion is accomplished by a 5th-harmonic injection-locked oscillator and a polarity shift circuit, eliminating mixers and phase-locked loops in traditional transmitter architectures, resulting into significant reductions in system complexity and power consumption. Class-E power amplifier enlarges the output signal power-efficiently, and the output power higher than 0dBm relaxes the sensitivity requirement of the corresponding receiver in vitro. The transmitter circuit is simulated and tapeout in UMC 180nm CMOS technology. The post-layout simulation results show that the transmitter achieves 0.11dBm output power, 46% PA efficiency, and dissipates 5.8mW overall power consumption, with 20Mbps date rate and 1960μm×1960μm chip area. The measurement results show that the injection-locking oscillator is capable of signal modulation and up mixing; however, there is stability issue with the Class-E power amplifier, which should be analyzed and fixed in next design.
With the fast development of the Internet of Things (IoT), connected-everything is becoming a reality. Nowadays several communication protocols co-exist for the IoT applications, including NB-IoT, ZigBee, Halow and BLE. A multi-band multi-mode wireless transceiver compatible with the above protocols is critical for design cost reduction and design-to-market time reduction. In the multi-band multi-mode transceiver, the generation of low-noise, high-precision local oscillator signal with large frequency ranger is still a design challenge.
The second part of this thesis studies and designs a local oscillator signal generation circuit for multi-band multi-mode IoT transceiver in TSMC 65nm CMOS technology. The generation circuit is composed of an LC tank voltage-controlled oscillator (VCO) and highly-symmetrical divide-by-2 circuits, outputing four-phase local oscillator signals with 25% and 50% duty cycles respectively, the VCO output signal frequency ranges from 3.2GHz to 5GHz. The VCO maximum power consumption is 1.9 mA, and the simulated phase noise is -119dBc/Hz at 1 MHz offset. The highest power dissipation of the divider is 0.41 mA, and the phase mismatch of the four-phase local oscillator signal is no larger than 2.1°. The core area of the local oscillator generation circuit is 360μm×450μm.