Length Three FIR Loop Filter
The simplest nondegenerate example of the loop filters of §6.8
is the three-tap FIR case (
). The symmetry constraint
leaves two degrees of freedom in the frequency response:10.1
![$\displaystyle {\hat G}(e^{j\omega T}) = {\hat g}(0) + 2{\hat g}(1) \cos(\omega T)
$](http://www.dsprelated.com/josimages_new/pasp/img1942.png)
![$ {\hat g}(0)+2{\hat g}(1)=1$](http://www.dsprelated.com/josimages_new/pasp/img1943.png)
![$\displaystyle {\hat g}(0) \ge 2{\hat g}(1) > 0.
$](http://www.dsprelated.com/josimages_new/pasp/img1944.png)
![$ {\hat g}(0)-2{\hat g}(1)\ge 0$](http://www.dsprelated.com/josimages_new/pasp/img1945.png)
![$ \omega T=\pm\pi$](http://www.dsprelated.com/josimages_new/pasp/img1946.png)
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Length FIR Loop Filter Controlled by ``Brightness'' and ``Sustain''
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Phasing with 2nd-Order Allpass Filters