[SI-LIST] Re: upper to How high the frequency to scan is sufficient for target impedance of Power distribution system

The KNEE frequency is generally accepted as a measure of the bandwidth of a
digital pulse. Before the Fknee the harmonic amplitude falls of at 20dB per
decade. After FKnee, the harmonics fall off much faster. Typically the
spectral amplitude is down roughly 6dB at FKnee. Howard Johnson recommends
0.5/tr as a suitable formula. The standby has been 0.35/tr as already
stated.

Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel:  303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.grasso@xxxxxxxxxxxx;  
Email Alternate: chasgrasso@xxxxxxxx
 

-----Original Message-----
From: Kong Chuan Susanto [mailto:kos@xxxxxxxxxxx] 
Sent: Thursday, April 29, 2004 10:58 AM
To: meng.yubao@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: uper to How high the frequency to scan is sufficient
for target impedance of Power distribution system

Hi Meng,

I have read some papers that use 'risetime/0.35' for the upper bound
frequency. However I'm not sure where this thing comes from. Perhaps
others can comment on this too. The lower bound basically is from DC.

Regards,
 
Chuan

> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx 
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of 
> meng.yubao@xxxxxxxxxx
> Sent: Monday, April 26, 2004 2:52 AM
> To: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
> Subject: [SI-LIST] uper to How high the frequency to scan is 
> sufficient for target impedance of Power distribution system
> 
> 
> HI:
>    For a highspeed digital system PCB, we should control its 
> PDS Impedance 
> not to exceed its target Impedance from low frequency uper to high 
> frequency, but how higher the upper frequency is good enough, and how 
> lower the frequency ? Deducing from the Pulse width of the PCB 
> simultaneous switch noise or from the signal rise/fall edge 
> and its pulse 
> width ? Can anyone give me some clear equation! 
> regards 
> meng yubao
> 
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