Alternative eLoran Pulses for Early Skywave Mitigation

Multipath and skywaves are sources of range errors in enhanced long-range navigation (eLoran), and an early skywave can particularly pose a threat to user safety by inducing range errors of over one kilometer. This study presents a novel eLoran pulse design that mitigates skywave-induced range errors while complying with SAE9990 pulse shape and spectrum specifications. Two optimized pulse shapes were developed using genetic algorithms (GA) and quadratic programming (QP). Simulation results demonstrate substantial performance gains; for a fixed skywave-to-groundwave amplitude ratio (SGR) of 0.3, the GA- and QP-based designs reduce range errors by 51.9 % and 69.0%, respectively. Both pulses effectively mitigate early-skywave–induced errors under simulated ionospheric polar-cap disturbance conditions with an SGR larger than 1. These results highlight the potential of optimization-based pulse shaping to enhance eLoran system accuracy under challenging propagation conditions.