Broad Impedance Bandwidth Research Articles

A low‐profile, wideband, circularly polarized, slotted, U‐shaped textile antenna for W‐BAN applications

AbstractWe propose a compact, wideband, U‐shaped, circularly polarized textile antenna (UCPTA) resonating at 2.45 GHz for wireless body area network (W‐BAN) applications. The radiator of the antenna is printed on the top of the substrate (size of mm3; ) and has a full ground plane on the other side. The proposed antenna's substrate consists of a single layer of denim (), and conductive copper tape was used to fabricate the patch. The antenna has a low‐profile design that is suitable for wearable applications. A small slot was introduced at the center of the U‐shaped patch to enhance the 3 dB axial ratio bandwidth (ARBW) up to 55.17%. The proposed antenna radiates with a 10 dB return loss (RL), impedance bandwidth (IBW) of 64.40%, and a simulated gain of 5.1 dBi. The wearable textile antenna with broadside radiation response is appropriate for off‐body communications. The prototype of UCPTA is fabricated for experimental validation. The measured results for the fabricated antenna were in good agreement with the simulated results. Further, it has been demonstrated that the antenna's performance is stable during structural deformation and human body loading. This textile antenna covers an ARBW in the frequency band of 2.1 GHz–3.72 GHz and has a broad IBW (2 GHz–3.9 GHz) for LTE (2.17 GHz), MBAN (2.360 GHz–2.4 GHz), WPAN (2.395 GHz–2.4 GHz), and WLAN (2.4 GHz–2.482 GHz) applications.

A 60 GHz Slotted Array Horn Antenna for Radar Sensing Applications in Future Global Industrial Scenarios.

This paper presents the design of a 60 GHz millimeter-wave (MMW) slot array horn antenna based on the substrate-integrated waveguide (SIW) structure. The novelty of this device resides in the achievement of a broad impedance bandwidth and high gain performance by meticulously engineering the radiation band structure and slot array. The antenna demonstrates an impressive impedance bandwidth of 14.96 GHz (24.93%), accompanied by a remarkable maximum reflection coefficient of -39.47 dB. Furthermore, the antenna boasts a gain of 10.01 dBi, showcasing its outstanding performance as a high-frequency antenna with a wide bandwidth and high gain. To validate its capabilities, we fabricated and experimentally characterized a prototype of the antenna using a probe test structure. The measurement results closely align with the simulation results, affirming the suitability of the designed antenna for radar sensing applications in future global industrial scenarios.

A Novel FSS Loaded Circular Slot Monopole Antenna for Microwave Breast Imaging Application

Breast cancer continues to be a major contributor to women's global mortality rates, emphasizing the need to explore alternative and supplementary early-stage detection techniques. This study delves into a circular slot monopole ultra-wideband (UWB) antenna equipped with a frequency-selective surface (CSMA-FSS) for early detection microwave imaging applications. To expand the impedance bandwidth of the traditional circular monopole antenna, a circular slit is introduced on a monopole structure. Additionally, a 10 × 10 unit cell FSS structure is integrated into the antenna as a far-field reflecting plane to enhance gain characteristics. The antenna, crafted with dimensions of 50 × 50 × 1.6 mm³ and a 1.6 mm thick FR4 substrate, operates across the ultra-wideband frequency spectrum, spanning from 3.1 GHz to 12 GHz, while consistently maintaining a reflection coefficient (S 11) value of – 10 dB or lower. Notably, the antenna showcases a gain of over 5 dBi across the entire 3.1 GHz to 12 GHz frequency range. The suggested antenna is ideal for microwave imaging applications due to its broad impedance bandwidth, impressive gain, and excellent directivity. Furthermore, it maintains a relatively uniform group delay, with a deviation of ±0.5 ns throughout the UWB band. In the time domain characteristics, the antenna exhibits excellent pulse handling capabilities and strong signal correlation, featuring an S 21 value of less than – 25 dB. The characteristics, observed in both the time and frequency domains, suggest that the proposed antenna holds significant potential for substantially enhancing breast cancer imaging system.

Performance enhancement of Vivaldi-shaped planar UWB antenna using a single-layer FSS reflector

This work proposes the design of a frequency-selective surface (FSS)-based planar monopole antenna for ultra-wideband (UWB) communication applications. The UWB response is observed by integrating a Vivaldi-shaped slot and by introducing a stepped-like pattern on the bottom edges of the radiating patch, while the back side is composed of a partial ground plane. This configuration results in a broad impedance bandwidth spanning from 3.11 to 20 GHz. For radiation performance enhancement of the proposed antenna, a single-layer UWB FSS reflector is placed beneath the antenna element at an optimized distance. The proposed FSS reflector employs a 3 × 3 array of fractal structure with a unit cell size of 12.25 × 12.25 mm2. The designed FSS reflector exhibits a linear phase response over a frequency range of 3.28 to 14 GHz, with a stop-band transmission coefficient less than -10 dB. The incorporation of the FSS reflector results in an increased gain, elevating it from 1 to 4 dBi at low-band frequencies, while at mid-band frequencies, the gain is increased from 1 to 6 dBi. The structural configuration of the proposed antenna yields directional far-field patterns, making it well-suited for UWB radar applications.

Vivaldi Tapered Slot Antenna for Microwave Imaging in Medical Applications

Microwave imaging has become an active research area in recent years, owing primarily to advancements in detecting the early stages of cancer. The study aimed to create a high-gain compact Vivaldi Tapered Slot antenna (VTSA) for microwave imaging in medical applications and also aims to address several challenges in the development of microwave imaging (MWI) technology for medical applications. These challenges include the ability to detect and identify abnormalities in human tissue and considering safe Specific Absorption Rate (SAR) limits for patients, the approach of balancing of penetration and resolution can be done on the design. The antenna operates at frequencies ranging from 1.7 to 3.1 GHz and is built on a low-cost Flame Retardant-4 (FR-4) substrate with a thickness of 1.6 mm. A compact exponential VTSA is initially presented while designing the proposed antenna for broad impedance bandwidth performances. The simulation used a back-to-back linear array of antennas with or without a phantom, specifically a without phantom (only antennas), a water phantom (cube shape), and an anomaly inside the water phantom. The results revealed a significant shift in the signal graph between the three results, indicating a difference in values between the three simulations. A transient domain solver calculation was used in the simulation. The designed antenna improved a gain of 6.09 dBi and a SAR of 0.326 W/kg by maximizing the edges of the exponential in the tapered section and the feedline slot area. The antenna exhibits differences in scattering parameters on each simulation of anomalies across the required frequency range. The result finds suitability of the experiment and simulation in assessing the microwave imaging capabilities. With the data presented, simulated antennas can be used for microwave imaging. The next study should aim on making a suitable imaging system with dimensions that supported in the antenna range and specifications.

Metamaterial-Based Series-Fed Antenna with a High Gain and Wideband Performance for Millimeter-Wave Spectrum Applications

This paper presents a high-gain, wideband series-fed antenna designed for 5G millimeter-wave (MMW) applications. The structure employs a substrate-integrated-waveguide (SIW)-based power splitter and metamaterials (MMs). The power divider functions effectively at 27.5 GHz, exhibiting an impedance bandwidth from 26.9 to 28.6 GHz. The series-fed dipole is assembled on the SIW-based power splitter, incorporating four dipoles with varying lengths and spacing. The dipoles are connected in series on both sides, running in parallel through a microstrip line. Effectively combining the resonances of the series-fed dipoles and the SIW results in a broad impedance bandwidth, ranging from 26.9 GHz to 34.75 GHz. The design has a gain extending from 9 to 10.5 dBi within the operating bandwidth. To improve gain performance without a substantial increase in antenna size, 11 × 6 MM unit cells were positioned in front of the antenna. As a result, the proposed antenna achieves a maximum gain of 14.1 dBi at 30.5 GHz while maintaining an operational bandwidth of 7.85 GHz. Additionally, due to the arrangement of the two MM-based series-fed dipoles, the antenna exhibits symmetrical dual-beam E-plane radiation at ±20° and 28 GHz in the end-fire direction. The developed system was experimentally validated and an excellent agreement between the simulated and measured data was demonstrated.

Design and Optimization of a Compact Super-Wideband MIMO Antenna with High Isolation and Gain for 5G Applications

This paper presents a super-wideband multiple-input multiple-output (SWB MIMO) antenna with low profile, low mutual coupling, high gain, and compact size for microwave and millimeter-wave (mm-wave) fifth-generation (5G) applications. A single antenna is a simple elliptical-square shape with a small physical size of 20 × 20 × 0.787 mm3. The combination of both square and elliptical shapes results in an exceptionally broad impedance bandwidth spanning from 3.4 to 70 GHz. Antenna dimensions are optimized using the trust-region algorithm to enhance its impedance bandwidth and maintain the gain within a predefined limit across the entire band. For that purpose, regularized merit function is defined, which permits to control both the single antenna reflection response and gain. Subsequently, the SWB MIMO system is constructed with four radiators arranged orthogonally. This arrangement results in high isolation, better than 20 dB, over a frequency band from 3.4 to 70 GHz band. Further, the system achieves an average gain of approximately 7 dB below 45 GHz and a maximum gain equal to 12 dB for 70 GHz. The system exhibits excellent diversity performance throughout the entire bandwidth, as evidenced by the low envelope correlation coefficient (ECC) (<3 × 10−3), total active reflection coefficient (TARC) (≤−10 dB), and channel capacity loss (CCL) (<0.3 bit/s/Hz) metrics, as well as the high diversity gain (DG) of approximately 10 dB. Experimental validation of the developed SWB MIMO demonstrates a good matching between the measurements and simulations.

The Design and Investigation of a Super Wideband Antenna with Dual-Band Notch Characteristics for MIMO Application

A printed monopole super wideband (SWB) antenna is presented in this paper. It consists of a beveled-shaped radiator and a tapered ground plane. It is investigated that tapering of the radiator and ground plane enhances the impedance matching and results in broad impedance bandwidth. The experimental result depicts that the antenna achieved 164.9% impedance bandwidth from 2.6 to 27.27 GHz. Furthermore, to prevent the interference caused by communication systems within the ultra-wideband (UWB) range, dual-band rejection at Wi-MAX (2.7–4 GHz). and X-band (8.5–12 GHz) are introduced by etching an H-shape and two back-to-back C-shaped notches in the radiator and feedline, respectively. The measured result demonstrates that both slots effectively reject the desired frequency bands with a small shift in the lower frequency edge from 2.41 to 2.6 GHz. In addition, the proposed antenna application is shown in the two elements MIMO system where a bowtie decoupling structure is utilized to improve the isolation. It is found that the presence of a decoupling structure improves the isolation by up to 60%. To characterize the diversity performance, parameters such as Diversity Gain (DG), Envelop Correlation Coefficient (ECC), Channel Capacity Loss (CCL), and Mean Effective Gain (MEG) are calculated and all are found in the acceptable limit.

Design and Optimization of Metamaterial-Based 5G Millimeter Wave Antenna for Gain Enhancement

In this brief, a low profile, broadband, high-gain antenna array based on optimized metamaterials (MMs) with dual-beam radiation is reported for 5G millimeters wave (mm-wave) applications. The design is a simple bow tie operating at a 5G band of 28 GHz. It consists of two bow ties with substrate integrated waveguide (SIW)-based power splitter. A broad impedance bandwidth of 26.3.29.8 GHz is obtained by appropriately combining the resonances of the bow ties and the SIW. Further, the antenna exhibits symmetrical dual-beam radiation at ±25∘ over a broad bandwidth in the end-fire direction due to the arrangement of the two radiators. A MM array has been etched in the same substrate shared with the antenna to improve the gain performance while preserving compact size. The trust-region (TR) gradient-based algorithm is used to optimize the structure dimensions and to achieve a maximum gain of 12.2 dB at 29 GHz. The developed MM-based antenna is validated experimentally with a good matching between the simulated and measured data. The system features a small size, low profile, high gain, broad bandwidth, and dual-beam in the E-plane, demonstrating its suitability for 5G mm-wave indoor scenarios.

Performance analysis of triple-band miniaturized hexagonal ultra-wideband antenna for wireless body worn applications

The creation of a network of tiny sensors installed in, on or around the human body has been facilitated by advancements in wireless communications and wearable devices. Because of its potential to transform healthcare delivery, Wireless Body Area Network (WBAN) has been increasingly important in modern medical systems over the last decade. Individual nodes (sensors and actuators) embedded in a person's clothing, body, or skin form a WBAN. Both academia and industry have increased their efforts in WBAN research and development. The wearable antenna, whether on or off the human body, is a critical component of contact with particular design in WBAN networks. Ultra-wideband (UWB) technology can provide high-capacity, short-range communications with minimal energy consumption, which is appropriate for wireless body area networks. The human body's involvement in such a device creates significant challenges for both the wearable antenna's construction and the broadcast paradigm. To achieve many functionalities, multi-band and broadband antennas are better solutions. The proposed multi-band antenna is constructed from a FR4 substrate with dimensions of (24 × 25 × 1.6) mm3. The proposed design was successfully tested with different configurations and enhanced with a broad impedance bandwidth of over 100 percent, where the UWB frequency spectrum encompassed the range from 3 to 9 GHz with a reflective coefficient of −15 dB and gain of 2.5 dBi, as well as fair radiation patterns in the Federal Communications Commission range. The SAR value of the devised antenna with and without SRR being 2 W/kg, 3.5 W/kg, respectively. This solution may be a worthy contender for meeting the UWB demands as a result, could be an excellent fit for wireless body technologies.

A Low-Profile Dual-Polarized Substrate Integrated Magneto-Electric Dipole MIMO Antenna

A magneto-electric dipole (MED) MIMO antenna with low-profile, dual-polarized, and substrate integrated properties is proposed. The antenna element is composed of four fan-shaped patches lying on the radiation plane and four vertical metal vias linking the patches and the ground. Compared with the common MED antennas, the proposed MED antenna element has a lower profile of 0.1λ. Besides, it is fed by microstrip lines via two orthogonal H-shaped slots, resulting in a broad impedance bandwidth of 40% (3-4.5 GHz) and a steady gain in the entire operational band. The ports isolation is higher than 27 dB, the cross-polarization discrimination (XPD) is higher than 37 dB, and the measured radiation efficiency is greater than 70%. Furthermore, four antenna elements are utilized to form a MIMO antenna, which can obtain better ports isolation characteristics under the condition that the element spacing is half wavelength. Finally, the MIMO antenna is simulated, fabricated and measured. The results verify the rationality of the design.

Low cross polarized leaf shaped broadband antenna with metasurface as superstrate for sub 6 GHz 5 G Applications

This article presents the design, circuit model analysis, and realization of a metasurface-based novel leaf-shaped antenna for sub 6 GHz 5 G NR frequency bands like n77 (3.3–4.2 GHz), n78 (3.3–3.8 GHz), n79 (4.4–5 GHz), and n90 (2.4–2.6 GHz) applications. Primarily, a leaf-shaped microstrip planar antenna is designed and provides a broad impedance bandwidth of 77.43% (2.2–4.98 GHz), a peak gain of 4.51 dBi, and a high radiation efficiency of 94.16%. The planar antenna is integrated with a 5 × 3 elements periodic metasurface (MS) array to enhance radiation performance. Both the radiating leaf planar and the MS layer have been designed on a low-cost FR4 epoxy substrate, and equivalent circuit models have been developed for both successively to validate the EM simulated results. The overall dimensions of the planar antenna with MS layer are 0.45 λ0 × 0.27 λ0 × 0.108 λ0, (λ0 corresponds to lowest resonant frequency f=2.7 GHz). The tested antenna with MS superstrate covers a broad range of operating frequencies from 2.29 to 4.78 GHz (2.49 GHz) with a − 10 dB impedance fractional bandwidth of 70.43% and has an excellent reflection coefficient of more than − 35 dB for the entire operating band. The experimental peak gain and higher radiation efficiency are 8.76 dBi and 96.6%, respectively. Moreover, all these parameters are extremely high in single-layer planar antennas, including the stable omnidirectional radiation pattern with very low cross-polarization of − 53.34 dB.

Design of wideband antenna using interdigital capacitance

A pair of wideband antenna serve as an impedance transformer for the proposed antenna, which consists of a dipole with periodic capacitive loading. Periodic capacitive loading is achieved at each sector by adding interlaced coupling lines. In order to create a broad impedance bandwidth, the periodic interlaced coupling lines split each arm of the dipole into five portions. Currents are dispersed on the various sections at different frequencies. The suggested antenna is an excellent choice for radar applications since it has a high gain and a low amount of cross polarisation. With the aid of innovative design methods including codirectional inclusion of interdigital capacitance, this research study proposes an interdigital capacitance for wideband (WB) applications interdigital capacitor (IDC). The suggested IDC antenna, which works between 4.70 and 11 GHz, has dimensions of 6.36x6.35x1.6 mm3. This page explores in-depth data on gain over frequency, far field patterns, and surface current distribution on antennas. The suggested antenna's feasibility is shown by simulation data that demonstrates excellent equality on return loss.

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.

A broadband single-layer substrate integrated waveguide cavity-backed slot array antenna with improved gain

ABSTRACT A single-layer substrate-integrated waveguide (SIW) cavity-backed slot array antenna with broad impedance bandwidth and improved gain is presented in this paper. In the element design, a multi-branch slot and a pair of inclined slots are designed on the top layer of the SIW as radiating structure and the grounded coplanar waveguide feeding structure are used for impedance matching, which ensures that the triple special resonant modes with the odd TE120 mode, the half TE120 mode, and a hybrid mode can be excited successfully to obtain broad impedance bandwidth and high gain, because of its low order and adjacent working frequencies points. Following this, an array antenna consisting of four elements and a four-way microstrip feeding network using only single-layer substrate structure is simulated and fabricated. The measured impedance bandwidth of the four-element array antenna achieves up to 34.4% and the measure peak gain at desired frequency band is 14.4 dBi with an aperture efficiency of 71.1%. The measured results prove that the proposed design has advantages of simple structure, broadband, and high gain, which is expected to be applied in high-speed vehicular communication system.

Eight-Element Antenna Array with Improved Radiation Performances for 5G Hand-Portable Devices

This study aims to introduce a new phased array design with improved radiation properties for future cellular networks. The procedure of the array design is simple and has been accomplished on a low-cost substrate material while offering several interesting features with high performance. Its schematic involves eight air-filled slot-loop metal-ring elements with a 1 × 8 linear arrangement at the top edge of the 5G smartphone mainboard. Considering the entire board area, the proposed antenna elements occupy an extremely small area. The antenna elements cover the range of 21–23.5 GHz sub-mm-wave 5G bands. Due to the air-filled function in the configurations of the elements, low-loss and high-performance radiation properties are observed. In addition, the fundamental characteristics of the introduced array are insensitive to various types of substrates. Moreover, its radiation properties have been compared with conventional arrays and better results have been observed. The proposed array appears with a simple design, a low complexity profile, and its attractive broad impedance bandwidth, end-fire radiation mode, wide beam steering, high radiation coverage, and stable characteristics meet the needs of 5G applications in future cellular communications. Additionally, the smartphone array design offers sufficient efficiency when it comes to the appearance and integration of the user’s components. Thus, it could be used in 5G hand-portable devices.

Compact broadband bi‐directional circularly polarized fan‐shaped patch with parasitic annular groove for S ‐band satellite applications

A novel bi-directional circularly polarized (CP) antenna with low profile, real planar configuration and broad axial ratio (AR) bandwidth is presented for S-band satellite relay communication application. The designed antenna consists of four fan-shaped patches, a sequentially rotating feed network and ground plane with annular gaps. Four fan-shaped patches are directly integrated with the feed network on the same FR4 substrate for good impedance matching and compact size. To realize the two-way radiation characteristics and excellent AR bandwidth, one parasitic annular groove on the ground plane is designed. The sequential rotation feeding network can provide good port characteristics within the available bandwidth and good AR. The properties of designed antenna was tested to validate its simulation. The final prototype is 83 × 83 × 0.8 mm3 in size and it can generate a broad impedance bandwidth for voltage standing wave ratio (VSWR) <2 of 36.6% (2.32–3.36 GHz), 3-dB AR bandwidth of 21.3% (2.6–3.22 GHz) and gain over 5.4 dB in the bi-directional direction. The miniaturization, low-cost and good CP radiation for this proposed antenna make it a better candidate for future applications in the field of spacecraft relay communication.

Wideband Back-Cover Antenna Design Using Dual Characteristic Modes With High Isolation for 5G MIMO Smartphone

A novel method of designing a wideband high-isolated dual-antenna pair using dual-characteristic modes (CMs) is presented for fifth-generation (5G) multiple-input multiple-output (MIMO) smartphone applications. A set of orthogonal CMs resonating from the square-loop slot is first introduced and works for the lower band. Then, another set of orthogonal CMs resonating from the edge branches is introduced with a shared compact radiator and works for the higher band. In combination with two sets of degenerated CMs and a capacitive coupling feeding structure, the proposed dual-antenna pair achieves a broad impedance bandwidth and high isolation without the need for any external decoupling structures. Based on this dual-antenna pair, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times $ </tex-math></inline-formula> 8 MIMO array is developed and integrated into the back cover of a smartphone, which realizes zero ground clearance on the system circuit board. To verify the design concept, prototypes of the antenna pair and MIMO array were fabricated and measured. It shows that experimental results agree well with the simulation results. More importantly, the presented <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times $ </tex-math></inline-formula> 8 MIMO array has high isolation of more than 20 dB is achieved across the operating band of 3.3–3.8 GHz.

Theory and Experiment on Stacked Circular Microstrip Patch Antennas for Low-Coupling Array Design

Based on the cavity model and Greenberger&#x0027;s addition theorem, a theory is formulated to analyze stacked circular microstrip patch antennas (S-CMPAs) for low-coupling array design. Expressions for electric fields are given. In general, the calculated electric fields agree with those simulated. Our theoretical analysis demonstrates that if the electric fields <i>E_x</i> excited by the stacked circular patches completely cancel each other out, the S-CMPA array will exhibit the self-decoupling characteristic. The vector fitting technique is adopted to extract the zeros and poles of the <i>S</i>₂₁ curve to get a deeper insight into the mutual coupling between the two S-CMPA elements. The zeros are desirable and account for self-decoupling characteristics. For experimental validation, a two-element S-CMPA array was designed, fabricated, and measured. Results show that both elements achieve a wide impedance bandwidth of 14&#x0025; (3.32&#x2013;3.82 GHz) and a low coupling level of less than &#x2212;25 dB between the two elements for the free-space half-wavelength spacing at the center frequency. In addition, the designed antenna is extended into a four-element linear antenna array, which still maintains broad impedance bandwidth and low coupling levels.

Performance analysis of Ta4C3 MXene based optically transparent patch antenna for terahertz communications

The Ta4c3 MXene based optically transparent patch antenna is designed to operate at 800 GHz. The Ta4c3 MXene is used as a patch and ground plane in the proposed transparent antenna structure. The optically transparent antennas are preferred for system miniaturization, where size and space are to be reduced as like satellite payload. The proposed antenna is designed using the finite element method (FEM) based electromagnetic solver, Ansys – HFSS. Terahertz antennas are necessary to fulfil the future transreceiver system requirements in indoor and inter satellite communications. The designed antenna has achieved broad impedance bandwidth (−10 dB) and better radiation performances in the operating band. The radiation performances of the antenna such as radiation efficiency, directivity and gain are discussed in detail. The utilization of Ta4c3 MXene for antenna design in terahertz band is discussed by comparing the radiation performances of the existing transparent antennas.