Antenna Beam Research Articles

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Context. The Sun is an extraordinary workbench, on which several fundamental astronomical parameters can be measured with high precision. Among these parameters, the solar radius R⊙ plays an important role in several aspects, for instance, in evolutionary models. Moreover, it conveys information about the structure of the different layers that compose the solar interior and its atmosphere. Despite the efforts to obtain accurate measurements of R⊙, the subject is still debated, and measurements are puzzling and/or lacking in many frequency ranges. Aims. We determine the mean, equatorial, and polar radii of the Sun (Rc, Req, and Rpol) in the frequency range 18.1 − 26.1 GHz. We employed single-dish observations from the newly appointed Medicina Gavril Grueff Radio Telescope and the Sardinia Radio Telescope (SRT) in five years, from 2018 to mid-2023, in the framework of the SunDish project for solar monitoring. Methods. Two methods for calculating the radius at radio frequencies were employed and compared: the half-power, and the inflection point. To assess the quality of our radius determinations, we also analysed the possible degrading effects of the antenna beam pattern on our solar maps using two 2D models (ECB and 2GECB). We carried out a correlation analysis with the evolution of the solar cycle by calculating Pearson’s correlation coefficient ρ in the 13-month running means. Results. We obtained several values for the solar radius, ranging between 959 and 994 arcsec, and ρ, with typical errors of a few arcseconds. These values constrain the correlation between the solar radius and solar activity, and they allow us to estimate the level of solar prolatness in the centimeter frequency range. Conclusions. Our R⊙ measurements are consistent with the values reported in the literature, and they provide refined estimates in the centimeter range. The results suggest a weak prolateness of the solar limb (Req > Rpol), although Req and Rpol are statistically compatible within 3σ errors. The correlation analysis using the solar images from the Grueff Radio Telescope shows (1) a positive correlation between solar activity and the temporal variation in Rc (and Req) at all observing frequencies, and (2) a weak anti-correlation between the temporal variation of Rpol and solar activity at 25.8 GHz.

A conical beam antenna array with filter characteristics for multi-rotor unmanned aerial vehicle measurement system

ABSTRACT This paper proposed a novel filter antenna with the conical beam, which consists of four magnetoelectric (ME) dipole antennas. By printing parasitic patches and etching open slots on the bottom of the substrate, two radiation nulls near the high frequency of the passband are introduced. Combined with the intrinsic radiation null of the ME-dipole antenna, the filtering response is obtained. In order to verify the design method, a prototype is manufactured and measured. The measurement results show that the impedance bandwidth (VSWR <2) of the antenna is 1.48 ~ 2.61 GHz (55.3%). In addition, the out-of-band suppression is more than 17.4 dB and the maximum radiation direction of the conical beam is stable around to Theta = 30°. The proposed antenna array can be promising candidates for multi-rotor unmanned aerial vehicle (UAV) measurement systems.

Radar nonlinear multi-target tracking method with parallel PHD filter

Since probability hypothesis density (PHD) filters do not need explicit data association, they have recently been widely used in radar multi-target tracking (MTT). However, in existing PHD filters, sampling times are generally considered the same for all targets. Due to the limitation of antenna beam width in radar applications, the same sampling time for all targets will lead to a mismatch between the predicted data and measurement data, reducing the accuracy of radar MTT. In order to eliminate the estimation error with less computational cost, a radar nonlinear multi-target tracking method with a parallel PHD filter is proposed in this article. The measurement area is divided into several subspaces according to the beam width of the radar antenna, and the PHD of all subspaces is calculated in parallel. Then, multi-feature information in radar echo assists tracking and improves real-time performance. Experimental results in various scenarios illustrate that the proposed method can eliminate the estimation errors introduced by sampling time diversity at the cost of less computation cost, especially in cluttered environments.

Synthesis of Antenna Array Radiation Pattern at Large Scanning Angles Using Genetic Algorithm

At present, in most modern communication systems, for example, in modern satellite terminals, the use of scanning beam antennas, i. e. antenna arrays is assumed. At the same time, at large scanning angles, the side lobe level (SLL) increases strongly and decrease in the gain is observed. In this regard, the problem of finding a procedure for synthesizing an amplitude-phase distribution (APD) with low SLL and high gain (G) at large scanning angles comes up. One of the ways to reduce SLL and compensate for the decrease in G is to synthesize the optimal APD (in terms of the maximum G and minimum SLL) using optimization algorithms. At the same time, taking into account the characteristics of the radiation pattern of the array emitters requires numerical electrodynamic calculation. The goal of this paper is to develop a procedure for the synthesis of APD with low SLL for linear and rectangular antenna arrays at various, including large, scanning angles and compensation for G reduction using a genetic algorithm and numerical electrodynamic calculation. The methods for studying the characteristics of antenna radiators are numerical electrodynamic modeling by the finite element method (FEM) in Ansys HFSS computer-aided design system and optimization of the APD for a given radiation pattern(RP) by a random search method using partial diagrams of antenna elements. The novelty is the combination of accurate numerical electrodynamic calculation of the RP of antenna elements and optimization search for APD for the synthesis of the required RP using partial diagrams. As a result, a procedure for APD synthesis of linear and uniform rectangular equidistant (for example, 8- and 64-element) antenna arrays has been developed, taking into account the exact electrodynamic characteristics of antenna elements and their mutual resistance. Radiation patterns were obtained taking into account the effect of neighboring elements, with the help of which, using a genetic algorithm, APDs on emitters were found at different scanning angles. The change in SLL and G of the antenna array is analyzed at different scanning angles using different APDs. The proposed algorithm allows to synthesize APD for a RP with low SLL and high G at scanning angles up to 40° for linear antenna array and up to 80° in the case of a uniform rectangular antenna array. The results of this work are relevant in the problems of radiation pattern synthesis, since the proposed solution provides a significant gain in the radiation pattern synthesis rate of APD of linear and rectangular antenna arrays, especially for systems with a large number of antenna elements. At the same time, it is possible to maintain a high G at large scanning angles, and achieve a significant reduction of SLL.

Spectral Smoothness of Ground Plane Backed Log-Periodic Dipole Antennas for Radioastronomical Applications

The spectral smoothness properties of the low-frequency array of the square kilometer array (SKA), namely, SKA-Low, are an important issue for its scientific objectives to be attainable. A large array of 256 log-periodic dipole antennas, installed on top of a 42 m circular ground plane, will work as an SKA-Low station in the frequency range of 50–350 MHz. In this article, the ground plane-induced effects are examined in terms of antenna beam spectral characteristics, while different antenna placements are considered. Results are produced both at the isolated antenna and at the array level in the band 50–100 MHz, by employing an approximate method for the speeding-up of array simulations. We attempt to distinguish the ground plane effect from that of mutual coupling among antennas, which appears to be more severe at specific frequencies, using 2 figures of merit. The discrete Fourier transform (DFT) components of gain pattern ratios identify the fundamental spatial components of the ripple, while the envelope correlation coefficient quantifies the penalty to considering an infinite ground plane.

Reinforcement Learning-Based Joint Beamwidth and Beam Alignment Interval Optimization in V2I Communications

The directional antenna combined with beamforming is one of the attractive solutions to accommodate high data rate applications in 5G vehicle communications. However, the directional nature of beamforming requires beam alignment between the transmitter and the receiver, which incurs significant signaling overhead. Hence, we need to find the optimal parameters for directional beamforming, i.e., the antenna beamwidth and beam alignment interval, that maximize the throughput, taking the beam alignment overhead into consideration. In this paper, we propose a reinforcement learning (RL)-based beamforming scheme in a vehicle-to-infrastructure system, where we jointly determine the antenna beamwidth and the beam alignment interval, taking into account the past and future rewards. The simulation results show that the proposed RL-based joint beamforming scheme outperforms conventional beamforming schemes in terms of the average throughput and the average link stability ratio.

A 28‐GHz Vivaldi Array Antenna With Power Divider Structure for Achieving Wide Band and Gain Enhancement

This article presents a planar Vivaldi array antenna based on a power divider structure. A half‐loop defected ground structure (DGS) is performed to decrease the mutual coupling between antennas in the bottom layer of the substrate. The proposed Vivaldi antenna has a 1 × 8 power divided microstrip line structure and performs well in antenna gain and beam directivity. To validate the design, the proposed high‐gain planar Vivaldi array antenna was manufactured, and the measured results were very similar to the simulated one. The size of the proposed antenna is 67 × 44 mm2, the application band is 25–27.3 GHz, and the measured peak gain is 12.6 dBi. The antenna is simulated with an electromagnetic power density (PD) of 28.5 W/m2 at 1 cm2 and 7.27 W/m2 at 4 cm2, which are in compliance with the FCC regulations. Therefore, this antenna is suitable for wearable devices and is applied to n257, n258, and n261.

УСУНЕННЯ ЗАВАД У ДИНАМІЧНИХ СПЕКТРАХ ЗА НАЯВНОСТІ ПОТУЖНОГО СИГНАЛУ ЧАСТИНА 1. ПОТУЖНІ ШИРОКОСМУГОВІ ІМПУЛЬСИ ТА ЛІНІЙНО ЧАСТОТНО-МОДУЛЬОВАНІ ЗАВАДИ

Subject and Purpose. The writers aim at developing and testing a new method of interference mitigation, proceeding from the example of radio emissions from Jupiter. Its effectiveness is compared with the results of other workers, equally relating to the case of a significant overlapping, within the time-frequency window under analysis, of the areas occupied by the useful signal and the interference. Methods and Methodology. The analysis has revealed several fundamental limitations associated with the use of standard statis- tical methods for identifying sources of interference. A new approach is proposed that allows separating useful signals from inter- ference in the time-frequency plane. It is based on the idea of transferring the statistical analysis from the space of signal amplitudes to such of linear patterns which are formed by maximal readings while the spectrograms are being scanned in time, frequency or otherwise. Results. Methods of statistical data processing have been suggested which allow analysis of signals of a variety of power lev- els against the background of interference of comparable intensity. This enables a detailed analysis of the time-frequency patterns demonstrated by signals with a broad range of parameter variations. The algorithms developed demonstrate stability against changes in the interference background conditions that may be caused either by human activity or by natural factors, such as, e.g. ionospheric perturbations, changes in the frontend frequency response of a receiver resulting from a changed antenna beam orientation, or else from Faraday’s polarization plane rotation in the radio emission being received. Conclusions. The necessity of creating new interference mitigation techniques is stipulated both by worsening of the general level of interference at radio frequencies, and by the growth of complexity in the sporadically emerging time-frequency patterns that result from the improved time and frequency resolutions in the course of signal reception. A significant progress has been achieved, owing exclusively to the fundamental modifications of the signal processing algorithms that are based on varying the direction of analysis in the time-frequency plane.

Design and simulation of phased array antenna 5G applications

Modern mobile communication faces challenges due to the limited frequency spectrum, driving the need for antennas that are simple, low-profile, and robust. Microstrip patch antennas and arrays are ideal choices due to their size, cost, and performance advantages. Polarization is crucial, especially in mobile and space communications, where antenna misalignment requires constant reorientation. Rectangular microstrip patch antennas can help mitigate signal loss and multipath effects in such scenarios. Phased array subsystems are becoming essential in next-generation mobile communication for their ability to electronically steer antenna beams without physical movement. Previous methods for rectangular microstrip patch radiation using orthogonal modes with a 90° time-phase difference resulted in poor axial ratio, gain, and return loss. These methods also used complex dual-feed excitation with an external 90° power divider and external phase shifters for beam steering. This paper proposes a simpler approach using a corner trimming technique for radiation and progressive phase excitations at source ports for phased arrays. The design and optimization for 26 GHz operation are achieved using simulation-based modeling software, ANSYS HFSS, on substrates like FR4 epoxy and Rogers RT or Duroid 5880. This paper includes the design and simulation of rectangular microstrip patches and 1x2 and 1x4 linear phased arrays to operate at 26 Ghz.

Simulating the Detection of the Global 21 cm Signal with MIST for Different Models of the Soil and Beam Directivity

The Mapper of the IGM Spin Temperature (MIST) is a new ground-based, single-antenna, radio experiment attempting to detect the global 21 cm signal from the Dark Ages and Cosmic Dawn. A significant challenge in this measurement is the frequency dependence, or chromaticity, of the antenna beam directivity. MIST observes with the antenna above the soil and without a metal ground plane, and the beam directivity is sensitive to the electrical characteristics of the soil. In this paper, we use simulated observations with MIST to study how the detection of the global 21 cm signal from Cosmic Dawn is affected by the soil and the MIST beam directivity. We simulate observations using electromagnetic models of the directivity computed for single- and two-layer models of the soil. We test the recovery of the Cosmic Dawn signal with and without beam chromaticity correction applied to the simulated data. We find that our single-layer soil models enable a straightforward recovery of the signal even without chromaticity correction. Two-layer models increase the beam chromaticity and make the recovery more challenging. However, for the model in which the bottom soil layer has a lower electrical conductivity than the top layer, the signal can be recovered even without chromaticity correction. For the other two-layer models, chromaticity correction is necessary for the recovery of the signal, and the accuracy requirements for the soil parameters vary between models. These results will be used as a guideline to select observation sites that are favorable for the detection of the Cosmic Dawn signal.

DESIGN OF A SWITCHED BEAM ANTENNA SYSTEM USING A 4 &amp;times; 4 BUTLER MATRIX FOR WIRELESS COMMUNICATION APPLICATIONS

Demand for quality service within the cellular network, which has many cells within the cluster, has certain requirements to satisfy the customer or subscriber at any cost. Hence, a reliable approach to provide quality service to the subscriber is needed, and in that attempt, a switched beam system is proposed, which is composed of a Butler matrix operating at 2 GHz for 5G wireless communication systems. The Butler matrix operates at 2 GHz, however, and has an overall bandwidth of 1.2 GHz, ranging from 1.8 GHz to 3 GHz. The beamforming operation is completed by incorporating an antenna array; typically for such applications a linear array with half lambda spacing is preferred. Here, the antenna array is made of a dielectric material, hence forming a dielectric resonator array operating at the same frequency as that of the Butler matrix. To complete the switched beam system, a radiofrequency source is chosen, typically USRP 2900 from National Instruments, to provide excitation to the Butler matrix throughout its operation. The simulation is carried out in Ansys HFSS and PCB Antenna Designer from MathWorks. This article gives the simulation as well as measured results of the Butler matrix and dielectric resonator antenna and draws a conclusion of the performance of the system based on simulated and measured results.

Practical CNN-Based Beam Selection for Wideband Single-Receiver Switched Beam Antenna

Practical CNN-Based Beam Selection for Wideband Single-Receiver Switched Beam Antenna

Designing an active electronically scanned array as part of onboard equipment of a high-speed radio communication channel

The active electronically scanned array being developed is designed to provide an all-weather high-speed radio communication channel “Spacecraft – Earth”. It is supposed to provide fast, inertia-free observation of space by swinging the antenna beam electrically, and, in fact, is a dynamic space-time filter of the spacecraft. The aim of the work is to identify the basic principles of functioning of the array as part of the spacecraft with inherent limitations in the mass-dimensional and energy characteristics of the onboard equipment and, at the same time, high requirements for the functional characteristics. This paper presents the calculation and the main results of designing an active electronically scanned array complying with the requirements for optimizing the parameters of the antenna system. To assess the effect of scanning on the phase characteristics of the chips, a nonlinear amplifier model was developed. A statistical analysis of the phase characteristics was carried out when the load resistance changed in accordance with the obtained distribution laws. When calculating the resulting directional pattern of the antenna array, destabilizing factors were taken into account in accordance with the results of the study of the prototypes of the antenna array being created. Phase errors were calculated, mainly determined by the errors of the terminal parts of the receiving paths. Measures were implemented to ensure the effect of such phase errors on the directional pattern of the array only on the far side lobes.

Comparison of features of phenomena in the high latitude ionospheric F-region induced by powerful HF radio waves radiated by antennas with narrow and wide beam patterns

Physical experiments in natural free plasma (ionosphere) using controlled injection of powerful HF radio waves (HF pump waves) into the high latitude upper (F-region) ionosphere allow the investigation of various nonlinear phenomena. HF pump waves with ordinary (O-mode) polarization are commonly used for the modification of the upper ionosphere (F-region). This is due to the fact that extraordinary (X-mode) polarized HF pump waves are reflected from altitudes significantly below the reflection altitude of the O-polarized HF pump wave and the altitude of electrostatic plasma waves. Because of that they are not able to generate such waves or, as a consequence, cause artificial plasma turbulence and accompanying phenomena. However, the results of experiments carried out by AARI researchers at the EISCAT/Heating facility (Tromsø, Norway) have clearly demonstrated for the first time that X-polarized HF pump waves are able to produce artificial ionosphere disturbances which may be much stronger compared with O-mode disturbances. This opens up new possibilities for the investigation of nonlinear phenomena and ionospheric disturbances in the upper ionosphere, leading to the development of technologies allowing one to observe the processes in the Arctic zone ionosphere. In contrast to the traditional investigations of artificial ionospheric disturbances induced by O-mode HF pump waves, X-mode disturbances in the upper ionosphere are poorly investigated, the mechanisms of their generation are not understood. Therefore, such investigations require serious experimental and theoretical development. We present investigation results of the influence of the HF Phased Array beam width at the EISCAT/Heating facility (Tromsø, Norway) on the features of artificial disturbances in the high latitude upper (F-region) ionosphere induced by powerful HF radio waves. The paper analyzes the features, behavior, and spatial structure of electron density and temperature (Ne and Te), Langmuir and ion-acoustic plasma waves, artificial field-aligned irregularities (AFAIs), and narrowband (±1кHz relative to heating frequency) stimulated electromagnetic emission (NSEE) induced by X-mode HF pumping by phased Arrays with a narrow beam width of 5–6° (A1) and a wide beam width of 10–12° (at — 3 dB level) (A3). It is shown that the spatial size in the north-south direction of the Neducts and HF-enhanced plasma and ion lines (HFPL and HFIL) depends on the width of the HF Heating facility antenna beam. It corresponds to the angle width of 7° for the A3 antenna and 4° for A1, which is approximately two times less than the width of th pattern of A3 and A1. The relationship between the Ne duct transverse size and the size of the region occupied by the X-mode artificial irregularities is found. It has been established that the intensities of all the discrete components in the NSEE spectra are 10–20 dB higher when a powerful X-wave is emitted to the antenna A1, providing ERP = 820 MW, compared to radiation to the antenna A3, providing ERP = 230 MW. A comparison is made of the influence of the radiation pattern width of the antennas A1 and A3 on the characteristics of disturbances during O- and X-mode HF pumping. It is shown that Ne ducts and narrow band stimulated electromagnetic emission during O-mode heating, at frequencies below the critical frequency of the F2 layer, are not excited at all when the pump wave is emitted by both antennas A1 and A3. However, perturbations in the electron temperature, AFAI intensity, and the size of the region occupied by AFAIs are greater during O-mode heating than during X-mode heating.

A Study of Direction-of-Arrival Estimation with an Improved Monopulse Ratio Curve Using Beamforming for an Active Phased Array Antenna System

When constructing a wireless communication network, the line of sight of radio waves is limited by the terrain features in a ground communication network. Also, satellite communication networks face capacity limitations and are vulnerable to jamming. Aviation communication networks can solve the above-mentioned problems. To construct seamless aviation communication networks, fast counterpart location estimation and efficient beam steering performance are essential. Among various techniques used for searching the counterpart’s location, the monopulse technique has the advantage of quickly estimating the location through a simplified procedure. However, the nonlinear characteristics of the monopulse ratio curve, which are inevitably caused by the general antenna beam shape, both limit the location estimation range and reduce the estimated location accuracy. To overcome these limitations, a method that improves the estimation accuracy and extends the range by correcting the sum and difference patterns using the beamforming technique of active phased array antennas was proposed. An antenna system model suitable for aviation communication networks was presented, and the proposed model was experimentally proven to be effective. An average angle error of 0.021° was observed in the estimation of the accuracy of the antenna location.

2–Bit Programmable Metasurface for Low Radar Cross Section Antenna and Beam Steering Applications

AbstractIn this paper, a 2‐bit water‐based programmable digital metasurface for beam steering and backscatter field reduction applications is presented, a reflective and transmissive type water based programmable metasurface (WPMS) for RCS reduction and the antenna's beam steering is suggested, respectively. It has been demonstrated that a 2‐bit water‐based programmable unit cell can reduce RCS by changing its state (0/1). If the unit cell channel is empty, the state is “0,” if the channel is filled, the state is “1.” So at different resonance frequencies, the four phase and reflection coefficient responses are achieved as "00"01"10"11". This functionality enables beam steering in both the elevation and azimuth axis and also backscattering reduction of the antenna. Furthermore, the impacts of the number of unit cells and reflection phase states on the far‐field pattern are examined. Beam steering of ±45° in the elevation is attained with 10‐dB impedance bandwidth of 4.25–4.40 GHz, radiation gain of more than 7.1 dBi is maintained. With the present antenna, it is possible to achieve volumetric beamsteering performance directly. The patterns of far‐field radiation that are predicted theoretically coincide well with full waves simulations. As such, the proposed prototype can be a good option for applications that require a low RCS platform including beam steering in radars, 5G/6G, etc.

A fast simulation method of ground clutter for airborne wideband radar based on measured SAR image

Ground clutter simulation is a key factor in the design and development of air-to-ground wideband radar. In this paper, the ground clutter simulation technology of stepped frequency airborne wideband radar is studied, and a fast simulation method of ground clutter based on SAR image is proposed. Firstly, the segmented area of high-resolution SAR image according to the radar illumination region is used as the input of the ground scattering coefficient to improve the fidelity of clutter simulation. Then, the antenna pattern is constructed by the uniform plane phased array, by which the power gain of the clutter point is modulated. Thirdly, the clutter echo of stepped-frequency radar is calculated according to the equidistant circle principle which improves the efficiency of computation. Finally, the proposed method is verified via computer simulation. The results show that the method can simulate ground clutter of radial space-variation effect induced by narrow antenna beam, verifying the effectiveness of the method. This method is applicable to various scenarios.

Low-frequency Radio Recombination Lines Away from the Inner Galactic Plane

Diffuse radio recombination lines (RRLs) in the Galaxy are possible foregrounds for redshifted 21 cm experiments. We use EDGES drift scans centered at −26.°7 decl. to characterize diffuse RRLs across the southern sky. We find that RRLs averaged over the large antenna beam (72° × 110°) reach minimum amplitudes of R.A. = 2–6 hr. In this region, the Cα absorption amplitude is 33 ± 11 mK (1σ) averaged over 50–87 MHz (27 ≳ z ≳ 15 for the 21 cm line) and increases strongly as frequency decreases. Cβ and Hα lines are consistent with no detection with amplitudes of 13 ± 14 and 12 ± 10 mK (1σ), respectively. At 108–124.5 MHz (z ≈ 11) in the same region, we find no evidence for carbon or hydrogen lines at the noise level of 3.4 mK (1σ). Conservatively assuming that observed lines come broadly from the diffuse interstellar medium, as opposed to a few compact regions, these amplitudes provide upper limits on the intrinsic diffuse lines. The observations support expectations that Galactic RRLs can be neglected as significant foregrounds for a large region of sky until redshifted 21 cm experiments, particularly those targeting cosmic dawn, move beyond the detection phase. We fit models of the spectral dependence of the lines averaged over the large beam of EDGES, which may contain multiple line sources with possible line blending, and find that including degrees of freedom for expected smooth, frequency-dependent deviations from local thermodynamic equilibrium (LTE) is preferred over simple LTE assumptions for Cα and Hα lines. For Cα we estimate departure coefficients 0.79 < b n β n < 4.5 along the inner Galactic plane and 0 < b n β n < 2.3 away from the inner Galactic plane.

Detecting Cosmic 21 cm global signal using an improved polynomial fitting algorithm

ABSTRACT Detecting the cosmic 21 cm signal from epoch of reionization has always been a difficult task. Although the Galactic foreground can be regarded as a smooth power-law spectrum, due to the chromaticity of the antenna, additional structure will be introduced into the global spectrum, making the polynomial fitting algorithm perform poorly. In this paper, we introduce an improved polynomial fitting algorithm – the Vari-Zeroth-Order Polynomial (VZOP) fitting and use it to fit the simulation data. This algorithm is developed for the upcoming low-frequency anechoic chamber experiment, yet it is a general method suitable for application in any single antenna-based global 21 cm signal experiment. VZOP defines a 24-h averaged beam model that brings information about the antenna beam into the polynomial model. Assuming that the beam can be measured, VZOP can successfully recover the 21 cm absorption feature, even if the beam is extremely frequency-dependent. In real observations, due to various systematics, the corrected measured beam contains residual errors that are not completely random. Assuming the errors are frequency-dependent, VZOP is capable of recovering the 21 cm absorption feature even when the error reaches 10 per cent. Even in the most extreme scenario where the errors are completely random, VZOP can at least give a fitting result that is not worse than the common polynomial fitting. In conclusion, the fitting effect of VZOP depends on the structure of the error and the accuracy of the beam measurement.

Modification of Simple Antenna Pattern Models for Inter-Beam Interference Assessment in Massive Multiple-Input-Multiple-Output Systems.

The occurrence of cross-beam interference in the received signal is one of the main problems that limit the possibilities of massive multiple-input-multiple-output technology (massive-MIMO) in fifth-generation (5G) systems. Thus, the evaluation of the level of this interference is one of the most important procedures in the spatial planning of currently wireless networks. We propose a novel modification of simple antenna pattern models, which is based only on changing the directivity of real antenna system patterns. This approach is independent of the antenna system's type, structure, and analytical description. Based on the developed modification, the original methodology for assessing the signal-to-interference ratio (SIR) from adjacent beams of a common antenna system is presented. The change in the radiation direction and the accompanying change in the complex shape and parameters of the real antenna beam pattern is one of the problems that significantly hinders the evaluation of the analyzed interference. Hence, in the presented methodology, we propose using our modification. In this case, the modification is reduced to a proportional change in the directivity concerning the real antenna system, which results from a change in the beam direction. The simulation studies used a multi-ellipsoidal propagation model and a real massive MIMO antenna pattern description from 3GPP. For the SIR error analysis, the 3GPP pattern is used as a reference. The simulation results show that modifying simple antenna pattern models allows us to obtain an SIR error of no more than 3 dB and 0.1 dB under line-of-sight (LOS) and non-LOS conditions, respectively.