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The Designer's Guide Community Forum › Design › Analog Design › how to determine loop bandwidth for PI with digital filter?

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how to determine loop bandwidth for PI with digital filter? (Read 7165 times)

supermoment Senior Member Offline Posts: 167	how to determine loop bandwidth for PI with digital filter? Apr 12^th, 2011, 8:15am how to determine loop bandwidth for PI with digital filter?
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how to determine loop bandwidth for PI with digital filter? Reply #1 - Apr 12^th, 2011, 9:01am what do you mean by PI loop BW..its an open loop system
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #2 - Apr 12^th, 2011, 5:12pm PI output go to a CDR loop
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how to determine loop bandwidth for PI with digital filter? Reply #3 - Apr 12^th, 2011, 9:35pm yes, so should ask CDR bandwidth riteee.... so this is a different question now. Tell me weather your CDR is 1st order or 2nd order from there we can decide.
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #4 - Apr 13^th, 2011, 1:12am since PI replacing the vco, there is no 1/s integral part. Then it should be 1st order. digital loop filter is used.
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how to determine loop bandwidth for PI with digital filter? Reply #5 - Apr 13^th, 2011, 5:02am correct but what about loop filter. General rule is if you need only phase tracking use first order, but if any frequency tracking required (like systems which are having ppm between TX and RX) then 2nd order imp. Thanks.
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #6 - Apr 13^th, 2011, 5:55am how to determine the loop filter? input does not have ssc. could you point me some of the good papers?
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how to determine loop bandwidth for PI with digital filter? Reply #7 - Apr 14^th, 2011, 10:12pm hi, http://www.ece.tamu.edu/~spalermo/ecen689/cdr_hlee_stanford_2006.pdf http://www.ece.tamu.edu/~spalermo/ecen689/dig_cdr_bb_pll_sonntag_jssc_2006.pdf Thanks.
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #8 - Apr 14^th, 2011, 11:25pm thank you
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #9 - Apr 24^th, 2011, 7:28am how could the PI has 2nd order loop?? 2nd order loop implies that the PI can adjust its clock frequency. The PI has only fixed frequency but the phase can be adjusted.
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: how to determine loop bandwidth for PI with digital filter? Reply #10 - Apr 24^th, 2011, 12:36pm good question, i also understand little bit. So please refer the above thesis. What i feel is rate of change of phase is frequency. If you know any answer for this let me know Thanks.
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supermoment Senior Member Offline Posts: 167	Re: how to determine loop bandwidth for PI with digital filter? Reply #11 - May 12^th, 2011, 6:09am got it. freq=d(phi)/dt (1st order) ramping freq = d(phi)^2/dt^2 (2nd order)
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