Research On Acquisition Technology For GNSS Systems Under The Weak Signal Environment

Its application has been almost everywhere when GNSS(Global Navigation Satellite System) development so far, the GPS Navigation of America, has deeply and widely applied to various fields, GLONASS of Russia, GALILEO of EU and Beidou navigation system China has been developing are also gradually popular. At present, navigation technology has played an important role in not only civil and military but other fields, the requirements for navigation and positioning technology and expectations have been exceeded, which bring great challenges to the navigation and positioning technology.Accurate positioning of GNSS has been needed in most applications. Signal synchronization process is the premise of GNSS accurately positioning, before enter the tracking process, we have to synchronization to acquisition the signal at first. But when under the weak signal environment, such as indoor, in tunnel, in forest and so on or under high-speed mobile environment, because of signal attenuation is more serious in propagation, the signal power received in wireless equipment is very low, usually the carrier to noise ratio C/N0is less than25dB-Hz, and the large influence by frequency offset will make signal can not be estimated accurately,then the traditional GNSS signal receiver can hardly work.At present, GNSS weak signal acquisition can be divided into assisted and non assisted two kinds. Non assisted GNSS based on promote signal energy and the reasonable choice of acquisition strategy. To solve these problems mentioned above, this dissertation is focus on the research of GNSS acquisition technology under weak signal environment, and put forward an improved method based on PMF-FFT, effectively verified by MATLAB simulation. On this basis, the main work of this paper can be summarized as the following four points:1. Studying of GNSS signal structure and acquisition technology, and the establishment of mathematical model.2. Analysing the principle and advantages of PMF used in acquisition algorithm.3.Summarying the existing acquisition algorithm of GNSS under weak signal environment based on PMF.4. Proposed an improved weak signal acquisition method for GNSS system based on studying of PMF-FFT, through add window reduce the loss of scallops and improve detection probability then effectively verified by simulation.