Advanced Electromagnetics

A Super-Wideband Miniaturized Graphene-Based Folded Monopole Antenna

L. Guo — Sat, 15 Feb 2025 00:00:00 +0100

A graphene-based folded monopole antenna with super-wideband bandwidth and a small volume is proposed in this paper. The antenna features a disc-loaded folded cylindrical configuration that mainly consists of graphene-powder and graphene-ink cylinders, along with copper discs. Two primary radiation modes are generated and combined to achieve the desired super-wideband bandwidth. The applied graphene-powder and graphene-ink cylinders serve as crucial radiating and tunable elements, rendering the antenna impedance matched across the super-wideband range. Furthermore, direct current (DC) excitation combined with conducting wires is utilized to improve impedance matching and enhance the operating bandwidth toward lower frequencies. The measured results indicate that the antenna has a super-wideband operating bandwidth across 0.114-0.202 GHz and 0.34-18 GHz (|S11| <-6 dB). The measured antenna peak gains range from -3.75-3.50 dBi. The antenna dimensions can be maintained at 0.006λL ×0.006λL × 0.011λL, where λL is the wavelength in free space at the lowest operating frequency.

Polarization-independent wideband meta-material rasorber with wide transmission window based on resistor loaded circular and split ring resonators

A. Kumar, G. Sen, J. Ghosh — Thu, 20 Feb 2025 00:00:00 +0100

A dual polarized with high absorption to right side and wide in-band transmission is proposed in this study. Our proposed design consists of four modified split ring resonators on the top layer and four lumped resistor of 150 Ω value is connected between them to absorb the incoming EM wave in the out-ofband frequency regime.The circular slotted cut on the lower layer is responsible for in-band transmission. The lower layer is behaving as a ground plane for out-of-band absorption and and passing a range of frequency for the transmission band. So, bottom layer is behave as a band-pass frequency selective surface filter. The design has an overall thickness of 0.18λ and a fractional bandwidth of approximately 113%. The entire design exhibits an insertion loss of 1.10 dB at the transmission band at around 5.93 GHz and exceeding 80% absorption from 2.8 GHz to 10.0 GHz. The proposed design is polarization insensitive due to its symmetrical design and angularly stable up to 45Åã for both both TE and TM polarization of wave. The novelty of the proposed design lies in its wide out-of-band absorption, wide in-band transmission, minimal thickness, high fractional bandwidth, good angular stability, cost-effectiveness, accessibility through the use of inexpensive materials for manufacture and simple design. To analyze the proposed rasorber, we have investigated the polarization behavior, surface current distribution and design other parameters. Lastly, the proposed structure has been constructed using PCB technology and validated in a semi-anechoic chamber. The simulated and measured responses exhibit a high degree of agreement.

In-House Design, Manufacturing, and Testing of a 2.856 GHz Combline Microwave Cavity Filter for the Low-Level RF Systems of Linear Particle Accelerators

Thu, 20 Feb 2025 00:00:00 +0100

A combline microwave cavity filter has been developed to generate the 2.856 GHz radio frequency (RF) tone to be used as the master reference of SPARC_LAB electron linac facility at the Frascati National Laboratories of the National Institute for Nuclear Physics (LNF-INFN). The filter must select the 36th harmonic from a frequency comb with a repetition frequency of 79.33MHz and reject the other harmonics. The comb is generated by the electric conversion of the laser pulse train from the oscillator of the photocathode laser. Since a filter for this very specific application is off-the-shelf, it was designed, manufactured, and tested in-house at LNF-INFN. The measured insertion loss at the center frequency is 2.2 dB, the bandwidth is 30MHz (percentage fractional bandwidth is 1.1 %). This narrow bandwidth is required to ensure effective rejection (insertion loss > 65 dB) of adjacent harmonics in the frequency comb, specifically at frequencies of 2.77633 GHz and 2.93533 GHz. The purpose of filtering is to ensure that the tone, distributed in the low-level RF system, remains clean and can be used to synchronize the most crucial machine subsystems, such as RF power units, accelerating cavities, diagnostic systems, and lasers.

Enhancing Plasma Density through Periodic Dielectric Grating Structures-Numerical Simulations

D. Kakulia, K. Tavzarashvili, I. Noselidze, G. Kajaia — Sat, 24 Aug 2024 00:00:00 +0200

This paper proposes an idea of the use of Dielectric Resonators (DRs) as concentrators of alternating magnetic fields for plasma density control applications. The study involves numerical simulations using the Method of Auxiliary Sources (MAS) to analyze Dielectric Frequency Selective Surfaces (DFSS) composed of periodic dielectric elements. Materials with variable dielectric permittivities, including E-Glass, Plexiglass, Taconic CER-10, and Teflon are considered, and their resonance properties are investigated. Results indicate that DFSSs can create strong magnetic fields at resonance frequencies, which can be utilized for plasma density regulation in processes like thin film deposition. The results demonstrate that materials with lower dielectric permittivity, such as Plexiglass and Teflon, exhibit higher resonance quality factors, while higher permittivity materials like E-Glass and Taconic CER-10 show poorer quality factors. The study emphasizes the potential of DFSSs in enhancing plasma density and improving industrial applications, highlighting the importance of precise geometric configurations and material properties in designing effective dielectric resonators.

Offset-fed Slotted Antenna Practically Loaded with Split Ring as Water Quality Sensor for X-Band Industrial Applications

A. Varshney, D. N. Gençoğlan — Wed, 14 Aug 2024 00:00:00 +0200

This article communicates an offset-fed split ring loaded slotted-antenna design, testing, and analysis for different water quality sensor. The antenna was designed to resonate at 10GHz on a low-cost FR-4 substrate of dimensions 0.621λ_o×0.467λ_o×.053λ_o, where λ_o is the free space wavelength. The measured antenna parameters are found in excellent agreements. The antenna achieves a gain of 7.61dBi with nearly unidirectional radiation pattern and a radiation efficiency of 76% at 10GHz. Further, the research is explored to use the antenna as a water sample sensor. Different water samples are tested with the antenna by dipping the antenna into the water samples and in the second case contactless measurements at 10mm apart from the upper water level in the container. The quality of water is examined by observing the shift in the resonant frequency (f_r), antenna quality factor with different total dissolved solvents (TDS) water samples, and changes in the reflection coefficient (S₁₁) values in the water samples. It is observed that the antenna shows less than 1.5% numerical sensitivity (NS) with f_r and high NS with the S₁₁. The S₁₁ and bandwidth of the antenna vary with different water samples. This antenna is suitable for X-band industrial and microwave laboratory applications.

Radiation Pattern Correction of Faulty Planar Phased Array using Genetic Algorithm

R. A. B. Saleem, A. A. Shah , H. Munsif , A. I. Najam, S. Khattak, I. Ullah — Wed, 24 Jul 2024 00:00:00 +0200

The probability of antenna array failure or malfunctioning cannot be ruled out, and hardware replacement of faulty elements is not always a viable solution. Therefore, academic and industrial interest in self-healing phased arrays are on the rise. In this work, the phase-only genetic algorithm (GA) optimization flow for the radiation pattern correction of a 4 × 4 phase faulty planar antenna array is proposed. Initially, a reference array pattern at the desired scan angle is generated. Then random phase faults are introduced across the 1 × 4 antenna elements in any one of 4 sub-arrays to produce maximum distortion in the reference radiation pattern of 4 × 4 planar array. The proposed GA re-computes the new excitation weights for the remaining non-faulty 3 sub-arrays to correct the overall radiation pattern of 4 × 4 array. This is achieved by calculating the array output power for reference and GA computed weights. The GA corrected patterns fairly follow the desired array patterns in terms of peak gain and reducing sidelobe levels for the desired scan angle. The efficiency of the optimized radiation patterns was evaluated in full-wave HFSS model and measurements validation. In this way, maintenance cost can be reduced with recovery of acceptable level of radiation pattern using software instead of physically replacing faulty antenna elements in the array.

Size Reduction of Wilkinson Power Divider using a Combination of Parallel Coupled Lines and Defective Microstrip Structures

B. P. Eppe, A. Ghosh, P. Mondal — Tue, 29 Oct 2024 00:00:00 +0100

This work describes a miniaturized power divider (PD) using the combination of two symmetrical parallel coupled lines (PCL) and a defective microstrip structure (DMS). The proposed PD is intended for 2.4 GHz wireless local area network (WLAN) applications. DMS structures are used to improve PD performance while also decreasing its size. Initially, to reduce the circuit size, quarter-wavelength lines were replaced with PCL’s. It is observed that the size of PD is 0.42λgX0.53λg, representing a 25.3% decrease. Furthermore, four DMS structures are integrated into the design to reduce the overall size by 43% as compared with conventional Wilkinson PD at 2.4 GHz. The final size of PD is 0.35λgX0.47λg. Required equations are provided for the optimization of the DMS structure. The proposed PD has a return loss, isolation performance, and power division of around 16 dB, -15 dB, and -3.3 dB, respectively. The designed PD is fabricated on the substrate of Rogers RT/duroid 5880 with εr=2.2.

Performance analysis of patch-type UHF-RFID tag antennas in the presence of mutual coupling

K. F. Gbamélé — Thu, 07 Nov 2024 00:00:00 +0100

In a context of high-density deployment of UHF RFID patch-type tag antennas, mutual coupling can have an impact on the detection rate due to the degradation of the link budget between certain tags and the reader. The aim of this paper is to analyze the performance of a system that takes account of electromagnetic mutual coupling as a function of the random positions of UHF RFID patch-type tag antennas in complex environments. The design of the patch-types tags, including the extraction of the Y admittance parameters, was studied using the HFSS electromagnetic simulation software. To validate the study approach, the results obtained were compared using MATLAB software. The results obtained provide additional information needed to gain an in-depth understanding of UHF RFID patch-type tag antenna systems to make them reliable and practical in a dense environment. Future research and development work may be inspired in the design of UHF RFID patch-types tag antennas for miniaturized applications.

Reconfigurable Metamaterial Antenna based an Electromagnetic Ground Plane Defects for Modern Wireless Communication Devices

T. A. Elwi, A. A. M. Al-Shaikhli, H. H. Al-Khaylani, R. K. Abdulsattar — Tue, 28 May 2024 00:00:00 +0200

In this paper, a design of a microstrip antenna based on metamaterial (MTM) and electromagnetic band gap (EBG) arrays. The patch is structured from 5×3 MTM array to enhance the antenna bandwidth gain product. The individual unit cell is structured as a split ring (SRR) with a T-resonator. The ground plane is defected with an EBG to suppress the surface waves diffraction from the substrate edges. The antenna is printed on a Roger substrate with permittivity of 10.2 and 1 mm thickness. It is found that the proposed antenna provides a frequency resonance around 2.45 GHz and 3.5 GHz with another band between 4.6 GHz to 5.6 GHz which are very suitable for Wi-Fi and 5G networks. Nevertheless, the antenna gain is found to vary from 3.5 dBi to less than 6 dBi. The antenna size is reduced enough to λ/5 of the guided wavelength to fit an area of 12 mm×20 mm. The proposed antenna performance is controlled with two PIN diodes for reconfiguration process. The antenna frequency resonance bands are found to be well controlled by stopping the current motion at the particular band. The antenna is fabricated and tested experimentally. Finally, the simulated results are compared to those obtained from measurements to provide an excellent agreement to each other with error of less than 3%.

Metal Mesh Metasurfaces as Dual-Band Bandpass Filters for Terahertz Frequencies

A. Perov — Wed, 14 Aug 2024 00:00:00 +0200

In the paper, we propose a new strategy to design of metal mesh filters (MMFs) based on spatial symmetry analysis of bound states in the continuum(BICs) and manipulating and control with resonances, when BICs transformed to the resonances due to spatial perturbations in the MMF structure. The design of a dual-band polarization-insensitive terahertz bandpass filter with wide upper stopband characteristics using a single conducting layer patterned with rectangular holes is presented. The transmission response of the MMF with two poles is obtained to realize dual-band characteristics and three zeros to suppress the stopband. The proposed design has achieved broadband bandpass transmission characteristics under both TE and TM polarizations with canter frequencies at 0.516THz and 0.734THz and 3dB bandwidths of 25% and 17%, respectively, and upper stopband from 0.887THz to 1.6THz with over 10dB suppression.