E [So(@)] 
I 
a= 
MIs 
E [R(r)] COs Tw 
1. Ir 
= » 1—— | R(r) cosrw > s(@), (2.86) 
hy ge N 
as M tends to > ©, but more slowly than N tends to > ©. Namely, N= ~, M—> 
but Ww — o also, for example as M was on the order of JN. 
When using the function wo(r), Eq. 2.85 is the same as, 
(N-1) 
Sow) = — yS wo(r) R(r) cosr@ (2.87) 
27 
r=—(N-1) 
where 
ces) 1 -N<-MsrsM<N (2.88) 
0 otherwise 
More generally, many forms of functions w(r) besides Eq. 2.88 are proposed as 
shown in Fig. 2.11. R(r) cos rw are even functions of r; therefore, if we take w(r) as 
real even functions of r, then 
i 1 N=1 ; 
§@) =— => wer) RQ) er”. (2.89) 
2m r=-(N-1) 
29 
