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A question on phase locked loop Hspice simulation

Hi, Everyone,

I posted a question on Phase Locked Loop several weeks ago and thank
you very much for everyone's reply.

Here I have another question related to hspice simulation on the phase
locked loops -- I want to measure the lock time of the loop using
hspice for 1000 times with different loop parameters. I tried to use
derivative of the VCO input signal and I tried to use the phase
difference between the reference signal and the VCO output....
basically, what I am using is the .measure command and find and when
function.

However, all the things I tried do not work -- it does not really
predict the lock time for me.

I read the hspice manual and I cannot find an existing function that
can directly do it. Anybody here has some ideas, please?

Thanks a lot!
 
T

Tim Wescott

Jan 1, 1970
0
Hi, Everyone,

I posted a question on Phase Locked Loop several weeks ago and thank
you very much for everyone's reply.

Here I have another question related to hspice simulation on the phase
locked loops -- I want to measure the lock time of the loop using
hspice for 1000 times with different loop parameters. I tried to use
derivative of the VCO input signal and I tried to use the phase
difference between the reference signal and the VCO output....
basically, what I am using is the .measure command and find and when
function.

However, all the things I tried do not work -- it does not really
predict the lock time for me.

I read the hspice manual and I cannot find an existing function that
can directly do it. Anybody here has some ideas, please?

Thanks a lot!
Are you having difficulty finding when the loop is in lock, or are you
having difficulty convincing HSPICE to measure it?

What sort of phase detector do you have?

What sort of loop filter do you have?

I'm not a big SPICE jockey, but the way I'd do this in SciLab or MatLab
would be to take average VCO input at the very end of the run as the
'settled' value, then backtrack until the VCO input was outside of some
bound around the settled value -- this would be easy in one of the above
analysis packages, but I couldn't begin to tell you how hard it would be
in SPICE.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
J

Jim Thompson

Jan 1, 1970
0
Are you having difficulty finding when the loop is in lock, or are you
having difficulty convincing HSPICE to measure it?

What sort of phase detector do you have?

What sort of loop filter do you have?

I'm not a big SPICE jockey, but the way I'd do this in SciLab or MatLab
would be to take average VCO input at the very end of the run as the
'settled' value, then backtrack until the VCO input was outside of some
bound around the settled value -- this would be easy in one of the above
analysis packages, but I couldn't begin to tell you how hard it would be
in SPICE.

This is a toughy. I'm not sure if you can force enough initial
conditions to get Spice to walk into lock rather than jumping
artificially to a lock solution.

Maybe force the VCO control voltage off-lock for a long period of
time, then release and let it walk in.

...Jim Thompson
 
E

EE123

Jan 1, 1970
0
Jim said:
This is a toughy. I'm not sure if you can force enough initial
conditions to get Spice to walk into lock rather than jumping
artificially to a lock solution.

Maybe force the VCO control voltage off-lock for a long period of
time, then release and let it walk in.

...Jim Thompson



I have several PLL articles using SPICE:
- Motorola AN1671 MC145170 PSpice modeling kit by Onis Cogburn
- Microwaves and RF November 1997 "SPICE Tools Provide Behavioral
Modeling of PLLs" by Orlando Pena
- Choi and Connelly have a book devoted to PLLs and SPICE

Good luck,
Dave
 
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