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NEW physical insights. Analogy to waveguide mode identifies that J1 is the TM01 mode and J6 is the TM21 mode, both with broadside radiation. Conventional methods, based on excited complex current distribution, usually lead to misleading conclusion.
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A unit-cell-free truncated impedance-sheet model (ISM) is proposed for the modeling and design of low-profile broadband metasurface antennas (MAs) composed of non-resonant unit cells using characteristic mode analysis (CMA). Different with conventional MAs with locally resonant unit cells, the non-resonant unit cells of the proposed MAs only contri...
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Citations
... CMT is widely used to study and analyze the electromagnetic feld of arbitrary metallic objects. It is characterized by the fact that the characteristic modes are related only to the intrinsic properties (shape, material, and size) of the metallic object and are independent of other applied excitations [16,17]. Te core of CMT is the generalized eigenvalue equation, which is as follows: ...
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.
... In order to solve the contradiction mentioned above, several MSAs have been presented in ref. [19,20,21,22,23,24,25]. The thick high-permittivity dielectric substrate can be employed to decrease the aperture size and widen the impedance BW for MSA [26,27]. ...
In this letter, we propose a compact broadband and high-gain metasurface antenna (MSA) loaded with meander-line, which is made up of 3×3 square patches and two rows of meander-line. The meander-line is printed underneath the side radiating gap of the square patches, aiming to enforce the inter-element equivalent inductance for reducing the radiation aperture and increasing the BW of the MSA, simultaneously. A large bandwidth of 40% (|S11|<-10 dB) with the boresight peak gain of 9.2 dBi is achieved, while the radiation aperture is only 0.46λ0×0.46λ0, which presents a good performance. A prototype of this MSA is manufactured and tested, the tested results correlated reasonably with the simulated ones.
... In addition, complex feeding structures may also affect the characteristic mode of the metasurface, which increases the difficulty of designing the metasurface antenna. For example, dipole feeding [41] and slot coupling feeding [35,36] introduce new modes that can be used to expand the bandwidth of the antenna, but this puts forward higher requirements for the collaborative design of metasurface and feeding structure, and it will increase the profile. ...
A millimeter-wave broadband metasurface-based antenna with a low profile is proposed. In order to guide the mode excitation, the characteristic mode analysis (CMA) is used for the design and optimization of the proposed antenna. Four sets of coplanar patches with different dimensions on a thin printed circuit board are used to generate four adjacent broadside modes, which are directly fed by a coaxial probe. Then, to expand low-frequency bandwidth, a new resonant mode is introduced by etching slots on the parasite patch. Meanwhile, the extra mode introduced does not significantly change the radiation performance of the original modes. Moreover, dual slots are etched on the mid patch fed by the coaxial probe, which moves the orthogonal modes of the chosen modes out of the operating band to reduce cross-polarization levels. The proposed antenna realized 25.02 % (30–38.58 GHz) impedance bandwidth with dimensions of 1.423×1.423×0.029λ0 3 (λ0 is the wavelength at 34 GHz in free space), and the realized gain in the band is 8.35–11.3 dB.
... The MTS antennas contain periodic arranged subwavelength units. Modal analysis for a truncated MTS reveals that it typically resonates at quasi TM30 mode and has a high gain-bandwidth product [32]. Using the multimode resonance of CMs, the MTS antennas can reach a wide impedance bandwidth of 45% in [33] and 79% in [34]. ...
Recent years, the theory of characteristic modes has emerged as a powerful analysis technique in antenna engineering, providing a means to reveal the natural resonant properties of objects and providing a variety of modal parameters. Based on these modal parameters, advanced techniques have been developed based on the theory of characteristic modes to address a wide range of electromagnetic radiation, scattering, and coupling problems. This review provides an overview of some of the latest characteristic mode-based techniques for wide-band design, circular polarization, radiation pattern control, scattering control, and mutual coupling control. In addition, future perspectives are discussed, highlighting the potential of characteristic modes for addressing even more complex electromagnetics problems.
... In addition, the design of antennas with scattering parameters of incident plane waves is often complicated, and the problem of miniaturization has not been solved, and we try to find a simple method to design MS lenses with a singlelayer structure. In the characteristic mode analysis (CMA) for different conductors, the surface can be decomposed into a series of mutually independent mode currents that are independent of other conditions (e.g., feed position) and only related to the properties of the conductor itself (e.g., size and shape), which provides accurate analysis and allows us to visualize the resonant characteristics of the antenna [13,14]. Based on CMA, the reference [15] proposed a method consisting of circular waveguide-fed single-layer metamaterial lens antenna consisting of 12 capacitive coupled elements distributed along a ring. ...
An asymmetric U-shaped millimeter-wave (MMW) metasurface (MS) transmitarray (TA) antenna is proposed based on characteristic mode analysis (CMA). The CMA of U-type unit shows two modes in the required frequency band and excites these two modes with a certain phase difference, so that the transmittance of the unit in the working band is greater than 0.8. The difference of lens unit is 360° by controlling the size change of the unit, and the transmission array is designed according to the phase distribution of the array. Through optimization simulation, the total size of the lens is 92.4 × 92.4 mm2, composed of 21 × 21 components and focal ratio of 0.85. The feed source is a SIW antenna, and then, the MS converts the quasispherical wave emitted from this feed source into a plane wave. The measured results show that the peak gain at 28 GHz is 22.3 dBi, the gain bandwidth at 3 dB is 5.8°, and the radiation efficiency is 81.6%. Due to the high gain and low-cost design, the proposed MS transmitarray antenna is suitable for MMW communication.
... Subsequently, in [27] and [28] patch was also chosen to address the requirements. In [27], a loaded metasurface antenna (MA) comprises of a square patch is proposed to achieve stable broadside radiation by suppressing higher-order modes in a multiport antenna system. ...
... Furthermore, the patch acted as a second resonator and contributed to an escalation of BW. In [28], a very similar patch for a triple-mode lowprofile MA is proposed, where an accurate and fast analysis was carried out on it by an impedance sheet model using characteristics mode analysis (CMA) [28]. Note that BW escalation was done employing the patch and reported in [27] and [28]. ...
... Furthermore, the patch acted as a second resonator and contributed to an escalation of BW. In [28], a very similar patch for a triple-mode lowprofile MA is proposed, where an accurate and fast analysis was carried out on it by an impedance sheet model using characteristics mode analysis (CMA) [28]. Note that BW escalation was done employing the patch and reported in [27] and [28]. ...
This article proposes a hybrid array antenna where a cavity-backed antenna is used jointly with a patch antenna using half-mode substrate integrated waveguide technology (HMSIW) to reduce antenna size. This hybrid structure consists of a flexible Rogers RO4003C substrate ( $\epsilon_{{r}} =3.55$ ) showing linearly polarized TE101 mode where the cross-polarization level (XPL) is less than −12 dBi. An inset feed has been utilized to excite the main cavity resonator, and later by proximity coupling, the parasitic patch is also excited in TE101 mode. By further dividing the outer patch, four new cases of antenna have emerged, and comprehensive investigations on their parameters based on simulation have been presented. It paints an upgrade of the antenna’s performance. As per simulations, further dividing of the patch helps to bring out positive changes in the antenna’s performance by escalating gain, bandwidth (BW), and efficiencies while also lessening XPL, sidelobe levels (SLLs), and associated loss up to a satisfying level. The proposed antenna is then fabricated and experimentally validated in its theoretical analysis. A couple of experimentally validated parameters make this fabricated sample suitable for wireless application and maintain good agreement with numerical simulation. CST Microwave Studio and HFSS carried out the associated numerical simulation.
... To reduce the complexity of mode analysis, the concept of impedance boundary condition (IBC) has been used for developing an equivalent impedance-sheet model (ISM) for efficient modeling and analysis of MAEs [15]- [17]. The ISM simplifies the design and analysis of an MTS to the design and analysis of a homogeneous impedance sheet for desired modes first and then the approximation of the impedance sheet by designing a single unit cell of the same grid impedance [18]. However, the early developed ISMs are limited to single-layer MTS [18] or two MTS layers of large separation [19], where the inter-layer capacitance and the resultant higher-order modes are out of concern. ...
... The ISM simplifies the design and analysis of an MTS to the design and analysis of a homogeneous impedance sheet for desired modes first and then the approximation of the impedance sheet by designing a single unit cell of the same grid impedance [18]. However, the early developed ISMs are limited to single-layer MTS [18] or two MTS layers of large separation [19], where the inter-layer capacitance and the resultant higher-order modes are out of concern. In addition, as conventional ISMs fail to handle inhomogeneity, the local field difference caused by feeding or loading structures is not accurately included. ...
... The dimensions of the sheets are unchanged, with a center-to-center element spacing of SP = 0.5 λ0 for avoiding grating lobes. Fig. 1(b) shows the MTS array of 3×3 square patches to approximate the sheet array, where the MTS is designed with a grid impedance of Zg = jXg = Zs [18], [24]. The two arrays are compared in Fig. 4, in terms of the MSs, surface currents, and far-field patterns of the first broadside radiating mode J1. ...
Conventional single-layer homogeneous impedance-sheet
models for single-layer metasurface (MTS) antenna elements cannot handle multi-layerinhomogeneous MTS antenna arrays of local field inhomogeneity caused by loadings and feedings. In this paper, a hybrid impedance-sheet model is proposed to overcome the above challenge with the aid of characteristic mode analysis (CMA). For proof of concept, a wideband multilayer metasurface antenna array (MAA) is designed, where capacitive loading is further proposed to manipulate the frequency interval of desired
modes for bandwidth improvement. With an element width of 0.29 λ0 and an overall size of 0.70 λ0 × 0.70 λ0 × 0.08 λ0 (λ0 is the wavelength in free space at 3.5 GHz), the proposed four-element MAA achieves a measured impedance bandwidth of 17.8% with |S11| <10 dB, gain of 9.1–12 dBi, and a least front-to-back ratio of 25 dB. The proposed method extends the application of CMA from metasurface antenna elements (MAEs) to MAAs, by enabling advanced mode manipulation techniques for simultaneous antenna miniaturization and bandwidth enhancement.
... In addition to pixel antenna design, characteristic mode analysis (CMA) has recently re-emerged as a useful design tool for compact antennas and was first proposed by Garbacz [25]. CMA has been widely used in the optimization of single port antennas [26], including circularly polarized [27], polarization reconfigurable [28], Q value optimization [29], pattern synthesis [30]- [32] and metamaterials [33], [34]. The characteristic modes found in CMA are orthogonal to each other and therefore naturally extends to the design of MIMO antennas [35]- [41]. ...
An optimization approach for multiport pixel antenna design using
${N}$
-port characteristic mode analysis (CMA) and sequential feeding port selection is proposed. CMA is utilized to characterize the maximum number of independent or orthogonal resonant modes that can be formed in the limited space constrained by the size of the pixel antenna. Once the maximum number of orthogonal resonance modes is found sequential feeding port selection is proposed to find the optimum feed positions to independently excite each of the orthogonal resonance modes. The resulting design does not need additional complex feeding networks or impedance matching circuits, making the physical implementation of the design straightforward, compact and practical. Two examples are provided to verify the performance of the proposed approach, including a 3-port pixel antenna and a 4-port pixel antenna operating at 2.4 GHz. The performance of the optimized antennas is very good, and verifies the usefulness of the proposed approach.
... Cooperating these two modes, metasurface antennas usually obtain an impedance bandwidth of around 30% [32]- [36]. In [37], by adding an aperture mode to the intrinsic metasurface antenna mode, the impedance bandwidth of the design is increased to be 44%. To further increase the impedance bandwidth, nonresonant unit cells are introduced and three modes, i.e., a quasi-TM01 mode, a quasi-TM21 mode, and a dipole mode, are excited to achieve an impedance bandwidth of 45% [38]. ...
A wideband metasurface antenna operating at millimeter-wave spectrum in substrate-integrated waveguide (SIW) technology is proposed. Coupled by a slot etched on an SIW section, the proposed metasurface antenna achieves a wide 10 dB impedance bandwidth in simulation from 19.2 to 42.4 GHz, indicating a fractional bandwidth of 75%. The development of the proposed metasurface antenna can be divided into four stages, i.e., a slot antenna, dielectric loading, adding covered metasurface, and connecting to a transition. The input impedance and the resonance of these stages are elaborated in detail to explain the working mechanism. Parametric study is carried out to inspect into the design process. By analyzing the
$E$
-field distributions, the proposed metasurface antenna is characterized by TM
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub>
mode, antiphase TM
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub>
mode, and TM
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub>
mode. Compared with other similar designs in the open literatures, the proposed metasurface antenna displays a widest impedance bandwidth. The dimension of the proposed metasurface antenna is
$0.80\,\,\lambda _{0} \times 0.72\,\,\lambda _{0} \times 0.24\,\,\lambda _{0}$
, where
$\lambda _{0}$
is the free-space wavelength at 30 GHz. The maximum gain within the interested frequency spectrum is 7.0 dBi.
... Hence, although the coding representation brings outstanding wideband absorption, it is difficult to summarize the general rules for further optimization [24][25]. The introduction of characteristic mode analysis (CMA) provides a solution for clarifying the excited modes of the structures under the planewave illumination [26][27][28][29]. In [30], we found the role of the absorption modes in wideband absorption by using CMA to analyze metabsorber with a square resonator. ...
Coding is an effective method of designing wideband metabsorber, but the resultant metabsorbers are usually associated with complicated shapes that hinders clear physics understanding of the wideband principle behind the scene. This study presents characteristic mode analysis (CMA) of two types of coding metabsorber composed of single-layer and bilateral resonators, respectively, generated by the genetic algorithm (GA) optimization methods. Compared with the conventional single-layer design, CMA results illustrate the wideband principle of the bilateral design introducing additional absorption modes. With a fractional bandwidth of 143.5%, the proposed bilateral metabsorber measures an absorption bandwidth of 5.9 – 35.9 GHz for 90% absorptance. CMA provides a low-threshold method to analyze the metabsorber with complicated resonators, thereby paving the way for the physical-oriented coding optimization improvement.
