Research on the application of a two-way comparison method in eLoran systems

eLoran is an important component of the international standard positioning, navigation and timing (PNT) system. High-precision time-frequency synchronization among transmitting stations is essential for stable PNT service, but conventional synchronization methods mainly rely on external techniques such as satellite common-view, optical fiber transfer, or transported clocks. To reduce this external dependence, this paper proposes a two-way time-frequency transfer method based on eLoran signals. In the proposed method, two eLoran transmitting stations receive each other’s signals carrying timing information, perform local time-difference measurements, and exchange observation data to obtain the time-frequency transfer result. Owing to the reciprocal propagation path between the two stations, the propagation delay can be largely canceled. Experimental results on 736 km and 486 km baselines verify the feasibility of the proposed method. The measured 10 000 s stability reaches 10⁻¹², respectively. The results show that the proposed method can realize time-frequency synchronization among eLoran transmitting stations by using the system’s own signals, thereby improving system autonomy and reducing dependence on external synchronization links.