A new algorithm for high-quality ionogram generation and analysis

Abstract

Standard digital ionograms that are generated by fast Fourier transform or autoregressivemodeling suffer from high interference levels due to other users of the HF channel whichproduce artifacts and distortion, hence complicating automatic processing and informationextraction. In this paper, a new method is proposed to obtain high-quality ionograms of thedesired layer reflections and automatically extract important information such as criticalfrequencies. Following the standard procedures, two sets of periodograms are obtained byusing rectangular and Blackman windows. These two periodograms are filtered and fusedutilizing an automatic edge-detection-based time-frequency detector. The fused ionogramprovides sharp description of the layer reflections with very low sidelobe structure (ringing).The performance of this new ionogram algorithm is tested using chirp sounder data collectedfrom an oblique midlatitude path. It is observed that the presented algorithm is highlysuccessful in obtaining robust and sharp ionograms free of artifacts. Furthermore, a newalgorithm is proposed for automated computation of dispersion and critical frequencies of themagnetoionic components detected on the ionogram. Since efficient signal-processingalgorithms are utilized, the proposed method can be implemented in real time.