[SI-LIST] Re: clock 2nd harmonic
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 17 May 2012 17:34:46 -0700
You have a combination of an energy source, high impedance loading, and
adequately efficient transmitter. You can attack either or both.
The energy source is anything that causes the duty cycle to be anything
other than exactly 50%, including distorted edges, loading going through
power cavities, etc. But it can also be the result of circuitry
operating from a multiplied version of the clock.
High impedance loading can be via a power cavity that has too high of an
impedance in the frequency range of the clk*2, or a component / device
structure that has a high impedance at clk*2. If you are exciting a
resonance near that frequency, then you can take steps to tame it.
There are lots of things that can make efficient transmitters. Look for
structures that are near the wavelength of clk*8. Look for signals
crossing slots, power layers coupling to each other or other best
practice violation.
Steve
On 5/17/2012 11:43 AM, Joel Brown wrote:
> I am having an EMI problem with the second harmonic of a 65 MHz clock.
> There is a strong emission at 130 MHz.
> What is most likely causing the second harmonic and how can I reduce it?
> The clock waveform does not look seriously distorted.
> Thanks
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
--
Steve Weir
IPBLOX, LLC
150 N. Center St. #211
Reno, NV 89501
www.ipblox.com
(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax
All contents Copyright (c)2012 IPBLOX, LLC. All Rights Reserved.
This e-mail may contain confidential material.
If you are not the intended recipient, please destroy all records
and notify the sender.
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
