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Summary: In this research work, a compact‐sized offset‐fed broadband monopole antenna is designed using a frequency selective surface (FSS) reflector to enhance gain, radiation efficiency, and FBR and validated experimentally. The designed antenna consists of a triple v‐slit on a rectangular‐shaped radiating patch, a modified partial ground, and a frequency‐selective surface (FSS). It exhibits a ‐10 dB impedance bandwidth of 9.37 GHz (6.55–15.92 GHz) and a fractional bandwidth of 83.4%, yielding significant portions of the C‐band (4–8 GHz), the X‐band (8 GHz–12 GHz), and covering a considerable part of the Ku‐band (12–18 GHz). The proposed prototype equivalent circuit model has been developed progressively to validate the electromagnetic simulation results. The measured peak gain is 14.25 dBi (6.8 dBi without FSS) at 14.2 GHz with an average radiation efficiency of ≥ 96% for the FSS integrated antenna. Furthermore, the proposed design improves the front‐to‐back ratio (FBR) by 15 dB throughout the broadband frequency range. The proposed antenna peak gain, reflection coefficient (S11), radiation efficiency, and radiation patterns show adequate similarity between the tested and simulated results and have numerous advantages, including very compact size, simple structure, minimum S11 (dB), high gain, and broadband capability. [ABSTRACT FROM AUTHOR]

The Netherlands‐China Low‐Frequency Explorer (NCLE) (Boonstra et al., 2017, https://www.ursi.org/proceedings/procGA17/papers/Paper%5fJ19‐2(1603).pdf; Chen et al., 2020, https://ui.adsabs.harvard.edu/abs/2020AAS...23610203C/abstract) is a radio instrument for astrophysical studies in the low‐frequency range (80 kHz–80 MHz). As a technology demonstrator, NCLE shall inform the design of future radio receivers that aim at low‐frequency radio astronomy. NCLE can make observations at very high spectral resolution (<1 kHz) and generate radio sky maps at an angular resolution of ≈1.5 radians. NCLE uses three monopole antennas, each 5 m long, and three identical analog signal chains to process the signal from each antenna. A single digital receiver samples the signal and calculates the auto‐correlated and cross‐correlated spectra. The instrument's analog and digital signal chains are extensively configurable. They can be fine‐tuned to produce broadband spectra covering the instrument's complete operating frequency range or sub‐bands. NCLE was developed within a veryshort timescale of 2 years, and currently, it is on board Queqiao, the relay spacecraft of the Chang'e‐ 4 mission, in a halo orbit around the Earth‐Moon L2 point. This paper outlines the science cases, instrument architecture with focus on the signal chain, and discusses the laboratory measurements during the pre‐launch phase. Key Points: Radio observations from the Moon at very low frequenciesRadio instrument technology demonstration for future lunar observatory and interferometryRadio receiver design for low‐frequency observation [ABSTRACT FROM AUTHOR]

This paper presents a novel circular fractal ring monopole antenna for ultra-wideband (UWB) hardware with dual band-notched properties. The proposed antenna consists of four crescent-shaped nested rings, a tapered feeding line at the front of the dielectric material, and a semicircular ground plane on the backside. In this design, the nested rings are used both as a radiation element and a band rejection element. The proposed antenna has a bandwidth of 9.03 GHz, which works efficiently in the range of 2.63 GHz-11.66 GHz with the dual notched bands of Worldwide Interoperability for Microwave Access (WiMAX) at 3.15 GHz-3.66 GHz and wireless local area network (WLAN) at 4.9 GHz-5.9 GHz, respectively. The antenna has a compact size of 20 mm X 30 mm X 1 mm (0.177 X 0.265 X 0.0084 λ0) and is implemented using a flame-retardant type 4 (FR4) material. It has a maximum gain of approxi-mately 4 dB in its operating range, and experimental results support the simu-lation predictions with high accuracy. The findings of this study imply that the designed antenna can be utilized in UWB applications.

This article presents two monopole antennas with an endfire radiation pattern in the UHF band that can be installed on dry walls or metallic cabinets as a part of wireless sensor nodes, making them a suitable choice for smart home applications, such as the wireless remote control of house appliances. Two different antennas are proposed to cover the RFID bands of North America (902–928 MHz) and worldwide (860–960 MHz). The antennas have wide horizontal radiation patterns that provide great reading coverage in their communication with a base station placed at a certain distance from the antennas. The structures have two ground planes, one in-plane and the other vertical. The vertical ground helps the antenna to have a directive radiation and also makes it easily installed on walls. The antenna feeding line lies over the vertical ground substrate. The maximum dimensions of the narrow-band antenna are L × W = 0.3 λ   × 0.14 λ , and those for the wide-band antenna are L × W = 0.39 λ   × 0.14 λ. The measured results show that the bandwidth of the proposed antennas for the North America and worldwide RFID bands are from 902 MHz to 939 MHz and 822 MHz to 961 MHz, with maximum gains of 4.2 dBi and 4.9 dBi, respectively. [ABSTRACT FROM AUTHOR]

A novel dual-wideband textile antenna designed for wearable applications is introduced in this study. Embedding antennas into wearable devices requires a detailed analysis of the specific absorption rate (SAR) to ensure safety. To achieve this, SAR values were meticulously simulated and evaluated within a human voxel model, considering various body regions such as the left/right head and the abdominal region. The proposed antenna is a monopole design utilizing denim textile as the substrate material. The characterization of the denim textile substrate is carried out using two different methods. The first analysis included a DAC (Dielectric Assessment Kit), while a ring resonator technique was employed for the second examination. Operating within the frequency bands of (58.06%) 2.2–4 GHz and (61.43) 5.3–10 GHz, the antenna demonstrated flexibility in its dual-wideband capabilities. Extensive simulations and tests were conducted to assess the performance of the antenna in both flat and bent configurations. The SAR results obtained from these tests indicate that the antenna complies with safety standard limits when integrated with the human voxel model. This validation underscores the potential of the proposed antenna for seamless integration into wearable applications, offering a promising solution for future developments in this domain. [ABSTRACT FROM AUTHOR]

Summary: The proposed antenna is a small wideband monopole with wideband circular polarization using heterogeneous bidirectional recurrent neural network for both narrow and wide band applications (NWB‐MAD‐HBRNN). The electromagnetic structure is designed, fabricated, and simulated with 1 mm thickness on FR4 substrate material along dielectric constant 4.3. The proposed antenna includes 4.3–8.85 GHz for ultrawideband applications; it contains reconfigurable narrow band for L‐band 1.27 GHz, LTE, and ultrawideband applications. To enhance the antenna impedance bandwidth (BW) along axial ratio bandwidth (ARBW), a slit is etched at the antenna patch, a rectangular stub is inserted into the ground plane, and semicircular stub is added to the top of antenna feed line. The better agreement is observed in the measured and simulated gain performance of 4.8 dB for LTE band applications. The proposed NWB‐MAD‐HBRNN design provides 13.50%, 18.91%, and 22.58% higher bandwidth and 18.36%, 20.38%, and 27.58% lower return loss than the existing designs, such as bio‐inspired wideband antenna for wireless applications based on perturbation technique (BWA‐WA‐PA), a compact circularly polarized modified printed monopole antenna for wireless applications (CCP‐MPMA‐WA), and new multiband monopole antenna for certain broadband wireless applications along wireless personal communications (PA‐MMA‐BWA), respectively. [ABSTRACT FROM AUTHOR]

Visualizing the near-field distribution of microwave field in a monopole antenna is very important for antenna design and manufacture. However, the traditional method of measuring antenna microwave near field distribution by mechanical scanning has some problems, such as long measurement time, low measurement accuracy and large system volume, which seriously limits the measurement effect of antenna microwave near field distribution. In this paper, a method of microwave near-field imaging of a monopole antenna using a nitrogen-vacancy center diamond is presented. We use the whole diamond as a probe and camera to achieve wide-field microwave imaging. Because there is no displacement structure in the system, the method has high time efficiency and good stability. Compared with the traditional measurement methods, the diamond probe has almost no effect on the measured microwave field, which realizes the accurate near-field imaging of the microwave field of the monopole antenna. This method achieves microwave near-field imaging of a monopole antenna with a diameter of 100 µm and a length of 15 mm at a field of view of 5 × 5 mm, with a spatial resolution of 3 µm and an imaging bandwidth of 2.7~3.2 GHz, and an optimal input microwave phase resolution of 0.52° at a microwave power of 0.8494 W. The results provide a new method for microwave near-field imaging and measurement of monopole antennas. [ABSTRACT FROM AUTHOR]

BACKGROUND: Food adulteration has long been considered a major problem. It compromises the quality, safety, and nutritional value of food, posing significant risks to public health. Novel techniques are required to control it. RESULTS: A graphene‐based T‐shaped monopole antenna sensor was tested for its ability to detect adulteration in liquid foods. Mustard oil was the pure reference sample used for product quality analysis. Olive oil and rice bran oil were adulterants added to the pure sample. It was found that the sensor could be immersed easily in the liquid sample and provided precise results. CONCLUSION: The graphene‐based T‐shaped monopole antenna sensor can be used for the quality assessment of liquid food products and is suitable for real‐time monitoring. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has linear polarization characteristics. By adding L-shaped parasitic branches and L-like grounded branches on both sides of the monopole, the 7 GHz operating frequency band can be moved to the 5.8 GHz frequency band, and circular polarization characteristics can be achieved in both the 2.45 and 5.8 GHz frequency bands. The size of the antenna is 48.7 mm × 42.1 mm × 1.016 mm. The simulated −10 dB impedance bandwidths of the antenna are 1.8–2.66 GHz and 5.48–6.98 GHz, respectively. The 3 dB axial ratio bandwidths are 2.34–2.67 GHz and 5.58–6.39 GHz, respectively, and it has dual-band circular polarization characteristics. In addition, the radiation characteristics of the antenna and its safety performance near the human body were analyzed. The antenna prototype has been constructed, and the measurement and simulation results have good consistency. The proposed antenna is suitable for application in wearable devices. [ABSTRACT FROM AUTHOR]

This paper presents a novel circular fractal ring monopole antenna for ultra‐wideband (UWB) hardware with dual band‐notched properties. The proposed antenna consists of four crescent‐shaped nested rings, a tapered feeding line at the front of the dielectric material, and a semicircular ground plane on the backside. In this design, the nested rings are used both as a radiation element and a band rejection element. The proposed antenna has a bandwidth of 9.03 GHz, which works efficiently in the range of 2.63 GHz–11.66 GHz with the dual notched bands of Worldwide Interoperability for Microwave Access (WiMAX) at 3.15 GHz–3.66 GHz and wireless local area network (WLAN) at 4.9 GHz–5.9 GHz, respectively. The antenna has a compact size of 20 mm × 30 mm × 1 mm (0.177 × 0.265 × 0.0084 λ0) and is implemented using a flame‐retardant type 4 (FR4) material. It has a maximum gain of approximately 4 dB in its operating range, and experimental results support the simulation predictions with high accuracy. The findings of this study imply that the designed antenna can be utilized in UWB applications. [ABSTRACT FROM AUTHOR]

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This research proposes omnidirectional circularly polarized monopole antennas (OCPA) with single-annular (SA-AMC) and dual-annular artificial magnetic conductor (DA-AMC) ground planes. The aim of the proposed antenna scheme is to circumvent the design rigidity of conventional OCPA whose inherent shortcoming is fixed bottom ground plane size. The OCPA with SA-AMC ground plane consists of a monopole element, four diagonally adjoined parasitic elements to convert linear to circular polarizations, and an SA-AMC ground plane. The OCPA with DA-AMC ground plane consists of a monopole element, four diagonally adjoined parasitic elements, and a DA-AMC ground plane. Unlike the conventional OCPA, the bottom ground plane radius $(R_{\text {g}})$ of the OCPA with SA- and DA-AMC ground planes can be varied between 18.4 – 188.4 mm; and 29.2 – 119.2 mm, respectively, without affecting the omnidirectionality and impedance and axial ratio (AR) bandwidths of the OCPA. Furthermore, the SA- and DA-AMC ground planes effectively improve the impedance ( $\left |{{S_{11}}}\right | \leq -\,10$ dB) and AR bandwidths (AR $\leq 3\,{}$ dB) while reducing leakage current on the coaxial feeder cable. The measured $\left |{{S_{11}}}\right |$ and AR bandwidths of the OCPA with SA-AMC ground plane, given the optimal $R_{g} $ of 18.4 mm, are 8.08% (5.34 – 5.79 GHz) and 4.38% (5.36 – 5.60 GHz), while those of the OCPA with DA-AMC ground plane, given the optimal $R_{\text {g}}$ of 29.2 mm, are 14.37% (5.10 – 5.89 GHz) and 19.85% (4.90 – 5.98 GHz). The novelty of this research lies in the use of SA- and DA-AMC structures to circumvent the design rigidity of the conventional OCPA. Essentially, the integration of the AMC structures offers design flexibility in the realization of OCPA.

This study experimentally demonstrates both inter-chip and intra-chip RF transmission for short-range microwave communication using on-chip antennas, implemented on a silicon photonic platform. The unification of antenna with photonic integrated circuits (PICs) reduces system loss for high data rate communication by eliminating parasitics. We designed, fabricated, and measured two antenna topologies (blade and triangular) for intra-chip communication and one (meander antenna) for both inter-chip as well as intra-chip communication. The three on-chip antenna topologies have resonance at 15.7 GHz, 13.2 GHz, and 12.6 GHz, and maximum transmission coefficient (S21) value above −30 dB for all antennas. Their operation is further validated by low return loss value (S11 ≤ −20 dB), indicating strong impedance matching with minimal power reflection. The intra-chip RF data transmission has been confirmed with bit- error-rate (BER) measurements of below 10−9 up to a data rate of 4 Gbps. We have also performed inter-chip communication between two on-chip antennas separated by a distance of upto 18 mm and accomplished 4 Gbps transmission with BER < 10−9. Our findings indicate that on-chip antennas integrated onto silicon photonic chips provides a seamless conversion between electrical and optical signals. This integration enables various on-chip RF wireless applications such as chip-to-chip and off-chip communication, along with wireless sensing off-chip. Furthermore, the incorporation of an integrated antenna facilitates the realization of integrated RF photodetector-antenna emitters on a silicon photonic chip, thereby significantly reducing size, weight, area, and power requirements.

In this work, a tapered fed circular-shaped monopole antenna for ultrawideband (UWB) applications integrated with four frequently-used band-notched properties is designed. By the design of notch structures inside the radiation patch, on the feedline, and on either side of the feedline, four notch bands covering from3.3–3.8 GHz, 5.25–5.75 GHz, 7.25–7.75 GHz, and 8.01–8.5 GHz are obtained possibly, which suppress the interference with WiMax, WLAN, satellite downlink and ITU applications, respectively. Based on these, the proposed antenna is operable from 1.4 GHz to 25 GHz with maximum coupling value of −20 dB covering almost operational band, and it has compact dimensions of $43\times 36\times 1.59$ mm3. Evolution and accomplishment of final results, involving the reduction of mutual coupling suppression, are illustrated gradually. The property of the monopole antenna considering reflection coefficient, isolation among different ports, realized gain, radiation pattern, efficiency, and envelope correlation coefficient (ECC) are studied. Moreover, experimental results are verified with the simulations. In addition, using the antenna inserted in chest badge, the chance of infection will greatly reduce. Ultimate, the proposed MIMO monopole antenna has a potential application in the medical, high precision machining, and biopharming relevant domains.

In this paper, a hybrid model chipless radio frequency identification (RFID) tag is introduced. It is constructed by using multi-resonator circuit with a bandstop filter simultaneously. Bandstop filter section is conventionally designed by quarter-wave open-circuited stubs, while the multi-resonator circuit is developed by coupling dual-band codirectional split ring resonators (CDSRRs) to a feeding line. Each stub and CDSRR can provide two and four frequency codes, respectively. The open-circuited stubs can form the resonant frequencies within wide frequency range, while the CDSRRs have notch band characteristics. The proposed hybrid model approach has the ability of combining notch and wide band resonant frequencies on a single circuit. A 12-bit chipless RFID tag is designed by locating two wideband monopole antennas vertically and horizontally at the end of the multi-resonator circuit. The monopole antennas are formed by using two orthogonal ellipses. 000000000000 and 100100100100 frequency coded two tags have been experimentally investigated. [ABSTRACT FROM AUTHOR]

The paper proposes a circularly polarized dual band single feed microstrip monopole antenna. The proposed antenna consists of a radiating patch, a shrink ground plane, and a 50 Ω microstrip transmission line feed. The radiating patch is a combination of three modified metallic strips, a modified rectangular strip and a semicircular strip. The ground plane consists of two modified open ended slots. The substrate area of the antenna is only 40 mm × 42 mm × 1.6 mm. The antenna has been designed by HFSS simulation software and after getting simulated results the antenna has been fabricated to verify its results. The antenna provides measured bandwidths (−10 dB impedance bandwidth) of 600 MHz (2.2–2.8 GHz) in the lower band and 2.1 GHz (7.5–9.6 GHz) in the higher band. The measured results show its 3 dB axial ratio bandwidth of 120 MHz (2.2–2.32 GHz) for lower band and 1.4 GHz (7.2–8.6) GHz for the upper band. The high measured peak gain of 8 dBi has been obtained from the proposed antenna. The lower band is useful for WiMAX application and upper band is useful for C band application. The desired radiation patterns (RHCP and LHCP) have been obtained from the proposed antenna. [ABSTRACT FROM AUTHOR]

In this paper, a portable tri-band MIMO antenna with 1 × 1 and 2 × 2 inputs and outputs is developed for wireless applications. A decagon-shaped ring and two U-shaped radiating structures make up the proposed antenna, which can generate three resonance frequencies. Without utilizing any decoupling structures, the suggested antenna achieves improved isolation. The coplanar waveguide structure supplies all of the antennas, which are printed on the front side of the FR-4 substrate, which has a surface area of 18 × 18 mm. The suggested antenna serves a wide range of applications, including WLAN (5.2 GHz), Wi-max (5.5 GHz), and 5G n34 band, with an impedance bandwidth of − 10 dB over 1.98–2.03 GHz, 3.55–3.70 GHz, and 4.8–6.4 GHz (2 GHz). For tri-band MIMO antenna, the gain is (0.28 dB, 1.3 dB and 2.7 dB) and efficiency is (80%, 83%, and 91.5%). For MIMO, tri-band antennas are placed in rotational symmetry with respect to the adjacent ports. Distance between MIMO tri-band antenna is 20 mm. Isolation for tri-band MIMO antennas is (− 40 dB, − 28.5 dB and − 27 dB). ECC for tri-band MIMO antenna is 0.003. The fabricated antenna and simulated results agree quite well. As a result, the suggested antenna can be employed for WLAN and 5G applications. [ABSTRACT FROM AUTHOR]

This paper proposes the design of a compact sub-6 GHz four-port flexible antenna for utilization in 5G applications. A two-arm monopole with a coplanar waveguide feed line printed on a flexible substrate was proposed to shape the single-element antenna. The single element was designed, fabricated, and measured first; then, four copies of the single element were organized on a single flexible substrate to compose the four-port antenna. The MIMO antenna was simulated, fabricated, and experimentally measured. All the simulations and measurements of the flexible single element and MIMO antennas are presented. The presented MIMO antenna showed good impedance characteristics, with a deep level of −24 dB from 3 to 4.12 GHz. The antenna had omnidirectional and bi-directional patterns in the φ = 0° and φ = 90° planes. As an important parameter evaluation for MIMO, the mutual coupling between the different ports was investigated. The diversity gain (DG), the total active reflection coefficient (TARC), the mean effective gain (MEG), the envelop correlation coefficient (ECC), and the channel capacity loss (CCL) parameters were investigated and showed good performance. All the obtained simulation results were in a high degree of agreement with the measurement results, supporting the usage of the suggested antenna in 5G communications. [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]

This paper describes the design and analysis of a reconfigurable radiation pattern dual-band antenna for Wi-Fi and WLAN applications. The antenna patch comprises two parts: the upper part, which consists of three symmetrical oval rings, and the lower part, which is shaped like a lotus flower. By controlling the ON and OFF states of lumped p-i-n switches to control the direction of the radiation beams, the proposed pattern reconfigurable antenna achieves three reconfigurable states. The beam's direction change is performed by two switches that are connected in the gap between the feedline and the arch. The proposed antenna operates at 2.4 and 5.5 GHz, covering the bands from 2.1882 to 2.55 GHz and from 5.31 to 5.96 GHz, respectively. Additionally, the directivity over the working bands is about 1.92 to 4 dBi while the gain lies in the range of 1.66 to 3.5 dB. Moreover, the voltage standing wave ratio (VSWR) varies from 1 to 1.20. The size of the antenna is 47×59.5 mm2 which is printed on a 1.6 mm thickness FR-4 substrate of 4.4 relative permittivity. Computer simulation technology Microwave Studio is used to design and study the recommended constructions. The proposed design achieves an acceptable value of VSWR, stable gain, and good directivity, which makes it a suitable choice for future radiation pattern reconfiguration applications. The proposed antenna is distinguished by a simple shape, compact size, respectable return loss, good radiation characteristics, and high efficiency. The obtained results from measurements are quite close to the simulations.

The dynamic-type seawater monopole antenna has the problem of direct connection between its radiation body and the seawater. This makes the radiation current flow into the seawater, which leads to low radiation efficiency. In this paper, a dynamic-type seawater monopole antenna of high efficiency is proposed using an inductive reactance isolated method. Based on this method, a dynamic seawater antenna of seawater inductance isolation structure is designed. According to its equivalent circuit diagram, the principle and design basis of isolation are analyzed. The FEKO software is then used to simulate the antenna's radiation efficiency. In addition, the impacts of the radius of the seawater inductance, the number of turns of the seawater coil, the diameter of the seawater coil, and the average turn spacing on the efficiency of the antenna are studied. Moreover, the experimental verification shows that the radiation efficiency of the designed dynamic seawater antenna with inductive reactance isolation structure can be greater than 70%. The value of the received carrier power in the case of inductance isolation is higher by 10 dB compared with the case without isolation. [ABSTRACT FROM AUTHOR]

The increasing prevalence of the Internet of Things (IoT) as the primary networking infrastructure in a future society, driven by a strong focus on sustainability and data, is noteworthy. A significant concern associated with the widespread use of Internet of Things (IoT) devices is the insufficient availability of viable strategies for effectively sustaining their power supply and ensuring their uninterrupted functionality. The ability of RF energy-harvesting systems to externally replenish batteries serves as a primary driver for the development of these technologies. To effectively mitigate concerns related to wireless technology, it is imperative to adhere strictly to the mandated limitations on electromagnetic field emissions. A TA broadband polarization-reconfigurable Y-shaped monopole antenna that is improved with a SADEA-tuned smart metasurface is one technique that has been proposed in order to accomplish this goal. A Y-shaped printed monopole antenna is first taken into consideration. To comprehend the process of polarization reconfigurability transitioning from linear to circular polarization (CP), a BAR 50-02 V RF PIN Diode is employed to shorten one of the parasitic conducting strips to the ground plane. A SADEA-driven metasurface, which utilizes the artificial intelligence-driven surrogate model-assisted differential evolution for antenna synthesis, is devised and positioned beneath the radiator to optimize performance trade-offs while increasing the antenna's gain and bandwidth. The ultimate prototype achieves the following: an impedance bandwidth of 2.58 GHz (3.27–5.85 GHz, 48.45%); an axial bandwidth of 1.25 GHz (4.19–5.44 GHz, 25.96%); a peak gain exceeding 8.45 dBic; and when a highly efficient rectifier is integrated, the maximum RF-DC conversion efficiency of 73.82% and DC output of 5.44 V are obtained. Based on the results mentioned earlier, it is considered appropriate to supply power to intelligent sensors and reduce reliance on batteries via RF energy-harvesting mechanisms implemented in hybrid wireless applications. [ABSTRACT FROM AUTHOR]

A penta-band circular polarized ultra-wideband (PBCP-UWB) antenna design is proposed for UWB applications. The PBCP-UWB structure comprises a circular radiator with L-shaped slits which is fed by a microstrip feed line. The proposed antenna is fabricated on an FR4 substrate. Further, the performance of the PBCP-UWB antenna is analyzed based on different parameters including impedance-matching bandwidth, fractional axial ratio, and radiation efficiency. The proposed antenna provides a fractional axial ratio bandwidth of 17.75% (3.81–4.53 GHz), 0.2% (6.91–7.05 GHz), 3.9% (9.29–9.66 GHz), 0.744% (10.71–10.79 GHz), and 1.671% (18.40–18.71 GHz), while its fractional impedance-matching bandwidth is 170%. The major advantage of the proposed PBCP-UWB antenna is its simplicity of design which results in good radiation efficiency. The measurement results for the fabricated antenna are found to be similar to those of the simulations. [ABSTRACT FROM AUTHOR]

A dual-band UWB coplanar waveguide monopole antenna is presented in this paper. The antenna proposed in this paper consists of an FR4 substrate, two ground planes, and a rectangular patch. The size of the antenna proposed is 24 x 25 x 1 mm³ with a slit of length and width of 5.7 and 0.5 mm, respectively. We received two operating bands, a C- and Ku-band, with both Bi and Omni-directional radiation patterns. The bandwidth values of the first (3.65-7.49) GHz and second (11.5-13.4) GHz band of the proposed antenna are 3.9 GHz and 1.7 GHz, respectively. The proposed antenna operating at a frequency 5.8 GHz has a maximum bandwidth of 4.5 GHz and minimum bandwidth of 1.6 GHz. The characteristics of this antenna show that the antenna proposed in this paper is suitable for dual-band and UWB communication systems. We achieved a wide bandwidth by improving the ground plane. [ABSTRACT FROM AUTHOR]

This paper presents a hepta-band planar monopole antenna which exhibits circular polarization (CP) at two bands and linear polarization at other five bands. Combination of rectangular slots to form a single E-shaped structure has been introduced in half ground to excite hepta-band operations. Asymmetric trapezoidal parasitic element is also placed under the monopole radiator positioned at upper half ground plane of antenna. Due to asymmetric effect attained by the placement of trapezium, CP is achieved at 4.2 GHz and 10 GHz with 3-dB axial ratio bandwidth of 4.21–4.29 GHz and 9.92–10.01 GHz, respectively. The antenna acquires remaining five resonant modes at 2.4 GHz, 5.4 GHz, 7.2 GHz, 8.86 GHz and 11.8 GHz with 10-dB impedance bandwidth of 90 MHz, 160 MHz, 100 MHz, 200 MHz and 410 MHz, respectively. Sensitive study of the E slot and trapezoidal structured geometry is conducted. The proposed antenna is designed on low cost FR4 (εr = 4.4, tanδ = 0.02). To ensure the practicability, the proposed antenna design is fabricated and measured. A good agreement of simulation and measurement validates the proposed designed. The antenna has potential to cover frequency bands of IEEE802.11, Bluetooth, WLAN, WiMAX, Satellite Communication, Short Range RADARs and Radio band applications. [ABSTRACT FROM AUTHOR]

In this paper, novel chipless radio frequency identification (RFID) tags are designed by using asymmetrical triple mode resonators constructed by an open loop resonator with two open stubs in different lengths. Three transmission zeros (bits) can be obtained by coupling a proposed resonator to a straight feeding line that connects input/output ports. Five frequency codes can be achieved with respect to the existence of the open stubs and the open loop resonator. By coupling eight asymmetrical triple mode resonators to the feeding line, a multi-resonant circuit is developed on a flexible substrate of Rogers 5870. Totally 24 bit frequencies can be achieved and it is possible to identify 58 different items. For the chipless RFID tags, two monopole wideband antennas in vertical/horizontal polarizations are integrated instead of the input/output ports. Two tags have been fabricated and tested to demonstrate the identification of different codes under smoothed and curved positions successfully. [ABSTRACT FROM AUTHOR]

This communication presents the significance of a four-port 2×2 multiple input multiple output antenna operating in mid-band frequency for 5G handheld device application. A microstrip-fed reference truncated decagonal monopole antenna operating at 3.9 GHz and a modified split-ring resonator (SRR)-based low-pass filter that excites at a cut-off frequency of 6.5 GHz are designed. On introducing a stub line in the SRR structure, the proposed filter shows a good out-of-band rejection beyond 6.5 GHz. By integrating the filter into the reference monopole, a wideband filtering monopole with improved stopband performance is obtained. A four-port MIMO array is constructed by orthogonally positioning the antenna with a center-to-center separation of 0.25 λ 0. To improve isolation, a pair of inverted L-stubs of varying lengths is introduced. The closed loop formed by the interconnection of stubs enhances isolation within the frequency range of 3–3.5 GHz. The fabricated prototype fosters an impedance bandwidth of 66.67%, isolation >18.5 dB, an average suppression of 15 dB, an average peak gain >3.7 dB, envelope correlation coefficient < 0.015, Actual Diversity Gain (ADG) > 9.9 dB, Effective Diversity Gain (EDG) > 8.8 dB, and efficiency >88%. The proposed design is suitable for 5G sub-6 GHz applications such as n48, n77, n78, n79 bands, WiMAX, and LTE bands 42, 43, 46, 47, 48. [ABSTRACT FROM AUTHOR]

A compound reconfigurable monopole antenna (CRMA) having ability to change its frequency, polarisation and also pattern is presented in this paper. Only 6 PIN diodes are positioned on the monopole and ground to achieve reconfigurable operations and thus the antenna can operate over 8 different states. The radiation patterns of the proposed antenna can be tilted into two different directions. In each direction, the antenna can shift its operation in between two different frequency bands, and for each band, switching between two orthogonal circularly polarised (CP) radiation can be possible. A prototype is fabricated and measured. Based on various parametric analyses, a simple design guideline is also presented. By considering its overall simple configuration, low profile, and planar geometry, proposed antenna can be a useful candidate for future wireless applications like cognitive radio, 5 G devices, and so on. [ABSTRACT FROM AUTHOR]

In this study, a high-gain wideband circularly polarized (CP) printed monopole antenna for wireless local-area network (WLAN), worldwide interoperability for microwave access or WiMAX, C-band, and multiple input, multiple output (MIMO) applications was proposed and demonstrated. The proposed antenna structure has an octal-shaped monopole antenna tilted by 20° from its longitudinal axis, excited by coaxial probe feeding, and partial ground plane. To achieve broadband CP performance, the ground plane was redesigned with etching slots. A 1.6-mm-deep FR-4 (εr = 4.3) substrate with dimensions of 70x55 mm2 is used to create and test a prototype of the suggested antenna. The proposed antenna's measurement results satisfy requirements for a broad ARBW of 107% (1.83-6.05 GHz), a broad impedance bandwidth of 139.39% (2-11.2 GHz), and a maximum gain of 7.28 dBi. [ABSTRACT FROM AUTHOR]

We designed, fabricated, and evaluated a monopole water antenna (WA) filled with pure water. A 2.4 GHz patch antenna (PA) was used for measurement comparison, and the current density distribution and 3D field strength radiation distribution and reflection coefficient of the PA had a fundamental mode and a higher-order mode at 3.5 GHz, whose polarization was 90 degrees different. The 2.4 GHz monopole WA could receive only the fundamental mode of the PA. The 3.5 GHz WA could receive the higher-order mode of the PA by rotating the WA by 90 degrees. The transmission coefficient of the 2.4 GHz WA decreased with the square of the spacing, similar to the spatial propagation characteristics of electromagnetic waves. Almost the same results could be expected if planar or three-dimensional antennas were used instead of monopole electrodes.

Visualizing the near-field distribution of microwave field in a monopole antenna is very important for antenna design and manufacture. However, the traditional method of measuring antenna microwave near field distribution by mechanical scanning has some problems, such as long measurement time, low measurement accuracy and large system volume, which seriously limits the measurement effect of antenna microwave near field distribution. In this paper, a method of microwave near-field imaging of a monopole antenna using a nitrogen-vacancy center diamond is presented. We use the whole diamond as a probe and camera to achieve wide-field microwave imaging. Because there is no displacement structure in the system, the method has high time efficiency and good stability. Compared with the traditional measurement methods, the diamond probe has almost no effect on the measured microwave field, which realizes the accurate near-field imaging of the microwave field of the monopole antenna. This method achieves microwave near-field imaging of a monopole antenna with a diameter of 100 µm and a length of 15 mm at a field of view of 5 × 5 mm, with a spatial resolution of 3 µm and an imaging bandwidth of 2.7~3.2 GHz, and an optimal input microwave phase resolution of 0.52° at a microwave power of 0.8494 W. The results provide a new method for microwave near-field imaging and measurement of monopole antennas.

A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has linear polarization characteristics. By adding L-shaped parasitic branches and L-like grounded branches on both sides of the monopole, the 7 GHz operating frequency band can be moved to the 5.8 GHz frequency band, and circular polarization characteristics can be achieved in both the 2.45 and 5.8 GHz frequency bands. The size of the antenna is 48.7 mm × 42.1 mm × 1.016 mm. The simulated −10 dB impedance bandwidths of the antenna are 1.8–2.66 GHz and 5.48–6.98 GHz, respectively. The 3 dB axial ratio bandwidths are 2.34–2.67 GHz and 5.58–6.39 GHz, respectively, and it has dual-band circular polarization characteristics. In addition, the radiation characteristics of the antenna and its safety performance near the human body were analyzed. The antenna prototype has been constructed, and the measurement and simulation results have good consistency. The proposed antenna is suitable for application in wearable devices.

Due to space limitations, multi frequency multiple-input multiple-output (MIMO) antennas have strong coupling problems caused by small unit spacing. In order to solve the above problems, a mine high isolation tri-band MIMO antenna has been designed. By loading two L-shaped branches at both ends of a rectangular branch to form a trident monopole antenna, the antenna has tri-band features. Two trident monopole antenna units are placed symmetrically. A T-shaped branch is loaded on the metal floor between the two units. The opposite current generated by parasitic branches is used to offset the coupling current without branches. Two symmetrical rectangular slots are etched to suppress the mutual coupling caused by surface waves on the floor by changing the current distribution on the floor. The high isolation of the antenna throughout the entire band is achieved. The simulation results show that the antenna operates in frequency bands of 1.85-2.70, 3.24-3.99, 4.65-5.80 GHz, can effectively covering coal mines' underground WiMAX/WiFi/4G/5G NR operating band. The isolation of the antenna in three bands is greater than 20, 22, 22 dB, respectively. It is 11, 9, 10 dB higher than the isolation of the antenna before decoupling; The envelope correlation coefficient is less than 0.2, indicating good diversity performance. The antenna has stable gain variation within the operating band and good omnidirectional radiation features. This antenna has the advantages of simple and compact structure, easy processing, and low profile. It has a wide range of application scenarios in wireless communication in coal mines.

This article presents a novel two‐element printed monopole MIMO design for dual‐band operation with high port isolation and compact size. Upper‐band (f2) decoupling is achieved by the optimal meandering of the monopole, while the lower band (f1) decoupling is attained by the insertion of a new T‐shaped neutralization line structure. Unlike conventional decoupling techniques, the proposed method offers independent control of decoupling performance at two widely spaced frequency bands, without any bulky structure. For validation, a printed monopole MIMO antenna designed to operate at 2.45 and 5.0 GHz, is fabricated and measured. Simulation and experimental results indicate that the proposed dual‐band antenna exhibit high port isolation (20 dB/25 dB) with enhanced efficiency (92%) and reduced ECC values (<0.05). [ABSTRACT FROM AUTHOR]

In this manuscript a stair case shaped planar monopole antenna for LoRa WAN application is proposed. The proposed unit element produces peak resonant at 2.41GHz with the operating bandwidth of 150MHz. The proposed structure has been constructed on FR4 substrate of thickness of 1.6mm with the dimension of 15 x24mm². The equivalent electrical dimension is 0.12 λo x 0.19 λo. A quad element MIMO structure has been constructed using the designed unit cell. The physical dimension of the MIMO array is 39 x 39 mm² and electrical equivalent is 0.31λo x 0.31 λo. The mutual coupling between the adjacent elements are <-18 dB. The measured Envelope Correlation Coefficient (ECC) of the antenna is < 0.05, gain is 1.17dBi and efficiency is 76.4%. [ABSTRACT FROM AUTHOR]

In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antenna’s gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antenna’s overall physical dimensions would be 38.8 mm×38.8 mm×25.2 mm (0.407λo×0.407λo×0.265λo), with λo denoting the lowest frequency’s free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antenna’s small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications. [ABSTRACT FROM AUTHOR]

This paper presents the design of a miniaturized polyimide-based antenna for ultra-wideband (UWB) communication. Miniaturization is achieved through the utilization of adhesive material with a high dielectric constant (high-Dk). The goal of this work is to investigate the impact of such material on the antenna performance and to optimize its design for UWB operation. The manufacturing of the antenna using the proposed structure is developed, and the prototype of an antenna for the UWB high band (6–9 GHz) is measured and analyzed. By leveraging the high Dk of the adhesive material, the simulation and measurement results show that the proposed antenna with a high-Dk adhesive film can achieve compact dimensions with good performance in terms of the gain and time domain characteristics. The results of this study show the potential of exhibiting a reduction in the size of the antenna and will contribute to the advancement of miniaturized UWB antenna technology. [ABSTRACT FROM AUTHOR]

A uniquely shaped layout of a wideband circularly polarized (CP) printed monopole antenna is planned in this article. The proposed antenna comprises a 7‐shaped slotted radiating patch, tapered feed line, and modified partial ground plane. Multiple parasitic strips are employed at optimum positions on the ground and radiating planes to improve the axial ratio bandwidth (ARBW). The electrical dimension of the designed antenna is 0.49λ0×0.44λ0×0.03λ0 $0.49{\lambda }_{0}\times 0.44{\lambda }_{0}\times 0.03{\lambda }_{0}$. The confirmed −10 dB impedance bandwidth (IBW) and 3 dB ARBW are 11.86 GHz (3.14–15 GHz), 130% and 6.32 GHz (4.04–10.36 GHz), 87.78% along with 75° $75^\circ $ coverage angle. The proposed antenna is suitable for different applications in communication systems such as WLAN, WiMAX, FM CW altimeter, and satellite for C‐ and X‐ band. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband Multiple-Input-Multiple Output (MIMO) Monopole antenna is proposed for frequency-notched applications. The proposed MIMO antenna consists of two identical Monopole antennas excited by two microstrip feeds. A stub is attached to the ground plane to improve isolation and impedance bandwidth. A quarter wavelength spur line is embedded on the feeding part of the antenna to achieve the notch frequency. The designed antenna exhibits −10 dB impedance bandwidth, covering the entire UWB spectrum. The L-shaped spur line contributes to the notch frequency at 5.5 GHz aiming to avoid interference from 5 to 6 GHz WLAN band. The planned model is fabricated and described in terms of impedance and radiation constraint measurements, compliant with those of results achieved from full wave simulation. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a fractal‐based compact new monopole antenna for wideband applications. The miniaturization has been achieved by incorporating Minkowski and Koch‐snowflake fractals. The proposed antenna design is etched on top of Rogers RT/5880 dielectric material with a dimension of 8.10×8.10 mm2. The antenna is designed, analyzed, fabricated, and tested in the laboratory. The proposed geometry operates over a 8.62–22.40 GHz with fractional bandwidth (FBW) of 88.84% and VSWR is less than 2. The proposed monopole antenna exhibits nearly omnidirectional radiation patterns over the entire resonating band with a gain of 1–2.91 dBi and a radiation efficiency of more than 60.5%. Also, the measured results of the prototype make an excellent agreement with the simulated counterpart. Further, the antenna gives good time‐domain characteristics. Therefore, the proposed miniaturized antenna can be used in X/Ku/K‐band applications. [ABSTRACT FROM AUTHOR]