{"id":433462,"date":"2025-06-06T02:21:15","date_gmt":"2025-06-06T02:21:15","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-to-determine-the-correct-t-as-the-xy-span-region-changes\/"},"modified":"2025-06-06T02:21:15","modified_gmt":"2025-06-06T02:21:15","slug":"how-to-determine-the-correct-t-as-the-xy-span-region-changes","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-to-determine-the-correct-t-as-the-xy-span-region-changes\/","title":{"rendered":"How to determine the correct T as the xy span region changes\uff1f"},"content":{"rendered":"

<p>”I want to simulate the transmission spectrum of a finite periodic structure. How should I set the FDTD boundary conditions correctly? I have simulated several scenarios, but I don’t know which one is correct. The first scenario is my reference simulation, where I assume the period is infinite. In this case, all FDTD boundary conditions are set to periodic. Specifically, I chose anti-symmetric boundary conditions for x min and x max, symmetric boundary conditions for y min and y max, and PML for z. The simulation region is one unit cell. The FDTD xy region size is the period of the unit cell. The boundary settings, structure, transmission monitor’s T, and electric field are as follows:<\/p><p><\/p><p><\/p><p><\/p><p>However, I want to simulate a finite periodic array.<\/p><p>I set up simulations with three different FDTD regions, all with the same FDTD settings, as follows:<\/p><p><\/p><p>The first simulation has an FDTD x span and y span = 12.6um:<\/p><p><\/p><p><\/p><p><\/p><p>The second simulation has an FDTD x span and y span = 14.6um:<\/p><p><\/p><p><\/p><p><\/p><p>The third simulation has an FDTD x span and y span = 18.6um:<\/p><p><\/p><p><\/p><p><\/p><\/p>\n","protected":false},"template":"","class_list":["post-433462","topic","type-topic","status-publish","hentry","topic-tag-3DFDTD-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27833"],"_bbp_topic_id":["433462"],"_bbp_subscription":["288211","473055"],"_bbp_author_ip":["157.254.20.6"],"_bbp_last_reply_id":["435898"],"_bbp_last_active_id":["435898"],"_bbp_last_active_time":["2025-07-02 10:29:13"],"_bbp_reply_count":["10"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["288211","473055"],"_btv_view_count":["219"],"_bbp_topic_status":["unanswered"],"_bbp_notification_enabled":["473055"],"_edit_lock":["1751455546:288211"]},"test":"10172100207stu-ecnu-edu-cn"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/433462","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\/433462\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=433462"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}