Biography
Enrollment Date: 2013
Graduation Date：2016
Degree：M.S.
Defense Date：2016.05.30
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design of Demodulation Circuit for Balises and WLAN
Abstract:
Nowadays, Eurobalise equipment is used to provide route information, road information for trains. For the needs of self-control, this paper designs the domestic balises with high performance demodulator aiming at the problem of low SNR and large frequency offset. At the same time, for the background of wireless local area network 802.11b and the TDOA indoor positioning technology, this paper designs a demodulation scheme used in indoor positioning scenarios to get better BER performance.
In this paper, the design of demodulation scheme for high-speed rail balises includes three algorithms. They are zero crossing detection algorithm, the best receiver algorithm, and a new FSK demodulation algorithm combined with Gardner bit synchronization. An interpolation method in time domain for eliminating burst interference is proposed in zero crossing detection algorithm. And the Gardner bit synchronization technology is applied in the new FSK demodulation. This paper completed the circuit design of the three demodulation algorithm, designed the systolic FIR filter, the efficient structure of CIC filter, the PLL circuit for carrier synchronization, and Gardner circuit for bit synchronization. Eventually these method are verified on FPGA, and the design of the decoder is applied in Beijing Metro Line 8 and south channel high iron. This paper completed the verification in actual environment, eventually the BER is below than 1e-6 when SNR is 11dB and the frequency offset is 4% of the carrier.
In this paper, the design of the 802.11b demodulation scheme includes the matched filter module, frequency offset compensation module, descramble module, parallel CRC module, CORDIC for anti-tangent module. This paper innovatively adds Barker correlation module, looking for the best sampling value module and improves the frame arrival detection module. In contrast to the common 802.11b demodulator, the requirement of SNR is reduced by 5dB based on BER of 6e-4. This paper implemented the 802.11b demodulation circuit, completed the circuits design of modules of frame arrival detection, frequency offset estimation, frequency offset compensation, and asynchronous FIFO. Finally this scheme is verified on FPGA. This paper uses LabVIEW to build the indoor positioning system, and the 802.11b demodulation code is embedded into the NI USRP FPGA. This paper verifies the 802.11b demodulation performance in the actual environment. The baseband symbol can be correctly demodulated when SNR is 20dB and frequency offset is 100Hz in the indoor environment.
To provide reference for the indoor positioning scheme, this paper studies RSSI measurement technology. According to the RSSI measurement technology, this paper designs two analysis methods, namely, empirical mode decomposition method and the Kalman filter method. Ultimately the Kalman filter method achieves better results.