[hpsdr] Phoenix again

[Rob Frohne]

Hi Richard,

A little googling and I found the documents at:

http://www.e2v.com/assets/media/files/documents/broadband-data-converters/doc0999A.pdf

and

http://www.einfochips.com/resourcecenter/designers_corner/Grounding%20in%20Mixed%20Signal%20PCB.pdf

Thanks,

Rob


richardh at iinet.net.au wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
> In fact doing a quick bit of reading it seems that I have made a number of
> mistakes with the original design. (grr why didnt I do the reading before :))
>
> Some of the mixer clock traces cross several sections of ground plane which are
> digital and then analog. This is probably the source of the spurs that I have
> had. It will probably be impossible to do this on a 2 layer board.
>
> I think I also have to separate the quadrature generation from the FPGA = the
> clock here should be treated as an "analog" signal = maybe the old Johnson
> counter implemented in tinyLogic , with chip select for transmit and receive.
>  
> It seems more important (according to the articles = see
> www.e2v.com/assets/media/files/documents/...data.../doc0999A.pdf and
> www.einfochips.com/.../designers.../Grounding%20in%20Mixed%20Signal%20PCB.pdf) to
> isolate both power and ground planes into digital and analog sections and run
> traces that connect between them over a "bridge" between them than worry about a
> connection at a single point.
>  
> I would be interested in comments 
>
> Richard
>
> On Sun Nov  1 14:10 , "richardh at iinet.net.au"  sent:
>
>   
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Anthony
>>
>> Thanks for the comments
>>
>> OK on the H mode mixer = this is somewhat more complex than the current
>> arrangement = what performance gain am I likely to see?
>>
>> I cant quite see the connection on the pdf files 
>> I presume you make a connection between the two at the GND point on the Atlas
>> connector = close to the +5V pins = is that correct?
>>
>> I tried to separate the Analog and digital planes on the original Phoenix 
>> I wonder if the problem lies with the fact that the DDS has an analog section =>
>> FPGA for quadrature generator section (this has a digital ground plane)  => back
>> to the analog plane fore the mixers. Maybe all these sections should be separated
>> and tied together at one point.
>> Alternatively, should I have a layer for digital and another layer for analog?
>>
>> Also = what is the name of the PCB manufacturer you are using?
>> I dont want to go through a process of finding one who I can work with if you
>> guys have already done so.
>> I take it they would want all layers in Gerber format.
>>
>> What sort of cost am I looking for if I have say 
>>
>> Top
>> Power Plane
>> signal plane 
>> Analog Ground plane 
>> Bottom/Digital ground plane 
>>
>> for prototypes?
>>
>> Does the order matter?
>>
>> Thanks for any feedback = I am a novice at this stuff
>>
>> Richard VK6BRO
>>
>>
>> On Wed Oct 28  7:53 , Anthony Taylor  sent:
>>
>>     
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-- 
Rob Frohne, Ph.D., P.E.
E.F. Cross School of Engineering
Walla Walla University
100 SW 4th Street
College Place, WA 99324
(509) 527-2075			 http://people.wallawalla.edu/~rob.frohne

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