Multichannel Propagation Research Articles

АЛГОРИТМ ОБНАРУЖЕНИЯ ФМ-СИГНАЛОВ НА ОСНОВЕ ВИНЕРОВСКОЙ ФИЛЬТРАЦИИ С ПРЕДВАРИТЕЛЬНОЙ НЕЛИНЕЙНОЙ ОБРАБОТКОЙ

In this paper, an algorithm for preprocessing of PSK - signals based on wiener filtration is proposed. The aim of preprocessing is to extract the phase discontinuities when filtering harmonic filling of a signal. This method allows us to avoid compensation of unknown frequency shift in the problems of determining the time delay of signals during multichannel propagation. The study checks the conditions of algorithm applicability and its stability to a noise level in the observed channels.

Phonon Interference in the 1D Array of Carbon Nanotubes

The dynamics of the 1D array of single-walled carbon nanotubes (CNTs), which interact by van der Waals forces, is considered. The molecular dynamics simulation shows that both the mutual displacements of the nanotubes and the deformations of their walls occur in the low-frequency oscillations domain. The composite model taking into account both types of the nanotubes’ motions is developed in the framework of the thin elastic shell theory. Such an approach allows us to reduce the problem to the dynamics of the linear lattice with contact interaction. The dispersion relations are represented analytically and the multichannel propagation that results in phonon interference (the acoustical analog of the Fano resonance) is observed in the presence of the array's irregularities. The latter can be formed with redundant nanotubes, which are placed over the array in the grooves between neighbor sites. The calculations of the transmittance have been performed by the transfer matrix method for several typical configurations.

On Golden Code Performances in Impulsive Noise MIMO Channels

Wireless technologies are the ones who provide fast communications on long distances. MIMO (Multiple-Input-Multiple-Output) Systems become an important factor in communication standards. At the beginning, this technology involved several antennas for both transmission and reception. Nowadays, in order to improve the performance of wireless transmissions, in addition to multi-channel propagation, error correction codes are used. Golden Code has some advantages, such as: maximum rate and diversity or coding gain. In this paper it is proposed an approach of using this code to mitigate the impulsive noise effects in a MIMO communication system. The Middleton Class-A noise was considered. The simulation was done for different values of the impulsive noise model parameters and showed that the probability density function depends on index impulse and on gaussian factor and the number of noise sources has no influence.

NALM-based, phase-preserving 2R regenerator of high-duty-cycle pulses

We explore the potential of the nonlinear amplifying loop mirror (NALM)-based phase-preserving 2R (reamplification and reshaping) regenerator for simultaneous regeneration of multiple wavelength-division-multiplexed (WDM) channels. While not considering nonlinear multi-channel propagation, we address two issues of the phase-preserving NALM that appear to us as the major obstacles in adopting it for realistic WDM applications: a high operating power and a detrimental effect of non-small (33% - 50%) pulse duty cycles. After thorough optimization, we find a new operating regime of this regenerator with the non-small duty-cycle capability and approximately an order of magnitude reduction of the required operating power. In addition, we show that the plateau in the input-output power transfer curve does not automatically lead to the reduction of the amplitude jitter, which is particularly noticeable for the non-small duty-cycle pulses.

Multichannel discharge between jet electrolyte cathode and solid anode

We investigate particularities of burning of multichannel discharge between a jet electrolyte anode and solid cathode within a wide range of parameters. We observe the multichannel discharge propagation over the humid plexiglas cathode surface and discover its various shapes. We reveal the transformation of conelike channels into contracted ones. We show that the multichannel discharge voltage and the current are characterized by normal probability distribution functions. We investigate the spectrum of the copper cathode surface.

Algorithm of nonlinear quasioptimal digital processing of angle-modulated signals

The paper considers an algorithm for nonlinear quasioptimal digital processing of signals with various types of angle modulation based on a generalization of the Capon minimum variance approach. The algorithm makes it unnecessary to compensate for the unknown frequency shift in the problem of determining the relative time delay of signals during multichannel propagation. Efficiency of the proposed method is demonstrated on phase- and frequency-shifted keyed signals which represent short information sequences.

Multichannel propagation and scattering of phonons and photons in low-dimension nanostructures

Multichannel propagation and scattering of phonons and photons in low-dimension nanostructures

Combined digital filtering of harmonic content of phase-shift keyed signals in the problem of estimation of the time delay

We propose a two-step method for digital filtering of phase-shift keyed signals filtering in the problem of determination of the time delay during the multichannel propagation. The first step is realized as an information-optimal linear filter with complex coefficients, while the second step, as a quadratic filter based on the minimum-variance criterion. The e.ciency of the proposed method is demonstrated for short PSK signals with various carrier frequencies against the background of additive and multiplicative noise. The developed algorithm can easily be implemented in real time on the basis of a digital signal processor.

Algorithm for nonlinear digital filtering of harmonic filling of phase-shift keyed signals

In this work, we propose a method for nonlinear digital filtering of phase-shift keyed signals with different carrier frequencies on the basis of separating the phase discontinuities of the input signals. The method allows one to avoid compensation for unknown frequency shift in the problems of determining the time delay of signals in the case of multichannel propagation. The efficiency of the proposed method is shown for the signals which are short informative packages with the phase-shift keying against the noise background in the presence of the Doppler effect.

Quasi-solitonic behavior of self-written waveguides created by photopolymerization

We investigated the condition of unique self-written channel and multichannel propagation inside bulk photopolymerizable materials. Light was introduced in the medium by a single-mode optical fiber. At a very low beam power of 5 muW , a unique uniform-channel waveguide without any broadening was obtained by polymerization. When the input power is increased to 100 muW , the guide becomes chaotic and multichannel. We connected two fibers separated by a 1-cm distance. The results open the door to studies of the optical and electro-optical properties of photopolymerized guides doped by nonlinear optical chromophores and to possible applications in integrated optical devices.

Precision method of determining the time delay in multichannel signal propagation

One of the important problems arising when processing signals propagating over several channels with various noise characteristics is a determination of their time delay [1]. In the case of two channels formulation of the problem reduces to the following form: We have two signals s 1 and s 2 …

Tunneling rates in a two-dimensional symmetric double-well potential surface by the exterior scaling procedure

Time-independent methods which were recently developed [J. Chem. Phys. 91, 6246 (1989); 93, 3413 (1990)] to calculate tunneling rates in bound systems are applied to a two-dimensional symmetrical double-well surface proposed by Makri and Miller [J. Chem. Phys. 86, 1451 (1987)] to describe intramolecular H-atom transfer. The methods are based on exterior complex scaling either with basis-set expansions or with an iterative multichannel propagation and matching procedure. Exterior complex scaling is used to identify the initial well (characterized by an unscaled reaction coordinate) and the final well (with a complex-scaled reaction coordinate). The quantized energies of the system become complex, with imaginary parts providing the rates.