Digital Signal Processing Reference
In-Depth Information
and using (7.12), we obtain the gain derived in Chapter 3 [eq. (3.55)], i.e.,
1 cos[ ωτ 0 (1 − α 1,1 )]
1 cos[ ωτ 0 (cos θ N
G
NS,1 [ h
( ω )] =
− α 1,1 )] .
(7.22)
The gain of h ( ω ) for a point noise source is
2
h H ( ω ) d ( ω, 1)
G NS,1 [ h ( ω )] =
|h H ( ω ) d ( ω, cos θ N ) | 2
1
( a 1,0 + a 1,1 cos θ N ) 2 ,
=
(7.23)
which corresponds to the theoretical gain of the first-order DMA.
Clearly, the first-order DMAs derived in this section are strictly equivalent
to the ones derived in Chapter 3.
7.3 Second-Order Differential Arrays
For second-order DMAs, we need to inverse the matrix Ψ 3 , which is given by
1 3
1
2
02 1
0 1
2
2
−1
3
Ψ
=
.
(7.24)
1
2
We deduce that the corresponding filter is
a 2,2
( ωτ 0 ) 2 + 3 a 2,1
a 2,0
2 ωτ 0
2 a 2,2
( ωτ 0 ) 2
2 a 2,1
ωτ 0
h ( ω )=
a 2,2
( ωτ 0 ) 2 + a 2,1
2 ωτ 0
.
1 a 2,0 ( ωτ 0 ) 2
a 2,2
3 ωτ 0 a 2,1
2 a 2,2
2+ 2 ωτ 0 a 2,1
a 2,2
1 ωτ 0 a 2,1
2 a 2,2
= a 2,2
( ωτ 0 ) 2
(7.25)
Replacing 1 + x + x 2 / 2 by e x in (7.25), we get
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