An Optimized Capture Algorithm for GPS Receiver
The paper studies and designs a differential guess-check capture algorithm. This paper first makes a brief overview on coherent, incoherent and differential integration, then it contrasts effects of longer coherent integral time and incoherent integral ti
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An Optimized Capture Algorithm for GPS Receiver Kun Zhai, Zhongliang Deng, Yuezhou Hu, Le Yang and Zhuang Yuan
Abstract The paper studies and designs a differential guess-check capture algorithm. This paper first makes a brief overview on coherent, incoherent and differential integration, then it contrasts effects of longer coherent integral time and incoherent integral time on the baseband loop, furthermore analyzes their features and shortcomings. The paper continues to discuss traditional capture algorithm, half-bits algorithm and full-bits algorithm. After analyzing theory and shortcomings, the paper proposes a kind of optimized differential guess-check capture algorithm. Through theoretical analysis and MATLAB software simulation verification, the paper simulated and compared the optimized algorithm with traditional loop algorithm on different data length 80, 180, 280 ms. The result indicates the optimized one has bigger correlation peak and smaller noise fluctuation. Moreover, as the processed data lengthens, the optimized algorithm has more obvious advantage. Finally, the methods to reduce the capture time are analyzed and simulated. This shows that the scheme design is effective and feasible. Keywords Baseband receiver algorithm High sensitivity
Integration time
Guess-check capture
69.1 Introduction Coherent integration and incoherent integration are key technologies for receiving weak GPS signals. Although the operation of incoherent integration can enhance the signal-to-noise ratio, the square calculation before integration can bring in square loss, which doesn’t exist in coherent integration. K. Zhai (&) Z. Deng Y. Hu L. Yang Z. Yuan School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China e-mail: [email protected]
J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2014 Proceedings: Volume I, Lecture Notes in Electrical Engineering 303, DOI: 10.1007/978-3-642-54737-9_69, Springer-Verlag Berlin Heidelberg 2014
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In reverse, coherent integration is affected by data bits jumping and frequency tracking deviation, while the incoherent process won’t be influenced by these two factors. Since the above, receiver can do long time (e.g. several hundred milliseconds, or even some seconds) incoherent integration. For this problem, this page presents an optimization algorithm. The algorithm can effectively avoid square loss, at the same time reduce the influence of data bits jumping, thereby increases the capture sensitivity, which furthermore improves the performance of the receiver.
69.2 Basic Algorithms for GPS Signal Acquisition 69.2.1 Coherent and Non-coherent Integration Algorithm Data is multiplied with complex scrambling code’s conjugate and the pilot after spread spectrum, so as to obtain accumulative result of different time slots. Coherent integration is done through this method. Mathematical formula [3] is shown as (69.1) X N ð69:1Þ RCOH ðs; fd Þ ¼ yk ðs; fd Þ k¼1 Incohere
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