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

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yolande_yj

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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
 

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
 

Re: [PLL] Relation between Freq Step and Phase Step response

khouly said:
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?
 

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
 

how about in time domain, transient simulation?
 

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
 

Re: [PLL] Relation between Freq Step and Phase Step response

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

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.
 

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