Slot Elements Research Articles

A Compact CSRR-Based Sensor for Characterization of the Complex Permittivity of Dielectric Materials

A sensor is proposed to characterize the complex permittivity of dielectric materials in a non-destructive and non-invasive way. The proposed sensor is based on a rectangular patch microstrip two-port circuit with a complementary split-ring resonator (CSRR) element. The slotted CSRR element of the sensor plays a key role in determining the electrical properties of the materials under test (MUT). The sensitivity analysis is determined by varying the permittivity of the MUT. The proposed sensor is simulated and analyzed using Ansoft HFSS software. A prototype was fabricated and measurements were made on two different samples of dielectric materials with complex permittivity values available in the literature. The simulated and measured results showed good agreement.

A portable non-invasive microwave based head imaging system using compact metamaterial loaded 3D unidirectional antenna for stroke detection

A metamaterial (MTM) loaded compact three-dimensional antenna is presented for the portable, low-cost, non-invasive microwave head imaging system. The antenna has two slotted dipole elements with finite arrays of MTM unit cell and a folded parasitic patch that attains directional radiation patterns with 80% of fractional bandwidth. The operating frequency of the antenna is 1.95–4.5 GHz. The optimization of MTM unit cell is performed to increase the operational bandwidth, realized gain, and efficiency of the antenna within the frequency regime. It is also explored to improve radiation efficiency and gain when placed to head proximity. One-dimensional mathematical modelling is analyzed to precisely estimate the power distribution that validates the performance of the proposed antenna. To verify the imaging capability of the proposed system, an array of 9 antennas and a realistic three-dimensional tissue-emulating experimental semi-solid head phantom are fabricated and measured. The backscattered signal is collected from different antenna positions and processed by the updated Iterative Correction of Coherence Factor Delay-Multiply-and-Sum beamforming algorithm to reconstruct the hemorrhage images. The reconstructed images in simulation and experimental environment demonstrate the feasibility of the proposed system as a portable platform to successfully detect and locate the hemorrhages inside the brain.

Dual polarized reflectarray antenna for operation in X and Ku bands

AbstractA stacked structure element consists of an arc phoenix patch and an I‐shaped slot is proposed for designing dual‐band reflectarray antenna. The arc phoenix element operates at Ku band, which above the I‐shaped slot element operating at X band. The advantages of this configuration are that the smaller size phoenix element has less shielding of the reradiation energy, and the property of the bottom substrate has no effect on up‐layer due to the I‐shaped element severs as ground plane. Furthermore, two orthogonal polarizations are produced by the radiation characteristics of the slot and the metal strip to eliminate coupling. Based on the element, a reflectarray antenna with a dimension of 140 mm generating two focused beams at orthogonal plane has been simulated, fabricated, and measured. The simulated and measured results are in good agreement in X and Ku bands.

Dual-Slot Cavity Antenna for mm-Wave Beamforming Array

A cavity-fed, dual-slot element and its 4-element linear array configurations for beam-steering applications at 28 GHz are described. The element cavity is formed from rectangular substrate integrated waveguide (SIW), perturbed at one of its corners to excite dual slots for increasing the impedance bandwidth. With a mobile terminal in mind, we look to both classical array principles and to the available theories for finite arrays with mutual coupling, to help guide the design. The impact of the finite ground-plane required to support the slot elements and array is investigated by simulation, including the impact on the patterns of using a cellphone chassis as a platform. A chassis-born 4-element (8 slots) configuration, suitable for beamforming in 28 GHz 5G networks is demonstrated for both linear polarizations. The simulation results are supported by pattern measurements of prototypes, a challenging task at 28 GHz.

Low‐profile complementary dipole antenna under quadruple mode resonance with nearly equal E‐ and H‐plane patterns

Design approach to a planar unidirectional, complementary dipole antenna under quadruple mode resonance is proposed. The design initiates from a planar complementary dipole antenna, with a pair of flat electric dipoles to be closely incorporated with a slot element. As theoretically predicted by the equivalent multi-source model, quadruple mode can be successfully excited to yield unidirectional antenna with a height of about 0.04-wavelength. As have been numerically demonstrated and experimentally validated at the 2.5-GHz band, the antenna can be implemented on air substrate of 5 mm (i.e., 0.041-wavelength). The prototype antenna can exhibit a wide impedance bandwidth up to 31.5%, in which an available quadruple-mode bandwidth of 5.2% is attained: The antenna can exhibit a maximum front-to-back ratio up to 13.0 dB, with nearly equal radiation patterns in both E- and H-planes. As is concluded, the quadruple resonant mode has been successfully incorporated to a slot element and then to yield fully-integrable, unidirectional, planar complementary dipole antennas for the first time.

A Substrate-Integrated Waveguide Leaky-Wave Antenna Based on Eye-Shaped Transverse Slot

At present, there are few reports of broadside antennas based on the transverse slots in SIWs, because those slot structures often exist as open stopbands (OSB), which restrict radiation in the broadside direction. In this communication, a new type of transverse slot element, eye-shaped transverse slot element with a high phase shift, is proposed. The phase constant of this element can vary linearly, which can lead to continuous beam scanning from the backward-to-forward direction. The relationship between the phase difference and the element size is obtained by simulation. What is more, a leaky-wave antenna with element spacing slightly larger than half-waveguide wavelength is described, and its internal field distribution is analyzed. The measured results show that the main beam can scan from −56° to 39° when the frequency increases from 9.1 to 13 GHz, while the gain ranges from 9 to 11.7 dBi in the passband with an effective length of 110 mm. Because of its small antenna length, wide beam scanning range, and high gain, the antenna can be widely used in wireless communication or radar systems.

Mechanically Reconfigurable Slot Array Using Accordion-Like Microactuators

A novel mechanically reconfigurable 8×11 slot array using accordion-like microactuators as an alternative to conventional electronically steered arrays is reported. The array scans 0° to –30° in elevation by simultaneously varying the inter-element spacing between sliding slot elements. To maintain low slidelobe levels, the radiating slots are designed to have nonuniform width. The array is fed by a single slotted waveguide from one side. The actuator provides continuous motion with a precision of 30 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /625) and is controlled via a printed circuit board (PCB) circuit. The accordion-like structure provides a uniform yet tunable spacing between each slot column, eliminating the need for costly and complex electronic scanning. This high precision approach reduces the system footprint, ensures high power handling capability, and ensures ease of integration in future applications. The structure, operating at 16 GHz, is fabricated using a laser-etching process and in-house additive manufacturing. Measurement results are congruent with simulations.

Formation of additional virtual reception channels when processing signals at the outputs of elements of the antenna array of a promising cellular base station

The results of research on the layout of the antenna array for a promising cellular base station in the frequency range 1,81,88 GHz, which includes a linear antenna array of 12 slotted elements with rectangular directors, the diagram forming scheme of which uses a modification of the Rotman lens, characterized in that for the sake of reducing its overall dimensions, the lens is folded in half the earth is located in the center, and on both sides of it-the halves of the lens body with exponential strip transformers. It is shown that to reduce the level of the side lobes of the antenna system in the reception mode, interpolation and extrapolation antenna arrays can be used. An extrapolation array can also be formed in order to increase the directional coefficient of the receiving antenna system and resolve radio sources that are not resolved by the real antenna array.

Filtering antennas: A technical review

Filtering antennas or filtennas realize both antennas and filter functions in a single structure with the sole purpose of reducing losses and size in the design of a radio system. This article presents a comprehensive view of various filtennas design techniques and their types, satisfying the requirements of different wireless communication standards. The codesign and synthesis approaches and multilayer structure, slot/slit, and parasitic elements are the frequently used techniques reported in the literature to date for the filtennas design. The codesign and synthesis approaches need an extra filter in the filtenna's design, thus making it more complex. Whereas multilayer, slot, and parasitic elements do not require additional filters, and help the radio design become compact in size. The individual elements, that is, filter and antenna used in the filtenna are designed by cutting slots, stacking, resonators, or metamaterial structures. There are two broad categories of filtennas, namely, planar and nonplanar. Most of the papers covered in this article are planar, whereas, under the nonplanar category, horn filtennas are analyzed. Performance in each case is compared in terms of size, complexity, and cost. Considering filtennas frequency of operation, they are classified as a single band, multiband, ultra-wideband, and their MIMO configurations are analyzed to improve the reliability of the wireless radio system. Finally, various types of filtennas are compared, and the design guidelines are elaborated, mainly focusing on their application aspect to achieve more compact radio design solutions. The different techniques related to designing filtennas have been compared, and their glance details are provided for a more realistic assessment of individual techniques used till date. Thus, the authors believe that this review article presents a helpful guiding platform for researchers working on filtenna design.

On Modeling the Operation of Slotted High-Lift Device Elements in a Spin Experiment at Low Reynolds Numbers

On Modeling the Operation of Slotted High-Lift Device Elements in a Spin Experiment at Low Reynolds Numbers

Frequency selective surface with complex topology elements

Relevance: The solution of specific problems in modern technology of microwave and UHF ranges, such as the implementation of reducing the radar signature of objects, spatial frequency-selective filters, reflectors requires the development and creation of a special class of electrodynamic structures - frequency-selective surfaces. Due to the uniqueness of their electrodynamic characteristics, it is possible to solve quite technically complex problems - suppression of excited surface waves, the creation of "forbidden" zones in the amplitude-frequency characteristics. The purpose of the work is numerical modeling and experimental study of electrodynamic characteristics of plane frequency-selective surfaces with slotted elements of complex topology. Evaluation of the influence of the geometric parameters of the slot inhomogeneity and the material constants of the dielectric substrate on the reflection and transmission coefficients of the frequency-selective surface. Materials and methods: The paper presents the results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies of the prototype parameters. Modeling was performed within the framework of the finite element method (FEM) using the ANSOFT HFSS / ANSYS software product. Characteristic measurements are performed in free space by direct measurement of attenuation values. Results: In the course of numerical experiments, it was found that two types of resonances can arise in the structure, associated both with the ratio of the geometric dimensions of the structural element and with the presence of double-sided shielding. The influence of the thickness of the dielectric substrate and the values ​​of the dielectric constant on the reflection and transmission coefficients is investigated. The frequency dependences of the reflection value are established with a change in the spatial orientation of the structure relative to the incident wave front. The dependence of the magnitude of the radio transparency of a two-layer frequency-selective surface on the angle of rotation of the structure around a given axis has been established experimentally. Conclusion: The presented results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies have shown the possibility of spatial frequency selection. The totality of the results obtained makes it possible to predict the creation of sufficiently technological and highly efficient frequency-selective surfaces in the microwave range.

Co-Design and Validation Approach for Beam-Steerable Phased Arrays of Active Antenna Elements With Integrated Power Amplifiers

An approach for designing a beam-steering active phased array of antenna elements with integrated power amplifiers (PAs) is presented. It is based on an amplifying active integrated unit cell (AiUC) concept, where the AiUC comprises a radiating slot element, a GaN high-electron-mobility transistor (HEMT), its input matching, and dc biasing/feeding circuitry. The HEMT is embedded in the antenna element, being directly impedance-matched to HEMT’s drain output, i.e., without using any intermediate and potentially lossy impedance matching network. The proposed co-design approach involves a full-wave analysis of the AiUC passive part (naturally including elements mutual coupling effects) along with the subsequent full-system harmonic balance simulations. Furthermore, we extend the standard definition of the scan element pattern (SEP) to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">active</i> SEP (ASEP) that accounts for nonlinear effects of PAs on the AiUC performance. We show that the ASEP is, in general, power-dependent and has a different shape compared with the SEP. The proposed approach has been demonstrated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band AiUC design example. It was verified through an active waveguide simulator, which is equivalent to the 23.7° H-plane beam-steering case. Measurements are in good agreement with simulations, revealing AiUC 47% peak drain efficiency and 33 dBm maximum radiated power. The predicted scan range is ±60° and ±37° in the E- and H-planes, respectively.

САМООЧИСНИЙ ФІЛЬТР ДЛЯ ЗАМКНУТИХ ГІДРОСИСТЕМ СІЛЬСЬКОГОСПОДАРСЬКОГО ОБЛАДНАННЯ

The issue of increasing the reliability and durability of hydraulic units of closed hydraulic systems of agricultural equipment is considered, due to better cleaning of the working fluid by filtration units. The design of a self-cleaning filter with hydraulic automatic control of backwashing of slotted filtration elements with a counterflow of the working fluid is proposed. A special stand has been developed for simulating the operation of a self-cleaning filter of closed hydraulic systems of agricultural equipment. Experimental studies on a special stand confirmed the efficiency of the proposed design and made it possible to identify its main advantages in comparison with domestic and foreign counterparts. Based on the analysis of transient processes with increased pressure pulsation of agricultural equipment of a closed hydraulic drive, the actual pressure drop at which automatic flushing is triggered was established, compared with the calculated one, in which it was impossible to take into account such real factors as friction in the sealing units, the characteristics of the springs, distortions, tightness of valve pairs, fluctuations in dimensional chains. The most optimal operating mode of auto-washing equipment with a choke diameter of 1.0 mm has been determined. The auto-washing equipment was switched on at a pressure drop of 1.5 MPa (15 atm) and in an improved mode – pressure pulsations with an amplitude of 2 MPa (20 atm) when the auto-wash was turned off decreased in time to 0.12 s. It is noted that the developed self-cleaning filter for closed hydraulic systems of agricultural equipment will improve the reliability and increase the service life of the elements of hydraulic units and the machine itself as a whole.

Performance Characterization of a Kenics Static Mixer Using Slotted Elements

The pharmaceutical, biomedical, bioenergy, and consumer products industries rely heavily on the mixing of fluids. The bulk of the processes that are undergone in these industries are laminar flowing fluids with the attendant need for low-pressure losses which the Kenics static mixers are better suited for. The mixing of fluids is achieved through the splitting and shearing at successive element junctions and stretching and folding along the length of the elements. The performance of Kenics static mixers can be enhanced by optimizing the total blade twist angle, however, the blade pitch has little or no impactful effect. The device geometry optimization is a criterion for its performance enhancement. This study investigates the output mixture strength of the Kenics static mixer using slotted mixer elements solved numerically with Finite Element Method code; COMSOL Multiphysics. The Kenics static mixer performance was optimized with the use of slotted mixer elements as it was observed that the slot width size and a varying number of slots on the mixer elements had an impact on its performance.

Rectangular Slot Array Antenna

Slot antenna elements are quite popular for use in flat-panel arrays, due to their compactness and relatively large bandwidth. According to Babinet’s Principle, slots and dipoles are duals in performance. Therefore, a vertically placed slot is horizontally polarized and a horizontally placed slot is vertically polarized. A rectangular slot array lends itself to a broad range of applications, e.g., tactical and weather radar. Such arrays can be gimbaled to point their beam in any azimuth and elevation angle of interest. In this effort, a slot antenna element is designed in WIPL-D Pro to operate over the 7.5 - 8.5 GHz frequency range. The element is designed to resonate at 8 GHz. The slot element is used to generate a 6x12 slot array normal to the xy-plane. Separate Taylor tapers (nbar = 5) are applied to the 6-row and 12-column elements to provide 25 dB and 30 dB sidelobe level (SLL) suppression, respectively. The input impedance and pattern performance for a single slot, as well as the slot array’s radiation performance show excellent broadband performance.

A Portable Electromagnetic Head Imaging System Using Metamaterial Loaded Compact Directional 3D Antenna

A non-invasive, low-powered, and portable electromagnetic (EM) head imaging system is presented using metamaterial (MTM) loaded compact directional 3D antenna. The antenna consists of two slotted dipole elements with $2\times 3$ and $3\times 3$ finite MTM array elements in top and ground, respectively, and folded parasitic elements that operate within the frequency range of 1.12 GHz to 2.5 GHz. The MTM array elements are optimized to enhance the overall performance regarding antenna bandwidth, realized gain, efficiency, and directionality in both free space and proximity to the head model. The mathematical modelling is also analyzed to justify the integration of MTM unit cells to the top and ground side of the antenna. The impact of MTM on SAR analysis is also performed. A tissue-mimicking 3D head phantom is fabricated and measured to validate the antenna performance. A nine-antenna portable setup is used with the fabricated phantom to measure and collect the scattering parameters that are later analyzed to detect and reconstruct the haemorrhage images by applying the updated IC-CF-DMAS algorithm. The overall performance demonstrates the feasibility of the proposed system as a portable platform to successfully detect, locate and monitor the haemorrhages inside the head in EM imaging system.

Modal approach to the method of calculating axisymmetric array antennas taking into account interaction of slot elements based on the electromagnetic field expansion in terms of the eigenfunctions of the outer region of the antenna surface

Modal approach to the method of calculating axisymmetric array antennas taking into account interaction of slot elements based on the electromagnetic field expansion in terms of the eigenfunctions of the outer region of the antenna surface

All Metal Focusing Transmitarray Antenna for High-Temperature Plasma Diagnosis

In this paper, an all metal focusing transmitarray antenna using a II-shaped slot element is proposed. The transmitarray is formed by stacking four identical metal phase shift layers and three identical square waveguide layers on each other. To meet the requirements of high-temperature plasma transmission diagnosis, a 2024 aluminum alloy material is used. The simulated results indicate that, unlike the feed antenna, the proposed antenna can concentrate most of the electric field energy into a small area. To verify the design, a fabricated prototype was processed and measured in the C-band. The results show that the proposed antenna achieves an average focal spot diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.3~\lambda _{0}$ </tex-math></inline-formula> at 5.7 GHz and it can work in the 5.4-6.0 GHz band. Furthermore, all metal focusing transmitarray antennas have great potential for high-temperature plasma diagnosis.

Design of a Planar Array of Low Profile Horns at 28 GHz.

A planar array of low profile horns fed by a transverse slotted waveguide array in the low millimeter-wave regime (28 GHz) is presented. The array of transverse slots cannot be directly used as antenna as it has grating lobes due to the fact that slot elements must be spaced a guided wavelength. However, these slots can be transformed into low profile horns that with their radiation patterns attenuate the grating lobes. To this aim, low profile horns with less than 0.6 height were designed. The horns include a couple of chips that contribute to further reduce the grating lobes especially in the H-plane. The good performance of the designed array was demonstrated by both simulations and experiments performed on a manufactured prototype. A 5 × 5 array was designed that has a measured realized gain of 26.6 dBi with a bandwidth below 2%, still useful for some applications such as some radar systems. The total electrical size of the array is 6.63× 6.63. The radiation efficiency is very high and the aperture efficiency is above 80%. This all-metal solution is advantageous for millimeter-wave applications where losses sustained by dielectric materials become severe and it can be easily scaled to higher frequencies.

Broadband high‐gain slot grid array antenna for millimeter wave applications

A broadband high-gain slot grid array antenna (SGAA) is proposed in this paper. Based on the electromagnetic complementarity principle, the metal elements in the traditional microstrip grid array antenna (GAA) are replaced by a wide slot element. Compared with the GAA, the proposed SGAA achieves broadband and high-gain performance. In order to demonstrate this concept, a prototype with 9-element SGAA is designed using wide slot radiation elements and fabricated on Rogers 5880 printed circuit board (PCB) substrates, which is fed by a 50 Ω coaxial probe. The measured and simulated results show a good agreement. The proposed SGAA achieves a measured peak gain of 14.8 dBi at 26.0 GHz, a 10-dB impedance bandwidth from 22.2 to 28.5 GHz with a fractional bandwidth of 24.9%. These results indicate that the SGAA is with high performance and it is suitable for the fifth-generation (5G) millimeter wave (mmW) wireless communication system.