Research And FPGA Implementation Of UWB Positioning System

Impulse Radio Ultra-WideBand technology, which can realize the integration of communications and positioning because of its good time-resolution capacity, is one of the top candidate solutions for short-range wireless communication. This paper focus on TOA estimation algorithm and baseband design of receiver for indoor environmental wireless positioning system.TOA estimation algorithm based on energy detection, which does not need direct high-speed sampling to the received signal or generation of precise matching-template at the receiving end, can reduce the hardware complexity and has been used widely. But TOA estimation algorithm still needs A/D sampling and a large number of calculation, which makes its performance is poor at low SNR conditions. A PLL-based TOA estimation algorithm was proposed in this paper to resolve above-mentioned shortcoming. Compared with MES algorithm, the results of simulations and circuit test show that the TOA estimation algorithm base on PLL has very small estimated variance, strong robustness, simple structure and low requirement to hardware performance.As a biased estimate, PLL-based TOA estimation algorithm does not apply to NLOS environment because of its larger estimation bias caused by dense multipath signal. In response to these problems, a delayed phase-locked loop TOA estimation algorithm based on branch imbalance was proposed,which reduce the gain of delay branch to make the position locked by PLL closer to the signal direct path. Simulation shows that the TOA algorithm based on DPLL has a smaller estimate bias than TOA algorithm based on PLL and can be used in the NLOS environment.This paper also described the composition of the baseband receiver. The method of digital phase shift timing was proposed to implement the time difference counter of baseband. It has high timing accuracy and can be realized by the FPGA, which reduces design complexity effectively. In addition, the design of RS-232 serial port transmitter and data cache interface was described in detail.Finally, the test results show that the ultra-wideband wireless positioning system has good accuracy and its positioning error ranges between15 and 30cm. What's more, the system is simple, low-cost and has engineering application value.