Planar near-field measurements of specular and diffuse reflection of millimeter-wave absorbers
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arXiv
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| Autori principali: | , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| author | Miura, Fumiya Takakura, Hayato Sekimoto, Yutaro Inatani, Junji Matsuda, Frederick Oguri, Shugo Nakamura, Shogo |
| author_facet | Miura, Fumiya Takakura, Hayato Sekimoto, Yutaro Inatani, Junji Matsuda, Frederick Oguri, Shugo Nakamura, Shogo |
| contents | Mitigating the far sidelobes of a wide field-of-view telescope is one of the critical issues for polarization observation of the cosmic microwave background. Since even small reflections of stray light at the millimeter-wave absorbers inside the telescope may create nonnegligible far sidelobes, we have developed a method to measure the reflectance of millimeter-wave absorbers, including diffuse reflections. By applying the planar near-field measurement method to the absorbers, we have enabled two-dimensional diffuse-reflection measurements, in addition to characterizing specular reflection. We have measured the reflectance of five samples (TK RAM Large and Small Tiles and Eccosorb AN-72, HR-10, and LS-22) at two angles of incidence in the frequency range from 70 GHz to 110 GHz. Compared with conventional horn-to-horn measurements, we obtained a consistent specular reflectance with a higher precision, less affected by standing waves. We have demonstrated that the angular response and diffuse-to-specular reflectance ratio differ among various materials. The measurements also imply that some absorbers may affect the polarization direction when reflecting the incident waves. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_04664 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Planar near-field measurements of specular and diffuse reflection of millimeter-wave absorbers Miura, Fumiya Takakura, Hayato Sekimoto, Yutaro Inatani, Junji Matsuda, Frederick Oguri, Shugo Nakamura, Shogo Instrumentation and Methods for Astrophysics Mitigating the far sidelobes of a wide field-of-view telescope is one of the critical issues for polarization observation of the cosmic microwave background. Since even small reflections of stray light at the millimeter-wave absorbers inside the telescope may create nonnegligible far sidelobes, we have developed a method to measure the reflectance of millimeter-wave absorbers, including diffuse reflections. By applying the planar near-field measurement method to the absorbers, we have enabled two-dimensional diffuse-reflection measurements, in addition to characterizing specular reflection. We have measured the reflectance of five samples (TK RAM Large and Small Tiles and Eccosorb AN-72, HR-10, and LS-22) at two angles of incidence in the frequency range from 70 GHz to 110 GHz. Compared with conventional horn-to-horn measurements, we obtained a consistent specular reflectance with a higher precision, less affected by standing waves. We have demonstrated that the angular response and diffuse-to-specular reflectance ratio differ among various materials. The measurements also imply that some absorbers may affect the polarization direction when reflecting the incident waves. |
| title | Planar near-field measurements of specular and diffuse reflection of millimeter-wave absorbers |
| topic | Instrumentation and Methods for Astrophysics |
| url | https://arxiv.org/abs/2406.04664 |