Design Of High Precision Indoor Wireless Positioning System

Positioning technology and people’s lives are closely related, and has attracted widespread attention. Positioning technology can be divided into outdoor and indoor location positionings by range. This thesis mainly is about indoor high-precision positioning.Analyzing the background and status of various indoor positioning technology, the main problems include:contradictions between positioning accuracy and positioning range; the limit to the line of sight (LOS) spreading; and impact of multipath effects; contradictions between positioning performance and design cost and etc. In order to realize an indoor positioning system of low complexity and high accuracy which including features of the non line of sight (NLOS) and scale applications. We studied several mainstream positioning systems on which we proposed and designed a indoor positioning solution based on microwave distanceIn order to eliminate the lost of phase measurement accuracy caused by clock oscillator deviation, In this paper, we use TDOA principle for positioning. For microwave phase measurement method can achieve higher range accuracy than pulse method. Therefore, the positioning method in this paper is based on the phase difference measurement. The specific method is to detect the phase difference by the same signal going through different paths.The linear frequency phase measurement is simple and of wide range when compared with the pseudo-random code phase measurement method and the carrier phase measurement method. Due to the limit to the bandwidth and frequency linearity, the accuracy can only reach the level of meters;while the pseudo-random code phase measurement is based on the principal of spread spectrum communication, it has better resistance to interference and can achieve code division multiple access, but it can not reach a very high chip rate because of the circuit design cost and bandwidth limit, thus positioning accuracy often confined at the lever of meters or above; when using high-frequency carrier positioning, though it has shortcomings integer cycle ambiguity which can be solved by multi-frequency measuring tape, accuracy will get greater improvement over the previous two. For measuring tape accuracy increases together with the increasing frequency and considering the accuracy and the circuit chip cost, we use the phase carrier frequency measurement which does not exceed 5GHz.Since high frequency signal phase changes quickly, it is difficult to make a direct phase measurement. We use the beat note phase measurement method to lower AD converter high sampling rate requirements of high-accuracy phase measurement. And it estimates high-accuracy phase difference from sample data.In order to achieve three-dimensional positioning, it measures the phase difference from three dimensions of which each dimension uses multiple measuring tape measurement.In case that the deviation of rough-foot observation mean value and true value is smaller than half fine-foot wavelength, it estimates the residuals between estimated value of fine-foot and observation value of rough-foot by Kalman filter. It constantly adjusts fine-foot estimates by estimated value of residual, constituting a negative feedback system until the estimated absolute value of residuals converges to the range within half a wavelength of the fine feet, thus fine-foot should have eliminated the integer cycle ambiguity;In case that the deviation of rough-foot observation mean value and true value is larger than half fine-foot wavelength. It uses a more intensive measuring tape (Double of the larger deviation of the adjacent measuring tape must shorter than the wavelength of the smaller measuring tape) composing integer cycle ambiguity progressively.Since there is a non-linear relationship between the distance difference corresponding to the phase difference and the coordinate in the hyperbolic model, we balance the contradictory between amount of calculation and accuracy of several filter algorithms, This article will take more than three dimensions of the phase as an observation vector, calculate target coordinates by UKF filter, achieve the goal of centimeter level positioning accuracy of three-dimensional, under the conditions of slow-moving or stationary target with less than 5% phase error.