FS6131
The transfer function of the feedback divider is:
KF
=
1
NF
Finally, the sampling effect that occurs in the phase detector is accounted for by:
K SAMP
( s)
=
⎜⎛1 −
⎜
⎜⎝
e −⎜⎝⎛ s
s
f REF
⎟⎠⎞
⎟⎞
⎟
⎟⎠
f REF
The loop gain of the PLL is:
K LOOP (s) = K PD K LF (s)KVCO (s)K F K SAMP (s)
100
10
1
The loop phase angle is:
0.1
0.01
0.1kHz
1kHz
10kHz
Frequency (fi)
Figure 8: Loop Gain vs. Frequency
100kHz
[ ] Θi = arg K LOOP ( j2πfi)
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