Input Impedance Of Antenna Research Articles

Планарная трехдиапазонная антенна морского аварийного радиобуя

In the article the results of the development of two modifications of planar antennas for marine emergency beacons are presented. The operating frequencies of the antennas are 121.5 MHz, 162 MHz and 406 MHz. The antennas dimensions are corresponding to the seat in the case of a commercially available radio beacon. High-quality matching with the use of LC filters is implemented at three operating frequencies. The implemented matching assures the possibility of using the radio beacon in various environments – in water and free space. Local resonances of the antennas input resistances are obtained at low frequencies. This made it possible to expand the matching bands and at the relevant operating frequencies. It also made it possible to increase the gain at these frequencies. According to the radiation characteristics, the developed antennas fully meet the requirements for emergency beacon antennas. The advantages of the antenna include the following. The antennas have a planar structure. Compared to existing analogues, the antennas have an increased gain at lower operating frequencies. The dimensions of the developed antennas are 202×34×1.5 mm. The radiating flat line of the Z-01 antenna model is made in the form of a meander (Z-shaped). To increase the electrical length of the Z-01 antenna, metallization was added on the back of the substrate, covering the area of horizontal segments of the radiating line. As a result, the horizontal sections of the radiating line are segments of non-radiating asymmetric microstrip lines. These waveguides are periodic inhomogeneities for the antenna radiating structure itself. The presence of such inhomogeneities causes the appearance of additional resonances of the antenna input impedance, which makes it possible to improve the antenna matching characteristics at lower operating frequencies. The design of the Z-02 model differs from the Z-01 in that distributed capacitive loads are introduced on the horizontal microstrip sections of the Z-shaped line to increase its electrical length. These equivalent capacities are implemented as a distributed counter-comb structure.

Adaptive Matching of Discrete Antenna Tuning Units of High Frequency Band to Varying Load Impedance

The issue of matching the antenna with thetransmitter-receiverplays a primary role in radio communications. The matching problem is relevant for different ranges and is solved in many ways. In the high frequency wave range, matching has a number of features when using an antenna coupler based on discrete elements consisting of capacitance and inductance boxes. The article discusses the concept of fast matching of high-frequency amplifying paths ofdecametric wavestransceivers with non-stationary loads using discrete antenna couplers. An innovative approach has been developed to the tuning process when changing the operating frequency and ensuring self-adaptation of the antenna coupler when changing the impedance, based on methods for quickly searching for the geometric proximity of points. A quick method for configuring the antenna coupler is proposed, eliminating the procedure for recalculating the input impedance based on the results of measuring the input impedance of the antenna coupler. When using it, the speed of setting the antenna coupler at the current operating frequency is limited only by the time of a single state change of the discrete power circuit, which in the case of electromagnetic relays is numerically equal to their switching time. The configuration of the antenna coupler using the method of fast search for the geometric proximity of points is based on a set of frequency cards with settings options. Such cards can be recalculated for the reference plane between the generator and the antenna coupler input for all combinations of discrete elements in accordance with the known matrix model of a discrete power circuit. This eliminates the complicated procedure of recalculating the input impedance of the antenna using complex numbers. The technical result of the proposed innovative method of antenna coupler configuringis simplification, tracking of systematic errors of the impedance meter, elimination of time-consuming calculations with complex numbers, expansion of the method functionality, reduction of the tuning duration and improvement its quality. The practical significance lies in the fact that the implementation of the proposed technical solutions in the high frequency range communications means can significantly (about 100 times) limit the duration of preparation for a radio communication session, eliminate the procedure for recalculating the antenna input impedance and reduce the resource requirements of switching elements.

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.

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

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.

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.

An efficient and accurate semi-analytical matching technique for waveguide-fed antennas

Several RF and microwave radiating devices, such as horn antennas, Fabry–Perot cavity antennas, and aperture-fed focusing devices, are excited through rectangular waveguides. The impedance matching of the overall system (from the waveguide feed to the radiating aperture) is a task of crucial importance that is often addressed by means of brute-force parameter-sweep full-wave analyses or blind optimization algorithms. In both cases, a significant amount of memory and time resources are required. For this purpose, we propose here a simple, yet effective solution, which only requires a single full-wave simulation and a semi-analytical procedure. The former is used to retrieve the antenna input impedance at the end of the waveguide port excitation. The semi-analytical procedure consists in a transmission-line equivalent circuit that models two waveguide discontinuities (namely two capacitive irises) within the waveguide section, whose position and geometric features are finely tuned to obtain a satisfactory impedance matching around the working frequency. The proposed method is shown to be effective in diverse and attractive application-oriented contexts, from the impedance matching of a Fabry–Perot cavity antenna to that of a wireless near-field link between two aperture-fed focusing devices. A remarkable agreement between full-wave simulations and numerical results is found in all cases. Thanks to its versatility, simplicity, and a rather low demand of computational resources, the proposed approach may become an essential tool for the effective design of waveguide-fed antennas.

Tri-arm MIMO array antenna pair for mobile phone applications

Abstract An 8 × 8 tri-arm multiple-input multiple-output (MIMO) array using novel even–odd mode decouplers is presented. To decouple the directly connected driven ports on the tri-arm antenna pair, a T-shaped stub working as an even-mode decoupler and a narrow strip working as an odd-mode decoupler are elaborately introduced. Therefore, the even-mode and odd-mode impedances cross with the antenna input impedance, and a deep coupling zero is achieved at this cross frequency. Finally, the proposed 8 × 8 MIMO array was developed, fabricated, and measured for further performance verification. The measured results show that the proposed array can have a wide isolation bandwidth of 17.2 % with a compact size of 0.44λ 0 × 0.08λ 0 and zero clearance requirement on the ground plane. The diversity performances are also investigated with the measured worst envelope correlation coefficient less than 0.05.

Designing of a multi-frequency vibrator antenna on meander line with resonant loads and fragmented “floating ground”

Problem definition. Many VHF communication devices include multi-frequency vibrator antennas, among which a special place is occupied by the vibrator antennas with reactive loads as the most compact and simplest to produce. However, inductive loads usually used in practice don’t provide current cut-off at higher operating frequencies, which results in deformations of radiation patterns, and resonant circuits loads don’t provide sufficient shortening of the vibrator antenna due to appearance of shunt inductances. There is a need to formulate the new idea of the designing the multi-frequency vibrator antenna, which has absolutely another mechanism of work, is needed. Purpose. The purposes of this article are: to suggest the idea of the design the multi-frequency vibrator antennas, based on hybrid of meander line with parallel LC-circuits and fragmented “floating ground”; to form an equivalent scheme for calculating characteristics; to develop a methodology for calculating this type of antennas characteristics (input impedance, VSWR, current distributions over the vibrator and far-field radiation patterns); to do the calculation of characteristics of the monopole antenna on meander line with loads and to make an experimental check of the theoretical results. Results. A design of the multi-frequency vibrator antenna on meander line with parallel LC-circuits loads and fragmented “floating ground” is shown. An equivalent scheme for calculating antenna characteristics is given, an algorithm of calculation of input characteristics and current distributions over the antenna (both meander and “floating ground”) is described. The calculation of input impedance, VSWR, current distributions and radiation patterns of the vibrator antenna with two LC-circuits loads in meander line is done. An experimental check of the theoretical results in VSWR and far-field radiation patterns is made. Applicability of the proposed idea and methodology for the design the multi-frequency vibrator antennas on meander line is shown by analyzing calculated and experimental data. Practical significance. The results of this work can be used to design the multi-frequency VHF vibrator antennas with resonant loads, which have the identical radiation patterns at all operating frequencies.

Modified Babinet Principle for Complementary Antennas in a Dielectric Half-Space

In this letter, the modified Babinet principle is applied to complementary antennas on the substrate interface. First, it is verified that the existing Babinet principle only holds for complementary metallic elements in the homogenized substrate. Then, the effective relative permittivity is introduced into the substrate interface through the zero-thickness effective substrate, which can keep the electromagnetic behavior (such as total electrical field and surface current density) of metallic element unchanged. Thereby, the modified Babinet principle can be established for arbitrary complementary metallic elements on the substrate interface. Finally, the proposed theory is applied to input impedances of complementary antennas on the substrate interface. The simulation strongly supports the proposed theory, regardless of the substrates and antenna sizes. The study not only establishes the modified Babinet principle for complementary metallic elements on the substrate interface, but also clarifies the electromagnetic influence of effective relative permittivity for the metallic element at the substrate interface.

Low-Scattering Phased Arrays With Reconfigurable Scattering Patterns Based on Independent Control of Radiation and Scattering

A novel approach for the independent manipulation of the in-band scattering and radiation patterns of phased arrays with high radiation efficiency is proposed. The in-band scattering and radiation mechanism of an array element is analyzed first. It is found that the antenna input impedance may lead to different effects on the antenna scattering and radiation patterns. Taking advantage of this difference, an array element incorporated with a biased pin diode is designed, which has two scattering states with 180° phase differences but a stable radiation state. By controlling the biasing state of the pin diode connected to each element, the scattering pattern of the proposed array can be manipulated dynamically. Meanwhile, the stable radiation pattern of the designed element ensures that the proposed phased array can dynamically radiate a beam scanning to a given direction with high efficiency during the manipulation of scattering patterns. The final designed linear array with pin diodes is able to operate at 2.6-3.4 GHz with a radiation beam scanning up to ±45°. Moreover, the reconfigurable scattering beams of the proposed array can point to arbitrary angles within ±60°, thus the in-band scattering is significantly reduced in a broad bandwidth. To validate this design, a prototype array is fabricated and measured. Measured results are in good agreement with the simulated results.

Super‐wideband two‐arm antenna for future generations of mobile communications

AbstractIn this paper, a modified rhombic‐shaped wide‐flare two‐arm antenna is proposed for super‐wideband applications of the next generations of mobile technologies. To enhance antenna input impedance and to improve its performance, the copper arms are lithographed on a dielectric substrate with multilayers and fed through a wideband balun that is designed to feed the balanced two‐arm antenna through the conventional (unbalanced) coaxial line. The proposed antenna is fabricated for experimental validation of the simulation results. It is shown through electromagnetic simulation as well as experimental measurements that the proposed antenna is operational in the range of frequencies (). Parametric study is performed to obtain the optimum design of the proposed antenna. The distributions of the surface current on the antenna arms at different frequencies are presented and discussed for more understanding of the antenna operation over the entire frequency band. It is shown that the antenna has a radiation efficiency of greater than 96%, percentage bandwidth of 164%, ratio bandwidth of 10, bandwidth‐to‐dimension ratio of 1360, and maximum gain that exceeds .

Matrix model parametric identification of antenna tuning units

HF radiocommunication modern development trends provide for improved handling and increased speed of antenna tuning units (ATU) functioning. The need to control the tuning process using a microcontroller based on the measurement results of antenna input impedance in the “on-line” mode requires an increase in the accuracy of modeling the transformative properties of these devices and subsequent calculations for the development of control commands by discrete tuning bodies. The more reliable the data in the memory of the microcontroller will characterize the real properties of the device's tuning bodies, the better their regulation will be. Based on the results of a full-scale experiment, the issues of parametric identification of the previously proposed conceptual matrix model of discreet power circuit are considered. Due to the complexity of technological modeling of circuits transformative properties, the task is to increase the accuracy of its numerical results for each device. With the found set of solutions for the model with the selected structure and a significant number of unknown parameters, its identification by the objective function extremum is not possible. Accordingly, the analysis of a priori identifiability (theoretical, with unambiguous definition of parameters) is carried out on the basis of a qualitative study of the structure of the model and the scheme of the “ideal” experiment (with determinism of all unmistakably measured values). The identifiability of the proposed power circuit model has been confirmed. The variants of the experiment, the algorithm for processing its results, as well as ways to obtain their guaranteed quality with the help of a vector circuits analyzer for a certain time at a given cost are described. The criterion for assessing the conformity of the model to a real power circuit is a measure of the number of its errors after measuring complex coefficients on a set of frequencies. Processing the results using the least squares method with interpolation for the entire frequency band reduces the errors and complexity of the experiment. Modeling of a 9-bit matching inductive body confirmed the correctness and effectiveness of the matrix description of the transforming properties of the wide band ATU and other solutions presented, as well as the possibility of full automation of this experiment.

Genetic Algorithm and Particle Swarm Optimization Approach for Prediction of Physical Parameters of Rectangular-Shaped Microstrip Antenna

This study presents the results of two optimization algorithms for estimating the resonant frequency, bandwidth, feed point, and input impedance of a rectangular-shaped microstrip antenna. To minimize the design cost and design time, genetic algorithms and particle swarm optimization methods have been applied and compared. The antenna design parameters were considered by using a genetic algorithm (GA) and particle swarm optimization (PSO) is implemented in the MATLAB® environment. The calculation results were assimilated with other studies in the literature in terms of accuracy. The computational results of the optimized parameters are having a good agreement with the experimental results. The optimized antenna was modeled and verified by the analyses performed using the CST Studio Suite® software.

Theory of a VLF Circular-Loop Antenna in an Anisotropic Magnetoplasma

The circular-loop antenna is one of the most basic antenna forms for very low frequency (VLF: 3–30 kHz) space-borne transmitting systems. However, the theoretical progress of the loop antenna in an anisotropic plasma is slower than that of the linear antenna due to its complexity. This article studies the theory of a VLF circular-loop antenna located in an anisotropic magnetoplasma. The current integral equation of the current is formulated by deriving the exact kernel function and boundary condition. By taking both the effects of O-wave and E-wave into consideration, the current distribution and input impedance of a circular-loop antenna are solved via the method of moments along with the numerical techniques. The results show that the current amplitude decreases with the loop radius. As the size of the loop increases, the current distribution resembles a cosine function with its phases jumping at several positions. Moreover, the input impedance of the antenna increases as the radius and operating frequency increase. The proposed approach is validated by comparing the computed impedance with that simulated by the commercial software FEKO. The preliminary study of VLF loop antenna theory can offer theoretical guidance in antenna design and efficiency improvement for actual VLF space-borne transmitting systems.

Electro-Geometrical Analysis of Transversal V-Fold Patch Antenna

This paper investigates an original concept of electro-geometrical analysis of flexible microstrip antenna. The research work is focused on the analysis of the innovative effect of “V”- shape folding on the resonance frequency and input impedance of microstrip patch antenna. The V-folded antenna is assumed to behave as an arm constituted by horizontal and tilted members which are geometrically characterized by the folding angle, a. The folding is characterized by the angle between the horizontal plane and the folded part of the patch antenna printed on a Kapton flexible substrate. The initially flat-configured planar antenna was designed to operate at about 2.45 GHz. The innovative design method of the V-shape folded flexible antenna is explained. Full wave electromagnetic simulations of different geometrical states of the flexible antenna were performed in the frequency range from 1 GHz to 5 GHz. Exceptional results of tilted surface radiating part of flexible patch antenna were found with a positive folding angle from amin=0° to amax=45°. It was understood for the first time in the area of antenna engineering that the resonance frequency is fluctuating according to typical sine damping in the function of the V-folding angle variation. The folded angle effect, which has never been understood before is discussed. In addition to the angle effect, the input resistance and input reactance of the V-folded flexible patch antenna is also plotted.

The Matrix Model of Discrete Matching Elements for HF Computational Automatic Tuning Units

The article is devoted to a new and relevant direction in the HF communication technology - the construction of high-speed computational antenna tuning units (ATU). The implementation of automatic ATU requires the designing of power circuits models adequate, as practice shows, the construction of models to physical reality in order to ensure their controllability. Practically powerful device elements are not in fact concentrated, the distributed nature of their parameters is noticeably manifested in the HF range. Matching ATU on the base of antenna input impedance measuring involves forming of accurate control commands for the elements, especially in conditions where the settings are narrow-band. A new approach to the description of a power circuit discrete elements transforming properties using the theory of linear passive four-pole and matrices, which has the ultimate accuracy, is proposed. A method to form a matrix description of on-off discrete elements of a power circuit based on the results of characteristic field measurements of the mounted device is presented. This approach made it possible to significantly reduce the amount of tabulated data describing the functional dependences of the complex coefficients of wave transmission matrices and to “smooth out” the experimental error. Complex cases are considered, which are of the greatest interest for practice - options for a four-pole cascade and parallel connection of reactive elements in the branches of the power circuit. The current state of computer technology makes it possible to sharply increase the complexity of the mathematical models used. The matrix model takes into account a significant variety of operating factors and does not require them to be “customized” to existing analytical methods. The adequacy, in this simulation, is determined by practical needs that arise in the design of power circuits of matching antenna devices and their tuning algorithms. In fact, the model is considered adequate if the errors in the calculation of the response function according to the model do not exceed the errors in its experimental determination. The proposed matrix approach made it possible to significantly improve the accuracy of modeling, while the error does not exceed 1 %. Also, this approach allows to find several options for setting a given quality and choose the best one for any parameter, while reducing the duration of the process up to 25 times. At the additional metrological advantages appeared in such devices serial production.

Wideband and Ultrathin 2×2 Dipole Array Antenna for 5G mmWave Applications

This letter proposes a wideband (24–40 GHz) and ultrathin (0.76 mm) 2×2 dipole array antenna for fifth-generation (5G) millimeter-wave (mmWave) applications. For the ultrathin array antenna, it is a challenge to match the antenna input impedance because it usually has an extremely low value. Herein, a tightly coupled frequency selective surface is proposed to provide additional resonances, and a capacitively coupled feeding method and H-walls are employed to increase the bandwidth. Furthermore, consistent measurement results are guaranteed by vertical launch connectors, and the calibration process owing to the distortion at the connectors is briefly described. In addition, the cumulative distribution function of effective isotropically radiated power scan patterns is presented at various frequencies. Finally, the performance of the proposed array antenna is compared with those of state-of-the-art mmWave array antennas.

An Impedance Relation and Its Application in Broadband Antenna Design

A triangular monopole antenna and a bitriangular slot antenna are designed and measured, respectively, in order to validate a relation between the input impedances of such noncomplementary antennas. The first application of the newly validated impedance relation is demonstrated with the creation of nonself-complementary antennas, which consist of the triangular monopole and the bitriangular slot. As expected, the nonself-complementary antennas indeed exhibit broad impedance bandwidths and stable radiation patterns. Furthermore, the novel nonself-complementary antennas have the advantages of simpler structures and feed than those of the existing nonself-complementary antennas. Hence, they can be easily and inexpensively manufactured.

Low-Cost Compact Integrated Rectenna for Implantable Medical Receivers

This work describes a novel fully integrated rectenna circuit using tunnelling-based devices for implanted medical devices. An ASPAT (Asymmetric Spacer Layer Tunnel Diode) was used as the active rectifier due to its high non-linearity and temperature insensitivity features. A miniaturized geometry rectenna ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 5$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) with improved matching characteristics was demonstrated, by integrating a Cockcroft-Walton rectifier with an L-shaped planar folded antenna structure operating at ISM frequency bands. The circuit performance was experimentally explored at various separation distance between transmitter and receiver units. For a 5cm transmission set-up, the rectenna with a single-stage rectifier delivered 0.8V output at 20dBm transmit power. An extended doubler configuration exhibited enhanced performance when multiple stages are used, is predicted to reach 0.24mW output power at 23dBm transmit power and yielding ~1.6V output voltage with an efficiency of 0.12%. These findings can assist in compensating for the degraded antenna gain attributed to the extremely small effective-radiating area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.04\lambda $ </tex-math></inline-formula> . Furthermore, the ability of controlling the antenna input impedance helps in circumventing the requirement for a matching circuitry thereby offering further reduction in chip size.