{"id":304242,"date":"2023-08-31T01:54:00","date_gmt":"2023-08-31T01:54:00","guid":{"rendered":"\/forum\/forums\/topic\/the-oscillation-of-auto-shutoff-level-in-long-fdtd-calculated-region\/"},"modified":"2023-08-31T02:06:29","modified_gmt":"2023-08-31T02:06:29","slug":"the-oscillation-of-auto-shutoff-level-in-long-fdtd-calculated-region","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/the-oscillation-of-auto-shutoff-level-in-long-fdtd-calculated-region\/","title":{"rendered":"The oscillation of auto-shutoff level in long FDTD calculated region"},"content":{"rendered":"<p>I conducted simulations of an antenna composed of a straight Si waveguide (red) with periodic SiN block (cyan).<\/p>\n<p><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693446126-mceclip3.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693446126-mceclip3.png\" width=\"392\" height=\"197\"><\/a><\/p>\n<p>When set a shorter FDTD range (e.g., 150 um) with the identical structure, the auto-shutoff level consistently satisfied the auto-shutoff threshold (default: 10^-6) without oscillations.<br \/><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693445606-mceclip0.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693445606-mceclip0.png\" width=\"684\" height=\"237\"><\/a><\/p>\n<p>However, when the FDTD simulation region was expanded to 1mm (x-axis), the auto-shutoff level displayed oscillations, even the overall trend consistently showed a gradual decrease in the auto-shutoff level.<\/p>\n<p><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693446037-mceclip2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693446037-mceclip2.png\" width=\"655\" height=\"240\"><\/a><\/p>\n<p>The FDTD boundary conditions were established as follows, with the Y_min boundary exhibiting anti-symmetry due to the structural symmetry along the y-axis.<br \/><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693445792-mceclip1.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/31-08-2023-1693445792-mceclip1.png\" width=\"229\" height=\"143\"><\/a><\/p>\n<p>I want to understand that why auto-shutoff level display a oscillation when FDTD calculated region is extended.<\/p>\n<p>Thank you.<\/p>\n","protected":false},"template":"","class_list":["post-304242","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["289867","33648"],"_bbp_author_ip":["23.206.193.59"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["587"],"_edit_lock":["1693447546:224848"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["304242"],"_bbp_forum_id":["27833"],"_bbp_engagement":["33648","289867"],"_bbp_voice_count":["2"],"_bbp_reply_count":["1"],"_bbp_last_reply_id":["304457"],"_bbp_last_active_id":["304457"],"_bbp_last_active_time":["2023-08-31 20:45:22"],"_bbp_likes_count":["1"]},"test":"kenny-hh-chendeltaww-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/304242","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/304242\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=304242"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}