Antenna Pattern Research Articles

Fine‐grained multi‐path channel estimation and matched reception by single metasurface antenna

AbstractThis paper investigates methods to enhance antenna's channel information extraction capabilities in wireless communications, particularly in challenging multi‐path environments. Focusing on the issues of channel information loss due to multi‐path superposition at the receiver and multi‐path fading during wireless channel propagation, this paper utilizes metasurface antennas to rapidly reconfigure antenna patterns and construct high‐dimensional projection spaces, thus improving information sensing resolution. Based on this, a channel‐matched receiving pattern design method is proposed to mitigate the communication performance loss caused by multi‐path fading. Furthermore, this paper analyses the comprehensive impact of various metasurface parameters on the performance of the proposed scheme, providing theoretical guidance for engineering implementation. Simulation results demonstrate that the proposed scheme can achieve the performance of multi‐path channel estimation and reception close to those of multi‐antenna arrays using a single radio frequency link.

Impact of Out-of-the-Swath Knowledge on the Antenna Pattern Correction Performance Applied to Conical Scanning Spaceborne Radiometers

Impact of Out-of-the-Swath Knowledge on the Antenna Pattern Correction Performance Applied to Conical Scanning Spaceborne Radiometers

Design of Low-Cost RF Detector for Electric Field Determination in Antenna Radiation Pattern Measurement

Antenna pattern measurement is a requirement for antenna characteristics determination. However, such sophisticated set-up measurement demands skilled authority. This project employed a low-cost RF detector (MAX4003) to capture the E-field and consequently assist in acquiring data for antenna radiation pattern. By fabricating a 3.0V circuit with MAX4003 and connecting to an Arduino, this compact module creates a basic interface between the antenna under test and user’s measurement PC. The results show the measured voltage from the RF detector is in good agreement with the manufacturer’s datasheet for 1.8GHz and 2.1GHz operating frequencies. The input power is also directly proportional to the output power. The project was further tested by conducting a full 360° antenna radiation pattern measurement. The results established a satisfying comparison to theoretical radiation pattern. Overall, the system benefits to individual such as students and researchers to replicate the same method in order to have a compact and attainable antenna measurement system.

Evaluation of a double-lens dielectric radome using a microstrip patch antenna for electromagnetic applications

The advancement of increasingly powerful antennas has increased the complexity of radome electromagnetic (EM) design and analysis. The antenna systems are protected from environmental influences by radomes, which are dielectric and electromagnetically transparent structures. Because the presence of the radome affects the performance parameters of the antenna, such as the radiation pattern, reflected power, and side lobe level, its design should not be done independently of the antenna analysis. The great majority of ground-based hemispherical radomes are used for satellite communication antennas, commercial and military radars, telemetry systems, and other uses. Patch antennas, reflector antennas, phased array radars, and other antenna systems are used in these applications. The operational effectiveness of a radome architecture for housing multiple patch antenna systems is proposed and evaluated. The proposed line of work includes antenna-radome interaction analyses, electromagnetic designs for radome walls, and radiation patterns for reflector antennas. COMSOL Multiphysics was used to develop the EM radome and examine the antenna-radome interaction. The findings of a comprehensive analysis into the differences in radiation patterns produced by patch antennas with and without radomes are presented in this article. At a frequency of 1.62 GHz, a plot and investigation of the far-field gain of the microstrip patch antenna with and without radome were done. The radome is estimated to add 0.09 dBi to the gain boost experienced by the microstrip patch antenna.Abbreviations: EM, Electromagnetic; DSF, Dielectric space frame radome; IFR, Induced field ratio; RF, Radio frequency; VSWR, Voltage standing wave ratio; FEM, Finite element method; SRR, Split ring resonator; CATR, Compact antenna test range; DUT, Device being tested; LHM, Left-handed metamaterials; PML, Perfectly matched layer; PTFE, Polytetrafluoroethylene.

Antenna pattern reconstruction for mid-band massive antenna array based on a single-cut field transformation algorithm in a compact multi-probe anechoic chamber setup

ABSTRACT It has become a common challenge on how to measure radiation patterns of massive antenna arrays working at high frequency with high efficiency and accuracy, which has attracted huge interest from both academia and industry. In this paper, a highly accurate and efficient far field (FF) pattern reconstruction strategy through conducting single cut near field (NF) to FF transformation algorithm based on spherical wave expansion (SWE) is proposed for fast measurements of large base stations (BSs) operating at mid-band. Our objective is to design a compact multi-probe setup to measure key radiation parameters of the massive array, with low-cost and high-efficiency. A BS of 16 × 16 elements operating at mid-band is adopted as the device under test (DUT) in this paper. Analysis is conducted on the impact of measurement distance, sampling range and sampling density on the reconstruction accuracy of the algorithm in the compact multi-probe anechoic chamber setup, demonstrating that the required key information of the main lobe of the DUT can be accurately reconstructed when the measurement range R = 1/20 FF distance, sampling resolution ∆θ = 3°, and sampling range θ ∈ [75°, 105°] are selected, respectively. The impact of phase center offset on the accuracy of FF pattern reconstruction is analyzed when only one sub-array is enabled, demonstrating the effectiveness of the algorithm for sub-array measurements.

Potential characteristics of direction finder with interference compensator and a direction finder with an adaptive antenna array with limitations in the event of interference in the main lobe of the antenna pattern

The displacement of the bearing estimate in a direction finder with an adaptive noise compensator, its sensitivity and the sensitivity of a direction finder with an adaptive antenna array with restrictions have been studied depending on the antenna radiation pattern, the angular position of the signal and local interference, the correlation of distributed noise and spectral densities of signal power, noise and interference. A comparative analysis of the accuracy and sensitivity of these direction finders in the event of interference in the main lobe of the antenna pattern was carried out for a linear equidistant antenna array.

Помехи неоднозначности сигналов космических РСА при использовании круглой зеркальной антенны

Reflector antennas are quite widely used in radar devices, including space-borne synthetic aperture radars (SARs). One of the problems of such SARs is to ensure the unambiguous measurement of the Doppler frequency of received signals. The shape of the Doppler spectrum of the echo signal is determined by the shape of the antenna pattern in the azimuthal plane. Thus, in general, the narrower the pattern (the larger the antenna size), the lower the level of the interference signal received at the side peaks of the ambiguity function. However, a significant increase in the antenna size is limited by the difficulties of its placement on the SAR launcher, which is especially important for small spacecraft. On the other hand, the required beam width in the elevation plane must satisfy two conditions: ensuring swath and ambiguity detuning. The time ambiguity interval is equal to half the distance of radio wave propagation during the pulse repetition interval. A technical contradiction arises between reducing the level of azimuthal and elevation ambiguity of SAR. The purpose of the article is estimation of azimuth and range ambiguities in a space-based SAR using a circular reflector antenna. In this regard, the material in the article is relevant. We consider a normal looking view which is performed using X-band space-borne SAR. The reasons for the emergence of ambiguities are considered. The necessary mathematical calculations are presented and calculations are made of the projection of circular antenna pattern and the achievable levels of azimuth and range ambiguity for space-based SARs. The obtained values were compared with similar data for a rectangular antenna. An analysis of the influence of the viewing angle and pulse repetition frequency on the ambiguity level was carried out. The results obtained make it possible to estimate the range and azimuth ambiguity level in space-borne SAR and present requirements for the need and level of additional suppression.

Dynamics of Some Perturbed Morse-Type Oscillators: Simulations and Applications

The purpose of this paper is to investigate some Morse-type oscillators. In its original form, it is a model for describing the vibrations of a diatomic molecule. The Morse potential generalizes the harmonic oscillator by introducing deviations from the classical theoretical model. In the present study, we perturbed the Morse differential equation by several periodic terms based on the cosine function and by a damping term. The frequency is driven by different coefficients. The size of the deviations is controlled by another constant. We provide two modifications w.r.t. the damping term. The Melnikov approach is applied as an indicator of the possible chaotic opportunities. We also propose a novel approach for stochastic control of the perturbations. It is based on the assumption that the coefficients of the periodic terms are the probabilities of underlying distribution. As a result, the dynamics are driven by its characteristic function. Several applications are considered. We demonstrate some specialized modules for investigating the dynamics of the proposed models, along with the synthesis of radiating antenna patterns.

Decoupled Dipole Arrays Empowered by Invisible Complex Poles in Epsilon‐Near‐Zero Metamaterials

AbstractEvanescent waves, characterized by an exponential decay in propagation, have witnessed significant advancements in far‐field imaging and near‐field sensing applications. However, incoming evanescent waves can excite guided resonance inside a dielectric slab, resulting in a rapid growth of transmission coefficient toward infinity at the pole points. Such evanescent‐wave excited resonance benefits super‐resolution applications yet causes severe crosstalk in highly integrated multi‐channel devices. Here, the invisible complex poles are discovered in the transmission spectra of epsilon‐near‐zero (ENZ) metamaterials and demonstrate the striking suppression of near‐field crosstalk enabled by the anomalous transmission beyond the critical angle. Equipped with an ENZ metamaterial spacer, collinear dipole arrays exhibit 9.2 dB improvement in near‐field isolation among interior dipoles at a distance of less than one wavelength. Experimental measurements show negligible influence on the intrinsic impedance matching and radiation patterns of the dipole antennas. The discovered field divergence effect from the disappearance of real‐valued pole singularity in ENZ metamaterials offers an alternative solution for highly compact arrays in full duplex communication and multiple‐input multiple‐output technology.

Direction-dependent Effects on Global 21 cm Detection

Cosmic dawn represents a critical juncture in cosmic history when the first population of stars emerged. The astrophysical processes that govern this transformation need to be better understood. The detection of redshifted 21 cm radiation emitted from neutral hydrogen during this era offers a direct window into the thermal and ionization state of the Universe. This emission manifests as differential brightness between spin temperature and the cosmic microwave background. The SARAS experiment aims to detect the sky-averaged signal in the frequency range 40–200 MHz. SARAS’s unique design and operational strategy to float the antenna over a water body minimizes spectral features that may arise due to stratified ground beneath the antenna. However, the antenna environment can be prone to configuration changes due to variations in critical design parameters such as conductivity and antenna tilt. In this paper, we connect the variations in antenna properties to signal detection prospects. By using realistic simulations of a direction- and frequency-dependent radiation pattern of the SARAS antenna and its transfer function, we establish critical parameters and estimate bias in the detectability of different models of the global 21 cm signal. We find a correlation between the nature of chromaticity in antenna properties and the bias in the recovered spectral profiles of 21 cm signals. We also find stringent requirements for transfer function corrections, which can otherwise make detection prospects prohibitive. We finally explore a range of critical parameters that allow robust signal detection.

Observation at radio frequencies of the hydroxyl (OH) absorption line in filaments and prominences above active regions of the Sun

When observing the Sun with RATAN-600 radio telescope using a spectropolarimetric complex in the range 1–3 GHz, as well as when observing coronal rain, absorption in the radio emission was discovered in the spectral region 1.5–1.65 GHz in active solar regions located under a cold filament or on the limb under a prominence. The observed line structure corresponds to the hyperfine splitting frequencies in the ground state of X2Π3/2 hydroxyl (OH) 1612–1720 MHz. When the observed active region passes through the knife-shaped beam pattern of the telescope antenna, the absorption band shifts in frequency due to a shift in the energy levels of the OH molecule in a magnetic field, which changes along the filament.

Наблюдение в радиодиапазоне линии поглощения гидроксила (ОН) в волокнах и протуберанцах над активными областями Солнца

When observing the Sun with RATAN-600 radio telescope using a spectropolarimetric complex in the range 1–3 GHz, as well as when observing coronal rain, absorption in the radio emission was discovered in the spectral region 1.5–1.65 GHz in active solar regions located under a cold filament or on the limb under a prominence. The observed line structure corresponds to the hyperfine splitting frequencies in the ground state of X2Π3/2 hydroxyl (OH) 1612–1720 MHz. When the observed active region passes through the knife-shaped beam pattern of the telescope antenna, the absorption band shifts in frequency due to a shift in the energy levels of the OH molecule in a magnetic field, which changes along the filament.

An efficient multi‐probe enabled midfield over‐the‐air test method for 5G base station antenna pattern reconstruction

AbstractWith the accelerated deployment of 5G massive multi‐input multi‐output (MIMO)‐structured base stations (BSs), accurate and efficient testing of massive MIMO arrays is essential to ensure that the 5G massive MIMO antenna array can perform as expected. The increasing trend of both antenna element and array physical size makes massive MIMO antenna pattern measurement in the direct‐far‐field OTA environment unrealistic due to the signal attenuation, long measurement time, and ultra‐high test system construction cost. Therefore, the necessity of a compact, efficient, low‐complex, yet accurate OTA test method is evident, especially for 5G massive MIMO BS arrays. This paper proposes a novel multi‐probe‐enabled midfield (MF) OTA test method for 5G massive MIMO devices in compact measurement settings where antenna pattern measurement can be efficiently performed. The detailed theoretical analysis for the 5G massive MIMO array MF antenna pattern reconstruction method is presented, and the simulated validation results based on the typical 5G BS antenna arrays are provided and analysed, which demonstrate the effectiveness of the proposed MF OTA test method and can provide insights into the radio frequency parametric measurement for 5G massive MIMO devices.

Radiation Behavior of Synthesized LiTi Ferrite Based Microstrip Antenna in X Band

The paper comprehensively explores the development, characteristics, and antenna applications of lithium titanium (LiTi) ferrite. Utilising a solid-state reaction technique, the study examines the substrate’s electrical, magnetic, and structural properties in detail. Additionally, it assesses the far-field radiation patterns of a magnetically-biased LiTi ferrite-based antenna. Key findings point to a noticeable reduction in mutual coupling and radiated power, along with an isotropic redistribution of minor side lobes. Comparative analysis with RT-duroid substrates in X band frequency spectrum highlights the LiTi ferrite-based antenna’s remarkable 62.85 % miniaturization and consistent directivity, along with a superior quality factor. These findings emphasise LiTi ferrite’s potential for compact, high-performance applications in demanding environments. LiTi ferrite’s advantages in miniaturisation and stability position it for specific applications, despite trade-offs in bandwidth, gain, and impedance compared to RT-duroid substrates.

Transparent antenna with RCS tunability based on graphene and metasurface in S band

In this paper, we propose a graphene-based radar cross section (RCS) tunable antenna that utilizes metal mesh and graphene, both of which are optically transparent. The graphene sandwich structure is introduced to replace traditional components like diodes, micro-electro-mechanical systems (MEMS), and varactors, acting as an electromagnetic wave controller and significantly simplifying the device's complexity. By applying different voltages, the electrical properties of graphene are altered, enabling the regulation of reflection, transmission, and absorption of electromagnetic waves. This not only modifies the antenna's pattern but also achieves a substantial reduction in out-of-band RCS. The radiation and scattering mechanism of the antenna is carefully elaborated. The numerical and experimental results match well, which validates the effectiveness of the proposed method. The optical transmittance of the device is 27.9% at 550 nm, and the out-of-band RCS reduction is 10.01 dB at 3.83 GHz. The transparent, RCS tunable antenna proposed has significant potential applications in optical and microwave stealth technology.

Design of Controlled Radiation Pattern Antenna Using Bent Monopole Antenna Array for Anti-Jamming Application

Design of Controlled Radiation Pattern Antenna Using Bent Monopole Antenna Array for Anti-Jamming Application

Defeating angle tracking: A comprehensive analysis of scan rate modulation jamming against sequential lobing radars

AbstractThe authors analyse the sequential lobing radar (SLR) resistance against the scan rate modulation (SRM) jamming technique. Unlike previous studies, the authors analyse SLRs with sinc antenna patterns, enabling investigation of the sidelobe region's vulnerability. By incorporating second‐order angular tracking loops (SOATLs), the first analysis of break‐lock probability for SLRs under SRM jamming is introduced. The analysis reveals the influence of SOATL parameters (damping ratio and natural frequency) on both angular root‐mean‐square‐error at low jamming‐to‐signal‐ratio (JSR) region and break‐lock probability at high JSR region. Additionally, the impact of squint angle on SLR resistance to SRM jamming is examined. Furthermore, the optimal duty cycle as a function of JSR, which maximises break‐lock probability is presented. Significantly, the theoretical results support the 20 dB JSR requirement for SRM effectiveness, often cited experimentally in literature, and extend the theoretical analysis of the SRM technique carried out for the main lobe region of SLRs. This finding bridges the gap between theoretical analysis and practical observations.

A new synthetic correlation electron cyclotron emission diagnostic for validating nonlinear gyrokinetic simulations of electron temperature turbulence.

To validate nonlinear gyrokinetic simulations of electron temperature turbulence, the experimental correlation electron cyclotron emission (CECE) measurements are to be compared using a synthetic CECE diagnostic, which generates modeled CECE measurement quantities by implementing realistic measurement parameters (e.g., spatial and wavenumber resolutions, radial location, etc.) to nonlinear gyrokinetic simulations. In this work, we calculate the radial and vertical spatial and wavenumber transfer functions, which are defined by the electron cyclotron emission emissivity radial profile and vertical probing antenna pattern, respectively. These transfer functions are applied to nonlinear gyrokinetic simulations of electron temperature turbulence using the continuum gyrokinetic code. A simultaneous comparison of the experimental electron temperature turbulence power spectrum and root-mean-square (RMS) level, as well as the radial correlation length with the new synthetic CECE diagnostic at a core location ρ ∼ 0.75 in an L-mode DIII-D tokamak plasma, is presented. The preliminary result shows that the synthetic CECE output underestimates the RMS level by ∼42% and overestimates the radial correlation length by ∼40%.

Extension of the BDS IGSO and MEO satellite antenna patterns with FengYun-3C and LuTan-1 onboard data

The International Global Navigation Satellite System (GNSS) Service (IGS) has recommended calibrating the extended satellite antenna Phase Center Variation (PCV) model for all navigation satellites to support low-Earth-Orbit (LEO) satellite applications. Owing to the absence of ground-calibrated PCVs for the BeiDou Navigation Satellite System (BDS), tracking data from global ground stations were used for in-orbit estimations. However, limited by the observed maximum nadir angle, PCVs based on ground data cannot cover the entire range of nadir angles observed using by LEO satellites. In this study, the FengYun-3C and LuTan-1 missions were used to extend the PCVs of the BDS Inclined GeoSynchronous orbit (IGSO) and medium-Earth-orbit (MEO) satellites. The PCVs corresponding to the ionosphere-free linear combinations of B1I/B2I, B1I/B3I, and B1C/B2a were calibrated in-orbit by extending the maximum nadir angle from 9° to 10° for the IGSO and from 13° to 15° for the MEO. There was good consistency among the estimated PCVs of satellites of the same type. In addition, these estimated PCVs were close to the corresponding satellite block-specific values estimated based on ground tracking data. The impact of the extended PCVs of the BDS satellite antenna was investigated by comparing them with the unextended PCVs model in the receiver antenna PCVs pattern estimation and precise orbit determination of the FengYun-3C and LuTan-1 satellites. The results showed that the extended BDS satellite PCVs effectively reduced the unmodeled error of the unextended BDS satellite PCVs in the low-elevation region of the LEO receiver antenna PCV patterns. In addition, compared with the introduction of phase center offset alone, the introduction of ground-based PCVs can improve the overlapping orbit differences (OODs) of LEO satellites, and the extended BDS satellite PCVs can further improve the OODs. Taking B1C/B2a as an example, the improvement ratio of OODs in the 3D direction of Lutan-1A increased from 5.2 % to 8.0 %, and that of Lutan-1B can rise from 1.7 % to 4.2 %.

Antenna Array Diagnosis in the Presence of Unknown Mutual Coupling using Optimization Technique

Antenna array diagnosis is an important operation in communication systems, whenever element (s) failure in the array that worsening the projected radiation pattern occur. There are various diagnostic techniques found in literature that employ compressive sensing. Conversely, the techniques are based on easy formulation of array factor with no incorporation of mutual coupling existing between the radiators. This article shows how this deficiency lead to defective and bad diagnosis when there is presence of mutual coupling using port-level coupling matrix and average embedded antenna pattern. Furthermore, the element excitations are optimized to reduce the effect of mutual coherence of system measurement matrix, causing reduced measurements required for effective fault detection. Numerical simulation and experimental results demonstrate how the incorporation of mutual coupling generates an adequate and reliable array diagnosis, which are not found in literature. For instance, when fault number is set at 5, and SNR equals 10 dB, the smallest measurements needed for the diagnosis, which is the most effective diagnosis, are achieved when the optimized excitations are used. In conclusion, the implementation of the developed framework using measurement probe in space, shows enough results towards the practical deployment for antenna systems in wireless communication system.