Research And Implementation Of Narrowband Interference Suppression In Satellite Navigation System

With the advantages of all-weather, uninterrupted broadcasting navigation signals, GNSS(Global Navigation Satellite System, GNSS) can realize the goal of real-time locating, navigation and supervision. GNSS has been widely used in many fields of production and life. However, via long distance in the complex wireless environment, satellite navigation signal is very weak while reaching the ground. Coupled with a variety of intentional and unintentional interference, this even makes the receiver do not work.Narrowband interference is a common interference. Therefore, in order to ensure the operation of the receiver, it’s necessary to add the interference suppression module to the receiver. Under the premise of a single antenna to receive navigation signals, the thesis mainly studys in-depth on the theory of time-domain and frequency-domain narrowband interference suppression technology, and implements the LMS filter and 50% overlap window method & spectral filter under the guidance of the theory.The navigation signal and narrowband interference have different characteristics in the time domain and frequency domain, therefore this thesis has done the following work:(1) Analyze the interference faced by the receiver, set the models of the received navigation signal and narrowband interference and use the models to analyze the influence that narrow-band interference brings to the receiver in detail.(2) Based on prediction estimate theory, study navigation signal narrowband interference suppression technology in the time domain. Study the the basic principle of LMS(Least Mean Square) and improved variable step-size LMS filter and LS(Least Squares), LSL(Least Squares lattice) filters, and simulate and compare the ability to suppress narrowband interference performance of each filter.(3) Introduce the basic principle of frequency-domain narrowband interference suppression, and study the mentioned modules and related algorithms. Analysis the reason leading to "spectral leakage" phenomenon and signal distortion, and introduce the method to mitigate them-- 50% overlap window method, anti-windowed. Frequency domain interference suppression module can be divided into two parts, interference detection and the elimination of interference. Therefore, the thesis also introduces the N-Sigma algorithm for adaptive computing interference threshold,and compare the condition midvalue filter, and modified it. Finally, the frequency-domain narrowband interference suppression scheme consisting of related algorithms is simulated and compared.(4) According to the simulation results, use Verilog to realize the time domain and frequency domain narrowband interference suppression module. Verificatied the function, the module are added to the receiving system. Then the entire system is tested and the test results are given.