在高频电磁场分析中，频率大小与网格划分，与PML层厚度有什么关系？

在高频 电磁场分析中，频率大小与网格划分，与PML层厚度有什么关系？如下列代码，总是出现aspect ratio 过大的问题，应如何修改？我是很初的初学者，各位大侠能不能帮帮我。谢谢
/prep7
_frq=5e14 ! working frequency
lamda=3.e8/_frq
scal=1.e-9
phi=0 ! incident phi angle
! define element and geometry
theta=0 ! incident theta angle
et,1,119,1 ! normal element
et,2,119,1,,,1 ! PML element
mp,murx,1,1.
mp,perx,1,1.
x0=scal*212.5
y0=scal*212.5
!aa=scal*212.5
rx=scal*225/2
ry=scal*150/2
plate_h=scal*200
block,-rx,rx,-ry,ry,0,plate_h
h1=lamda/15
h2=0.3*h1
_n1=6
_n2=4
_npml=8
*dim,_c,array,10
_c(4)=0
_c(3)=_c(4)-0.1*lamda
_c(2)=_c(3)-0.25*lamda
_c(1)=_c(2)-_npml*h1
_c(5)=_c(4)+plate_h
_c(6)=_c(5)+0.1*lamda
_c(7)=_c(6)+0.25*lamda
_c(8)=_c(7)+0.25*lamda
_c(9)=_c(8)+_npml*h1
*do,_i,5,8
block,-x0,x0,-y0,y0,_c(_i),_c(_i+1)
*enddo
*do,_i,4,2,-1
block,-x0,x0,-y0,y0,_c(_i),_c(_i-1)
*enddo
alls
vglue,all
numcmp,all
/number,1
! meshing master surfaces and copy mesh to slave surfaces
et,3,200,5
type,3
esize,h2
asel,s,loc,x,-x0
asel,a,loc,y,-y0
asel,r,loc,z,_c(3),_c(6)
amesh,all

esize,h1
asel,s,loc,x,-x0
asel,a,loc,y,-y0
asel,u,loc,z,_c(3),_c(6)
amesh,all
alls
NUMSTR,elem,1
asel,s,loc,x,-x0
agen,2,all,,,2*x0
asel,s,loc,y,-y0
agen,2,all,,,0,2*y0
alls
nummrg,all