Radioelectronics and Communications Systems最新文献

Abstract

The paper presents a novel approach for mitigating the detrimental effects of the high peak-to-average power ratio (PAPR) inherent in non-orthogonal multiple access (NOMA) waveforms using the selective mapping (SLM) technique. NOMA, a prominent multiple access scheme in modern wireless communication systems, facilitates concurrent transmission of multiple users over the same time-frequency resource. However, NOMA is susceptible to elevated PAPR, causing efficiency degradation and inter-symbol interference. The proposed method leverages SLM to address the PAPR challenges in NOMA waveforms. By generating a set of diverse phase sequences, SLM constructs alternative versions of the original NOMA signal. The phase sequence resulting in the lowest PAPR is then selected for transmission. This dynamic adaptation significantly reduces peaks in the transmitted signal, thereby enhancing efficiency, minimizing distortion, and reducing the risk of nonlinear amplification. Extensive simulations are conducted to evaluate the efficiency of the projected procedure. The results demonstrate remarkable PAPR reduction in NOMA waveforms compared to conventional transmission methods. Additionally, the method maintains signal quality, improving the Bit Error Rate (BER), power spectral density (PSD) and enhancing the overall reliability of the radio framework. The paper concludes with insights into the feasibility of integrating SLM into existing NOMA-enabled systems, offering a promising avenue for optimizing the efficacy of advanced radio networks.

Abstract

Cost efficiency is an essential metric in the design of major part of what is expected to be the 5G network. Some of the 5G solutions, mainly those involving mmWave technology and network densification, are extremely expensive. Much of what was said about 5G rollout strategies has been said with regard to the world’s major leaders in 5G technology and telecom infrastructure investment. However, a much more numerous group of countries often referred as emerging markets or middle-income economies has never hold a leadership in the development of cellular technologies. To date, few of them have fully leveraged the potential of 4G systems while many still have not ensured a return on investment in 3G. This gave rise to the views that these countries are not ready for 5G challenges. However, all of them are doomed to enter the era of another industrial revolution, where exactly 5G is to become the main driver. Yet, the use cases and the portfolio of services of the future networks will apparently depend on economic realities of the country where it will be deployed. There is a rather vague picture at the moment of how the 5G rollout may take place in this part of the world and that is the main reason for this study. In this paper, we outline the technical challenges and economic tensions associated with the developing of 5G physical infrastructure and address spectrum allocation issues with a particular focus on the needs of the future enhanced mobile broadband component. Then we discuss the role of government in establishing favorable regulatory framework, providing supportive policies and finding local drivers to facilitate 5G rollout and the challenges, confronting the operators paving their way to 5G.

Abstract

In this paper an impact of external magnetic field on current-voltage characteristics of a planar silicon photothyristor is researched experimentally. It is shown that magnetic field of one polarity with induction of 0.4 T results in such decrease of the breakover voltage U_B as well as an LED emission at current of 8 mA. But magnetic field of the opposite polarity allows to increase U_B. There are represented the formulas for calculation of the dependence of U_B on magnetic field. Increase of magnetic sensitivity is achieved by placement of the area with high rate of injected charge carriers recombination at the opposite side of the electrodes at the base side. Double contactless control of the thyristor U_B with light and magnetic field allows to increase essentially its functional possibilities. Since the thyristor can only be turned on by light emission, it can also be turned off by the magnetic field impact. It is shown that existing industrial optical couplers can be used as optrons controlled with light emission and magnetic field, but magnetic control thyristor can be used as a simple switch.

Abstract

In this study, two dynamic algorithms are verified for transmit antenna selection aimed at achieving the energy efficiency in massive MIMO, namely: Random User Selection (RUS) and Maximum Channel Gain (MCG). Massive MIMO setups are investigated over N radio cables via centralized massive base station (BS), which uses RUS and MCG to provide management to U clients. Massive MIMO networks are shown for 8×8, 16×16, 25×25, and 50×50 setups using RUS and MCG. The proficiency of the proposed scheme on setup network has been investigated with RUS and MCG, and then the effect on performance characteristics, such as sumrate, user throughput and energy efficiency has been analyzed. The power efficiency has also been improved by increasing the number of Massive MIMO antennas. Compared to RUS, algorithm MCG provides a better service to users located far from the base station antenna.

Abstract

In this paper on a basis of functional analysis methods we justified theoretically the possibility of different orders root-polynomial functions application for interpolation and approximation of the boundary trajectory of an electron beam in case of its propagation in ionized gas with compensation of the space charge of the beam electrons. It is shown, that the root-polynomial functions satisfy to the second-order differential equation, describing the boundary trajectory of the beam electrons under such physical conditions. The results of interpolation and approximation of the boundary trajectory of the electron beam by root-polynomial functions from the second to the fifth order under the following physical conditions are presented. The interpolation results are compared with the corresponded results of the differential equation solution for the boundary trajectory of the electron beam using Runge-Kutta numerical method of the fourth order. These results are considered as reference ones for the interpolation task. To solve the approximation problem, in this paper an iterative algorithm based on the calculation of both values of the function and its derivatives at reference points is proposed. The approximation task is solved for a sample of numerical data obtained by experimental electron-beam equipment for real processes of current electron-beam technologies, which led to a rather large value of the experimental measurement error due to the effect of random factors associated with thermal treatment of products with electron beam. Test calculations show that the error of interpolation and approximation of numerical data, describing the boundary trajectory of electron beam in case of its propagation in ionized gas, does not exceed a few percent. The theoretical and practical results obtained in this paper are interesting for a wide range of specialists who are engaged in the physics of electron beams, the development of electron-beam technological equipment and implementation of current electron-beam technologies into industry.

Abstract

The scientific and practical significance of the synthesis of demodulators in solving the problem of monitoring unknown radio emissions has been substantiated. Features of the photoelastic effect are discussed in the context of constructing an amplitude demodulator. A mathematical model of the signal generation process at the output of the demodulator has been developed. It is shown that the output signal of this model is a copy of the information contained in the radio signal at the input of demodulator. In this case, the amplitude demodulator also performs the function of a low-pass filter with a characteristic cutoff frequency. A method for calculating the demodulator cutoff frequency based on the transient response is proposed. A breadboard of acousto-optic amplitude demodulator based on Bragg’s cell with the central frequency of 80 MHz has been created. A number of experimental studies were conducted to verify the established concepts. The demodulation processes of signals with amplitude and pulse modulation were considered. It has been proved by experiment that the acousto-optic amplitude demodulator reproduces information with accuracy sufficient for practice. An example of determining the cutoff frequency of acousto-optic amplitude demodulator by employing the shape of the output pulse is presented.

Abstract

The spectral sensitivity change of a silicon photodiode with its temperature is analyzed in the article. This research area is relevant because silicon photodiodes are used as sensitive elements in temperature control systems of the vapour-phase epitaxy process. Technical characteristics of the obtained semiconductor devices are mostly determined by the quality of heterostructures used for their manufacture. The optical pyrometry method is used for the surface temperature precise control of the A3B5 solid solutions active layers during metalorganic chemical vapour deposition (MOCVD). Since the surface relief and parameters during deposition change significantly, classical pyrometry leads to significant measurement errors, so the pyrometry method with radiation compensation is used. This method combines the wafer surface radiation measurement and its reflectivity. This allows to determine the surface temperature true value, the layer thickness and the heat distribution uniformity on the wafer in real time.

However, for high precision, it is necessary to take into account the temperature coefficient of the silicon photodiode ampere-watt sensitivity change. The basics of MOCVD technology are discussed in this article. The features of the epitaxy process in the reactor with high-precision temperature control are highlighted.

The analytical and empirical study of change in silicon photodiode ampere-watt sensitivity and its effect on measurement accuracy are given. The research results improve the accuracy of real temperature measurement using pyrometric parameter control systems in MOCVD technology and help to understand and to take into account the influence of temperature factors on measurement accuracy to improve this technology.

Abstract

The paper proposes a new iterative algorithm for finding the transverse dimension of the cold cathode of high-voltage glow discharge electron guns, based on formulation of a nonlinear equation for the functional dependence of the cathode size on the discharge current and solving this equation using the Steffenson iterative method. A distinctive feature of the proposed calculation method is taking into account the dependence of high-voltage glow discharge current on the plasma boundary position. To obtain the corresponding nonlinear equation, we use the approximate theory of one-dimensional discharge gap and well-known statement of the discharge theory that the anode plasma occupies a definite volume, which is determined by concentration of charged particles, regardless of the geometry of the electrode system. There are specified the geometric parameters of the electronic system of the high-voltage glow discharge with a spherical cathode and a hollow anode, and also well as restrictions on the system of parameters that satisfy the requirements of completeness, consistency, and closure are introduced. On a basis of the numerical analysis of the proposed iterative algorithm convergence process, we show that in case of the restrictions on the introduced parameters system are satisfied, the method convergence is usually ensured. We compare the calculations results of the transverse dimension of the cathode of high-voltage glow discharge guns with correspondent experimental data. The comparative analysis results showed that proposed iterative algorithm application results in the difference between calculations and experimental data does not exceed a few percent. The research results and proposed iterative method for calculating the transverse dimension of the cold cathode of high-voltage glow discharge guns are of great practical value and can be directly used at the initial stage of designing gas discharge guns to assess their technological possibilities.

Abstract

Designing of microwave systems based on composite materials involves the need of thorough understanding of interaction processes of electromagnetic waves with such materials and factors that affect this interaction. Polymer-based composites filled with materials having a high degree of electromagnetic energy absorption make it possible to combine electric properties of composite material with the mechanical elasticity, chemical resistance, and good fabrication properties. Selecting materials and their processing techniques, it is possible to achieve the required properties, both electrodynamic and mechanical. Composite properties are essentially influenced by such factors as the size and shape of filler particles, the volume fraction of filler, etc. Therefore, this paper considers different types of fillers for producing polymer-based composites, namely, magnetic materials, metals, carbon, and dielectrics with high dielectric permittivity. Advantages and disadvantages of the above fillers are analyzed. It has been shown that in the millimeter wavelength range, the relevent composites are those, in which the absorption is implemented due to the inclusion of polar dielectrics into their composition.

Abstract

The paper proposes a circuit and calculation method for dual-band microstrip balun that along with equal-amplitude and counterphase distribution of signal between outputs in two bands, ensures the transformation of complex load impedances, which are different in these bands, into a real value of input impedance of the source. In this case, the matching of device input and outputs is achieved with a high decoupling level of the latter. The proposed structure consists of cascade connection of four sections of coupled lines, two reactive elements that are implemented by stubs and the decoupling links of outputs. Three variants of circuits are presented for implementing the specified structure. The presence of elements in the circuit, the parameters of which can be specified, ensures the flexibility of designing process without any restrictions on values of loading impedances. In addition, the calculation process takes into account the difference of phase velocities of modes of microstrip coupled lines. For checking the properties of the proposed circuit and its designing technique, a microstrip balun for two working bands of frequencies with average values of 1.4 GHz and 2.8 GHz at different complex load impedances was manufactured and experimentally tested. The results of measurements well agree with the results of electromagnetic simulation; they also show that in both bands, the unbalance of amplitudes and phases at the balun outputs does not exceed 1 dB and 10 degrees, respectively, confirming the expediency of using the proposed circuit and its designing method.