Low C/N0Carrier Tracking Loop Based on Optimal Estimation Algorithm in GPS Software Receivers

Miao Jianfeng, Chen Wu, Sun Yongrong, Liu Jianye

Research output: Journal article publicationJournal articleAcademic researchpeer-review

19 Citations (Scopus)


Suppressing jitter noises in a phase locked loop(PLL) is of great importance in order to keep precise and continuous track of global positioning system(GPS) signals characterized by low carrier-to-noise ratio(C/N0). This article proposes and analyzes an improved Kalman-filter-based PLL to process weak carrier signals in GPS software receivers. After reviewing the optimal-bandwidth-based traditional second-order PLL, a Kalman-filter-based estimation algorithm is implemented for the new PLL by decorrelating the model error noises and the measurement noises. Finally, the efficiency of this new Kalman-filter-based PLL is verified by experimental data. Compared to the traditional second-order PLL, this new PLL is in position to make correct estimation of the carrier phase differences and Doppler shifts with less overshoots and noise disturbances and keeps an effective check on the disturbances out of jitter noises in PLL. The results show that during processing normal signals, this improved PLL reduces the standard deviation from 0. 010 69 cycle to 0. 007 63 cycle, and for weak signal processing, the phase jitter range and the Doppler shifts can be controlled within ±17° and ±5 Hz as against ±25° and ±15 Hz by the traditional PLL.
Original languageEnglish
Pages (from-to)109-116
Number of pages8
JournalChinese Journal of Aeronautics
Issue number1
Publication statusPublished - 1 Feb 2010


  • global positioning system
  • Kalman filters
  • phase locked loop
  • signal processing
  • software radio

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanical Engineering


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