matlab-hfss-ap求助

x0=1mm;y0=12mm;r1=0.5mm;Hsub=10mm;r2=1.5mm;
hfssCylinder(fid,'Cyl1','Z',[X0,Y0,0],r1,Hsub,'meter');
hfssAssignMaterial(fid,'Cyl1','copper');
hfssCircle(fid,'Cyl2','Z',[X0,Y0,0],r2,'meter');
hfssSubtract(fid,{'GroundPlane'},{'Cyl2'});
hfssCircle(fid,'Port','Z',[X0,Y0,0],r2,'meter');
hfssSubtract(fid,{'Port'},{'Cyl1'});
hfssCylinder(fid,'Pin','Z',[X0,Y0,0],r1,Hsub,'meter');
hfssAssignMaterial(fid,'Pin','copper');
hfssAssignLumpedPort(fid,'P1','Port',[X0-r2,Y0,0],[X0-r1,Y0,0],'meter');
请问第7行什么意思，在matlab-hfss-api中怎么一个圆怎么减去一个圆柱体呢?这些程序是设置端口激励的
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