Application of Novel Signal Processing Algorithms for the Detection and Minimization of Skywave Interfering Signals in Loran Receivers

Abstract

Skywave interference commonly affects Loran receivers’ performance. Traditional skywave rejection methods that use fixed, worst-case, sample timing are far from optimal. This chapter reports on novel signal processing techniques for measuring in real-time the delay and strength of the varying skywave components of a Loran signal relative to the groundwave pulse. The merits and limitations of these techniques will be discussed. Their effectiveness will be assessed by theoretical analysis, computer simulations under a range of realistic conditions, and by testing using off-air signals. A prototype Loran system employing the proposed techniques is also presented. This work establishes a basis on which to design a Loran receiver capable of adjusting its sampling point adaptively to the optimal value in a constantly-changing skywave environment. Such receivers promise to improve significantly the accuracy and reliability of positioning under adverse operational conditions.