[SI-LIST] Re: Bandwidth & AC coupling capacitor

I would suggest finding out where the losses are or where the first pole occurs 
and then building a LC compensation network to address the problem with 
rolloff.  Peak it where the rolloff occurs.  Use compensation and equalization 
circuits to fix it. 

This is how it has been done in other technologies such as analog video for 
years. 
Its an age old problem. 

Richard Jungert

> Date: Sun, 31 May 2009 03:34:29 -0700
> From: weirsi@xxxxxxxxxx
> To: icermail@xxxxxxxxx
> CC: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Bandwidth & AC coupling capacitor
> 
> It is all about the series impedance and impedance continuity.  Your PCB 
> etch is nominally a 50 Ohm signal transmission line.  From about an 
> octave above the mounted SRF, the capacitor looks like an inductor with 
> some loss.  If the interconnect in the region of the capacitor is 
> arranged such that the parasitic shunt capacitance Cshunt = Lcap_mounted 
> / 2500, then for wavelengths that are long compared to the length of the 
> region surrounding the capacitor, the L/C approximates the impedance of 
> the rest of the transmission line and there is little impedance 
> discontinuity.
> 
> Steve.
> 
> 
> icer world wrote:
> >       When use AC coupling for interconnection,the capacitor is about 
> > 0.1-0.01uF.However,the resonance frequency of this kind capacitor is below 
> > 100MHz,Would signals above 1GHz such as PCIe signals can pass it without no 
> > bandwidth reduced?Can anyone give me a explanation? Thanks!
> >
> >
> >       
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> -- 
> Steve Weir
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