Metamaterial based superdirectivity
<p>A model-supporting, simple, compact, robust and high efficiency two- element parasitic superdirective array comprising electrically small reso- nant metamaterial elements, namely singly split resonator rings (SSRRs), is predicted by an analytical model and is verified by CST simulation re-...
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| Other Authors: | |
| Format: | Thesis |
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2017
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| _version_ | 1797072765188046848 |
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| author | Li, L |
| author2 | Shamonina, E |
| author_facet | Shamonina, E Li, L |
| author_sort | Li, L |
| collection | OXFORD |
| description | <p>A model-supporting, simple, compact, robust and high efficiency two- element parasitic superdirective array comprising electrically small reso- nant metamaterial elements, namely singly split resonator rings (SSRRs), is predicted by an analytical model and is verified by CST simulation re- sults. The analytical model is built by combining a method of calculating a two-SSRR array's far fild radiated energy density and a well working equivalent circuit for a two-SSRR parasitic array. This model is capable of easily but accurately predicting the far field radiation behaviours of an electrically small parasitic array of two SSRRs (the two SSRRs are not necessarily standard and identical), based on certain information of the array, namely the SSRRs' dimensions, the SSRRs' electrical components (<em>L</em>, <em>C</em> and <em>R</em>), the SSRRs' rotating orientation angles (α<sub>1</sub> and α<sub>2</sub>), the two SSRRs's separation (<em>d</em>) and the array's operation frequency. The impor- tance of this analytical model in designing parasitic superdirective arrays is discussed. Simulation results show that the model predicted two-SSRR parasitic superdirective structure (the `CC' structure) can achieve an end- fire directivity of 4.36, with an elements' separation <em>d</em> = 4<em>mm</em> working at 1:914GHz, and can maintain an efficiencyciency as high as 98:6%. After a short discussion of the design principle behind the `CC' structure, improved su- perdirective structures of are identified and studied based on simulation results. Among these structures, the 'CCLr' structure can achieve the largest directivity value of 5.06 (very close to 5.25, the theoretical limit value of a two-dipole array) with a moderate efficiency of 81:4%. A com- parison between these two-SSRR parasitic superdirective structures (the `CC' and its improved versions) and two commercial two-element Yagi an- tennas show that these two-SSRR structures achieve better directive per- formances than the commercial two-element Yagi antennas do. Through performing the study of near field energy ow for magnetic dipole based structures (analytical results) and SSRR based structures (simulation re- sults), with the help of the concept of causal surfaces, the physical reason behind the superdirectivity phenomenon is revealed.</p> |
| first_indexed | 2024-03-06T23:12:25Z |
| format | Thesis |
| id | oxford-uuid:65f10679-cbf2-4c86-897e-8121225c44eb |
| institution | University of Oxford |
| last_indexed | 2024-03-06T23:12:25Z |
| publishDate | 2017 |
| record_format | dspace |
| spelling | oxford-uuid:65f10679-cbf2-4c86-897e-8121225c44eb2022-03-26T18:28:45ZMetamaterial based superdirectivityThesishttp://purl.org/coar/resource_type/c_db06uuid:65f10679-cbf2-4c86-897e-8121225c44ebORA Deposit2017Li, LShamonina, EStevens, C<p>A model-supporting, simple, compact, robust and high efficiency two- element parasitic superdirective array comprising electrically small reso- nant metamaterial elements, namely singly split resonator rings (SSRRs), is predicted by an analytical model and is verified by CST simulation re- sults. The analytical model is built by combining a method of calculating a two-SSRR array's far fild radiated energy density and a well working equivalent circuit for a two-SSRR parasitic array. This model is capable of easily but accurately predicting the far field radiation behaviours of an electrically small parasitic array of two SSRRs (the two SSRRs are not necessarily standard and identical), based on certain information of the array, namely the SSRRs' dimensions, the SSRRs' electrical components (<em>L</em>, <em>C</em> and <em>R</em>), the SSRRs' rotating orientation angles (α<sub>1</sub> and α<sub>2</sub>), the two SSRRs's separation (<em>d</em>) and the array's operation frequency. The impor- tance of this analytical model in designing parasitic superdirective arrays is discussed. Simulation results show that the model predicted two-SSRR parasitic superdirective structure (the `CC' structure) can achieve an end- fire directivity of 4.36, with an elements' separation <em>d</em> = 4<em>mm</em> working at 1:914GHz, and can maintain an efficiencyciency as high as 98:6%. After a short discussion of the design principle behind the `CC' structure, improved su- perdirective structures of are identified and studied based on simulation results. Among these structures, the 'CCLr' structure can achieve the largest directivity value of 5.06 (very close to 5.25, the theoretical limit value of a two-dipole array) with a moderate efficiency of 81:4%. A com- parison between these two-SSRR parasitic superdirective structures (the `CC' and its improved versions) and two commercial two-element Yagi an- tennas show that these two-SSRR structures achieve better directive per- formances than the commercial two-element Yagi antennas do. Through performing the study of near field energy ow for magnetic dipole based structures (analytical results) and SSRR based structures (simulation re- sults), with the help of the concept of causal surfaces, the physical reason behind the superdirectivity phenomenon is revealed.</p> |
| spellingShingle | Li, L Metamaterial based superdirectivity |
| title | Metamaterial based superdirectivity |
| title_full | Metamaterial based superdirectivity |
| title_fullStr | Metamaterial based superdirectivity |
| title_full_unstemmed | Metamaterial based superdirectivity |
| title_short | Metamaterial based superdirectivity |
| title_sort | metamaterial based superdirectivity |
| work_keys_str_mv | AT lil metamaterialbasedsuperdirectivity |