[PLL] Relation between Freq Step and Phase Step response?

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yolande_yj

Joined: 20 Jan 2005
Posts: 146

31 May 2006 8:41 pll step response

Hi, in PLL design, what is the relation between frequency step response and phase step response?Or what is the relation between Freq(ω) and Phase(ω)? Thanks

khouly

Joined: 20 Oct 2003
Posts: 2479
Helped: 343
Location: EGYPT

31 May 2006 20:02 what is a pll step response

the frequency step is a ramp in phase ,
so the phase step is differnitation of frequncy step"which is ramp in phase"

so to get frequncy steo respose "apply a step" then put an integrator before the pll

khouly

yolande_yj

Joined: 20 Jan 2005
Posts: 146

31 May 2006 22:14 Re: [PLL] Relation between Freq Step and Phase Step response

khouly wrote:

the frequency step is a ramp in phase ,
so the phase step is differnitation of frequncy step"which is ramp in phase"

integration?
How can I apply a phase step?

safwatonline

Joined: 19 Nov 2005
Posts: 1418
Helped: 172
Location: EGYPT

31 May 2006 22:46 [PLL] Relation between Freq Step and Phase Step response?

apply in linear model "AC model"

khouly

Joined: 20 Oct 2003
Posts: 2479
Helped: 343
Location: EGYPT

01 Jun 2006 1:05 Re: [PLL] Relation between Freq Step and Phase Step response

if u use a linear model in s domain , just use a step source , this will be the phase step

khouly

yolande_yj

Joined: 20 Jan 2005
Posts: 146

01 Jun 2006 3:00 [PLL] Relation between Freq Step and Phase Step response?

how about in time domain, transient simulation?

Vamsi Mocherla

Joined: 06 Sep 2004
Posts: 482
Helped: 62

01 Jun 2006 7:04 [PLL] Relation between Freq Step and Phase Step response?

Dear Yolande,

In a PLL, you can actually inject the phase step by adding a source at the input of VCO in the PLL, in series with the loop filter output. Remember that the the control voltage will determine the phase/frequency

yolande_yj

Joined: 20 Jan 2005
Posts: 146

01 Jun 2006 7:12 Re: [PLL] Relation between Freq Step and Phase Step response

Vamsi Mocherla wrote:

Yes, but if I apply a voltage step to the VCO, that will cause frequency step, not phase step.

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safwatonline

Joined: 19 Nov 2005
Posts: 1418
Helped: 172
Location: EGYPT

01 Jun 2006 7:28 [PLL] Relation between Freq Step and Phase Step response?

i never did this before but u may try it ,
1- try to do a model for a source like
V=A*sin(w*t+phi) ; the source get the phi as input "i think it is a simple verilogA code"
then just add a step to the phi i/p.

i didnt try this but it may work.