📄 total3.f90
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!*********************************************************************************************************
!****************************************END OF PROGRAM****************************************
!***********************************************************************************************************
!外推远区场（或者RCS）
!***************************************************************
!** Extrapolation of Radar Cross Section of Far Field **
!** Based on FDTD Calculations **
!** **
!** TYPE :main program **
!** CALLS :Bessel Functions **
!** LANGUAGE :Fortran90 **
!** INTPUT FILE NAME :????????.bnd **
!** OUTPUT FILE NAME :????????.dat **
!***********************************************************************
!***********************变量定义****************************************
complex Jz !输出面上电流密度（TM极化，TE极化为磁流密度，以下类似）
complex Mx !磁流密度
complex My !磁流密度
complex Ctemp,ctemp1 !临时复数变量
complex E(-1250:1250,4) !输出边界切向电场
complex H(-1250:1250,4) !输出边界切向磁场
real WaveLength !波长
integer WL !数值波长
integer TEMFlag ! TM=1 TE=-1
real IncidentAngle !FDTD计算中的入射角（度）
real Phi !观察角（度）
real StartAngle,EndAngle,DegreeStep !输入角起始值、终止值、布进
character *30 FileName !散射数据（由FDTD近场计算程序得到）
character *1 Blank,Respond
logical FileExist
integer FileNameLength, Record
!*************初始化**************
!write(*,*) char(7)
10002 write(*,'(///////////////////)')
write(*,*)''
write(*,*)'Extrapolate Base on FD-TD Boundary to Far Zone'
write(*,*)'to Caculate Radar Cross Section'
write(*,*)'(Two-Dimension&TM mode)'
write(*,*)''
write(*,*)''
Blank=''
WRITE(*,'(11X,34hThe scatterer data file name is :,$)')!
READ(*,'(a30)')FileName
FileNameLength=index(FileName,Blank)-1
inquire(file=FileName(1:FileNameLength)//'.BND',exist=FileExist)
if(FileExist)then
OPEN(1,file=FileName(1:FileNameLength)//'.BND',access='direct',recl=8)
else
write(*,'(1x,5x,15hFile not found.)')
write(*,'(1x,15x,33hPress [Enter] to redo from start.)')
read(*,'(a1)')Respond
goto 10002
endif
read(1,rec=1)WaveLength
read(1,rec=2)WL
read(1,rec=3)TEMFlag
read(1,rec=4)IncidentAngle
read(1,rec=5)Imin
read(1,rec=6)Imax
read(1,rec=7)Jmin
read(1,rec=8)Jmax
read(1,rec=9)Itmin
read(1,rec=10)Itmax
read(1,rec=11)Jtmin
read(1,rec=12)Jtmax
read(1,rec=13)Iomin
read(1,rec=14)Iomax
read(1,rec=15)Jomin
read(1,rec=16)Jomax
read(1,rec=17)TimeStep
write(*,*)''
WRITE(*,'(11X,15hKnown message :)')
WRITE(*,'(13x,11hWaveLength=,e12.4,4H m = ,i4,5H Grid)')WaveLength,WL
if(TEMFlag.eq.1) then
write(*,'(13x,12hWaveMode:TM,5x,17hIncident angle =,f7.2,8h degrees)')IncidentAngle
else
write(*,'(13x,12hWaveMode:TE,5x,17hIncident angle =,f7.2,8h degrees)')IncidentAngle
end if
write(*,'(13X,25hAbsorbing boundary is : ,4i6)')Imin,Imax,Jmin,Jmax
write(*,'(13X,25hConnective boundary is : ,4i6)')Itmin,Itmax,Jtmin,Jtmax
write(*,'(13X,25hThe output boundary is :,4i6)')Iomin,Iomax,Jomin,Jomax
write(*,'(13X,14hTimeStop is : ,i6)')TimeStep
write(*,*)''
write(*,'(11X,19hMake choice below :)')
write(*,'(13x,34hStartDegree,EndDegree,DegreeStep: ,$)')
read(*,*)StartAngle,EndAngle,DegreeStep
!begin
pi=3.1415927
rk=2*pi/float(WL) !contant of propogation K!
Z=sqrt(pi*4.0e-7/8.854e-12) !wave inpedence of free space!
!********************读入散射场数据Es,Hs***********************
!********************并计算n x Es, n x Hs**********************
Record=17
do i=Iomin,Iomax
Record=Record+1
read(1,rec=Record)E(i,1) !Mz0=Esz,Jx0=Hsx
Record=Record+1
read(1,rec=Record)H(i,1)
Record=Record+1
read(1,rec=Record)Ctemp
E(i,3)=-Ctemp !Mz0=-Esz
Record=Record+1
read(1,rec=record)Ctemp1
H(i,3)=-Ctemp1 !Jx0=-Hsx
end do
do i=Jomin,Jomax
Record=Record+1
read(1,rec=Record)E(i,2) !Mz0=Esz,Jx0=Hsx
Record=Record+1
read(1,rec=Record)H(i,2)
Record=Record+1
read(1,rec=Record)Ctemp
E(i,4)=-Ctemp !Mz0=-Esz
Record=Record+1
read(1,rec=Record)Ctemp1
H(i,4)=-Ctemp1 !Jy0=-Hsy
end do
close(1)
if(TEMFlag.eq.-1)then !若为TE模，则做以下转换
do i=iomin,iomax
E(i,1)=E(i,1) !Ez-->Hz
E(i,3)=E(i,3)
H(i,1)=-H(i,1) !Hx-->-Ex
H(i,3)=-H(i,3)
end do
do i=jomin,jomax
E(i,2)=E(i,2) !Ez-->Hz
E(i,4)=E(i,4)
H(i,2)=-H(i,2) !Hy-->-Ey
H(i,4)=-H(i,4)
end do
Z=1./Z
end if !reciprocal
!******************沿着四条输出边界积分Jz,Mx,My**********************
OPEN(2,file=FileName(1:FileNameLength)//'.dat') !存储RCS的文件
do dg=StartAngle,EndAngle,DegreeStep !散射角循环
Jz=(0.,0.)
Mx=(0.,0.)
My=(0.,0.)
write(*,1)dg
1 format(1H+,10x,'Now caculate degree',f6.1)
Phi=dg*pi/180.
do I=Iomin,Iomax
Ctemp=cmplx(0.,(float(I)*cos(Phi)+(jomin-0.5)*sin(Phi))*rk)
Ctemp=cexp(Ctemp) !exp(j*k*r);x=i,j=jomin-.5
Mx=Mx+E(i,1)*Ctemp !下边界
Jz=Jz+H(i,1)*Ctemp
Ctemp=cmplx(0.,(float(I)*cos(Phi)+(jomax+.5)*sin(Phi))*rk)
Ctemp=cexp(Ctemp) !exp(j*k*r);x=i,j=jomin-.5
Mx=Mx+E(i,3)*Ctemp !上边界
Jz=Jz+H(i,3)*Ctemp
end do
do I=Jomin,Jomax
Ctemp=cmplx(0.,(float(I)*sin(Phi)+(iomax+.5)*cos(Phi))*rk)
Ctemp=cexp(Ctemp) !exp(j*k*r);x=iomax+.5,y=i
My=My+E(i,2)*Ctemp !右边界
Jz=Jz+H(i,2)*Ctemp
Ctemp=cmplx(0.,(float(I)*sin(Phi)+(iomin-.5)*cos(Phi))*rk)
Ctemp=cexp(Ctemp) !exp(j*k*r);x=iomin-.5,y=i
My=My+E(i,4)*Ctemp !左边界
Jz=Jz+H(i,4)*Ctemp
end do
!*************************计算雷达散射截面(RCS)并输出************************
RCS=abs(Mx*sin(Phi)-My*cos(Phi)+Z*Jz)
RCS=.25*rk*rcs*rcs*Wavelength/float(WL)/Wavelength
write(1,*)dg,rcs
RCS=10.*log10(RCS)
write(2,*)dg,RCS
end do !结束散射角循环
close(2)
write(*,*) CHAR(7)
end
!****************************************************************************
!****************************END OF PROGRAM**********************************
!****************************************************************************
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