Analyse On Positioning Precision In Area Navigation System Based On DS Spread Spectrum

Satellite navigation systems shouldn't be the only way, independent radio area navigation system should be developed with great effort. Considering characteristics of radio propagating offshore and flexibility of radio area navigation system, when distance is less than 1000km, center frequency of navigation signal should be chosen in 2MHz. Adopting spread spectrum technique, it can reduce emission power and achieve high precision location offshore.This thesis analyzes the principle and architecture of area navigation system and investigates the problems related with positioning precision, which are modeled and realized with simulation tool, Matlab.Spread spectrum code emitted by navigation station has correlative operation with the signal produced by receiver, through measuring the place of maximal correlative function, we can measure the spreading time of the navigation station's signal, so we can measure the distance between navigation station and receiver. Therefore the capability of spread spectrum code is the key to the capability of area navigation system. In this thesis parallel phase-shifting sequence as spread spectrum code is given, which has better capability.High precision positioning is based on carrier phase measurements. How to confirm integer ambiguity is very important. In order to achieve high precision results and advance efficiency within a short observation time, the integer ambiguity has to be solved fast and correctly. In this thesis, an arithmetic in single epoch without integer ambiguity resolution and cycle slip detection and repair is given for single frequency receiver. Applying the arithmetic, we can get the same high positioning precision.In the area navigation system, we may suppose all of navigation stations and the users on the same horizontal level. In this paper, the GDOP(geometric dilution of precision) expression of area navigation system is deduced. Using the matrix theory the lowest GDOP and that GDOP is smaller with more navigation stations are proved in theory. It is also proved that GDOP is smaller with differential measurement than pseudo range measurement. In practice, we can use...