Time Difference Measurement Technology By Internal Synchronization In Passive TDOA Location

In the current wireless location field, TDOA (Time Difference of Arrival) is becoming an important technology because of the high accuracy, speed and anti-jamming ability. This method is based on the radio-ranging, which gained the distance by measuring the transmission time of the radio signals. The essence of the distance ranging is also the time difference measurement. How to accurately obtain the difference and provide the necessary data support is the important objective of this study.In view of the usual time difference measurement method, a kind of method by internal synchronization is put forward. Every station receives the same signal through different paths, and compares the received signals'and transmitted signals'waveform, then obtains the time difference by the correlation of these two signals. This time difference data is sent to the main station so as to complet the TDOA location. This time difference measurement system takes the Altera's Cyclone FPGA chip EP1C3T144 as the core processor, using the direct time-domain cross-correlation algorithm to extract the time difference of the same signal through different paths. It provides Ethernet interfaces, USB interfaces and RS232 serial ports, in order to adapt to different interfaces of the receiver and wireless transmission equipment.This dissertation first introduces the background and significance of this research. The typical application and development status of passive TDOA location system are described. The advantages and disadvantages of common methods are summarized. The theory of time difference measurement by internal synchronization and correlation algorithm is introduced in detail. According to the needs, the time difference measurement signal is selected. The overall structure of the system based on FPGA is put forward including the design of hardware circuits. Then, the correlation algorithm and the control of interfaces are realized. The design ideas, program processes and simulation results are also given. The time difference measurement of multi-objectives is discussed preliminaryly. Finally, the improvement recommendations for the future work are given and analyzed. It has proved that this time difference measurement system can avoid the use of a high degree of synchronous clock between the stations and the set up of signal transmission channels.