how to model dead-zoon of phase detector of PLL in simulink?

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beabroad

Joined: 25 Nov 2003
Posts: 184
Helped: 1

27 Jun 2005 3:19 phase detector simulink

i am using simulink to model PLL.
i followed the paper:
Modeling of fractional-N division frequency synthesizers with SIMULINK and MATLAB
Brigati, S.; Francesconi, F.; Malvasi, A.; Pesucci, A.; Poletti, M.;
Electronics, Circuits and Systems, 2001. ICECS 2001. The 8th IEEE International Conference on Volume 2, 2-5 Sept. 2001 Page(s):1081 - 1084 vol.2

i am now follow Fig. 3. to model PFD
it suggest to use H(s) = 1/(DZ/ln2*s + 1), DZ is the dead-zoon time window.
however, i find the output is not reasonable.
anyone did this or give me some suggestion? thanks.

Y.C Park

Joined: 20 Dec 2004
Posts: 53
Helped: 2

27 Jun 2005 8:36 dead zone for phase detector

HI

I think Dead zone means that even if ifference to reference and feedback signal is happen but charge pump could not recognized.

Normally PFD is desgined by digital circuitry. It's dead zone is very very small(~ psec) It does not cause PLL's performance.

But Noraml charge pump made by cadcode current mirror.
We wanna operate charge-pump in saturation region (if CMOS)
it take a few nano seconde is needed charge pump going into saturation.

Keep in mind that PLL is Locked by charge pump output signal not PFD input signal.

Anyone has another thinking. Please let me know.
Thanks!!!

beabroad

Joined: 25 Nov 2003
Posts: 184
Helped: 1

27 Jun 2005 21:54 simulink detector

do you mean that CP is more important than PFD?
and my question now is how to model CP nonideality?

Y.C Park

Joined: 20 Dec 2004
Posts: 53
Helped: 2

28 Jun 2005 6:31 phase detector in simulink

Exactly I think.

I'd never done PFD modeling.
Is it necessary PFD Modeling?

I think =(Charge Pump gain)*PFD time(from set to reset)
How about your thinking?

I hope attached file will help you.
(I have made this attached file about 1 or 2year ago.
Please give me a feedback if something wrong)