[hpsdr] Power supply filtering

[Jeroen Bastemeijer]

Dear All,

I had a look at the posts with regards to the use of (for example) 
spread spectrum. Spread spectrum techniques used for clocking in PCs 
were once introduced as a trick to stay below the noise levels as 
specified by FCC-regulations (and the like). They were not introduced to 
boost the performance of the PC.
As I indicated in one of my first mails about Demeter, it seems better 
to have a known, but adjustable switching frequency. This will give a 
peak somewhere in the spectrum but it could be shifted (by adjusting the 
switching frequency).
The spread spectrum might be another solution, but my feeling says it 
will only make things worse.

On the other hand: The idea would be to use a PIC to set the SMPS to a 
certain frequency. Some software could be used to make the "stable" 
switching frequency a spread-spectrum frequency.... This enables people 
who live in a noisy area (the city or near heavy industries) to spread 
the noise and not having to bother about the switching frequency of 
their power supply. (The SMPS noise might be below the surrounding noise 
level.....)

I made a print-out of a few SMPS-spread-spectrum references, will read 
them in the weekend (I hope).

Furthermore, I agree with Andreas reaction: A table with the power 
consumtion for each card for each voltage is necessary to keep 
everything under control. The power supply should be "strong" enough, 
but the Atlas should be capable of distributing the power. Another 
option would be to use wires to bring the power to the real power-hungry 
boards.

Henry, I agree with you that Demeter should be flexible. The idea at 
this moment is that certain parts can be left-out (e.g. when someone 
doesn't need the mobile operation option). However, the PCB would like 
odd, with certain unpopulated areas.... are you suggesting we should use 
a really modular setup for Demeter as well? With small PCB's for each 
voltage and or function?

73 Jeroen PE1RGE

Doug Gibbs wrote:

>***** High Performance Software Defined Radio Discussion List *****
>
>Has anyone considered using a spread spectrum switching regulator 
>controller to reduce the EMI effects? See the following links:
>
>
>http://www.eetasia.com/ARTICLES/2006OCT/PDF/EEOL_2006OCT09_EMD_RFD_TA.pdf?SOURCES=DOWNLOAD
>
>http://www.maxim-ic.com/appnotes.cfm/an_pk/1077
>
>http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=3577
>
>
>Doug - W8NFT
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-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl
GPS: Lat N52.00002 Lon E4.37157 Alt 46.2m


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