Frequency-Locked Detector Threshold Setting Criteria Based on Mean-Time-To-Lose-Lock (MTLL) for GPS Receivers

Tian Jin; Heliang Yuan; Na Zhao; Honglei Qin; Kewen Sun; Yuanfa Ji

doi:10.3390/s17122808

Frequency-Locked Detector Threshold Setting Criteria Based on Mean-Time-To-Lose-Lock (MTLL) for GPS Receivers

Sensors (Basel). 2017 Dec 4;17(12):2808. doi: 10.3390/s17122808.

Authors

Tian Jin¹, Heliang Yuan², Na Zhao³, Honglei Qin⁴, Kewen Sun⁵, Yuanfa Ji⁶

Affiliations

¹ School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. jintian@buaa.edu.cn.
² School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. yuanheliang@buaa.edu.cn.
³ School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. zhaona@buaa.edu.cn.
⁴ School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. qhlmmm@sina.com.
⁵ School of Computer and Information, Hefei University of Technology, Hefei 230009, China. kewen.sun@hfut.edu.cn.
⁶ Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin 541004, China. jiyuanfa@163.com.

Abstract

Frequency-locked detector (FLD) has been widely utilized in tracking loops of Global Positioning System (GPS) receivers to indicate their locking status. The relation between FLD and lock status has been seldom discussed. The traditional PLL experience is not suitable for FLL. In this paper, the threshold setting criteria for frequency-locked detector in the GPS receiver has been proposed by analyzing statistical characteristic of FLD output. The approximate probability distribution of frequency-locked detector is theoretically derived by using a statistical approach, which reveals the relationship between probabilities of frequency-locked detector and the carrier-to-noise ratio (C/N₀) of the received GPS signal. The relationship among mean-time-to-lose-lock (MTLL), detection threshold and lock probability related to C/N₀ can be further discovered by utilizing this probability. Therefore, a theoretical basis for threshold setting criteria in frequency locked loops for GPS receivers is provided based on mean-time-to-lose-lock analysis.

Keywords: GPS receiver; frequency locked loop; frequency-locked detector; mean-time-to-lose-lock.