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| 2. |
- Ludick, D. J., et al.
(författare)
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A comparison of domain decomposition techniques for analysing disjoint finite antenna arrays
- 2014
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Ingår i: 8th European Conference on Antennas and Propagation, EuCAP 2014. - 2164-3342. - 9788890701849 ; , s. 2411-2415
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work is to present a quantitative comparison between three Method-of-Moments based domain decomposition techniques that are used for the analysis of large, disjoint finite antenna arrays. The methods considered are the Characteristic Basis Function Method, the Domain Green's Function Method, and a newly proposed improved version of the DGFM, i.e., the i-DGFM. The computational complexities of the techniques are compared in terms of runtime and memory usage. Both active and passive antenna arrays are considered.
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| 3. |
- Ludick, D. J., et al.
(författare)
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Accelerating the CBFM-enhanced jacobi method
- 2017
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Ingår i: 19th International Conference on Electromagnetics in Advanced Applications, ICEAA 2017; Verona; Italy; 11 September 2017 through 15 September 2017. - 9781509044511 ; , s. 346-349
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Konferensbidrag (refereegranskat)abstract
- The Characteristic Basis Function Method (CBFM)-enhanced Jacobi method has been introduced as an improvement to the standard iterative Jacobi method for finite array analysis. This technique is a domain decomposition approach based on the Method of Moments (MoM) formulation. In some cases, e.g. array environments with a low degree of mutual coupling, the runtime benefit of the CBFM-enhanced Jacobi method is not as significant when compared to that of the Jacobi technique. The reason for this is that additional computational overhead is introduced during each iteration, i.e. setting up and solving the CBFM reduced matrix equation. In this work the adaptive cross approximation (ACA) algorithm is used to accelerate this step in the CBFM-enhanced Jacobi method.
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| 4. |
- Ludick, D. J., et al.
(författare)
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Accelerating the Domain Green's Function Method through adaptive cross approximation
- 2014
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Ingår i: Proceedings - 16th International Conference on Electromagnetics in Advanced Applications, ICEAA 2014. - 9781467357104 ; , s. 636-639
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Konferensbidrag (refereegranskat)abstract
- © 2014 IEEE. The Domain Green's Function Method (DGFM) is a Method-of-Moments (MoM) based domain decomposition approach that is useful for the analysis of large, irregular antenna arrays. Mutual coupling between array elements is accounted for with the formulation of an active impedance matrix equation for each of the domains/array elements. The active current distribution on the entire array geometry is then obtained by solving these smaller matrix equations pertaining to the elements. The active impedance matrix calculation entails a summation of the MoM matrix diagonal and off-diagonal sub-matrices. For arrays containing a large number of elements this summation can lead to matrix fill times similar to that of the global MoM calculation. To mitigate this significant computational overhead, while still maintaining a sufficient degree of accuracy, the adaptive cross approximation (ACA) algorithm is applied to accelerate this part of the DGFM.
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| 5. |
- Ludick, D. J., et al.
(författare)
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Applying the CBFM-enhanced domain Green's function method to the analysis of large disjoint subarray antennas
- 2013
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Ingår i: Proceedings of the 2013 International Conference on Electromagnetics in Advanced Applications, ICEAA 2013. - 9781467357074 ; , s. 94-97
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Konferensbidrag (refereegranskat)abstract
- This paper considers the efficient numerical analysis of large, finite antenna arrays comprising of disjoint subarrays by using the Domain Green's Function Method (DGFM) [1] in conjunction with the Characteristic Basis Function Method (CBFM) [2]. In the CBFM-enhanced DGFM we consider large arrays consisting of multiple disjoint subarrays and impose the infinite array type assumption, i.e. that the currents on subarrays are identical except for a complex-valued scaling factor. Scan impedance matrices are then constructed for each of the subarrays from the block-partitioned CBFM reduced impedance matrix which account for the mutual coupling in the array environment. Runtime and memory usage scale efficiently for the CBFM-enhanced DGFM as we limit the computational complexity to that required to analyse a single subarray. The paper discusses the hybridisation of the DGFM with the CBFM, and illustrates the results of applying the proposed solution technique to an example consisting of a large finite array of disjoint subarrays. © 2013 IEEE.
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| 6. |
- Ludick, D. J., et al.
(författare)
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Applying the NGF-enhanced Domain Green's Function Method to the analysis of antenna arrays and ground planes of finite sizes
- 2014
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Ingår i: Proceedings - 2014 International Conference on Electromagnetics in Advanced Applications, ICEAA 2014. - 9781467357104 ; , s. 632-635
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Konferensbidrag (refereegranskat)abstract
- In this work, antenna arrays will be analysed in the presence of ground planes that are both of finite extent. A hybrid approach between a partitioned MoM scheme called the Numerical Green's Function (NGF) and the Domain Green's Function Method (DGFM) is presented, viz., the NGF-enhanced DGFM. The method allows for computationally efficient simulations, in that various array configurations can be investigated without solving again the part of the problem associated with the ground plane.
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| 7. |
- Ludick, D. J., et al.
(författare)
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Comparison of the iterative jacobi method and the iterative Domain Green'S Function Method for finite array analysis
- 2016
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Ingår i: 10th European Conference on Antennas and Propagation, EuCAP 2016, Davos, Switzerland, 10-15 April 2016. - 2164-3342. - 9788890701863
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work is to compare two iterative techniques that may be used for the analysis of large, disjoint finite antenna arrays, viz. the iterative Jacobi method and the iterative Domain Green's Function Method. These methods are conceptually similar, in that they offer alternative ways to improve non-local current distributions during the iterative process. The error convergence of each method will be studied at the hand of an example.
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| 8. |
- Ludick, D. J., et al.
(författare)
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Efficient Analysis of Large Aperiodic Antenna Arrays Using the Domain Green's Function Method
- 2014
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Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 62:4, s. 1579-1588
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Tidskriftsartikel (refereegranskat)abstract
- An efficient method-of-moments (MoM) based domain decomposition technique, viz., the domain Green's function method (DGFM), is presented for analyzing large antenna arrays. The DGFM is a perturbation technique where mutual coupling between array elements is accounted for during the formulation of an active impedance matrix for each domain/array element. The active current distribution on the entire array geometry is obtained by solving the smaller matrix equations related to the elements, and not that of the problem as a whole. This leads to a significant saving in both runtime and memory usage. The method also takes into account the edge effects attributed to the finite size of the array, complex excitations with nonlinear phase shift and is not limited to periodic array configurations. The DGFM is an approximation and assumes a slowly varying current distribution between domains. A novel way to mitigate the aforementioned, by including secondary coupling effects, is also discussed. Furthermore, an efficient active impedance matrix fill strategy is presented where the active impedance matrix summation is truncated to include only a certain number of terms. Parallelization using both distributed and shared memory programming models have also been applied to the DGFM, to further optimize runtime and memory usage.
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| 9. |
- Ludick, D. J., et al.
(författare)
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Enhancing the Jacobi Method with the CBFM for array antenna analysis
- 2017
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Ingår i: IEEE Antennas and Propagation Society International Symposium. - 1522-3965. - 9781538632840 ; , s. 727-728
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Konferensbidrag (refereegranskat)abstract
- The analysis of sparse, disjoint finite antenna array structures is considered in this work. The Method-of-Moments (MoM) based CBFM-enhanced Jacobi technique is presented, and offers an improvement over the standard iterative Jacobi method in terms of convergence and accuracy. By applying the Characteristic Basis Function Method (CBFM) during each iteration the effect of mutual coupling between the array elements can be accounted for more accurately than in the standard Jacobi method. The convergence rate of the method is found to be better than that of the Jacobi technique.
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| 10. |
- Ludick, D. J., et al.
(författare)
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Full-wave analysis of the expanded very large array
- 2017
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Ingår i: 19th International Conference on Electromagnetics in Advanced Applications, ICEAA 2017; Verona; Italy; 11 September 2017 through 15 September 2017. - 9781509044511 ; , s. 1762-1765
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Konferensbidrag (refereegranskat)abstract
- In this work we present the full-wave analysis of the Expanded Very Large Array (EVLA) radio telescope. The analysis methods include that offered by the commercial electromagnetic simulation software package, FEKO, using solvers such as the multi-level fast multipole method (MLFMM) and iterative MLFMM / large element physical optics (LE-PO) techniques. The aforementioned solvers exhibit different memory and runtime performances, as well as varying accuracy levels with which parameters such as the polarisation and gain of the radio telescope can be calculated. The purpose of this work is to review these methods in more detail, when applied to a large structure such as the EVLA.
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