Biography
Enrollment Date: 2012
Graduation Date：2015
Degree：M.S.
Defense Date：2015.06.03
Advisors：Baoyong Chi
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Research on Low Power Design Techniques of Wireless Receiver Analog Baseband
Abstract:
With the improvement of communication technology, more and more communication systems are booming. For example, the Internet of things is becoming portable and intelligent, the global satellite navigation system is becoming multi-mode compatible, extending civilian areas. The limited spectrum exacerbates crosstalk between different communication systems, the rise of consumer electronics increases demand for power consumption. In this case, this thesis studies the key technologies of low-power analog baseband circuit. It is applied in short distance wireless receiver and multimode GNSS navigation receiver.
Short distance wireless receiver is used in the Internet of things system, for narrow band application. Designing difficulty lies in the low frequency flicker noise and DC-offset. To solve this problem, this thesis adopts a new structure of two-stage filter with programmable gain amplifier inserted. Main work includes: programmable gain amplifier (PGA), DC-offset calibration (DCOC), IQ mismatch calibration. PGA provides 60 dB dynamic range with 1dB step. PGA2 uses improved source degenerated architecture, greatly improving the gain accuracy. To achieve low-power design, three improvements are made. First, RC-blocking and digital-assisted DCOC are used instead of the traditional loop elimination. Second, resistor-input IQ calibration circuit replaces the traditional transconductance-input structure. Third, Class-AB op-amp instead of traditional two-stage miller compensation op-amp is adopted to enhance driving ability.
Multimode GNSS receiver belongs to broadband application, this thesis replaces the traditional filter and PGA structure with the Biquid structure. The Biquid structure realizes filtering and gain control functions at the same time, so power of one circuit module will be saved. Through internal resistor, gain and bandwidth can be configured. By IQ coupling resistor, low pass and complex band pass mode can be switched. To optimize low-power design, an Anti-Pole-splitting technique is adopted to increase GBW of op-amp. Due to the changes of RC value under different process corner, the maximum bandwidth fluctuation reaches 30%. A bandwidth tuner circuit is designed to ensure the product of RC constant.Simulation and test results verified the designing requirements very well. In short distance wireless receiver, PGA provides 5-65 dB gain range, the largest gain error is 0.15 dB，power consumption is 3.1mW. After DCOC calibration, the maximum DC-offset can be reduced to 20 mV. Image rejection ratio reaches 46dB by IQ calibration. NF of the receiver is 6.86dB. In multimode GNSS receiver, the maximum bandwidth of Biquid is 19MHz, providing 44 dB dynamic range, power consumption is 3.6mW. By bandwidth tuner circuit, the largest bandwidth error is less than 5%. Comparing with other references, the analog baseband in this thesis has the advantage of low power consumption while satisfying designing requirements.