Biography
Enrollment Date: 2011
Graduation Date：2014
Degree：M.S.
Defense Date：2014.05.27
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design of Baseband for UHF RFID Smart Tag
Abstract:
The wireless signal recorder can be widely used in long-time tests or surveys to record the communication process of the experiment. For example, the detection of the transponder used in high-speed rail can be done automatically by the recorder, rather than consuming manpower for observation and recording. In addition to functions including receiving, recording, analysis and evaluation of the communication process, the recorder should provide accurate receiving time or the time difference between the receptions of two signals, in order to fix the position of the signal source by TDOA or TOA.
Based on the application background above, this paper achieve the wireless signal recorder system on the NI PXI-E bus platform using virtual instrumentation and software radio technology. Unlike other signal recorders, the noise between signals is filtered to compress the data size, instead of continuously recording instrument. There are three optional data logging modes. For the short duration signals, the end position of the segment signals is detected by multi-point amplitude. For periodic signals, effective information is recorded by presetting the length of each acquisition time. As for longer duration of the valid signal, a solution is proposed. To save the complete signal information, a fixed length of the original signal is stored after the trigger and the remaining portion is stored in the demodulated digital symbols. Besides the function of traditional wireless signal recorder, time refining module is designed to measure the difference between the receiving times, thus meeting the needs of the position applications for signal source. The original signal segment stored is used to calculate the exact reception time.
In the first place, the system architecture is designed and software and hardware platforms are selected for the sake of achieving high-speed data transmission, processing and streaming disc. The entire system requires the RF receiver, FPGA and software APP to work together. The main function of the FPGA is to achieve the signal trigger, real-time demodulation and other signal processing functions. Meanwhile, friendly controlling interface for the wireless signal recorder system is devised in the software. In addition, a variety of common signal demodulations are provided in the software for users, as well as signal analysis and quality evaluation, including the display of constellation , eye diagram , EVM and other parameters. PSK modulated signal is used for the system verification.
In this article, the performance of the methods used to measure the time difference is compared by Matlab simulation. According to the structure of the recorder, correlation method is chosen to achieve time measurement. The algorithm test results to the accuracy of 100ps using two different modulation and frequencies signals.