Antenna Coupling Research Articles

Design of 5G MIMO 2x2 Broadband Antenna At 26 GHz Frequency Using Double U-Slot Method and Defected Ground Structure

The 5G technology is a telecommunications innovation that offers incredibly high-speed data transfer. It is expected to outperform its predecessors significantly. In utilizing 5G services, efficient devices are crucial, and solutions like Multiple Input Multiple Output (MIMO) systems play a key role. MIMO is an antenna system with numerous transmitting and receiving elements, enabling simultaneous transmission and reception. A 26 GHz frequency microstrip antenna is modified using a double U-slot, and the Defected Ground Structure (DGS) method is employed to reduce antenna coupling effects and enhance bandwidth. This antenna features a directional radiation pattern that focuses in a specific direction, thereby increasing efficiency. Prior to optimization, the return loss was at around -14.15 dB, VSWR was approximately 1.49 dB, and bandwidth was 0.65 GHz. After optimization, the return loss improved to between -27.06 and -28.09 dB, signifying performance enhancement. Despite a slight increase in VSWR to 1.08 to 1.09 dB, it remains within acceptable limits. The bandwidth increased to 1.06 to 1.13 GHz. These results indicate that optimization successfully boosted antenna performance, resulting in higher data transfer efficiency. This technology has the potential to revolutionize the telecommunications landscape with faster and more reliable services through advanced 5G networks.

Research on the Coupling Effect of HIRF on UAV

The electromagnetic environment of low-altitude airspace has become extremely complex due to the rapid advancement of radio technology. In particular, the electromagnetic energy of HIRF (High Intensity Radiation Field) that is frequently emitted by radar, radio stations, radios, and various ships/airborne impacts negatively aircraft flight safety. In this paper, based on the modeling of a consumer UAV, the HIRF effect is simulated using UWB-HPM, and the electric field variation law at key position and antenna coupling law of the UAV under plane wave irradiation in different directions are analyzed with the help of CST simulation software. The results show that for front-door coupling, the shorter the pulse width of the interference signal is, the stronger the interference for the antenna is, while for back-door coupling, irritation direction and pulse width play a significant role in the coupling effect.

A compact radio-frequency ion source for high brightness and low energy spread negative oxygen ion beam production.

A high brightness and low energy spread (∆E) ion source is essential to the production of a high-quality primary ion beam applied in secondary ion mass spectrometry (SIMS). A compact 13.56MHz radio-frequency (RF) ion source with an external planar spiral antenna has been developed as a candidate ion source for the production of negative oxygen ion beams for SIMS application. This ion source is designed with a three-and-a-half-turn water-cooled planar antenna for RF power coupling, a multi-cusp magnetic field for effective plasma confinement, and a three-electrode extraction system. The experimental results show that more than 50 µA negative oxygen ion beams have been extracted, which consist of 56% O-, 25% O2-, and 19% O3-. The ion energy distribution of the negative oxygen ion beam exhibits a Gaussian distribution with a minimum ∆E of 6.3eV. The brightness of the O- beam is estimated to be 82.4Am-2 Sr-1V-1. The simulation, design, and experimental study results of this RF ion source will be presented in this paper.

High‐accuracy DOA estimation via parallel sparse nested array with extended aperture and reduced mutual coupling

AbstractThis letter proposes a novel parallel sparse nested array and then provides a matrix reconstruction‐based method with three steps, to enhance the performance of direction of arrival (DOA) estimation in practice. The spacings between the closest antennas along x‐ and y‐axes, are coprime and much greater than half‐wavelength in the proposed array, which contributes to efficiently eliminate the mutual coupling and achieve larger aperture with limited physical antennas. By using the oblique projection operator with iteration, the proposed method can employ all items of covariance matrix of the received data to construct a virtual covariance matrix with increased degrees of freedom, for effectively improving angle estimation performance. Then the unique and high‐accuracy DOA estimation is obtained via the coprime‐ness. The simulation results show the superiority of the proposed array and method for DOA estimation in the presence of mutual coupling and limited antennas.

Utilizing of 500 MHz Ground Penetrating Radar Antenna Coupling at Different Interval Heights Clearance

Understanding the characteristics of the GPR antenna for underground utility detection purposes is critical to ensuring that buried pipes and cables can be accurately located. Considering the ground coupling antenna is the most effective way to carry out the GPR scan, most of the operators applied this setup to ensure the maximum amount of the electromagnetic wave could be penetrated into the ground. However, the contact between the GPR and the ground surface causes the bottom of the antenna enclosure to become scratched and worn out. Due to the cost and time involved in transportation to replace the antenna protector, a few GPR operators changed the protector to the cheapest one, which affects the characteristics of the antenna and could alter the depth of the underground utilities. A 500 MHz GPR antenna are tested to identify the optimum antenna coupling based on the accuracy assessment at various interval clearance heights in order to reduce damage and preserve the antenna. An experiment was carried out at Department of Survey and Mapping Malaysia (JUPEM) Kuala Lumpur’s Underground Utility Test Base. Based on the result of the signal strength, the higher the antenna is lifted, the higher the rate of the signal becomes weak or lost. For the depth accuracy test, the high differences in depth when the antenna is lifted up at 4cm to 6cm based on the result of comparison with the standard values provided by the JUPEM. On the other hand, the accuracy of each antenna height is compared and validated based on the Residual Mean Square Error (RMSE). Overall, this study could lead to the conclusion that the result of the assessment is within the acceptable RMSE tolerance, which is below 0.1m. The objective of the research is successfully achieved when the antenna at a 3cm to 6cm interval height setup provides the best clearance based on the criteria of signal strength, depth comparison, and accuracy assessment. Finally, the issue of contact between the antenna and the ground surface, which causes the antenna to become scratched and worn out, could be reduced and preserved as a result of the findings.

Velocity analysis of a lateral wave

In practice, the reflected EM signal cannot be clearly observed in GPR data due to the high water content and other reasons. However, the antenna coupling signal through the ground interface is dominated in all the GPR measurements. This direct coupling signal that travels through the ground interface is called a lateral wave. The properties of the lateral wave directly depend on the subsurface properties, especially electrical parameters. We have numerically analyzed a lateral wave and its velocity. Subsequently, the relationship between lateral wave and dielectric permittivity was determined by polynomial regression. Analytically, it is challenging to analyze a lateral wave due to the parameters that can influence wave propagation. Antenna characteristics, surface roughness, etc need to be considered. Numerically, we designed a GPR system with a subsurface layer and observed a lateral wave. This numerical analysis can give a chance to use a lateral wave for near-surface soil water content. This analysis gives a more precise estimation of surface water content. Moreover, we analyze the antenna height effect that influences radar signals. We numerically observed that the GPR signal is highly affected by antenna height. The antenna height effect depended on the wavelength of the applied electromagnetic wave. By adjusting the antenna height, the unobservable GPR signal can be clearly detected.

Direction of arrival estimation for BLE: Antenna array design and evaluation

The use of smart antenna arrays in wireless communication systems is becoming increasingly popular, as they improve the performance of the radio link and allow the integration of communication and sensing functions. In this paper, we present the design and performance evaluation of a uniform circular antenna array (UCAA) with 12 monopole antennas and RF switches to select the active antenna for the signal direction of arrival (DoA) estimation. The antenna configuration was optimized through simulations for a different number of antennas and antenna array radius. The frequency tuning of the antennas considered the coupling of the active antenna with adjacent antennas. The performance of the antenna array was evaluated by (1) simulations that examined the proximity of the antenna to the edge of the antenna array and the influence of adjacent antennas on the performance of the active antenna, and (2) measurements in outdoor and indoor environments. The results of the simulations show that antenna coupling can cause nulls in the radiation pattern, which affects the DoA estimation by reducing the signal-to-noise ratio. In a semi-controlled environment, we achieved a DoA estimation error of less than 1 degree by using the Bluetooth Low Energy (BLE) Angle of Arrival feature.

Mutual Coupling Reduction of a Dual-Band Four-Port Patch Antenna With Co-Polarized Radiation Pattern by Controlling Electric Fields

In this paper, a novel design approach to decrease the mutual coupling (MC) of a single dual-band four-port microstrip patch antenna (MPA) with a co-polarized radiation pattern is proposed via characteristic mode analysis. Initially, the traditional MPA under mode 1 to mode 4 is theoretically studied. This proves that the four modes maintain a high MC of approximately -2 dB. To address this issue, shorting pins 1 and pins 2 are inserted below the radiator, leading to a more than 12 dB MC reduction between the two ports along the x-axis. After that, the MC between the two ports along the y-axis is deeply studied. This proves that the electric field nulls of the MPA could be moved near unexcited ports and reduce the MC by combining mode 1 with mode 2 (or mode 3 with mode 4). Hence, shorting pins 3 are loaded for mode combination and low MC. In addition, shorting pins 4 are loaded to reshape the radiated fields in the upper band. Moreover, the impedance matching and bandwidth are improved by cutting the ring slots. Finally, a four-port MPA is fabricated and tested. The results show that it has satisfactorily gained a low MC of below -15 dB between the four ports in dual bands. Meanwhile, it holds low-profile, single-layer, single-element, and co-polarized radiation pattern properties.

A new hybrid method for mutual coupling minimization of an antenna array

<span lang="EN-US">In this paper, a simultaneous application of geometric modification on patch elements and electromagnetic band gap (EBG) electromagnetic bandgap structures (hybrid method) has been suggested for 3.5 GHz wireless communication applications, to minimize the mutual coupling between radiating elements of microstrip array antennas. The suggested EBG slotted structure is composed of a one square ring and three squares placed on Rogers RO3010 having 10.2 and h=1.27 mm which presents respectively its dielectric constant and thickness. In this approach, the patch elements are geometrically modified, while also employing EBG structures, formed by four EBG cells, placed between the array elements at a near distance. The modification of the geometry of the antenna and the introduction of EBG reduces the mutual coupling of an array antenna with approximately 33 dB on the one hand and improves the antenna gain by approximately 0.43 dB on the other hand. Initially, slots are introduced in the patch geometry and then four EBG unit cells are inserted between two patches, operating at 3.5 GHz. The antenna array design parameters were optimized.</span>

Series-Fed Coupled Split-Ring Resonator Array Antenna With Wide Fan-Beam and Low Sidelobe Level for Millimeter-Wave Automotive Radar

This paper proposes a millimeter-wave series-fed coupled split-ring resonator array (SCSRRA) antenna with a wide fan-beam pattern and low sidelobe level (SLL) for automotive radar. The proposed array antenna has the advantages of low cost, low profile, and low manufacturing difficulty. The proposed array antenna uses a split-ring resonator as a radiating element coupled from a microstrip line. The split-ring resonator has the advantage of suppressing cross-polarization due to feed phase errors. To reduce the surface wave through the ground edges and enhance the beamwidth, we added the mushroom-shaped electromagnetic bandgap (EBG) structure. Amplitude tapering to reduce the SLL was implemented by adjusting the distance between each element and the microstrip line. The prototype SCSRRA antennas operating at 79 GHz were fabricated, and the characteristics of the wide fan-beam pattern and low SLL were experimentally verified.

SITAR: A Code for ICRH Antenna–Plasma Coupling

We have developed an ICRF (ion cyclotron range of frequency) heating antenna code, SITAR (Simulation of ICRH anTennA Resistance), for stripline antenna to find out its impedance in the presence of plasma. The antenna is of finite poloidal and toroidal dimensions and screened from the plasma by the Faraday shield that shorts out the toroidal components of the radio frequency field. Antenna lead current as well as toroidal and poloidal current of antenna have been taken into account. A slab geometry model for coupling of antenna with tokamak plasma and a linear model of the perpendicular refractive index for the propagation of ICRF wave in the evanescent region have been considered. The plasma in the coupling region is described by a cold plasma dielectric tensor with nonuniform density and toroidal magnetic field along the radial direction.

Scattering Parameter Measurements of the Long Wavelength Array Antenna and Front End Electronics

We present recent 2-port vector network analyzer (VNA) measurements of the complete set of scattering parameters for the antenna used within the Long Wavelength Array (LWA) and the associated front end electronics (FEEs). Full scattering parameter measurements of the antenna yield not only the reflection coefficient for each polarization, S11 and S22, but also the coupling between polarizations, S12 and S21. These had been previously modeled using simulations, but direct measurements had not been obtained until now. The measurements are used to derive a frequency dependent impedance mismatch factor (IMF) which represents the fraction of power that is passed through the antenna–FEE interface and not reflected due to a mismatch between the impedance of the antenna and the impedance of the FEE. We also present results from a two-antenna experiment where each antenna is hooked up to a separate port on the VNA. This allows for cross–antenna coupling to be measured for all four possible polarization combinations. Finally, we apply the newly measured IMF and FEE forward gain corrections to LWA data to investigate how well they remove instrumental effects.

Engineering Designs of Dual-Polarized Antennas With Reduced Profile and Mutual Coupling for 5G Microcell Application

In this letter, a miniaturized, low profile and low mutual coupling antenna array with stable radiation pattern for fifth-generation microcell is presented. The antenna element contains three parts, folded dipole radiator, vertical feeding baluns, and reflector. Four striplines with end connections and stepped slots etched on the main radiator are adopted to enhance the impedance bandwidth and miniaturized the antenna's aperture in the low-profile configuration. While folded stripline structure is applied to reduce the mutual coupling in dual-polarized antenna. The height of proposed antenna is only 0.1 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength referring to the center operation frequency) and the antenna's aperture is only 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Measured results show that the antenna array has good performances, exhibiting low voltage standing-wave ratio (VSWR < 1.5), high isolation (> 30 dB), and wide bandwidth (3.2–3.9 GHz, 20%). Stable radiation patterns are measured across the operating bandwidth.

A Single-Layer S/X- Band Shared Aperture Antenna with MIMO Characteristics at X-Band for Airborne Synthetic Aperture Radar Applications

New frequencies can be supported with very effective space use by using the shared aperture antenna This work presents on designing a dual-banddual-polarized (DBDP) S/X-band shared aperture antenna (SAA) for synthetic aperture radar (SAR) applications operating at S-band frequency (3.2 GHz) and X-band frequency (9.65 GHz). The single-layer SAA DBDP S-band antenna is designed in a square-shaped patch with coaxial feeding in both vertical and horizontal polarization. The X-band antenna design is in 1 × 3 vertical series with microstrip feeding and arranged at four corners of the proposed antenna. The S-band antenna is mainly used for airborne applications such as air traffic control and surface ship radar. In contrast, the X-band antenna application is maritime vessel traffic control, defense tracking, and vehicle speed detection for law enforcement. To verify the antenna, a prototype is fabricated and measured with s-parameters. The proposed design exhibits that the gain of the S-band is 7.2 dB and for the X-band is 12.4 dB, and the isolation is achieved more than −35 dB, and for this antenna, we achieved a bandwidth of 0.12 GHz for S-band and 0.27 GHz for X-band. However, the X-band antenna is a multi-input and multioutput antenna that is to be validated by using MIMO characteristic parameters such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), mean effective gain, and mutual coupling. The MIMO characteristic parameter of X-band antenna values is found to be in a similar manner to both simulated and measured values. For this X-Band antenna, ECC, DG, CCL, and mutual coupling were achieved as below 0.05, 9.5 dB, 0.5 bps/Hz, and −30 dB to −55 dB, respectively. The total size of the antenna is 100 mm × 100 mm × 1.6 mm.

System‐based specifications for better design of ground‐penetrating radar antennas

AbstractCurrently, no publicly available comprehensive set of specifications exists for the design of ground‐penetrating radar antennas. Specifications are presented and derived for the design of a ground‐penetrating radar antenna based on the antenna's interaction with the rest of the radar system. Typically, ground‐penetrating radar antenna engineers are given basic parameters such as gain and bandwidth to design an antenna. An antenna can be designed to meet those specifications but may not perform well in a ground‐penetrating radar imaging system. By considering the whole system, including the operation parameters, expected targets, and signal processing algorithms, we can constrain the less‐commonly considered performance aspects of an antenna to perform more reliably in a deployment. We propose quantitative specifications for the antenna's coupling, beamwidth, boresight radar cross‐section, pulse integrity, residual ringing, and front‐to‐back ratio. Meeting these antenna specifications will decrease the probability that a deficiency in the antenna design impacts the radar's image output. Finally, a summarised design equation table that will be helpful in the ground‐penetrating radar antenna community at large is offered.

Parametric study of midplane gas puffing to maximize ICRF power coupling in ITER

Midplane gas puffing close to the ion cyclotron range of frequencies (ICRF) antennae has been demonstrated to be robust in improving ICRF power coupling in current tokamaks. It is also shown in a previous study (Zhang 2019 Nucl. Mater. Energy 19 364–71) that in ITER, midplane gas puffing with a puff rate of ∼4.5 × 1022 electrons s−1 can increase the antenna loading/coupling resistance by about a factor of two. In this paper, a comprehensive parametric study has been carried out to characterize the influence of midplane gas puffing on ICRF power coupling in additional and broader range of parameter scans. The new parameter scans include the gas puff rate, the poloidal location of the gas pipe orifices (GPOs), the separatrix density, the particle perpendicular diffusion coefficient, the radial distance between the plasma and antenna as well as the antenna phasing. The 3D edge plasma fluid and neutral transport code EMC3-EIRENE code has been used to simulate the 3D distributions of plasma density in the presence of gas puffing, which are then used in the antenna code ANTITER II to calculate the antenna coupling. The simulation results indicate that the ITER ICRF local midplane gas injection layout (with the GPOs located on one side of each antenna port) increases the ICRF power coupling significantly in all studied plasma scenarios and antenna parameters. We are hence confident that the chosen layout for the ICRF local gas injection on ITER is appropriate. We are also confident that the ITER local gas injection will allow boosting the ICRF coupling with all studied plasma conditions and antenna phasings.

An Inductively Coupled CP Slot Antenna Based on Intrinsic 90° Phase Difference and its Flexible Application in Wideband CP Radiation

In this article, a design concept to take advantage of two coupled slots and their inductive coupling to provide the necessary <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\mathrm {\circ }}$ </tex-math></inline-formula> phase difference for circular polarization (CP) realization is presented. Initially, two individual identical slots are arranged in coupling to each other in a perpendicular position, thus acquiring a pair of orthogonal linear polarization (LP) with equal amplitude. Simultaneously, an inherent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\mathrm {\circ }}$ </tex-math></inline-formula> phase difference is naturally produced by the inductive coupling between two slot radiators. In order to clearly illustrate the evolution principle of this proposed CP realization method, the whole structure is in general modeled as an equivalent three-port network for efficient study. Based on these two achieved conditions, a CP slot antenna with one minimum AR point of 4.7% AR bandwidth (ARBW) is satisfactorily realized. After that, based on this proposed design concept, an additional slot is introduced to construct a new inductive coupling, thus facilitating two AR points under triple-mode resonance. With this arrangement, a wideband CP slot antenna with an improved ARBW of 14.1% is successfully implemented, which in turn validates the effectiveness and flexibility of this CP design approach. Finally, both the CP slot antenna element and the wideband CP antenna are implemented, fabricated, and tested. The measured results of the antenna prototypes are found in good agreement with the simulated results, thereby confirming the design concept.

Improving Mutual Coupling in MIMO Antennas Using Different Techniques

Improving Mutual Coupling in MIMO Antennas Using Different Techniques

Neutralization‐line‐based decoupling for miniaturized MIMO antenna array

AbstractIn this paper, a miniaturized multiple‐input, and multiple‐output (MIMO) antenna array is proposed based on quarter‐mode substrate‐integrated waveguide. The decoupling structure of composite neutralization lines (NLs) is used to improve the isolation of the MIMO antenna array. Each NL comprises a simple metal strip attached to each of the two antenna radiators to create an extra coupling path that opposes the primitive antenna coupling to reduce mutual coupling. Eventually, the 2 × 2 MIMO antenna array is fabricated and implemented to verify the design. The measured impedance bandwidth of S11 less than −10 dB ranges from 3.48 to 3.52 GHz, and the peak gain of the element is 4.87 dBi, the mutual coupling levels between the orthogonal and the parallel antenna elements are −19.2, −22.6, and −17.9 dB, respectively, making it a suitable candidate for MIMO systems.

Research on size coupling and sensitivity analysis of SAR antenna truss rod

To eliminate the influence of the size coupling of SAR antenna truss rod on assembly accuracy, this paper defines the assembly sequence, part datum, tolerance, assembly operation, and measurement operation of the model by establishing the tolerance analysis model of the assembly dimension chain and measurement target. The assembly simulation process of the deployment mechanism is simulated, the plane deviation of the antenna panel of the deployment mechanism is analyzed, and the contribution and sensitivity data of each component ring size to the closed ring size are obtained. The simulation results show that the in-plane angle error of the antenna panel is mainly affected by the length of the component ring rod. By focusing on controlling the dimensional tolerance of the truss rods with high sensitivity, the assembly accuracy of the antenna deployment system can be guaranteed. Sensitivity is the magnification of assembly deviation by the transmission of deviation source, which reflects the influence of the change of composition tolerance on the change of functional requirements. According to the sensitivity analysis, the key dimensions that affect assembly accuracy can be obtained. The assembly requirements of high-quality and low-cost products can be achieved by strictly controlling the dimensional tolerance of key components and relaxing the tolerance of non-key components.