Biography
Enrollment Date: 2013
Graduation Date：2016
Degree：M.S.
Defense Date：2016.05.30
Advisors：Baoyong Chi
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Research on Design Techniques of Receiver Analog Baseband for Low-Power WiFi Applications
Abstract:
In the recent few decades, diversities of short range wireless communication technologies have played an increasingly role in the daily life and work, of which, the certain Wi-Fi communication protocol working at Sub-GHz, is drawing more and more attention in the industry and academic fields. With the rapid development of communication, the Internet of things, consisting of mobile devices, is exerting influence on the human lifestyle. For the sake of improving the endurance performance, a low-power wireless transceiver is of great necessity.
The application background of this thesis is based on a wireless communication transceiver working at Sub-GHz, which is mainly applied in low power situation. The thesis proposed a low power reconfigurable analog baseband which is located between RF front and ADC. As an essential part of receiver, the baseband is designed for filtering, amplifying, channel selecting and image rejection.
Considering the PVT variation, the bandwidth of baseband might fluctuate a lot. The digital-controlled filter tuning is implemented for calibrating the RC constant and accurate bandwidth. This thesis implemented the DCOC circuit to solve the problem that the DC offset would be aroused under the influence of the mismatch of layout and process variation. A technology of splitting up the load MOSFET is applied to improve the phase margin of common mode feedback loop when it comes to operational amplifier design. Besides, the Class AB output stage employing Quasi Floating Gate circuit is implemented to improve the performance of linearity. Finally, this thesis achieved a 680um*550um layout with 65nmCMOS.
This thesis proposed a method combining filters and PGA to reduce the consumption of baseband. In order to design a reconfigurable filter, this thesis implemented a cascade structure containing Reversed Tow-Thomas TIA and Multi-Feedback bi-quad, which achieved low pass and complex band pass filter. The bandwidth of LP mode is 4MHz and that of CBP mode is 1MHz/2MHz with 2MHz center frequency. In order to relieve the design of ADC, this thesis achieved 58dB dynamic range with 1dB/step. This thesis employed a TCA as the 1st stage of baseband to improve the loop gain with the large output resistance, which improved the linearity and DC stability. The baseband achieved the output 1dB compression point more than 9dBm and the noise figure less than 30dB in different corners. The baseband in this thesis cost less than 2.8mW consumption in all kinds of mode and corners with a 1.2V supply voltage.