Advanced Electromagnetics

Dual-Band Metamaterial Microwave Absorber using Ring and Circular Patch with Slits

M. S. Sim — 2023-12-16

This paper proposes a dual-band metamaterial microwave absorber operating at 2.5 GHz and 5.8 GHz. The absorber consists of a ring and a circular patch with slits resonator structures printed on a FR4 dielectric substrate backed by a ground layer. The main advantage of the absorber lies in its design flexibility in which each absorption band is independent and can be individually tuned by changing the dimensions of each resonator structure. The absorber unit cell is simulated and parametrically optimized using Computer Simulation Technology (CST) software. The absorption mechanism is analyzed through surface current analysis. The absorber prototype, with dimensions of 200 × 200 × 1.6 mm³ and consisting of an array of 7 × 7 unit cells, is fabricated and experimentally investigated using antennas in free-space measurement. The absorber exhibits over 97% absorption at both resonance frequencies. Furthermore, the absorber is demonstrated to be applicable in sensing applications for dielectric constant determination. With its design simplicity, wide-angle receptive, and polarization insensitive behavior, it is envisaged that the proposed absorber will find practical use in absorbing and sensing applications.

Thinned Smart Antenna of a Semi-circular Dipole Array for Massive MIMO Systems

A. Khan — 2023-12-09

Massive MIMO (multiple-input multiple-output) is a multi-user MIMO technology that can provide high-speed multimedia services in 5G wireless networks using sub-6 GHz and millimeter wave bands. The massive MIMO (MMIMO) installs array antennas in the base stations, using hundreds of transceivers with other RF modules. One of the drawbacks of the MMIMO system is its huge power consumption, and the beamforming network with RF modules for a large number of antennas is the main contributor to the power consumption. In this paper, a novel beamforming method is proposed for the low power consumption of an MMIMO system. The proposed thinned smart antenna (TSA) of a semi-circular array produces a secure beam toward the user’s terminal with reduced interference. By thinning the antenna array, some of the antenna elements are kept off, resulting in less power consumption, while the array pattern remains the same as a fully populated array with a reduced side lobe level (SLL). The sub-6 GHz band of 5 GHz is used for the design of thinned array antennas. The genetic algorithm (GA) is used to determine the array sequence in thinning, and the adaptive signal processing algorithms least mean square (LMS), recursive least square (RLS), and sample matrix inversion (SMI) are used for the beamforming of the TSA, and the corresponding algorithms are GA-LMS, GA-RLS, and GA-SMI. The power saving of 40% to 55% is achieved using TSA. The maximum SLL reductions of 13 dB, 12 dB, and 14 dB are achieved for TSA using GA-LMS, GA-RLS, and GA-SMI algorithms, respectively.

A Decoupling method using Split Ring Resonator (SRR) for Tri-band MIMO Antenna for WLAN LTE Band and 5G applications

A. C. J. Malathi — 2024-04-09

MIMO antenna design has always been a topic of interest in wireless technology. Although it has many benefits, the key challenge is to minimize mutual coupling between antenna elements. This study presents a decoupling technique between two tri-band antennas for LTE, WLAN, and 5G applications. For 3.5GHz, a monopole is initially created; the other two resonant frequencies are produced by changing the partial ground plane. Then, a MIMO antenna system is created using two tri-band monopoles. The resonators of low band can minimize the mutual coupling for two higher bands by suppressing surface wave propagation. Finally, coupling is reduced in the low band by using a Split Ring Resonator (SRR) to cancel out the original coupling. The reported MIMO antenna spans the 2.4/5.8GHz WLAN and LTE bands, as well as the 3.5 GHz 5G bands, with a mutual coupling of less than -18 dB.

Stop-band type NGD RLC-resonant circuit sensitivity analysis

J. R. Sambatra — 2023-12-09

This paper investigates on the rarely studied negative group delay (NGD) RF circuit with innovative stop-band (SB) behavior. In difference with the classical filter, the SB-NGD function is identified in function of frequency bands where the group delay (GD) presents negative sign. The ideal diagram specifying the SB-NGD function is introduced by indicating all the appropriate parameters. The S-parameter analytical model of the circuit is established. The SB-NGD analysis is developed. The main specifications of the SB-NGD circuit are expressed in function of its constituting components. Then, the design synthesis equations enabling to determine the SB-NGD circuit in function of the desired specifications as the center frequency and GD are built up. To illustrate concretely the feasibility of the SB-NGD function, a circuit proof-of-concept composed of LC-series network is theoretically analyzed. A parametric analysis on the SB circuit elements is accomplished to appraise the influence of each element on the SB-NGD specifications. To validate the unfamiliar SB-NGD theory, a prototype is fabricated and tested. The GD measured response of the considered circuit is compared by simulations and analytical calculations. SB-NGD responses showing a good agreement between the calculation and simulation are obtained with a 15 MHz center frequency, 44 ns GD and 3 MHz bandwidth.

Magnetic Properties and Applications of Glass-coated Ferromagnetic Microwires

V. Zhukova — 2023-11-10

A remarkable magnetic softness and giant magnetoimpedance (GMI) effect at GHz frequency range havebeen observed in glass-coated microwires subjected to appropriate postprocessing. Co-based microwires present higher GMI effect. Insulating and flexible glass-coating allows use of magnetically soft amorphous glass-coated microwires for stresses or temperature monitoring insmartcomposites using free space facility. Such composites with magnetic microwire inclusions can present tunable magnetic permittivity. We report on in-situ the evolution of the transmission and reflection parameters of the polymer containing magnetic microwire inclusions during the polymerization process. A remarkable change of the reflection and transmission in the range of 4-7 GHz upon the matrix polymerization is observed. Observed dependencies are discussed in terms of the effect of the temperature and stresses variation on magnetic properties of glass-coated microwires during the thermoset matrix polymerization. Obtained results are considered as a base for novel sensing technique allowing non-destructive and non-contact monitoring of the composites utilizing ferromagnetic glass-coated microwire inclusions with magnetic properties sensitive to tensile stress and temperature.

Wideband E-shaped Patch Antennas for Advanced Wireless Terminals

Y. Rahmat-Samii — 2023-03-20

Low-profile patch antennas have become ubiquitous in wireless terminals, especially as devices have become smaller and demand more functionality out of their RF subsystems. While their shape and size is attactive for many applications, their narrow bandwidth hinders their usage in many systems. With the rise of computer-aided design, many patch antenna design concepts have been presented with enhanced bandwidth capabilities. The E-shaped patch antenna, whose original shape presented in the early 2000’s resembles the letter E, offers compelling performance with reasonable manufacturing complexity. In it most basic form, this antenna was linearly polarized and either wideband or dual-band. Over the last two decades, many variations of the E-shaped patch have been presented in literature: circularly polarized, miniaturized, frequency reconfigurable, or even polarization reconfigurable. This paper summarizes these efforts in realizing novel functionalities with a relatively simple design geometry.

Dual band Orthogonal Polarized 2-port MIMO Antenna for Cognitive Radio Applications

S. Mohapatra — 2024-01-28

An arrangement of orthogonally aligned antennas over two planes of a substrate is designed in this paper. The design is a novel miniaturized cognitive model operating at LTE, C-band and X-band with sufficient band stop notch. The antenna is etched over a 0.8 mm thick FR-4 Epoxy substrate of dimension 15 mm x 15 mm. On one side the antenna is a hexagonal slotted microstrip antenna and on the other side is a partial CPW type hexagonal patch antenna. The top hexagonal patch antenna is a wide band from 1800 MHz to 12000 MHz. With the use of a slot on the patch creates one notch from 2240 MHz to 5090 MHz and another notch is created at 6200 MHz to 8100 MHz. Thus, the working bands comprise of LTE 1900, Wi-Fi 5G and X-band under a single polarization. Similarly, the second antenna has its first resonance at LTE 1900 and the second resonance at X-band with a polarization orthogonal to the antenna at top. Being a miniaturized antenna, the cognitive radio provides gain ranging from 2.0 dB at lower frequency to 5.4 dB at higher frequency. The isolation over the operating bands suggests non-interference between the antennas.

A Typical Slotted SIW Cavity-backed Antenna for Dual frequency operations in U-NII Bands

R. Sengupta — 2023-05-21

A low profile circular shaped cavity-backed substrate integrated waveguide (SIW) antenna with two-typical intersecting rectangular slots on the ground plane is designed to operate in the dominant TM010 mode at a frequency of 5.19 GHz in U-NII-1 band for wireless applications. The initially designed antenna produces a gain of 4 dBi with a narrow impedance bandwidth extending from 5.17 – 5.22 GHz. The antenna design is further modified by insertion of another shifted two-typical intersecting rectangular slots to finally resemble that of Hash shape; resulting in dual band antenna operation at 4.9 and 5.93 GHz. The gains obtained are 3.7 dBi and 1.4 dBi for 4.9 and 5.93 GHz respectively with an impedance bandwidth covering 4.88 - 4.92 GHz and 5.92 – 5.94 GHz respectively. The antenna prototype is fabricated using Arlon AD270 substrate material. Parametric studies are performed in terms of return loss and gain of the antenna. All simulations are carried out using HFSS v19.0 and show similar behavior to their experimentally measured counterparts.

Electromagnetic guided mode resonance in dielectric grating affected by transformation of refractive index periodicity

A. Abramov — 2023-02-12

The present work studied effects of transformation of refractive index periodicity on electromagnetic wave propagation through grating waveguides. In lieu of the standard refractive index periodicity, although its unit cell consists of two kinds of materials, we consider few such unit cells as a new supercell, where the material parameters in a standard unit cell are changed. It has been shown how by changing parameters of the periodicity to control the wavelength and intensity of resonant optical mode (guided mode resonance) arising inside grating area. High quality factor calculated for the specific angle of incidence and periodicity parameter. Thus, we demonstrated that transformation of refractive index provides additional tools of controlling the GMR, and that means the sample can be designed more functional in terms of real application.

Electrothermal Analyses of Bandpass NGD RLC-Network Topologies

E. J. R. Sambatra — 2023-03-11

This paper develops an original study of temperature effect on the unfamiliar bandpass (BP) negative group delay (NGD) lumped passive circuits. The paper presents the first study of electrothermal analysis of electronic circuits classified as BP-NGD topologies. The considered BP-NGD passive cells are mainly constituted by RLC-resonant networks. The equivalence between two basic BP-NGD topologies constituted by RLC-series and RLC-parallel networks is elaborated via the voltage transfer function (VTF) analogy. Then, the theoretical demonstrations are introduced to define the main specifications as the NGD center frequency, NGD value, attenuation and NGD bandwidth. The electrothermal innovative study is developed based on the temperature coefficient resistor (TCR) of elements constituting the BP-NGD circuits. With proofs of concept of RLC-series and RLC-parallel circuits operating with -500 ns NGD value at 13.56 MHz, calculated and simulated results showing are in excellent agreement. The sensitivity analyses of BP-NGD specifications in function of ambient temperature variation from 0°C to 100°C are investigated. The BP-NGD response variations versus frequency and temperature are characterized with thermo-frequency cartographies and discussed.