设计切比雪夫I型模拟低通滤波器
设计切比雪夫I型模拟低通滤波器，求出转移函数G(p)subroutine chebsh(l,k,ln,d,c,phi2,ierror)
c----------------------------------------------------------------------
c routine CHEBSH: To design low-pass Chebyshev analog filter:
c H(s)=D(s)/C(s)
c If IERROR=0: no errors detected
c =1: invalid filter order l and k
c in Chapter 7
c--------------------------------------------------------------------
dimension d(0:4),c(0:4)
pi=4.*atan(1.)
ierror=1
if(l.le.0.or.k.gt.int((l+1)/2)) return
ierror=0
do 10 i=1,ln
d(i)=0.
c(i)=0.
10 continue
d(0)=1.0
c(0)=1.0
orderk=k-(l+1.)/2.
if(orderk.eq.0) goto 20
c(0)=(sin((2*k-1)*pi/(2*l))*(exp(phi2)-exp(-phi2))/2.0)**2 +
$ (cos((2*k-1)*pi/(2*l))*(exp(phi2)+exp(-phi2))/2.0)**2
c(1)=2.*sin((2*k-1)*pi/(2*l))*(exp(phi2)-exp(-phi2))/2.0
c(2)=1.
return
20 c(0)=(exp(phi2)-exp(-phi2))/2.0
c(1)=1.0
return
end
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