Vol 63, No 11 (2018)
- Year: 2018
- Articles: 11
- URL: https://journals.rcsi.science/1064-2269/issue/view/12439
Electrodynamics and Wave Propagation
Calculating the Input Impedance of a Microstrip Antenna with a Substrate of a Chiral Metamaterial
Abstract
The paper presents a technique for calculating the input impedance of a microstrip radiator placed on a substrate of a chiral metamaterial. A singular integral equation with the Cauchy singularity with respect to the unknown current density distribution on the radiator surface is derived. Dependences of the input impedance on the radiator length for different types of chiral substrates are calculated.
Features of Propagation of Electromagnetic Waves in Sol-Gel Optical Waveguides under Varying Temperature
Abstract
Features of the temperature dependence of effective refractive index neff (ERI) of optical waveguides based on sol-gel materials have been studied and behavior of the ERI temperature coefficient (TC) have been determined. It has been found experimentally and theoretically that, with properly selected film parameters, the ERI TC can have a negative, zero, or even small positive value within a certain temperature range. Clear mathematical description of the dependence of the ERI TC on the waveguide parameters and the partial power of the wave in the waveguide has been given.
A Novel Two-Dimensional Material Based Optical Fiber Surface Plasmon Resonance Sensor for Sensing of Organic Compounds in Infrared Spectrum Window
Abstract
Glucose, sucrose and fructose are typical organic compounds having carbon-hydrogen-oxygen atoms. Their sensing is important in many bio-medical applications. In this paper we present a 2D material-based fiber optic surface plasmon resonance sensor for refractive index sensing of some typical organic compounds. 2D material graphene in combination with active metal gold is used in the sensing region. Fiber core is covered with gold and graphene layer. The sensor is simulated using COMSOL Multiphysics simulation software. To measure the sensing performance of sensor we see the effect of two physical parameters of the sensor, thickness of the Au-metal and graphene layer on the sensing performance. The use of graphene layer enhances the sensitivity of SPR sensor. The angular interrogation method of SPR excitation is used for sensor simulation in COMSOL Multiphysics.
Antenna and Feeder Systems
Theory of an Integral Equation of Electromagnetic Wave Diffraction by a Segment of an Impedance Circular Cylinder
Abstract
Theory and Methods of Signal Processing
On the Potential Application of Direct Digital Synthesis in the Development of Frequency Synthesizers for Quantum Frequency Standards
Abstract
A new method for generation of the output signal of a frequency synthesizer of quantum frequency standards is considered. It is demonstrated that this method provides an opportunity to enhance spectral characteristics of the output signal, expand the range of output frequencies, and reduce the tuning step of the output frequency. A considerable (more than 10%) improvement in the frequency stability of a cesium-133 quantum standard and a 2.4-fold improvement in its temperature coefficient of frequency are reported.
Performance Enhancement of Multi-Antenna Relay Link in LTE Het-Net
Abstract
In this paper, the relay link performance for an Amplify and Forward (AF) multi-antenna relay based heterogeneous LTE (Long Term Evolution) network is enhanced with two novel techniques, the Golden codes and Error Vector Magnitude (EVM) based Constellation Combiner (ECC). The performance evaluation of the proposed co-operative LTE Het-Net is done in a real time indoor environment using Wireless open Access Research Platform (WARP). The proposed techniques for the LTE Het-Net are compared with traditional Alamouti Scheme with Maximal Ratio Combing (MRC). From the obtained results it is seen that the LTE network with proposed techniques gives a 12% improvement in EVM than the conventional LTE network.
Effect of Oblique Projection Beamforming on the Achievable Rate in Massive MIMO System
Abstract
The mitigation of interference is an ubiquitous problem in wireless communication systems for which a number of signal processing techniques have been developed. This problem is made more critical in the presence of an increased numbers of interfering cells, interfering users and antennas, as it is the case in massive MIMO systems. As a consequence, the conventional methods see their performance degrades. In this paper, we propose to incorporate Oblique Projection (OP) with conventional ZF beamforming in the downlink of a massive MIMO communication system and investigate the achievable data rate at the reception. Resulting beamformer uses oblique projection spaces to separate the received signal into two subspaces: the one pertaining to the desired user signal and the other to interference signals, thus achieving a high degree of interference suppression. It is shown that the OP beamforming performs better than Maximum Ratio Transmitting (MRT) and the transmit MMSE beamforming counterparts.
Electron and Ion Optics
Electron-Optical Systems with a Shielded Cathode and an Elliptical Ribbon Beam
Abstract
Abstract—Based on the theory of high-density electron flows with the elliptical current tubes, a model of a ribbon beam from a shielded cathode in the case of emission in the ρ mode has been built. Algorithms of formation of high-compression flows passing into the Brillouin mode without oscillations with preserved elliptical cross section not rotated or strained have been developed.
Physical Processes in Electron Devices
Study of an Access Monitoring and Control System Working in the Presence of Electrostatic Discharges
Abstract
Functioning of an access monitoring and control system is experimentally studied in the presence of electrostatic discharges. Several types of malfunctions of the functional units of the system related to the effect of noise of electrostatic discharge are revealed. Mathematical models are proposed for evaluation of electromagnetic noise in communication lines of the access monitoring and control system in the presence of electrostatic discharge. A few methods for an increase in the noise immunity of the access monitoring and control system in the presence of electrostatic discharge are proposed and analyzed.
Novel Radio Systems and Elements
Several Applications of Diamonds in High-Power Optics and Electronics
Abstract
Broadband Frequency Synthesizer for Acoustooptics
Abstract
A broadband digital frequency synthesizer for acoustooptical filters has been designed and studied. The range of synthesized frequencies has been expanded as compared to synthesizers based on phase locking. The interface for control of the proposed design has been developed. Using the user can enter frequency values by himself. A prototype of a dual-channel frequency synthesizer with possibility of independent operation of channels has been produced.