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.
Improving the Efficiency of Data Transmission Over the HF Radio Channel with Bandwidths of 3-24 kHz
Studies addressed the problem of increasing the efficiency of data transmission over the HF radio channel with bandwidths of 3-24 kHz. There are presented methods and algorithms developed for evaluating occupancy of the radio channel by processing the received data on the noise level in the HF band for adapting the digital HF communication system according to sounding data.
Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate
Nano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry.