{"id":389865,"date":"2024-10-15T20:38:51","date_gmt":"2024-10-15T20:38:51","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/deviating-simulation-results-for-different-box-sizes-abc-and-febi\/"},"modified":"2024-10-15T20:38:51","modified_gmt":"2024-10-15T20:38:51","slug":"deviating-simulation-results-for-different-box-sizes-abc-and-febi","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/deviating-simulation-results-for-different-box-sizes-abc-and-febi\/","title":{"rendered":"Deviating Simulation Results for different Box Sizes (ABC and FEBI)"},"content":{"rendered":"<p>&lt;p&gt;Hello there!&lt;\/p&gt;&lt;p&gt;I encountered a problem of deviating S21 results for the simulation of two dipole antennas facing each other. If the antennas are placed in free space, I only achieve consistent results for different box sizes by utilising FEBI. This aligns with the conclusions of the following post:&lt;br&gt;https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/what-is-the-radiation-box-size-in-hfss-if-we-have-two-antennas-2\/&nbsp;&lt;\/p&gt;&lt;p&gt;However, if I place the same antennas inside a block of dielectric material, S21 results are not consistent for both ABC and FEBI. The minimum distances of ABC (153.8mm) and FEBI (57.7mm), starting from the block surfaces, are the preset paddings for HFSS&#8217;s open region command (operating frequency is 650 MHz). I extended these values up to 300mm, thus exceeding lambda\/4 (pushing the paddings &gt;300mm is possible but takes very long simulation times).&lt;\/p&gt;&lt;p&gt;Has anyone encountered similar problems or by chance knows a solution to the problem?&lt;\/p&gt;&lt;p&gt;PS: It&#8217;s worth mentioning that S11 results are very consistent in all cases.&lt;\/p&gt;&lt;p&gt;Thank you and best regards&lt;\/p&gt;&lt;p&gt;Maximilian&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/10\/15-10-2024-1729024137-S21_ABC.PNG\" alt=\"\" width=\"718\" height=\"263\" \/>&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/10\/15-10-2024-1729024180-S21_FEBI.PNG\" alt=\"\" width=\"706\" height=\"258\" \/>&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-389865","topic","type-topic","status-publish","hentry","topic-tag-hfss"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hello there!I encountered a problem of deviating S21 results for the simulation of two dipole antennas facing each other. 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