| 1. |
- Capek, Miloslav, et al.
(författare)
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Numerical Benchmark based on characteristic modes of a spherical shell
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - 9781538632840 ; 2017-January, s. 965-966
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Konferensbidrag (refereegranskat)abstract
- Characteristic modes of a spherical shell are found analytically and compared with numerical solutions acquired from both in-house and commercial packages. These studies led to a proposal of several independent benchmarks, all with analytically known results. Dependence on mesh size, electrical size and other parameters can easily be incorporated. It is observed that all contemporary implementations have limitations.
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| 2. |
- Capek, Miloslav, et al.
(författare)
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Unified Approach to Characteristic Modes
- 2021
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Ingår i: 2021 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting : APS/URSI 2021 - Proceedings - APS/URSI 2021 - Proceedings. - 9781728146706 ; , s. 893-894
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Konferensbidrag (refereegranskat)abstract
- An algebraic link between transition matrix and impedance matrix is utilized in this work to unify characteristic mode decomposition originally proposed by Garbacz with a framework proposed later on by Harrington and Mautz. The resulting formulation is unique to all method of moments formulations, valid for all linear and lossless materials, and has many favorable properties. The unified prescription is applicable to surface equivalence, body-of-revolution, or volumetric method of moments formulations. The unification paves a way to establish characteristic modes as a standalone technique in time-harmonic domain being independent of method of moment paradigm, i.e., to utilize - for example - finite element method instead.
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| 3. |
- Capek, Miloslav, et al.
(författare)
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Validating the Characteristic Modes Solvers
- 2017
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 65:8, s. 4134-4145
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Tidskriftsartikel (refereegranskat)abstract
- Characteristic modes (CMs) of a spherical shell are found analytically as spherical harmonics normalized to radiate unitary power and to fulfill specific boundary conditions. The presented closed-form formulas lead to a proposal of precise synthetic benchmarks that can be utilized to validate the method-of-moments matrix or performance of CM decomposition. Dependence on the mesh size, electrical size, and other parameters can systematically be studied, including the performance of various mode tracking algorithms. A notable advantage is the independence on feeding models. Both theoretical and numerical aspects of CM decomposition are discussed and illustrated by examples. The performance of state-of-the-art commercial simulators and academic packages having been investigated, we can conclude that all contemporary implementations are capable of identifying the first dominant modes while having severe difficulties with higher order modes. Surprisingly poor performance of the tracking routines is observed notwithstanding the recent ambitious development.
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| 4. |
- Jelinek, Lukas, et al.
(författare)
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Maximum Radiation Efficiency of Implanted Antennas Employing a Novel Hybrid Method
- 2021
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Ingår i: 2021 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting, APS/URSI 2021 - Proceedings. - 9781728146706 ; , s. 1339-1340
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Konferensbidrag (refereegranskat)abstract
- A hybrid combining T-matrix method and electric field integral equation is used to formulate fundamental bounds on radiation efficiency of an implanted antenna. Resulting quadratic optimization problem is solved using a dual formulation. The results present the versatility of the described computational scheme and show the optimal current densities that are the least impaired by dissipation in the tissue.
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| 5. |
- Losenicky, Vit, et al.
(författare)
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Dissipation Factors of Spherical Current Modes on Multiple Spherical Layers
- 2018
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 66:9, s. 4948-4952
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Tidskriftsartikel (refereegranskat)abstract
- Radiation efficiencies of modal current densities distributed on a spherical shell are evaluated in terms of dissipation factor. The presented approach is rigorous, yet simple and straightforward, leading to closed-form expressions. The same approach is utilized for a two-layered shell and the results are compared with other models existing in the literature. Discrepancies in this comparison are reported and reasons are analyzed. Finally, it is demonstrated that radiation efficiency potentially benefits from the use of internal volume which contrasts with the case of the radiation Q-factor.
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| 6. |
- Losenicky, Vit, et al.
(författare)
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Method of Moments and T-Matrix Hybrid
- 2022
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 70:5, s. 3560-3574
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid computational schemes combining the advantages of a method of moments formulation of a field integral equation and T-matrix method are developed in this article. The hybrid methods are particularly efficient when describing the interaction of electrically small complex objects and electrically large objects of canonical shapes such as spherical multilayered bodies where the T-matrix method is reduced to the Mie series making the method an interesting alternative in the design of implantable antennas or exposure evaluations. Method performance is tested on a spherical multilayer model of the human head. Along with the hybrid method, an evaluation of the transition matrix of an arbitrarily shaped object is presented and the characteristic mode decomposition is performed, exhibiting fourfold numerical precision compared to conventional approaches.
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| 7. |
- Tayli, Doruk, et al.
(författare)
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Accurate and Efficient Evaluation of Characteristic Modes
- 2018
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 66:12, s. 7066-7075
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Tidskriftsartikel (refereegranskat)abstract
- A new method to improve the accuracy and efficiency of characteristic mode (CM) decomposition for perfectly conducting bodies is presented. The method uses the expansion of the Green dyadic in spherical vector waves. This expansion is utilized in the method of moments (MoM) solution of the electric field integral equation (EFIE) to factorize the real part of the impedance matrix. The factorization is then employed in the computation of CMs, which improves the accuracy as well as the computational speed. An additional benefit is a rapid computation of far fields. The method can easily be integrated into existing MoM solvers. Several structures are investigated illustrating the improved accuracy and performance of the new method.
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| 8. |
- Tayli, Doruk, et al.
(författare)
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Accurate and Efficient Evaluation of Characteristic Modes
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A new method to improve the accuracy and efficiency of CM decomposition for perfectly conducting bodies is presented. The method uses the expansion of the Green dyadic in spherical vector waves. This expansion is utilized in the MoM solution of the EFIE to factorize the real part of the impedance matrix. The factorization is then employed in the computation of CM, which improves the accuracy as well as the computational speed. An additional benefit is a rapid computation of far fields. The method can easily be integrated into existing MoM solvers. Several structures are investigated illustrating the improved accuracy and performance of the new method.
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