Fig. 2.26. High—pass filter. 
The simplest equation for this type will be 
Y,= 5X1 —X,) (2.132) 
Then 
1 2 
S| [el —e 1 | syxw) 
1 
= ail —cos w}sxx(w). (2.133) 
6. Pre—whitening digital filter (Fig. 2.27) 
Sxx(w) 
Syy(w) 
-T 0 Tl 
Fig. 2.27. Pre—whitening filter |syy{@)/Sxx(@) |". 
If a digital filter such as 
Y,; = QoX, + Q1Xj,-1 + Q2X-2 » . . ArXik.--, (2.134) 
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