Vol 59, No 5 (2016)

We present the results of a four-year (2009–2012) study of the decimeter radio wave propagation using signals from the global navigation satellite system (GNSS) and simultaneous measurements of the tropospheric surface layer parameters in the city of Kazan. Inter- and intra-annual variabilities of the temporal structure functions of the zenith tropospheric delay (ZTD) of decimeter radio waves are analyzed. It has been found that the contribution of irregularities with time scales of up to 24 h to the ZTD fluctuation variance varies, depending on the surface weather parameters (temperature and pressure). Correlation coefficient between the approximation exponents of the ZTD temporal structure function of decimeter radio waves and surface temperature reaches 0.77 for fluctuations with time scales of up to 8 h. It has been established that synoptic processes and the underlying surface affect the formation of mesoscale fluctuations on the phase path of radio signals from the navigation satellite systems.

We study experimentally the possibility to shift the minimal wavelength of the radiation generated by an orotron with a double-row periodic structure, which is manufactured by using the sparkdischarge technology, into the submillimeter wavelength range. It is shown that one can realize this possibility at an accelerating voltage of less than 20 kV and the minimal height of the transit channel being equal to 0.1 mm only by increasing the operating current and using sophisticated focusing mirrors simultaneously. The results of studying the tuning of the generation frequency of an orotron with a structure period of 0.182 mm in the 140–402 GHz are presented. The possibility to generate at a wavelength of 0.7 mm is discussed.

We propose a new method of compensating for the wavefront aberrations during the image processing. The method employs the digital-holography potential. The developed algorithms allow one to find the wavefront distortions caused by the optical-path nonuniformities during the interference recording of images without additional measurements (i.e., without using the reference point source and measuring the wavefront distortions). The possibility of decreasing the wavefront aberrations from tens to several radians using digital methods is demonstrated.

We consider the problem of the discrete-message transmission using the codes on the basis of the Shannon theorem, the Feinstein lemma, and the Hamming codes. In this case, the transmission quality is estimated using deterministic rather than random couplings among the messages and signals. It is shown that the coding redundancy, as well as the error-free transmission condition are not sufficient for realizing such a transmission. The signal-to-noise ratio is a more accurate parameter determining the transmission quality. The use of the Hamming code for long message sequences becomes efficient only if the threshold value of the signal-to-noise ratio is exceeded.