Theory Of Characteristic Modes Research Articles

Characteristic Mode Solution of Complex-Coefficient Complex-Solution Differential Equations

Computation of complex-coefficient complex-solution differential equations is a problem that arises in various domains of science and engineering. This paper aims at applying the Theory of Characteristic Modes (TCM) approach along with the Method of Moments (MoM) in solving these problems with emphasis on procedures for higher differential equations. Several available methods, known in literatures, are available for solving the problem. The complexity of the available methods differs based on the accuracy of the solution. In this paper, the general method is first presented and then a simplified version of it is proposed to solve high order differential equations. Two examples are illustrated, a third and a fourth order complex-coefficients complex-solution differential equations, to show the simplicity of the proposed method. The proposed approach can be also introduced along with other methods to solve these special occurrences differential equations and other boundary value problems.

Characteristic mode based self isolated MIMO antenna design for millimeter wave 5G communications

The paper introduces a self-isolated quad-port multi input multi output antenna system designed for fifth-generation wireless communication. The reported antenna structure possesses an overall dimension of 12.4 × 12.4 × 0.508 mm3 and is derived from a single-element antenna, featuring a circular patch accompanied by a sectoral slot. To achieve the desired frequency band, an additional circular patch is purposefully placed over the main radiator. The development of each design stage in the antenna structure is investigated using the theory of characteristic mode. This configured multi-element antenna structure achieves a broad operational bandwidth spanning 4.5 GHz, encompassing frequencies from 26.1 GHz to 30.6 GHz, rendering the antenna well-suited for deployment in the millimeter-wave frequency bands of n257, n258, and n261 respectively. A total gain of 6.27 dBi is achieved with port isolation of −24 dB. Furthermore, the antenna undergoes validation for diversity metrics, including envelope correlation coefficient, diversity gain, channel capacity loss, total active reflection coefficient, and mean effective gain. The antenna is fabricated and experimentally validated with the simulated counterpart. Later, a comparative analysis has been conducted which revealed that the proposed antenna demonstrates > 80 % increase in compactness compared to existing antenna designs documented in the literature.

Wideband metasurface-loaded rectenna for azimuth-insensitive electromagnetic energy absorption using characteristic mode analysis

In this paper, a wideband metasurface-loaded (MTS-L) rectenna system is proposed to capture electromagnetic (EM) energy at arbitrary azimuth angles. The radiation patterns of different modes in the original MTS configuration are analyzed using the characteristic mode theory, and potential modes with omnidirectional radiation are screened out. By the arrangement of patches, the roundness performance of the radiation pattern can be ameliorated, and the omnidirectional characteristic is obtained over a wide frequency band. Subsequently, the surface current density of the selected mode is carefully and artificially designed to facilitate probe excitation as well as refrain from introducing complex power-combining networks. A wideband rectifier circuit is designed as the load of the proposed antenna. Eventually, measured results show that it operates from 4.6 to 9.6 GHz with a fractional bandwidth of 70.4%, and the peak system efficiency is 52.2%. The proposed system demonstrates excellent potential for wireless power transmission and EM energy harvesting in indoor environments.

A Low-Profile Circularly Polarized Millimeter-Wave Broadband Antenna Analyzed with a Link Budget for IoT Applications in an Indoor Scenario.

Broadband antennas with a low-profile generating circular polarization are always in demand for handheld/ portable devices as CP antennas counter multipath and misalignment issues. Therefore, a compact millimeter-wave antenna is proposed in this article. The proposed antenna structure comprises two circular rings and a circular patch at the center. This structure is further embedded with four equilateral triangles at a 90° orientation. The current entering the radiator is divided into left and right circular directions. The equilateral triangles provide the return path for current at the differential phase of ±90°, generating circular polarization. Structural development and analysis were initially performed through the characteristic mode theory. It showed that Modes 1 to 4 generated good impedance matching from 20 to 30 GHz and Modes 1 to 5, from 30 to 40 GHz. It also demonstrated the summation of orthogonal modes leading to circular polarization. The antenna-measured reflection coefficient |S11| > 10 dB was 19 GHz (23-42 GHz), and the axial ratio at -3 dB was 4.2 GHz (36-40.2 GHz). The antenna gain ranged from 4 to 6.2 dBi. The proposed antenna was tested for link margin estimation for IoT indoor conditions with line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. The communication reliability with co- and cross-polarization was also studied under these conditions, and the results proved to be satisfactory.

Design of compact UWB antenna using characteristic mode analysis and its quad-port MIMO realization with novel isolation technique

This paper presents a miniaturized Quad-Port MIMO antenna for UWB application. Employing Characteristic Mode Analysis, the single element UWB antenna is analysed to achieve a compact design. Using the Theory of Characteristic Mode, the significant modes and their current distribution are analysed, which helps to modify the radiator and ground plane to generate more significant modes to yield a wider frequency band. Four circular-shaped radiators with tapered feeds are placed orthogonally on the FR4 substrate to improve isolation, and partial ground planes are located on the opposite surface. Furthermore, a modified Pattee-cross-shaped parasitic element is introduced between the antenna elements and shorted with the ground planes via metallic shorting pins. This novel technique improves isolation compared to the conventional integration method of the partial ground planes through strip lines. The proposed antenna achieves less than −20 dB mutual coupling over most of the frequency band ranging from 2.51–18 GHz.

Multi-band circularly polarized antenna for WLAN and WiMAX applications based on characteristic mode theory

Abstract A multi-band circularly polarized antenna is proposed for WLAN (2.4/5.3/5.8 GHz) and WiMAX (3.5 GHz) applications. The proposed antenna is constructed of a radiation patch and a reflecting metal ground. Characteristic mode theory is utilized to analyze the modes of the patch and based on these results the antenna is optimized. The −10 dB impedance bandwidths of the proposed antenna are 53.53% (2.4–4.15 GHz) and 47.28% (5.25–8.5 GHz), respectively. The antenna radiates left-handed circular polarization in the lower band and right-handed circular polarization in the upper band. A maximum gain of 10 dBic is achieved for the proposed antenna.

High-performance low-profile green electromagnetic interference shielding material for 5G mm-wave using characteristic mode theory

With the rapid development of 5G communication technology, high-frequency electromagnetic interference (EMI) shielding plays a vital role in the normal operation of electrical and electronic equipment and systems, and has attracted surging interest in 5G mm-wave applications. However, many current EMI shielding materials contain highly conductive materials, resulting in strong secondary reflection and environmental pollution. Here, we propose a green high-performance EMI shielding material for 5G mm-wave based on a metamaterial absorber (MMA). Characteristic mode theory and equivalent circuit are employed to inversely design the unit cell’s dimension and structure, as well as the resistive value of the proposed MMA. We reveal that from 22 to 43.5 GHz, the shielding effectiveness of higher than 30 dB, and the standard green index of SER < 3.01 dB and g s ⩾ 1 can be realized whether the MMA is flat or even bent. Excellent agreement between the measured and simulated results verified the high performance of the proposed EMI shielding MMA. The transmittance of over 85.84% can be achieved within the 380 ∼ 800 nm spectrum. The proposed green EMI shielding material integrates multi-functionalities of low profile, flexibility, polarization-insensitiveness, wide-angle, and optical transparency, and can find potential applications in EMI shielding in complex electromagnetic environments.

Solution and Analysis of Scattering Field of Power Transmission Lines Based on Characteristic Mode Theory

Solution and Analysis of Scattering Field of Power Transmission Lines Based on Characteristic Mode Theory

Design of a Monopole Antenna for WiFi-UWB Based on Characteristic Mode Theory

Design of a Monopole Antenna for WiFi-UWB Based on Characteristic Mode Theory

Notice of Violation: A 3D Printed Multi-Mode Conical Dielectric Resonant Antenna With Stable Omnidirectional Radiation Patterns for 5G Vehicle Picocell Applications

Notice of Violation <br><br>“A 3D Printed Multi-Mode Conical Dielectric Resonant Antenna With Stable Omnidirectional Radiation Patterns for 5G Vehicle Picocell Applications” <br>by Xuyi Zhu, Bing Zhang, Zhijiao Chen, Yanping Zhou, Kama Huang, Tiancang Zhang, Juan Yang, and Xiao An <br>published in the IEEE Transactions on Vehicular Technology, Digital Object Identifier: 10.1109/TVT.2022.3196909. <br><br>The authors of this paper violated the IEEE’s Publication Principles. An author name was included in the Early Access version of this paper who did not contribute to the work and was added without their consent. The non-contributing author’s name has been removed <br><br> <br/> A multi-mode 3D-printed conical dielectric resonant antenna (DRA) with a stable omnidirectional pattern is proposed. It covers the band of 1.75-3.64 GHz and 4.96-6.01 GHz. Multiple modes in the conical DRA are effectively excited which are the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01δ</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">03δ</sub> modes intrinsic to the dielectric resonator (DR). The combination of probe and sleeve is used to feed the DR to excite additional modes such as the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">03</sub> modes and the sleeve mode respectively to further extend the bandwidth of the antenna. The sleeve also helps to tune the current distribution of the probe's high-order modes when the DRA is mounted on a finite-size ground plane. The profile of the conical DRA is properly designed to overcome the tilt of the radiation pattern by the ground plane, by which stable omnidirectional radiation patterns are achieved across the whole operating frequency band. The characteristic mode theory and an eigenmode solver are used to verify the numerical analysis. The 3D printing technology is used to fabricate the DRA. Powered LEDs are placed inside the 3D printed DRA to enable its lighting function. The proposed antenna can be fixed on the vehicle's roof for vehicle-to-everything (V2X) communication. It has satisfactory electromagnetic compatibility (EMC) with other vehicle-mounted electronic devices. It is a good candidate for 5G vehicle picocell applications.

Integral Operator-Based Characteristic Mode Theory for Conducting, Material, and Lossy Structures

Integral operator-based theory of characteristic modes (CMs) for conducting, material, and lossy structures is reviewed. CMs are defined as solutions of a generalized eigenvalue equation (GEE). These GEEs are presented for various surface and volume integral operators and material structures. Interpretation of the characteristic eigenvalues in terms of electromagnetic power is studied based on the Mie expansion and integral operator formalism. Orthogonality and diagonalizing properties of the CMs are summarized. Challenges related to dielectric-magnetic bodies, lossy structures and spurious modes are discussed, as well as differences between the surface and volume operator approaches.

Miniaturized circularly polarized metasurface antenna based on characteristic mode analysis

AbstractA miniaturized circularly polarized (CP) metasurface (MTS) antenna is investigated based on characteristic mode theory (CMT). The 4 × 4 square patch structure was used as the initial structure for characteristic mode analysis (CMA) and improvement using CMT to guide the evolution of antenna structures. The square ring is bent and the capacitive strips are introduced to obtain the final miniaturized MTS. Comparing the proposed MTS with traditional MTS, the proposed antenna size is significantly reduced. To give the proposed antenna a CP, a feeding structure with a 90° phase difference is designed to excite a pair of orthogonal target patterns. The final antenna structure has a reduced overall size and has circular polarization characteristics. For verification, the proposed CP MTS antenna is fabricated and measured. The measured results show an impedance bandwidth of 2.9–3.65 GHz and 3 dB axial ratio bandwidth of 3.1–3.57 GHz, and a stable gain in the operating frequency band.

Using characteristic mode theory to design and analyze an X-band polarization conversion metasurface

This paper proposes a new framework based on the characteristic modes analysis (CMA) to design polarization conversion metasurfaces (PCMs). This approach relies on the information inferred from the characteristic currents of the dominant modes (DMs). To demonstrate the advantages of this strategy, a multi-functional PCM is designed for the X-band frequencies. Besides, this paper expands and develops the characteristic mode rotation (CMR) method to investigate the intrinsic behavior of PCMs. Based on the extended CMR method, the physical concepts behind polarization conversion purity and angular stability at the resonance frequencies are revealed in a new manner. Finally, a prototype of the designed polarizer is fabricated and its reflection coefficients are measured. A great agreement between simulation and measurement results is obtained.

Design of low-profile four-modes patterns metasurface antenna using characteristic mode analysis

In this paper, we propose a novel design approach for multi-mode antenna radiation patterns using characteristic mode (CM) theory. Specifically, we observe that the response of the multi-mode radiation pattern is a superposition of modal current responses, which can be controlled through port excitation. By combining the port excitations, we achieve the desired multi-mode radiation pattern. The feed structure can also be designed using CM theory. The validity of this intuition is confirmed through CM analysis. Subsequently, we use the proposed theory to design an antenna structure with a profile height of 0.07 λ0 (λ0 is the wavelength of the electromagnetic wave at 2.8 GHz in vacuum). This antenna is capable of achieving four orthogonal radiation patterns. Simulation and measurement of the antenna demonstrate that the four radiation patterns can operate simultaneously within a bandwidth of 17% (|S11|<−10 dB), with worst-case port isolation of −24 dB.

Research on Electromagnetic Scattering Influence of Transmission Towers on Medium Wave Antenna Based on the Characteristic Mode Theory

Electromagnetic scattering from UHV transmission towers is a major factor affecting the safety and stability of the surrounding antenna signal system. In this paper, the electromagnetic scattering effect of ±800 kV UHV DC transmission tower on the medium-wave antenna is investigated based on the characteristic mode theory (CMT). The simulation model of the tower and antenna is established, and the mode selection is carried out according to the percentage of the contribution of the characteristic mode to the total electromagnetic scattering. The effects of electromagnetic scattering under three conditions, namely, the number of towers, the distance between towers and antennas, and different frequencies, are investigated separately. The simulation results show that as the number of towers increases from 1 to 3, it leads to an increase in the electromagnetic scattering impact by about 49.5%. The shape distortion of the antenna’s directional map becomes more pronounced and is accompanied by the extension with the direction of the power line. The distance between the tower and the antenna is shortened from 500 m to 125 m, resulting in the growth of the influence of electromagnetic scattering by about 36.4%, and the directional gain of the antenna increases along the direction of the transmission line. As the frequency increases from 600 kHz to 1400 kHz, it leads to the rise of electromagnetic scattering effect of about 32.7% and the antenna directional map becomes more complicated. The research results will provide technical support for developing protective measures against electromagnetic scattering from UHV DC transmission towers to medium-wave antennas.

Dual-wideband radiating surface using interleaved electric and magnetic currents: Underlying physics and experimental verification

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%.

Wearable antenna sensor based on bandwidth-enhanced metasurface for elderly fall assistance detection

With the aggravation of aging, sudden falls have become one of the important causes of death. This article presents a metasurface-based wearable antenna sensor for fall assistance detection of the elderly. The dimension of the wearable metasurface antenna sensor (WMAS) is (50 × 50) mm2, and it works in the C-band-based wireless body area network. Both the metasurface and the slot antenna are printed on the flexible felt substrate, achieving wearability and comfort. The theoretical principle of realizing circular polarization is explained by analyzing the metasurface unit and the metasurface unit array using characteristic mode theory. By loading the metasurface onto the slot antenna, the operating bandwidth is increased by 189 %, and polarization conversion is achieved. As the applied pressure increases, the coupling degree of the metasurface and the slot antenna increases, and the bandwidth and the number of resonance points of the WMAS will increase accordingly. Based on this characteristic, by setting benchmarks for the bandwidth and the number of resonance points, it can be determined whether the elderly have fallen or not. The measured sensitivity of WMAS operating bandwidth and axial ratio bandwidth is 165 MHz/mm and 320 MHz/mm, respectively. By constructing a human tissue model to measure the radiation degree of WMAS to the human body, the results show that the specific absorption rate values are in line with international standards. Experimental results show that the proposed WMAS with broadband, circular polarization, and high sensibility is a promising candidate for assisted fall detection in the elderly.

Reradiation Interference Suppression of Power Transmission Lines Based on Characteristic Mode Theory

In order to decrease the reradiation interference (RRI) of power transmission lines, aiming at the defects that the existing RRI suppression methods cannot be applied to the constructed power transmission lines, and cannot suppress all the RRI extreme values in the frequency band, this paper innovatively proposes a RRI suppression method based on characteristic mode (CM) theory. Firstly, we briefly introduce the CM theory and decompose the total scattering field into the superposition of the characteristic electric fields; secondly, the influence of inductance and capacitance characteristics of the reactive loads on radiation behavior of the CMs is analyzed, and the ideal position for reactive loading is also discussed to reduce the contribution of CM to the total RRI; finally, a simulation experiment is carried out in AM broadcasting band, and the modal weighting coefficients of main CMs affecting the RRI is greatly reduced in the frequency band by reactive loading. Simulation results show that compared with the existing method, the proposed method can reduce the peak value of RRI by 43.9% and the overall RRI by 29.7%. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

A New Unit-Cell Design for a 2-Bit Reflective Metasurface for RIS Applications

In this research, a novel unit-cell design for a 2-bit reflective metasurface using the theory of characteristic modes is presented. The initial unit-cell consists of three sub-patches with 2-PIN diodes integrated within the gaps between sub-patches. The initial structure provides limited tuning of the phase curves with the change in switching states of PIN diodes. To provide the phase deviation required for the 2-bit operation, the symmetry of the modal currents is used to propose multiple slots in the sub-patches. Slots are introduced to lower the resonant frequencies, as well as provide tuning of the resonance of modes and consequently phase change between different switching states. For further resonance tuning and phase optimization, two vias are loaded in the middle patch to provide a 90° phase difference between each switching state. Simulated results show that the proposed unit-cell design with the aid of characteristic modes has a smaller size and provides 2-bit operation in the frequency range of 3.9–4.04 GHz.

Investigation of the Radiation Mechanism of Heatsinks Based on Characteristic Mode Theory

Investigation of the Radiation Mechanism of Heatsinks Based on Characteristic Mode Theory