Modeling and studying ionograms of oblique sounding of HF radio channels for radio links of various length using a digital ionosonde with USRP platform
The paper analyses the outcomes of numerical studies into the effect of phase dispersion on broadband elements of a FMCW signal with varying central spectrum frequencies corresponding to the central frequencies of radio channels. We used the International Reference Ionosphere (IRI) model as the background ionosphere, which takes into account the spatiotemporal variability of the radio channel. The data corresponding to the extreme values in the annual distribution of solar activity were selected for modeling ionograms. The effect of the second-order phase dispersion on power delay profile distortions was analyzed.
BPSK signal shaping and processing for digital SDR ionosonde
The paper presents the algorithms of BPSK signal shaping and processing for vertical incidence ionospheric sounding with the use of a hardware platform USRP which implements SDR technology. The principle “ADC to an antenna”, which provides completely digital processing, allows to apply new algorithms. The developed algorithms allow to obtain a quality images of ionograms with the use of low-power signals (less than 20 W). The algorithm of coherent spectral integration, which causes the increase in the SNR, and the algorithm of narrowband interferences mitigation, which uses median equalization, are presented. The efficiency of the algorithms was verified in the full-scale experiments on vertical incidence ionospheric sounding in Yoshkar-Ola.
Midlatitude ionospheric HF channel reciprocity: Evidence from the ionospheric oblique incidence sounding experiments
Ionospheric HF channel reciprocity is investigated at middle latitudes on the basis of ionospheric oblique incidence sounding experiments. Two identical Wuhan Ionospheric Oblique Incidence Sounding Systems (WIOISS), located at Wuhan (30°32′N, 114°21′E) and Wanning (18°58′N, 110°31′E), are used to carry out the campaign. Comparisons of group distance and Doppler shift between Wuhan‐Wanning and Wanning‐Wuhan HF ionospheric propagation paths indicate that the reciprocity of the ionospheric HF channel is satisfied at midlatitude region. A 3‐D ray tracing simulation is also implemented to evaluate the group distances of the two paths. Midlatitude ionospheric HF channel reciprocity, as verified both experimentally and theoretically in the present study, can be useful for HF communication systems and sky wave over‐the‐horizon radars.