{"action":"created","issue":{"url":"https://api.github.com/repos/Qucs/qucs/issues/342","labels_url":"https://api.github.com/repos/Qucs/qucs/issues/342/labels{/name}","comments_url":"https://api.github.com/repos/Qucs/qucs/issues/342/comments","events_url":"https://api.github.com/repos/Qucs/qucs/issues/342/events","html_url":"https://github.com/Qucs/qucs/issues/342","id":102628970,"number":342,"title":"Using a substrate with er=1 produces invalid results (NaN) in S-Parameter simulation","user":{"login":"StefanD986","id":13921689,"avatar_url":"https://avatars.githubusercontent.com/u/13921689?v=3","gravatar_id":"","url":"https://api.github.com/users/StefanD986","html_url":"https://github.com/StefanD986","followers_url":"https://api.github.com/users/StefanD986/followers","following_url":"https://api.github.com/users/StefanD986/following{/other_user}","gists_url":"https://api.github.com/users/StefanD986/gists{/gist_id}","starred_url":"https://api.github.com/users/StefanD986/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/StefanD986/subscriptions","organizations_url":"https://api.github.com/users/StefanD986/orgs","repos_url":"https://api.github.com/users/StefanD986/repos","events_url":"https://api.github.com/users/StefanD986/events{/privacy}","received_events_url":"https://api.github.com/users/StefanD986/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2015-08-23T15:11:49Z","updated_at":"2015-08-23T21:38:14Z","closed_at":null,"body":"When using a substrate with the relative permittivity \"er\" set to 1.0, the S-Parameter Simulation yields only results with \"NaN\". See below for an example schematic.\r\nI had a look at the equations of the Models and my guess is: With EpsilonR set to 1 it equals Epislon_R_eff. In some equations for the Microstrip models is \"EpsilonR - EpsilinR_eff\" in the denominator, and then probably causes the NaN result.\r\n\r\nMy configuration is: \r\nQucs 0.0.18 (installed via guitorri/homebrew-tap)\r\nMac OSX 10.10.5\r\n\r\n\r\n```\r\n<Qucs Schematic 0.0.18>\r\n<Properties>\r\n  <View=0,0,800,800,1,0,0>\r\n  <Grid=10,10,1>\r\n  <DataSet=epsilonR_bug_example.dat>\r\n  <DataDisplay=epsilonR_bug_example.dpl>\r\n  <OpenDisplay=1>\r\n  <Script=epsilonR_bug_example.m>\r\n  <RunScript=0>\r\n  <showFrame=0>\r\n  <FrameText0=Title>\r\n  <FrameText1=Drawn By:>\r\n  <FrameText2=Date:>\r\n  <FrameText3=Revision:>\r\n</Properties>\r\n<Symbol>\r\n</Symbol>\r\n<Components>\r\n  <Pac P1 1 240 220 18 -26 0 1 \"1\" 1 \"50 Ohm\" 1 \"0 dBm\" 0 \"1 GHz\" 0 \"26.85\" 0>\r\n  <MLIN MS1 1 410 170 -26 15 0 0 \"Subst1\" 1 \"1 mm\" 1 \"10 mm\" 1 \"Hammerstad\" 0 \"Kirschning\" 0 \"26.85\" 0>\r\n  <GND * 1 240 250 0 0 0 0>\r\n  <Pac P2 1 510 210 18 -26 0 1 \"2\" 1 \"50 Ohm\" 1 \"0 dBm\" 0 \"1 GHz\" 0 \"26.85\" 0>\r\n  <GND * 1 510 240 0 0 0 0>\r\n  <.SP SP1 1 300 480 0 51 0 0 \"lin\" 1 \"1 GHz\" 1 \"10 GHz\" 1 \"19\" 1 \"no\" 0 \"1\" 0 \"2\" 0 \"no\" 0 \"no\" 0>\r\n  <SUBST Subst1 1 620 260 -30 24 0 0 \"1\" 1 \"1 mm\" 1 \"35 um\" 1 \"2e-4\" 1 \"0.022e-6\" 1 \"0.15e-6\" 1>\r\n</Components>\r\n<Wires>\r\n  <240 170 380 170 \"\" 0 0 0 \"\">\r\n  <240 170 240 190 \"\" 0 0 0 \"\">\r\n  <510 170 510 180 \"\" 0 0 0 \"\">\r\n  <440 170 510 170 \"\" 0 0 0 \"\">\r\n</Wires>\r\n<Diagrams>\r\n</Diagrams>\r\n<Paintings>\r\n</Paintings>\r\n```"},"comment":{"url":"https://api.github.com/repos/Qucs/qucs/issues/comments/133941290","html_url":"https://github.com/Qucs/qucs/issues/342#issuecomment-133941290","issue_url":"https://api.github.com/repos/Qucs/qucs/issues/342","id":133941290,"user":{"login":"StefanD986","id":13921689,"avatar_url":"https://avatars.githubusercontent.com/u/13921689?v=3","gravatar_id":"","url":"https://api.github.com/users/StefanD986","html_url":"https://github.com/StefanD986","followers_url":"https://api.github.com/users/StefanD986/followers","following_url":"https://api.github.com/users/StefanD986/following{/other_user}","gists_url":"https://api.github.com/users/StefanD986/gists{/gist_id}","starred_url":"https://api.github.com/users/StefanD986/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/StefanD986/subscriptions","organizations_url":"https://api.github.com/users/StefanD986/orgs","repos_url":"https://api.github.com/users/StefanD986/repos","events_url":"https://api.github.com/users/StefanD986/events{/privacy}","received_events_url":"https://api.github.com/users/StefanD986/received_events","type":"User","site_admin":false},"created_at":"2015-08-23T21:38:14Z","updated_at":"2015-08-23T21:38:14Z","body":"I guess an ```er=1``` occurs only theoretically and I found it more or less by accident. (the only thing that I can imagine might be Aerogel substrates?)\r\nSo its probably not worth the hassle to try to rewrite the equations. But what might be a good idea to help anyone in the same situation to identify the cause of the ```NaN```results, is to throw a warning in the simulation log if ```er==1```."}}