Antenna Impedance Research Articles

Optimal design of Vivaldi antenna with corner reflector: a Multiobjective Minimax Method

The paper presents the optimization of a reflector-backed Vivaldi antenna which was designed to operate at the 1.8, 2.1, and 3.5 GHz frequencies used in the fourth and fifth generation of wireless systems. Reducing antenna back radiation is the primary goal of the optimization; at the same time, however, antenna impedance matching has to be preserved for the considered set of frequencies, this way generating a conflict of goals. The proposed design method is based on a minimax formulation of each goal against frequency and a Pareto-like tradeoff of solutions. Both goals were achieved as a consequence of the optimization process, and the antenna now exhibits a voltage standing wave ratio below 3, front-to-back ratio of 14 dB and a gain in the front direction not smaller than 8 dBi.

Enhanced breast tumor localization with DRA antenna backscattering and GPR algorithm in microwave imaging

With the rapid rate of increasing breast cancer cases across the globe and restrictions of existing early stage detection techniques, microwave imaging based cancer and malignant cell diagnosing methodology is finding its way. Microwave imaging technology has higher accuracy of detection in the variation of tissue properties. In this article, a dielectric resonator based wide band antenna is designed and investigated for microwave imaging (MWI) of early breast cancer detection due to its improved accuracy. The designed antenna has compact size, broad frequency spectrum, high gain and broadside radiation characteristics. To attain the wider bandwidth from (6.5 GHz–12.5 GHz), two rectangular shaped dielectric slabs are used. Wide band microwave frequency band supports the high resolution images. A C-shaped defected ground structure is used to tune the impedance matching. Dielectric resonator based antenna has higher gain and reduces the squints in antenna impedance. Two-asymmetrical dielectric slabs contribute in the excitation of different resonating modes which in turn enhance the bandwidth. It also contributes to excite multiple resonance mode that in turn enhance the bandwidth. Antenna performance is first numerically and experimentally verified in free space. Then, simulation based performance is examined for the microwave imaging. Numerical phantom with equivalent tissue properties is designed with and without the tumor. Unhealthy cells have higher water percentage and larger dielectric constant as compared to healthy cells. It causes the different in the back scattered signal of antenna, which is analyzed to diagnose the tumor or cancer. Here, a maximum deviation of 16 dB is observed in the backscattered signal. Furthermore, surface of the breast tissue is scanned along the x-axis and y-axis at different angels. The collected signals are used to reconstruct the microwave image of the interior. Mean value data of backscattered signals is used to locate the existence of unhealthy cells and GPR algorithm is used to calculate the depth of a 4 mm tumor in breast tissue. Proposed structure has shown efficient performance for microwave imaging.

28/38 GHz compact rhombic-shaped antenna for future generations of mobile communications

ABSTRACT It is mandatory for the modern antennas to be designed to operate in the millimetre-wave (mm-wave) range of the electromagnetic spectrum for future generations of mobile communication requires multiband operation of a single antenna. The present work proposes a dual-band antenna to operate at 28 and 38 GHz . The design stages of the proposed antenna and examples of the parametric study performed to arrive at the final antenna design are demonstrated and discussed in detail. The proposed antenna is constructed as a main patch with parasitic element that is capacitively coupled to the main patch through a narrow slot. The main patch is a rhombic-in-shape and excited through a microstrip live with inset feed. This rhombic shaped patch antenna is originally designed to operate at 28 GHz . To achieve the dual-band operation, the geometry of the main patch is modified and is loaded by a parasitic element. The antenna is fabricated for experimental assessment through measurement of the antenna impedance, radiation patterns, maximum gain and radiation efficiency. The proper operation at 28 and 38 GHz is confirmed by experimental verification of the simulation results. Both the simulation and measurements show that the proposed antenna has 50 Ω -matched impedance over the frequency bands 27.7 − 28.4 GHz and 37.7 − 38.4 GHz . The proposed antenna has been designed to enhance the communications system performance when used in the mobile networks through noise rejection by limiting the operation within relatively narrow bands around the resonant frequencies. The values of the maximum gain obtained at 28 and 38 GHz are 6.98 and 8.8 dBi , respectively. The radiation efficiencies of the proposed antenna are 89 % and 87 % , respectively, and the total efficiency is also calculated.

Progress on Single-Feed Quality Wideband Linear Wire Array

This paper presents the latest developments regarding the single-feed Quality Wideband Linear (QWL) wire array antenna, known for its broadband and high-gain electromagnetic characteristics and robust design. A systematic review of recent advances in relation to the QWL antenna is provided, covering its driven element, director, reflector, low common-mode current interference connector, and array series-feed configuration. For the first time, an analytical expression and a quick design formula for the input impedance of the QWL antenna’s driven element, the linear Wideband High-gain Electromagnetic Structure (WHEMS) antenna, are presented. Theoretical analysis demonstrates the potential for broadband performance using the WHEMS antenna. The rugged design of the QWL array antenna offers engineering advantages such as simple feeding, low wind resistance, a lightweight construction, low cost, and structural robustness. The QWL antenna has already found applications in various industrial sectors, with potential for broader use in the future, contributing to further advancements in antenna technology.

A Review of Microstrip Patch Antenna-Based Passive Sensors.

This paper briefly overviews and discusses the existing techniques using antennas for passive sensing, starting from the antenna operating principle and antenna structural design to different antenna-based sensing mechanisms. The effects of different electrical properties of the material used to design an antenna, such as conductivity, loss tangent, and resistivity, are discussed to illustrate the fundamental sensing mechanisms. Furthermore, the key parameters, such as operating frequency and antenna impedance, along with the factors affecting the sensing performance, are discussed. Overall, passive sensing using an antenna is mainly achieved by altering the reflected wave characteristics in terms of center frequency, return loss, phase, and received/reflected signal strength. The advantages and drawbacks of each technique are also discussed briefly. Given the increasing relevance, millimeter-wave antenna sensors and resonator sensors are also discussed with their applications and recent advancements. This paper primarily focuses on microstrip-based radiating structures and insights for further sensing performance improvement using passive antennas, which are outlined in this study. In addition, suggestions are made for the current scientific and technical challenges, and future directions are discussed.

Broadband magnetoelectric antenna driven by multiple high-overtone bulk acoustic wave modes

High-overtone bulk acoustic waves driven magnetoelectric (ME) antennas operate in the acoustic resonant frequency range, exhibiting continuous narrowband electromagnetic radiation. ME antennas based on cooperative excitation of multiple high-overtone bulk acoustic waves are expected to achieve broadband performance and are worthy of in-depth exploration. High-overtone bulk acoustic resonator (HBAR) antennas with polished and rough acoustic reflection interfaces were fabricated and tested to investigate the influence mechanisms of acoustic modes in the HBAR on the radiation bandwidth, as well as the relationship between antenna impedance and radiation response. Far-field radiation characteristics indicate that the antenna with rough acoustic reflection interfaces featuring more high-overtone bulk acoustic wave modes suppress radiation dips of up to 5 dB at anti-resonant frequencies without sacrificing radiation gain. The radiation gain of the antenna was calculated using the gain-comparison method to be −35 dBi, with a −3 dB bandwidth of 120 MHz and a fractional bandwidth of up to 11.4%. Finally, a comparison of the radiation characteristics of the HBAR piezoelectric antenna without the magnetic film demonstrates that the broadband radiation of the HBAR ME antenna originates from dynamic magnetic flux driven by high-overtone bulk acoustic waves.

Quasi-Two-Dimensional Code for the Calculation of Antenna Impedance of the ICR Heating System

Quasi-Two-Dimensional Code for the Calculation of Antenna Impedance of the ICR Heating System

Mutual Impedance of Antennas Placed on a Multilayer Dielectric

Mutual Impedance of Antennas Placed on a Multilayer Dielectric

Quad-port 28/38 GHz Antenna with Isolation Improvement for 5G Wireless Networks

A 28/38 GHz quad-port cross-shaped antenna printed on a 0.203 mm Roger RO4003 substrate is designed and fabricated for 5G networks. The antenna consists of a rectangular patch radiator with three triangle slots to enhance the antenna's impedance matching. The four elements are arranged in a cross-shaped layout to achieve the desired compactness of 29 mm × 24.2 mm × 0.203 mm. A thin parasitic strip is inserted between the second and fourth elements to enhance the port isolation. The designed antenna is simulated by utilizing the CST simulator. The antenna achieved S11 < -10 dB at 28 / 38 GHz, with isolation ≥ 20 dB. Furthermore, the E- and H-planes within the anechoic chamber are evaluated to validate the MIMO antenna radiation patterns and gain. The MIMO parameters are calculated, simulated, tested, and its outcomes are under the standard level which confirms the MIMO diversity feature. The ECC of the structure is < 0.001, the DG ≥ 9.95 dB. and the CCL was ≤ 0.2 bit/s/Hz across the dual working band.

Theory of Input Impedance of a Slot Antenna With Two Parasitically Excited Wires

Theory of Input Impedance of a Slot Antenna With Two Parasitically Excited Wires

Antenna as a Sensor: An Improved Vehicle Detection Solution via the Use of Antenna Impedance and Magnetic Signature

Antenna as a Sensor: An Improved Vehicle Detection Solution via the Use of Antenna Impedance and Magnetic Signature

Terahertz Antenna Impedance Matched to a Graphene Photodetector

Terahertz Antenna Impedance Matched to a Graphene Photodetector

Wideband Terminal Antenna System Based on Babinet's Principle for Sub-6 GHz and Wi-Fi 6E/7 Applications.

In this paper, a novel input impedance analysis methodology based on Babinet's principle to broaden bandwidth is proposed, and a broadband multiple-input and multiple-output (MIMO) antenna system is designed, fabricated, and measured for fifth-generation (5G) and Wireless Fidelity (Wi-Fi) 6E/7 mobile applications. By analyzing the input impedance of open-slot antennas and planar monopole antennas using numerical calculations, the characteristics of the input impedance can be obtained. We find that combining the two antenna types in parallel can significantly enhance the bandwidth. Then, the four-dimensional image calculated by MATLAB based on the parallel impedance formula is processed to validate the methodology. Thus, a broad antenna element based on the impedance property analysis methodology is achieved, which operates ranging from 2.6 GHz to 7.46 GHz. Moreover, the equivalent circuit of the antenna element is established to further verify the validity of the methodology. Finally, a broadband MIMO antenna system consisting of eight antenna elements is designed, fabricated, and measured, and the isolation performance is better than 12 dB. Acceptable total efficiency higher than 45% is also obtained with envelope correlation coefficients (ECCs) lower than 0.05. The proposed impedance property analysis methodology innovatively proposes a new way to increase bandwidth, which can be widely applied in various antenna designs. Also, reasonable results show that the proposed MIMO antenna system is a good candidate for 5G and Wi-Fi 6E/7 mobile applications.

Miniaturized Vivaldi antenna with multiband and high-gain for millimeter-wave applications

ABSTRACT A novel miniaturised quad-band printed Vivaldi antenna is proposed for millimetre-wave applications. It can be seen as a two-arm antenna where the antenna arms bound the tapered Vivaldi slot. The antenna arms are printed on the opposite sides of a flexible millimetre-wave substrate. Three periodic structures are added to the antenna geometry and printed in the area surrounding the radiating slot structure to improve the impedance matching over the antenna’s four operational frequency bands and enhance the gain. These periodic structures are parasitic ring array loaded to the antenna arms, ring-array reflector inserted between the antenna arms and the ground plane, and metamaterial director printed in front of the antenna arms. A prototype of the proposed antenna is fabricated for experimental assessment of the antenna performance. The experimental measurements show good agreement with the simulation results. The proposed antenna impedance is matched over the four frequency bands centred at 25 , 35 , 45 , and 55 GHz . The bandwidth of each operational band is about 5 GHz with percent bandwidths of 20 % , 15 % , 11 % , and 9 % , respectively. The corresponding values of the maximum gain are 7.5 , 10.5 , 12 , and 13 dBi , respectively. The radiation efficiency is maintained above 93 % over the entire frequency band (20–60 GHz).

Microwave analogy of Förster resonance energy transfer and effect of finite antenna length

The near-field interaction between quantum emitters, governed by Förster resonance energy transfer (FRET), plays a pivotal role in nanoscale energy transfer mechanisms. However, FRET measurements in the optical regime are challenging as they require nanoscale control of the position and orientation of the emitters. To overcome these challenges, microwave measurements were proposed for enhanced spatial resolution and precise orientation control. However, unlike in optical systems for which the dipole can be taken to be infinitesimal in size, the finite size of microwave antennas can affect energy transfer measurements, especially at short distances. This highlights the necessity to consider the finite antenna length to obtain accurate results. In this study, we advance the understanding of dipole–dipole energy transfer in the microwave regime by developing an analytical model that explicitly considers finite antennas. Unlike previous works, our model calculates the mutual impedance of finite-length thin-wire dipole antennas without assuming a uniform current distribution. We validate our analytical model through experiments investigating energy transfer between antennas placed adjacent to a perfect electric conductor mirror. This allows us to provide clear guidelines for designing microwave experiments, distinguishing conditions where finite-size effects can be neglected and where they must be taken into account. Our study not only contributes to the fundamental physics of energy transfer but also opens avenues for microwave antenna impedance-based measurements to complement optical FRET experiments and quantitatively explore dipole–dipole energy transfer in a wider range of conditions.

Novel input impedance analysis of differential feed microstrip antennas using the bi‐characteristic‐impedance transmission line (BCITL) model

AbstractThis letter presents a novel analysis of the input impedances of differential feed microstrip antennas using the bi‐characteristic‐impedance transmission line (BCITL) model instead of the conventional two‐port parameters. The expressions of associated input impedances using the novel BCITL model are found to be simple, compact, and robust with better physical insights. In addition, measured results are also provided to validate the accuracy of the BCITL model.

Predicting the antenna properties of helicon plasma thrusters using machine learning techniques

When designing helicon plasma thrusters, one important characteristic is the impedance of the radio-frequency antenna that is used to deposit power into the plasma. This impedance can be characterized both experimentally and numerically. Recently, a numerical tool capable of predicting the antenna impedance, called Adamant, has been developed. However, Adamant takes a long time to run and has high computer resource demands. Therefore, this work has been done to evaluate whether machine learning models, trained on Adamant-generated data, can be used instead of Adamant for small design change evaluations and similar works. Six different machine learning models were implemented in MATLAB: decision trees, ensembles, support vector machines, Gaussian process regressions, generalized additive models and artificial neural networks. These were trained and evaluated using nested k-fold cross-validation with the hyperparameters selected using Bayesian optimization. The performance target was to have less than 5% error on a point-to-point basis. The artificial neural network performed the best when taking into account both maximum error magnitudes and generalization ability, with a maximum error of 3.98% on the test set and with considerably better performance than the other models when tested on some practical examples. Future work should look into different solver algorithms for the artificial neural network to see if the results could be improved even further. To expand the model’s usefulness it might also be worth looking into implementing different antenna types that are of interest for helicon plasma thrusters.

Increasing the probing depth of pulsed GPR by reducing the antenna impedance

At the present time, dipole antennas with resistively loaded vibrators are widely used in pulsed georadar. The main property of such antennas is the emission of an electromagnetic wave into the subsurface medium with rapid attenuation of the ultra-wideband pulse to the end of the vibrators without reflection. When the total resistance of the vibrator decreases below 200 Ohms, parasitic self-oscillations appear in this antenna, limiting the increase in power supplied to the antenna. Development of a dipole antenna for subsurface ground penetrating radar with the ability to reduce the antenna impedance below 200 Ohms to increase the radiated power and increase the depth of ground penetrating radar. The design of a dipole antenna with several resistively loaded vibrators connected in parallel is proposed. The total resistance of a single vibrator is selected based on the stability requirements to prevent parasitic self-oscillations, but the impedance of the dipole antenna decreases in proportion to the number of connected vibrators. A dipole antenna with five dipoles connected and arranged parallel to each other has a gain 10 dB higher compared to a dipole with a single resistively loaded dipole. Compared to a plate antenna 3 meters long and 25 cm wide, a five-vibrator dipole antenna of the same length has a gain of 3.3 dB higher. Another advantage of the proposed antenna is its higher resolution. At the same time, insulated vibrators made of flexible conductors allow twisting to reduce the overall diameter of the dipole antenna, which allows its use in difficult engineering and geological conditions. Experiments with three-meter dipole antennas showed an increase in sounding depth in the Moscow region from 14 to 20 meters.

Compact triple band notched UWB MIMO antenna with integrated GSM

SummaryThis paper introduces an innovative four‐element Ultra‐wideband (UWB) MIMO structure featuring an integrated global system for mobile (GSM) antenna with the ability to achieve dual and triple band‐notch capabilities. The antenna's distinctiveness is achieved through the utilization of four directional meandered line shaping decoupling structures (MLSDS), an orthogonal arrangement, and multi‐slot techniques. The incorporation of orthogonal separation alongside four directional MLSDS significantly reduces the mutual interference between radiating elements. By placing MLSDS on both sides of the substrate, effective coverage of the GSM band is achieved. The development of the MIMO structure unfolds through four distinct phases. The initial stage lacks MLSDS, while the second stage incorporates MLSDS. The third and fourth stages respectively introduce MLSDS with dual and triple notch characteristics. The presence of MLSDS enhances the antenna's impedance bandwidth (IBW). The intended notches are tailored to address interference from bands like Band n41, WLAN, and X‐band. Furthermore, the proposed antenna has undergone simulation, measurement, and comparative analysis with existing models, focusing on diversity performance metrics. The results reveal its exceptional diversity performance, positioning it as a potential choice for creating a portable UWB‐MIMO system.

Ground plane alteration extremely wideband SPAS pair-based MIMO antenna with improved isolation and band notched characteristics

A novel and effective Slotted Pentagonal Adjacent Structure (SPAS) pair based Ultra Wideband (UWB) Multiple-Input Multiple-Output (MIMO) antenna is presented in this research paper. The proposed antenna with a compact size of 0.25 λ0 × 0.50 λ0 mm2 consists of a two slotted pentagonal patch element along with ground plane alteration (GPA). Four hexagonal metallic rings with opposite split orientation are embedded in the patch elements to achieve three notch bands. This proposed loop-based split ring resonator (SRR) design focuses on miniaturization or compactness while maintaining effective notch performance. According to the experimental results, the suggested UWB MIMO antenna's impedance bandwidth ranges from 4.0 GHz to 40.25 GHz cover with triple notch bands IEEE INSAT extended C-band (6.05 GHz to 7.16 GHz), X-band (8.9 GHz to 10.28 GHz) and K-band (24.65 GHz to 26.95 GHz). High isolation of > 24 dB is achieved by integrating a parasitic strip with ‘O’ shaped SRR slot in between the radiating elements. The fabricated compact antenna has good radiation patterns, high gain, TARC < −10 dB, high efficiency and low envelope correlation coefficient which is suitable for advanced wireless communications.