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ABSTRACT The rapid expansion of Internet of Things (IoT) applications presents unprecedented challenges for antenna design, demanding solutions that are versatile, efficient, and capable of operating across multiple frequency bands. This paper addresses these challenges through the development of a design of a multiband antenna using Auxiliary Classifier Wasserstein Generative Adversarial Network for IoT applications (DMA‐ACWGAN‐IoT). Here, the Auxiliary Classifier Wasserstein Generative Adversarial Network (ACWGAN) is employed to generate synthetic data representing electromagnetic field distributions and antenna characteristics across various frequencies. The proposed metamaterial‐based Multiple‐Input Multiple‐Output (MIMO) antenna contains four discrete elements, each provided by a micro strip feed. The structures overall width and length are 60 and 52 mm. The metamaterial is printed on a patch and dispersed from the fields with the most effective coupling. The proposed structures strong impedance bandwidth works at 8.3 GHz, 10.8 GHz, 12.3 GHz, 13.7 GHz, 16.1 GHz, and 18.1 GHz, fabricating the proposed antenna prototype using a substrate made of FR‐4 material. The proposed DMA‐ACWGAN‐IoT design provides 6.5 dB maximum gain and 25.40%, 21.60%, and 20.05% higher efficiency compared to existing dual band antenna design with resonance frequency prediction under machine learning models (DBA‐PRF‐ML), machine learning verification depending on a distinctive SWB multiple slotted four‐port high isolated MIMO antenna loaded with metasurface for the applications of IoT (SWB‐MIMO‐IOT‐ML), and dual‐band miniaturized composite right–left‐handed transmission line ZOR antenna along machine learning method for microwave communication (DB‐ZORA‐MC‐ML). [ABSTRACT FROM AUTHOR]

Summary: A simple planar wideband four‐port MIMO antenna of size 2.75휆l × 2.75휆l × 0.04휆l (휆l is the wavelength when fl is 24.26 GHz) with high isolation that offers the 24.26 to 30.2 GHz bandwidth covering the 5G FR‐2 spectrums is proposed in this work. Total fractional bandwidth of 21.8% has been achieved that covers the n257 (26.5 to 29.5 GHz), n258 (24.25 to 27.5 GHz), and n261 (27.5 to 28.35 GHz) 5G spectrums. Popular rectangular radiator‐based 4‐port MIMO antenna with symmetric stubs loaded parallel to feed line and tapered semi‐circular cut in the lower corners of patch is incorporated that exhibits an excellent isolation that is below −27 dB through the entire spectrum and the extreme realized separation is −40 dB. The projected MIMO radiator is premeditated on RT/duroid 5880 of 0.508 mm depth and permittivity (εr) of 2.2. The maximum radiation efficiency and gain of the proposed antenna are 93.07% and 6.48 dBi, respectively. The MIMO antenna parameters such as envelope correlation coefficient (ECC) were achieved lesser than 0.003, diversity gain (DG) was achieved around 10 dB, channel capacity loss (CCL) was achieved lower than 0.15 bits/s/Hz, and mean effective gain (MEG) was achieved between −3.6 dB and −3 dB throughout the impedance band, which exhibit the excellent MIMO properties, and thus, the projected antenna is appropriate for 5G/beyond 5G wireless technologies. [ABSTRACT FROM AUTHOR]

The growing need for remote healthcare monitoring and personalized treatment has driven the evolution of Wireless Body Area Networks (WBAN). This paper presents a new multiband antenna design for WBAN, featuring a dual wideband antenna that operates from 2.22 to 3.52 GHz and 4.98–11.13 GHz. The design also includes an integrated 4 × 4 artificial magnetic conductor (AMC) surface and a 4 × 3 frequency selective surface (FSS) superstrate layer that works together to reduce back radiation and improve radiation performance. The AMC unit cell produces a quintuple zero-degree reflection phase response at 2.5 GHz, 4.8 GHz, 6.5 GHz, 9.1 GHz, and 11 GHz, and the FSS superstrate generates a multiband response of the transmission coefficient at 3.24 GHz, 6.68 GHz, and 9.25 GHz, behaving as a Double Negative material at their corresponding resonant frequency. The integrated antenna design measures 0.425λ0 × 0.425λ0 × 0.17λ0 (λ0 at 2.45 GHz) and covers the most common wireless frequency bands, with an impedance bandwidth of 23.74% (2.19–2.78 GHz), 1.739% (3.99–4.06 GHz), and 72.46% (5.13–10.96 GHz). Furthermore, the integrated antenna showcases a peak gain of 11.98dBi at 7.5 GHz, a notable Front-to-Back Ratio of 25.15 dB at 8.2 GHz, and a minimal specific absorption rate (SAR) of 0.0142 W/kg at 9 GHz. These accomplishments resulted in a considerable 99.45% reduction in the overall average SAR values and achieved an 83% radiation efficiency. The effectiveness of the proposed multiband antenna design was evaluated by fabricating and testing an experimental prototype using a Vector Network Analyzer and Anechoic Chamber. Overall, the integrated AMC and FSS structures enable multiband resonance and improved radiation performance, making the presented antenna design a promising solution for future WBAN applications. [ABSTRACT FROM AUTHOR]

A proposed multiband drone shaped fractal antenna (Antenna-1) is introduced in this paper that targets the most required frequencies used for radio frequency energy harvesting applications, including WLAN-2.4G, WLAN-5G, WLAN-6G, Mobile DCS1700, Mobile LTE and WIMAX services. A novel fractal shape is designed and combined with a standard square geometrical shape in order to implement the front patch of the antenna. The antenna is simulated with CST Studio Suite software and fabricated on FR-4 substrate. Different antenna stages with parametric study and optimization were implemented to get the best performance from the drone shape fractal antenna. The multiband (Antenna-1) supports six resonate frequencies (1.7155 GHz, 2.424 GHz, 3.36 GHz, 3.789 GHz, 5.843 GHz, 6.886 GHz) with peak gain of (2.83 dBi) at the frequency 2.45 GHz and a maximum bandwidth of (0.4281 GHz) at the frequency 5.8 GHz that make it a suitable antenna for radio frequency energy harvesting applications. [ABSTRACT FROM AUTHOR]

A reconfigurable metamaterial multiband antenna operating an octa-band resonating mode is designed for IoT wireless applications. Metamaterial cell split ring resonator (SRR) and quasi-complementary split ring resonator (CSRR) are printed on the back and front sides of the proposed antenna design to achieve the multiband characteristics. The PIN diode is implemented in a slotted ground section of the antenna structure to get different wireless standards by switching the diode ON/OFF. During reverse biased (OFF) mode of diode antenna operating at eight resonant frequencies 2.42, 4.34, 5.81, 8.45, 11.02, 13.98, 16.12, and 18.87 GHz covering the IoT wireless standards such as S, C, X, Ku, and K band to identify a variety of wireless applications such as WLAN, WAIC, ITU, Satellite, and radar communication. Simple structure, stable radiation pattern, multiband operation, frequency band reconfigurability feature, reasonable gain, and efficiency are the significant features of the proposed metamaterial multiband antenna. [ABSTRACT FROM AUTHOR]

The escalating demand for versatile wireless devices has fostered the need to reduce the antenna footprint to support the integration of multiple new functionalities. This poses a significant challenge for the Internet of things (IoT) antenna designers tasked with creating antennas capable of supporting multiband operation within physical constraints. This work aims to address this challenge by focusing on the optimization of an antenna booster element to achieve multiband performance, accomplished through the design of a band-reject filter. This proposal entails a printed circuit board (PCB) measuring 142 mm × 60 mm, with a clearance area of 12 mm × 40 mm, incorporating an antenna booster element of 30 mm × 3 mm × 1 mm (0.07 λ). This configuration covers frequencies in the LFR (low-frequency range) from 698 MHz to 960 MHz and the HFR (high-frequency range) from 1710 MHz to 2690 MHz. A theoretical analysis is conducted to optimize bandwidth in both frequency regions. Finally, a prototype validates the analytic results. [ABSTRACT FROM AUTHOR]

A novel design for Vivaldi antenna is introduced to operate in more than one frequency band in the millimeter-wave spectrum range with high gain. The proposed Vivaldi antenna is planar and printed on both sides of Rogers 3003C flexible substrate. A parasitic annular ring is added to each arm of the Vivaldi antenna to adjust the impedance matching and maximize the gain. The dimensions of the antenna are optimized using the CST microwave simulator to obtain the best impedance matching bandwidths and highest gain in a compact-size antenna. The 28-GHz band is then selected due to its importance to enhance the gain and improve the operating bandwidth for the 5G applications. A gain of 10 dBi and bandwidth of 6.1 GHz are obtained at 28 GHz. A multiple-input multiple-output (MIMO) antenna system is then designed for pattern diversity for the fifth-generation mobile applications. The performance of the MIMO system is evaluated regarding the envelope correlation coefficient and the diversity gain showing good results. The optimized antenna is fabricated and its return loss and radiation patterns are measured showing good consent between the simulations and the practical work. The MIMO antenna system is also fabricated, and its performance is measured regarding the reflection and coupling coefficients showing good agreement between the measurements and simulations. [ABSTRACT FROM AUTHOR]

In this project, a metamaterial-inspired multiband antenna with a size of 32 × 22 × 1.6 mm3 is designed on FR4 dielectric material that operates at eight wireless standards with gain enhancement application. The antenna has electrical dimension of 0.2581 λ × 0.1775 λ × 0.0129 λ (32 × 22 × 1.6 mm3), at a lower resonant frequency of 2.42 GHz. The proposed design has slots with Quasi CSRR (complementary split ring resonator) and SRR (split ring resonator) cell, respectively. Antenna achieves octa-band resonant modes for IoT and wireless applications S-band WLAN, bottom C-band WAIC, WLAN, bottom X-band, superior X-band, bottom Ku-band, superior Ku-band and bottom K band with optimized radiation properties. By the implementation of the proposed frequency selective surface (FSS) with design, antenna gain is improved for the resonant bands. [ABSTRACT FROM AUTHOR]

In this paper, a metamaterial-loaded hybrid fractal multiband antenna, using Moore and Koch curves regarding wireless standards, is presented. The antenna has an electrical dimension of 0.344 λ × 0.257 λ × 0.0187 λ (29.5 × 22 × 1.6 mm3) at 3.5 GHz and is fabricated on FR-4 epoxy substrate. The structure resonates at multiple frequencies, i.e. 3.5, 4.41, 5.8, 8.26, 10.48, 13.35 and 14.42 GHz with appropriate impedance matching (S11 ≤ −10 dB) and achieves the peak gains 1.98, 2.38, 2.62, 3.91, 2.24, 3.28 and 4.11 dBi, respectively. The comparison of the simulated and measured results shows a good agreement. The frequency selective surface (FSS) is fabricated and tested. FSS is implemented with the antenna structure to enhance the antenna gain at achieved operating bands. [ABSTRACT FROM AUTHOR]

The increasing demand for wireless communication has emphasized the need for multiband antennas. This study presents a novel design for a multiband antenna with reduced specific absorption rate (SAR), high gain, and improved front-to-back ratio (FBR) achieved through the integration with a 4 × 4 artificial magnetic conductor (AMC) surface. The proposed antenna covers a wide range of wireless frequency bands, including Industrial, Scientific, and Medical, Wireless Local Area Network, Worldwide Interoperability for Microwave Access, Wi-Fi 6E, and 7, with resonating frequencies at 2.4, 3.2, 5.5, 7.5, and 10 GHz. The AMC unit cell creates four zero-degree reflection phases with double negative properties at 2.5, 3.8, 5.5, and 7.5 GHz. The compact design measures 0.23λ 0  × 0.296λ 0  × 0.0128λ 0 and placed 0.104λ 0 above an AMC surface of size 0.512λ 0  × 0.512λ 0  × 0.1296λ 0. This structure enhances the gain by up to 8.55dBi at 6.01 GHz. The proposed antenna has −10 dB impedance bandwidth for these corresponding frequencies viz 2.34–2.43 GHz (3.77%), 2.81–3.83 GHz (30.72%), 4.82–6.21 GHz (25.20%), 7–7.65 GHz (8.87%), and 8.06–10.31 GHz (24.5%). An overall average percentage reduction value of SAR taken at these frequencies has been found to be 96.11% with AMC structure. The antenna sample was successfully fabricated, and the experimental results have been found to match well with the simulation results. This integrated design offers a promising solution for wearable off-body communication devices. [ABSTRACT FROM AUTHOR]

A novel and compact frequency tunable patch antenna for Cognitive radio applications (4-8 GHz) operating on seven different frequencies is presented in this article. Essential characteristics of this antenna are large tuning range and sufficient gain. Radiating patch of the antenna is a circular shaped structure and ground plane is modified with different slotted structure for reconfiguration purpose and capacitors are used to isolate the biasing terminals of the battery from RF power. The radiating patch divided into four parts by cutting slots in required manner and PIN diodes are placed at the appropriate position to reconfigure the antenna. These RF switches vary the length of the slots and also change the resonant frequencies. Frequencies generated by the antenna are 4.62 (4.55-4.68) and 6.68 (6.60-6.84) GHz, 5.33 (5.19- 5.47), 5.59 (5.44-5.74), 5.81 (5.70-5.92), 6.12 (5.99-6.26) and 6.96 (6.85-7.15) GHz. Total substrate size of the antenna is 23×24 mm² with thickness of 1.6 mm. Dielectric substrate material used is FR-4 having dielectric constant of 4.4 and loss tangent 0.002 for simulation and fabrication purpose. Parameters of the antenna are analyzed, and simulation and measured results shows an excellent agreement. [ABSTRACT FROM AUTHOR]

A novel multiband patch antenna with a modified hexagonal structure is introduced in this paper to target the most required frequencies used for radio frequency energy harvesting applications, including WLAN-2.4G, WLAN-5G, WLAN-6G (Wireless Local Area Network), Mobile LTE (Long Term Evolution), and WIMAX (Worldwide Interoperability for Microwave Access). A novel fractal shape is designed and combined with a conventional hexagonal geometrical shape in order to implement the front patch of the antenna. The proposed antenna is simulated with CST Studio Suite software and fabricated on FR-4 substrate. Different antenna stages with parametric study and optimization were implemented to get the best performance from the proposed antenna. The proposed multiband antenna (Antenna-1) supports four resonate frequencies (2.4045 GHz, 3.568 GHz, 4.6405 GHz, 5.869 GHz) and has a high gain of (3.2 dBi) at the frequency of 2.4045 GHz. The proposed antenna covers all of the WLAN-2.4G (IEEE 802.11) frequency band and achieved a maximum bandwidth of (0.5101 GHz) at a frequency of 5.869 GHz, making it a suitable antenna for radio frequency energy harvesting applications. The measured results have shown good agreement with the simulation results. Furthermore, an evaluation of this proposed work in comparison to other published works highlighted the advantages in terms of antenna thickness, size, gain, and the number of supported operating frequencies. Also, the comparison showed that the FR-4 substrate used to implement this proposed work is much cheaper than other substrate types used to implement other published works. [ABSTRACT FROM AUTHOR]

5G mobile communication technology has attracted much attention in the past three years. However, the development of antennas that can cover three types of 5G bands at once has not been studied. This paper proposes an antenna covering the three frequency bands of 2.3 GHz, 3.5 GHz, and 26 GHz for 5G communication. The proposed antenna uses a microstrip patch design with 50-ohm inset feeding. FDTD mathematical analysis through simulation has been carried out and confirmed that the proposed antenna meets the required specifications in 5G technology. The simulation result shows that the proposed antenna has a good reflection coefficient in the target frequencies of -22.6 dB, -28.26 dB, and -22.48 dB, respectively.

We propose a miniaturized frequency-reconfigurable multiband antenna with bandwidth enhancement. The main radiating patch is shorted from one edge to reduce the antenna footprint. An inverted U-shape microstrip line is integrated onto the antenna structure to excite more resonant frequencies. Indeed, by shorting the U-shape's arms, seven frequency bands can be created and controlled. The activation of the two p-i-n diodes is ensured by employing a simple symmetrical DC bias network. Furthermore, by adjusting the arms' lengths, two resonances are combined to enhance the working bandwidth. Measurements reveal that the antenna resonates around the operating frequencies of 2.91 GHz, 3.55 GHz, 3.69 GHz, 3.83 GHz, 4.14 GHz, 4.18, and 4.24 GHz. The antenna exhibits stable patterns, with a measured peak gain and efficiency of 5.5 dBi and 86%, respectively. The antenna is compact; thus, it is recommended in wireless systems requiring multiband function with stable patterns and a reduced area. [ABSTRACT FROM AUTHOR]

This letter investigates the properties of a novel multi-band fractal antenna with a triangular geometry that can expand its bandwidth, provide multiband functionality, and enable the best smart antenna technology. The antenna employs an FR4 as support with dimensions of 75×75 mm2 and a thickness of 1.6 mm. A microstrip line with an impedance of 50 ohms feeds the patch. The high-frequency structure simulator (HFSS) is applied to develop and simulate the patch. The vector network analyzer AVR ROHDE and SCHWARZ ZVB20 carried out the experimental tests of the prototype antenna. The suggested antenna’s simulation results show that it runs on five main frequency bands: 1.840 GHz, 2.770 GHz, 2.940 GHz, 4.330 GHz, and 5.790 GHz, with a high gain that can exceed 6.01dB and an efficiency of 82%. In the operational bands, the voltage standing wave ratio (VSWR) is between one and two. The results from the simulation and the experiment are extremely similar. [ABSTRACT FROM AUTHOR]

A compact, coplanar waveguide (CPW)-fed multiband antenna is developed and analyzed in this paper for quad-band applications. Christmas tree-like monopole antennae with three symmetric slots are designed on a low-cost FR4 epoxy substrate with the overall dimensions of 0.312λ1 × 0.364λ1 × 0.0083λ1 where λ1 is the wavelength corresponding to the lower cut-off frequency. Three rectangular-shaped slots of different dimensions are etched on the three triangular-shaped stacked patches to enhance the current carrying path due to which the proposed antenna resonates at the required frequency bands. Different antenna parameters such as reflection coefficient (S11), gain, radiation efficiency, surface current, radiation pattern, group delay and magnitude response of transfer function (S21) are analyzed for inspecting the antenna performance. The quad-band antenna offers measured bandwidths of 3.1–3.9 GHz (22.86%), 5.46–5.98 GHz (9.1%) 9.76–11.74 GHz (18.42%) and 17.55–19.25 GHz (9.24%). The antenna shows nearly omnidirectional radiation patterns in all resonating bands with the highest gain of 4.5 dBi and measured radiation efficiency greater than 70% in all the bands. The antenna also offers stable group delay response and linear S21 response in its operational spectrums. All these characteristics ensure the antenna's applicability in IEEE 802.16 WiMAX band, 5.5 GHz Wi-Fi band, 5.8 GHz ISM band, terrestrial broadband, radiolocation and earth explorer satellite applications. [ABSTRACT FROM AUTHOR]

In this letter, a compact circular cavity‐backed, circularly polarized substrate integrated waveguide (SIW) multiband antenna is proposed. In the outer circular cavity, an array of two periodic metal slots, tilted at an angle, resonate at 25.32, 26.44, and 28.83 GHz, and the inner circular cavity's periodic slots radiate at 28.01 GHz. Two concentric SIW cavities are structured in such a distinct manner that no loss due to leakage takes place thus, achieving a maximum isolation of −43.8 dB at 28.83 GHz. The miniaturized antenna has dimensions of 2.2λo × 2.2λo × 0.1λo where λo is the operating wavelength. It achieves a maximum gain of 9.1 dBi at 26.44 GHz, and VSWR < 2 is achieved at all frequency bands. The antenna is circularly polarized at 26.44 and 28.01 GHz as well. The design results are plotted in the Ansys high‐frequency structure simulator version EM19.2 tool. The proposed antenna is fabricated and tested using an Anritsu Vector Network Analyzer version v4.0 with an anechoic chamber setup. [ABSTRACT FROM AUTHOR]

With the advanced communications systems, the integration of 5G bands, including sub‐6‐GHz and millimeter‐wave (mm‐wave) bands with the existing lower bands of 3G/4G has become an essential need for the future mobile handsets. This article proposes an integration between a large‐frequency‐ratio dual‐band tapered slot antenna with a multisection meander monopole antenna on a handset board. The tapered slot Vivaldi antenna (TSVA) functions as a resonant open‐ended slot at low frequencies (sub‐6 GHz) while also acting as a high‐gain Vivaldi antenna at higher frequencies (mm‐wave 28 GHz). The modification of the slot geometry, that is, generating multisections within the slot, is shown to improve the impedance bandwidth. Furthermore, the meander‐line monopole antenna covers the bands of the existing mobile generation (3G/4G) at 0.8, 1.8, 2.1, and 2.3 GHz. Most importantly, the compact size of the proposed antenna is realized by utilizing the side wall of a mobile board. [ABSTRACT FROM AUTHOR]

A small-size multiband antenna with 14 bands is presented in this paper for wireless applications. The studied antenna mainly consists of a folded monopole antenna and an M-shaped structure. Furthermore, the antenna has a simple design with a compact dimension of 26.8 × 10.8 mm2. The studied antenna is printed on FR4 substrate with a depth of 0.8 mm and fed by a coaxial cable. The −10 dB bandwidths measured are 210 MHz (1200–1410 MHz), 100 MHz (2200–2300 MHz), 193 MHz (3000–3193 MHz), 180 MHz (3330–3510 MHz), 390 MHz (4110–4500 MHz), 4971 MHz, 577 MHz (5300–5877 MHz), and 700 MHz (7100–7800 MHz), which can cover 3G/4G/5G/Wi-Fi/WiMAX, C, and S bands. The gain and efficiency of the presented antenna are 1.3–4.00 dBi and 46%–60.2%, respectively. [ABSTRACT FROM AUTHOR]

In this article, a meta-material inspired penta-band fractal antenna is proposed for wireless applications. It is constructed by integrating the Complementary Split Ring Resonator (CSRR) and decagon fractal structure. The decagon is the regular polygon with 10 sides. Three layers are constructed in the proposed design to obtain the multiple operating frequencies with better performance. Top layer has the decagon structure with ten slots and second-order Koch loop radiating element. The rectangular patch layer and CSRR layer are the bottom layers. Dielectric material FR4 is selected to design the suggested antenna. The measurement results reveal that the projected antenna has five resonant frequencies at 2.63 GHz, 3.98 GHz, 4.78 GHz, 5.52 GHz and 5.91 GHz with a bandwidth of 230 MHz, 300 MHz, 80 MHz, 200 MHz, and 290 MHz. Gain is observed about 3.29 dB, 4.44 dB, 5.71 dB, 4.22 dB and 3.99 dB at the corresponding resonant frequencies.

In this paper, a low-cost resin-coated commercial-photo-paper substrate is used to design a printed reconfigurable multiband antenna. The two PIN diodes are used mainly to redistribute the surface current that provides reconfigurable properties to the proposed antenna. The antenna size of 40 mm × 40 mm × 0.44 mm with a partial ground, covers wireless and mobile bands ranging from 1.91 GHz to 6.75 GHz. The parametric analysis is performed to achieve optimized design parameters of the antenna. The U-shaped and C-shaped emitters are meant to function at 2.4 GHz and 5.9 GHz, respectively, while the primary emitter is designed to operate at 3.5 GHz. The proposed antenna achieved peak gain and radiation efficiency of 3.4 dBi and 90%, respectively. Simulated and measured results of the reflection coefficient, radiation pattern, gain, and efficiency show that the antenna design is in favorable agreement. Since the proposed antenna achieved wideband (1.91–6.75 GHz) using PIN diode configuration, using this technique the need for numerous electronic components to provide multiband frequency is avoided. [ABSTRACT FROM AUTHOR]

Multiband antenna arrays have the capability of effectively working in multiple frequency bands and thus significantly simplify the antenna system. To further reduce the system overhead, this paper discusses the joint design of antenna selection and adaptive beamforming for multiband antenna arrays, where the sidelobe level is also controlled so as to alleviate the effect of unknown sporadic interference. Based on the maximum signal-to-interference-plus-noise ratio (SINR) criterion and sidelobe level constraints, the proposed multiband sparse array design is formulated into a nonconvex constrained nonlinear optimization problem with an l 0 , 2 -mixed norm regularization. This problem ensures that the same antenna positions are selected at all operating frequencies while the beamformer weights of each frequency are optimized independently. By exploiting the semi-definite relaxation and the reweighted l 1 , ∞ -norm approximation, the problem is converted into a series of convex subproblems and is then effectively solved by the proposed iterative reweighted method. Numerical results show that the proposed multiband sparse array significantly reduces the sidelobe levels in all operating frequencies while maintaining the maximum SINR, so it provides superior performance of interference suppression. [ABSTRACT FROM AUTHOR]

Low cost, miniaturization, and high gain are the most essential prerequisites for multiband antennas (MBA). Therefore, a tactical effort is made in this paper to realize a small-size MBA (X, Ku, K-band) with considerable gain. The E-shaped patch embedded in a substrate integrated waveguide (SIW) cavity contributes to the primary radiation. The E-shaped patch with defective ground structure (DGS) helps to achieve multiband operation. Two additional metallic vias are placed near the tapered position to improve the impedance matching as compared to conventional tapered microstrip transition. The equivalent circuit model (ECM) is developed to examine the resonant frequencies. The circuit elements are identified and tabulated with equivalent changes in the geometric parameters. The parametric variation using ECM and the full-EM model are presented. The SIW structure provides the advantage of improved gain and small cross-polarization levels. The proposed antenna size is 0.68 × 0.95 × 0.05 λ03. The performance parameters of the fabricated prototype are tested and found to exhibit the same behavior as depicted by simulated results. The measured peak gain at 10.29, 11.87, 14.15 and 19.36 GHz are 5, 6.5, 5.2, 5.92 dBi, respectively. The proposed structure finds applications in stringent radar applications and satellite communications in emergency circumstances (e.g. electronic news gathering (ENG) and satellite news gathering (SNG), television outside broadcast and electronic field production). This antenna also reveals the significant advantages of being lightweight and gain efficiency. [ABSTRACT FROM AUTHOR]

In this letter, a deca-band substrate-integrated waveguide (SIW) antenna with filtering function is proposed. The number of slots was increased from 4 to 10, and the quad-band antenna design is extended to a deca-band antenna. At this time, good impedance matching characteristics are maintained without changing other parameters except the patch length. The fabricated deca-band antenna has 10 resonances between 3–4.4 GHz and a broadside radiation pattern characteristic at each resonance frequency, and the measured gain is 1.8–4.2 dBi.

The escalating demand for versatile wireless devices has fostered the need to reduce the antenna footprint to support the integration of multiple new functionalities. This poses a significant challenge for the Internet of things (IoT) antenna designers tasked with creating antennas capable of supporting multiband operation within physical constraints. This work aims to address this challenge by focusing on the optimization of an antenna booster element to achieve multiband performance, accomplished through the design of a band-reject filter. This proposal entails a printed circuit board (PCB) measuring 142 mm × 60 mm, with a clearance area of 12 mm × 40 mm, incorporating an antenna booster element of 30 mm × 3 mm × 1 mm (0.07 λ). This configuration covers frequencies in the LFR (low-frequency range) from 698 MHz to 960 MHz and the HFR (high-frequency range) from 1710 MHz to 2690 MHz. A theoretical analysis is conducted to optimize bandwidth in both frequency regions. Finally, a prototype validates the analytic results.

A modified Minkowski multiband fractal antenna is proposed for satellite applications. In this work, at first, the Minkowski fractal is applied to the conventional square patch. Then, modification is done at the patch corners. Finally, a modified Minkowski fractal is implemented to design the proposed fractal antenna. The addition of fractals along with these modifications helps in achieving compact size and the required bands for the proposed satellite applications. The antenna is resonating at five different bands at 7.7 GHz, 16.8 GHz, 18.2 GHz, 24.2 GHz, and 28.7 GHz with a VSWR < 2. The resonant frequencies cover the satellite frequencies in the C, Ku, K, and Ka bands. The radiation patterns have unidirectional shapes for all five bands, with a gain of 5.8 dB to 9 dB and a front-to-back ratio above 15 dB. The antenna has radiation efficiencies of 80%-95%, covering all the resonating bands. The multiband fractal antenna, with its compact size and improved radiation characteristics, can be a suitable candidate for different satellite applications. [ABSTRACT FROM AUTHOR]

Body centric Networks (BCNs) are the most important and attractive part of the next generation (5G and beyond) wireless technologies having a plethora of applications in day to day life. However the design of antennas for BCNs is a challenging task. Such antennas should have small size, light weight, higher gain and larger bandwidth besides having a stable radiation pattern under the influence of human body effects. This paper presents a miniaturised Ka/V dual band mmWave microstrip antenna for 5G BCN applications. The antenna has very small dimensions of 2.28 × 3.06 × 0.14 mm3 and operates at 33.5 GHz (Ka band) and 60.8 GHz (V band). The performance of the antenna is examined for “Off-body, On-body and In-body” BCN application scenarios. The radiation pattern, return loss, peak gain and −10 dB bandwidth results reveal that the antenna performs quite well at all interested frequencies. A comparative study with state of art mmWave antennas also shows the effectiveness of the proposed antenna.

Microstrip antennas have many advantages as they are low-profile, suitable for conformal structure, and integrated with electronic circuits. The antenna characteristics can be easily modified by shape transformation. In this work, a multiband microstrip antenna is developed. The antenna operates in 2.4 GHz, 3.5 GHz and 3.15 GHz reconfigurable as well as tunable modes. A pin diode switch and another varactor diode switch are used for the frequency band reconfiguring and tuning respectively. The switches are integrated into two coupled parasitic transmission lines without disturbing the main radiator structure. Using a pin diode, the operating band is switched between 3.15 and dual 2.4 and 3.5 GHz bands. Simultaneously by applying a reverse bias voltage to the varactor diodes, frequency tuning is done in respective bands. The simulated model of the antenna is fabricated and tested. The measured results are found satisfactory. [ABSTRACT FROM AUTHOR]

Radio Frequency Energy Harvesting is found to be the best alternative to conventional batteries for providing endless power to the sensor networks connected to perform various applications in the smart city. The electromagnetic energy density in the ambient environment is very low and not uniform, which demands a high gain multi-band rectenna system operating at mostly available energy bands and a suitable rectifier circuit that offers large PCE performance. This paper introduces a triple-band monopole rectenna with enhanced performance for smart city applications. A defective ground structure (DGS) has been investigated for a significant increase in gain with an increasing number of resonant frequencies. The proposed antenna operates over a band of frequencies that lies within 1.25–3 GHz, which covers 1.8/2.1/2.45 GHz frequencies. The antenna offers the gain values of 4.16/6.54/10.2 dB at 1.8/2.1/2.45 GHz frequencies, respectively. A single diode series-connected rectifier has been opted to efficiently operate over a wide range of input power levels from −10 dBm to 5 dBm and offers a minimum conversion efficiency of 60% within the operating bands at 0 dBm input power. The rectenna system is experimentally measured and the measured output voltage at 2.45 GHz frequency is 1.123 V. [ABSTRACT FROM AUTHOR]

A compact planar antenna is proposed to operate in five millimeter-wave frequency bands at 28, 51, 55, 59, and 63 GHz. The antenna is designed to produce circular polarization at 28 GHz and linear polarization at the other four frequencies. The 28 GHz frequency band is recommended for long range communications, whereas the other four frequencies are recommended for short range communications due to the atmospheric absorption in this range of the millimeter-wave frequencies and to provide more secure communications. The reasons behind the selection of the specific values of the higher frequency bands (51, 55, 59, and 63 GHz) are (i) to provide enough number of multiple bands at such unlicensed frequency range to be used as alternatives for different applications, (ii) to give about 4 GHz separation between the center frequencies of each band and, (iii) finally, to avoid the operation at 60 GHz, in particular, due to the peak atmospheric absorption of millimeter-wave encountered at this frequency. The antenna is constructed as a square patch surrounded by five parasitic elements that are capacitively coupled to the square patch so as to realize the location of the resonant frequencies of the higher frequency bands. The antenna is fabricated and its performance is experimentally evaluated. The proposed antenna is shown to operate efficiently over the five frequency bands 28, 51, 55, 59, and 63 GHz providing impedance matching bandwidths of 2.0, 0.9, 1.2, 1.1, and 1.6 GHz, respectively. The corresponding values of the maximum gain are 7.0, 6.8, 6.0, 6.0, and 8.0 dBi, respectively. Also, the corresponding radiation efficiencies are 90, 90, 91, 78, and 86%, respectively. The 3 dB-axial ratio bandwidth at 28 GHz is about 1.2 GHz. [ABSTRACT FROM AUTHOR]

In this work, a miniaturized quad-band monopole antenna design is presented for IoT applications. The proposed antenna comprises simple quarter-wavelength I-shaped, an inverted L-shaped, meander lines monopole radiators with microstrip feed line, tapered ground plane having dimension of 32 × 15 mm 2 and fabricated on an FR4 substrate. The radiation characteristics, such as reflection coefficient, VSWR, gain, efficiency, and radiation patterns, are analyzed from simulation and measurement results. The proposed quad-band antenna resonates at 1.8 (1.7–1.96) GHz, 2.4 (2.26–2.47) GHz, 3.35 (3.1–3.7) GHz, and 5.4 (5-5.65) GHz for GSM, WLAN, 5G, WiMAX applications respectively. Further, the proposed antenna has a fractional bandwidth of 14.4% at 1.8 GHz, 8.75% at 2.4 GHz, 17.9% at 3.35 GHz and 12.03 % at 5.4 GHz. It also exhibits omnidirectional radiation pattern with a gain of 1.5, 1.75, 2.5, and 3.7 dbi at 1.8, 2.4, 3.35, 5.4 GHz respectively and >75% total efficiency at its operating bands. The suitability of the designed antenna for IoT applications is validated through the hosting device model with copper sheet and plastic housing. The simulation and measurement results are having good agreement. [ABSTRACT FROM AUTHOR]

In this work, we propose a novel multiband meander line antenna that can operate at three different frequency bands and offer suitable performance for wireless body area network (WBAN) applications. The net geometry of the antenna is 36 × 30 × 1.524 mm 3 . The proposed low-profile antenna is analytically modeled and designed in full wave ANSYS HFSS using Rogers TMM4 as the substrate, followed by in-lab prototyping. The designed antenna resonates at 4.5 GHz, 5 GHz, and 5.8 GHz and maintains positive gain, efficiency, and acceptable specific absorption rates at each resonant band. The effectiveness of the antenna for WBAN applications is demonstrated using an in-lab manufactured phantom. The fabrication process of the phantom is described, and dielectric characterization of the phantom mimicking different human tissue layers is presented. Considering results with and without human body phantoms available in the full wave ANSYS HFSS tool, a comparative analysis between simulated and measured antenna parameters concludes this work. Both the simulated and measured results show good agreement. [ABSTRACT FROM AUTHOR]

A novel highly miniaturized triple band structure based on Z‐slots‐shaped antenna is presented in this letter, with only 0.0015 λ02 ${{\rm{\lambda }}}_{0}^{2}$ footprint, where λ0 ${{\rm{\lambda }}}_{0}$ is the free space wavelength at 1.3 GHz. The proposed design can generates three resonant frequency bands (1.3–1.62 GHz), (2.22–2.59 GHz), and (3.24–3.65 GHz) with −10 dB reflection coefficient, a triple band function is achieved by etching tow connected Z‐shaped‐slots in the radiating element and the differential evolution algorithm is then used to control the currents path, the prototype of the proposed antenna is printed on a single substrate layer and fed via coplanar waveguide CPW technology. The measured and simulated results are in good agreement, and validate the design principle, the results show that the antenna has a compact size (19.5 × 17.6 mm2), aside from its planar design, simple manufacturing, and low cost to fabricate, this antenna exhibits stable omnidirectional radiation patterns in E plane as well as bidirectional radiation patterns in H plane, making it an ideal device for multiband applications. [ABSTRACT FROM AUTHOR]

A dual‐wideband planar dipole antenna for WLAN and WiMAX applications is proposed. The antenna is mainly composed of a U‐shaped dipole which is fed by a parallel double transmission line. The U‐shaped dipole is employed to generate a wide lower band and a narrow higher band. To expand the higher band, two pairs of strips are used to symmetrically embed in the U‐shaped arms of the dipole. The tested results demonstrate that this antenna achieves two wide bandwidths about 53.6% (2.33–4.02 GHz) and 23.7% (5.04–6.45 GHz) at the higher and lower frequency band, which can satisfy the requirement of the whole 2.4/5.2/5.8‐GHz WLAN and 2.5/3.5/5.5‐GHz WiMAX bands. [ABSTRACT FROM AUTHOR]

Flexible inkjet-printed antenna is presented. The proposed antenna is designed on a synthetic paper substrate with an area of 35 × 40 mm2 to provide frequency bands for many popular wireless applications. Simulation and measurement are used to study the performances, including the frequency bands, radiation patterns, peak gains and efficiency, of the antenna in two severely bending conditions with a curvature radius of 20 mm in the forward and backward directions. The antenna printed in photo papers material could not be fully flexible due to cracks introduced to the coating material on the surface of the photo paper. Hence, the resin coated material was only suitable for curved devices. The synthetic paper material used in this paper does not have a resin coating, therefore, the antenna does not lose its flexibility and can be bent in both the forward and backward directions without any cracks. Results show that bending in these two conditions has insignificant effects on the performances of the antenna. With a curvature radius of 20 mm in the forward direction, the measured peak gain and efficiency of the antenna are in the ranges from −3 to +2 dBi and 40% to 60%, respectively. The results together with the low cost make the antenna most suitable for many flexible 5G communications devices.

This article represents a Multiple Input Multiple Output (MIMO) hybrid fractal antenna with wider bandwidth. The hybrid fractal MIMO antenna is created by integrating Minkowski and Koch curves on a half octagonal radiating patch. A wider impedance bandwidth 20.4GHz (1.0 to 21.4GHz) and 6.10GHz (23.9 to 30GHz) along with fractional bandwidth of 182.14% and 22.63% has been achieved by using an amalgamated fractal configuration and a tapered microstrip line feed. The proposed antenna retains high isolation between -20 to -50dB in the entire frequency range along with the DG value greater than 9.99 dB and the ECC less than 0.02. The operating frequency increases from 1.5GHz to 8.5GHz with gain of 8dBi .The gain is almost flat and varies between 4dBi to 7dBi in the frequency range from 8.5GHz to 21.1GHz. Further, in the frequency range from 23.9 to 25.9GHz, the gain rises exponentially to 14dBi Hence, the proposed hybrid fractal MIMO antenna is a proficient candidate for 5G, 3.5GHz band (3.4 – 3.6GHz), 5G NR (New Radio) frequency bands (3.3 – 5.0GHz), LTE band 46 (5.15 – 5.925GHz), EU (European Union) 5G frequency band (5.9 – 6.4GHz), UWB applications (3.1 – 10.6GHz) and 5G 26GHz frequency band.

Advances in information technology have dramatically enhanced mobile phones. Power capacity is one of the most significant limitations of a mobile phone. As a result, efficient energy management in such devices is critical everywhere. The goal of this research is to find a way to charge electronic devices wirelessly using radio frequency (RF) electromagnetic (EM) waves (Rectenna using energy detection-based spectrum sensing). Mechanical deformations cause frequency detuning, which lowers the effectiveness of antennas and rectennas that would otherwise allow wireless communication and RF energy harvesting in the far field. A rectenna based on a stretchable multiband antenna is designed as a self-powered system to perform reliably and integrate RF power received across its multiband despite mechanical deformations. Depending on what the battery needs, the proposed multiband antenna will work at 900 MHz, 1800 MHz, 2100 MHz, and 2.45 GHz as both an RF transducer and an RF energy harvester. Depending on the received RF power density (high), the receiving RF wave will be utilized for both communication and RF energy harvesting (RF-EH) when the battery's current voltage is less than 20% (referred to as “low voltage”). Otherwise, the received RF wave will be used only for RF-EH. The installed multiband rectifiers function perfectly in terms of efficiency and bandwidth. This proposed technique would reduce the charging crisis by 60–90% depending on the location of the mobile phone or receiver of ambient EM signals. This paper could help researchers in the field of RF energy-based wireless charging systems.

In this paper, a flexible and compact multiband wearable antenna with a simple and low-profile structure is proposed and investigated. It is able to operate over the frequency ranges from 0.824 GHz to 0.975 GHz and from 1.90 to GHz to 6 GHz, covering the most of identified frequency bands for biomedical applications. Moreover, the antenna demonstrates robust on-body performance and provides a suitable balance between small antenna size, high on-body radiation efficiency (between 5% and 11% for operating frequency bands), and a low value of the maximum 10 g specific absorption rate (0.47 W/kg) on a homogeneous semisolid phantom. [ABSTRACT FROM AUTHOR]