[SI-LIST] Re: Bandwidth & AC coupling capacitor
- From: steve weir <weirsi@xxxxxxxxxx>
- To: icer world <icermail@xxxxxxxxx>
- Date: Sun, 31 May 2009 03:34:29 -0700
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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