Design of tracking loop based on the Pseudo Navigation Message

If a satellite data bit transition boundary is straddled by the predetection integrate interval, the integration result for that interval would be degraded. Doppler Effect causes data bit transition boundaries slip in the predetection integrate intervals. When the data transition occurs at the halfway point, the integration signal will be totally canceled for that interval, and the tracking loops will lose lock at the same time. On the basis of analyzing this problem, be aimed at the “Compass II” signals, the paper presents a method named Pseudo Navigation Message Tracking. The proposed method through constructing a pseudo navigation message sequence whose data bits transit once per millisecond to judge whether the prompt predetection integrate interval straddles a satellite data transition boundary, then use the judgment result to assist the update of the tracking loop and to locate the data bit transitions in the bit synchronization process.