Том 61, № 8 (2016)

The navigation signals with sine binary offset carrier (sinBOC), cosine BOC (cosBOC), and alternative BOC (AltBOC) modulations are discussed. A technique for calculating the correlation functions (CFs) of the single components of modulating functions (MFs) inherent to the given signals, which is based on the inverse Fourier transform (IFT) of energy spectra, is proposed. This technique makes it possible to derive analytical expressions for the CFs characterizing the single components of the MFs of sinBOC and cosBOC signals and complete AltBOC waveforms with a constant envelope at the multiplicity coefficients N_m = 2‒4. The graphs of CFs are constructed. Several illustrating examples, in which most attention is paid to sinBOC, cosBOC, and AltBOC signals employed in the Galileo satellite radio-navigation system and the global positioning system, are presented.

A two dimensional problem of diffraction of a plane electromagnetic wave by a cylindrical gold shell is considered in the case when the boundaries of the shell are circular cylinders with displaced centers. The influence of the excentricity of the boundaries on the properties of plasmon resonances in the optical band is studied. The near and far fields and scattering spectra are calculated by rigorous methods. It is found that the excentricity of shell’s boundaries gives rise to additional resonances. Analytical theory of scattering for thin shells is developed in the quasi-static approximation. It is shown that, in this case, the scattering and absorption spectra essentially depend on the displacement of the centers of the cylindrical boundaries but are independent of the direction of this displacement.

An algorithm for control of the phases of an active phased array antenna (APAA) with dome lens that takes into account distorting influence of the lens and combines tabular and computational methods for control of the antenna element phases is proposed. An algorithm for control of the amplitude transmission coefficients of receiving channels of the APAA modules for formation of a difference pattern with deep direction- finding null is also proposed.

The results of numerical simulation of electrodynamic characteristics of a slow-wave structure shaped as a folded waveguide and an electron–optical system of a three-millimeter-band pulse travelling wave tube with an output pulsed power of up to 50 W are presented. The matching devices, the interaction space, and the electron–optical system are calculated, which allows determination of their constructive parameters. The effect of loss caused by the roughness of the surfaces of the walls of the electrodynamic system on the output characteristics of the device is estimated.

Conditions for reconstructing a distorted image by the deconvolution from a phase distribution over the aperture, detected by a wavefront sensor, are studied.

Effective excitation of a surface wave, in particular, the Zenneck wave, over a plane boundary of a highly conductive medium is considered.

The effect of an external static radial electric field on the characteristics of a superradiation pulse of an ensemble of cyclotron oscillators is investigated in a numerical experiment. It is demonstrated that this external field alters the amplitude, the width, and the peak time of the radiation generated by this active medium.

In this paper, we focus on the study of electromagnetic waves that allow the communication between two antennas located on the surface of the human body. The link between the antennas leads to the appearance of space wave, whose level increases with height above the skin, and a surface wave which, on the contrary, decreases with the altitude. We use the wave propagation model of Norton with the notion of Somerfield’s attenuation. We give the limits of validity of this formalism in the area containing mainly surface waves. To generate this type of waves, the excitation sources used are small elementary electric dipoles with normal polarization.

Conventional slotted waveguide antennas are well known and prominently used for many military and even marketable applications. This is due to their different advantageous electrical and mechanical characteristics. It is also well known that this type of antennas is a typical array of slots with which the width of the main beam can be controlled in only one plane by using a different number of elements in such antennas. Numerous research, discuss the capability of using an array of such antennas in order to narrow down the main beam in both planes and even achieve a scanning phased array. In this paper, a new and broader approach is presented concerning beam width control of the typical configuration of such antennas. This work presents the ability to control the main lobe in both planes using only one slotted waveguide to a certain extent. Different simulation results are considered at the 2.4 GHz frequency demonstrating improved effectiveness in terms of directivity and high gain as well as minimizing the side-lobe level and mechanically controlling the main lobe of the antenna.

In this paper, an efficient decision based scheme is proposed for the restoration of grayscale and colour images that are heavily corrupted by salt and pepper noise. The processed pixel is examined for 0 or 255; if found true, then it is considered as noisy pixel else not noisy. If found noisy the four neighbours of the noisy pixels are checked for 0 or 255. If all the four neighbours of the corrupted pixel are noisy, the mean of the four neighbours replaces the corrupted pixel. If any of the four neighbours is a non-noisy pixel, calculate the number of corrupted pixels in the current processing window. If the count is less than three then the noisy pixel is replaced by an unsymmetrical trimmed median. If the current window has more than three noisy pixels, then unsymmetrical trimmed mean replaces the corrupted pixels. If all the pixels of the current processing window are noisy then instead of unsymmetrical trimmed mean, global mean of the image is replaced as output. The uncorrupted pixel is left unchanged. The proposed algorithm is tested on various grayscale and colour images and found that it gives excellent PSNR, high IEF and lowest MSE. Also it consumes average time with excellent edge preservation even at higher noise densities. The quality of the results of proposed algorithm is superior when compared to the various state of the art methods.

Chaotic signal shows amounts of advantages in the application of radar systems for its easy generation and control. The model of combined chaotic maps based on Bernoulli map is proposed in this paper. Then, the chaos based frequency modulated (FM) radar signal is put forward and the frequency spectrum, ambiguity function are also analyzed in theory. In simulation, the phase spaces, Approximate entropy (ApEn) and balance of the combined chaotic maps are investigated, which shows the combined maps sequences have greater performances than the initial sequences. Additionally, the Peak side-lobe level (PSL) and Integrated side-lobe level (ISL) of signal autocorrelation are discussed, and they drop greatly with the combined chaotic maps after frequency modulation. Simulation results also show that the FM signal based on combined chaotic maps has flatter frequency spectrum in the whole frequency band and a thumbtack ambiguity function.