[hpsdr] Fwd: Re: Ground planes/ Phoenix boards

[Kevin - M0KHZ]

richardh at iinet.net.au wrote:
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>
>
>
>
> I have had to use the ground plane for some signals and power. Power is generally 
> around the edge of the board and the signal lines are for driving the DDS (low 
> traffic) and the mixer oscillator drive from the CPLD lines - these are probably 
> the most problematic, but I couldnt do it on one plane.
> I have just got the first PCBs in my hand today. One is going to Phil Harman and 
> one to Ramakrishnan VU3RDD. 
>
> I have two available for someone to build as a first cut - any 
> takers?
>
> Richard VK6BRO
>
> On Tue Feb 26 21:41 , mike mj.hamel at verizon.net> sent:
>
>   
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>> Hi Richard,
>>
>> I have had difficulties with doing that because there are situations 
>> where the grounds may be separated everywhere except at one point, 
>> however there are other signal interconnections that are not necessarily 
>> at that one point.
>>
>> Put another way, by splitting planes you are allowing a potential 
>> difference to exist in the grounds everywhere except the common point, 
>> which can make things noisy on Vcc and the signal lines. In my 
>> experience split planes are just generally very difficult to get right 
>> for high frequencies.
>>
>> Again, "your mileage may vary" as they say, but it has been a pain every 
>> time I've tried splitting planes, even where IC manufacturers recommend 
>> it. I've never had an issue due to using a single plane, except 
>> complaints about not enough thermal relief on certain ground connections.
>>
>> As for multilayer, there is some improvement in noise caused by ground 
>> shifts but whether it's worth it depends on the design. If it will route 
>> ok on 2 layers, and your placement allows a good signal flow, stay with 
>> 2 layers. It's easier to troubleshoot and cheaper. I only do multilayer 
>> when the component density is too high to support a clean design and a 
>> good placement from a signal perspective.
>>
>> 73,
>>
>> Mike
>> WO1U
>>
>> richardh at iinet.net.au wrote:
>>     
>>> In the first draft of Phoenix I have used a double sided board (would we gain 
>>>       
> much 
>   
>>> by using multilayer boards? - would the cost be justifed?)
>>> I have attempted to split the digital + analogue sections and join them at one 
>>> point.
>>> So far have had no comments re the layout - I guess it is difficult for someone 
>>>       
> to 
>   
>>> look at it.   
>>> I guess we will have to wait for the first build - should receive the first 
>>>       
> boards 
>   
>>> any day now...
>>>
>>> Richard VK6BRO
>>>
>>> On Tue Feb 26  3:57 , mj.hamel at verizon.net> sent:
>>>
>>>       
>>>> ***** High Performance Software Defined Radio Discussion List *****
>>>>
>>>> Others may have a different take on this but I strongly recommend one big 
>>>>         
>>> continuous ground plane, and control current paths by component placement. Split 
>>> planes work OK for audio and LF but with mixed analog and digital and RF 
>>>       
> definitely 
>   
>>> go with a full ground plane.
>>>       
>>>> YMMV
>>>>
>>>> Mike 
>>>> WO1U
>>>>
>>>>
>>>>
>>>>         
>>>>> From: Howard Long hlong at btinternet.com>
>>>>> Date: 2008/02/25 Mon AM 09:02:11 CST
>>>>> To: hpsdr at lists.hpsdr.org
>>>>> Subject: [hpsdr] Ground planes with multiple parts in both analog and
>>>>>           
> 	digital 
>   
>>> domains
>>>       
>>>>> ***** High Performance Software Defined Radio Discussion List *****
>>>>>
>>>>> Folks
>>>>>
>>>>> Traditionally with a signle device such as a CODEC straddling the analog and
>>>>> digital domains, there seems to be a fairly uniform agreement to use a
>>>>> common ground plane with an insulating split between analog and digital
>>>>> sections of the board and a single connection under the CODEC.
>>>>>
>>>>> How do you deal with a situation where there are multiple devices in both
>>>>> the digital and analog domains?
>>>>>
>>>>> I have read this article
>>>>> http://www.google.com/search?hl=en&q=mixed+signal+pcb+layout that seems to
>>>>> suggest the use of a single unsplit ground while maintaining physical
>>>>> partitioning between the mixed signal/analog devices and their digital
>>>>> counterparts.
>>>>>
>>>>> I wonder if anyone has any views on this? In my particular case I have a
>>>>> CODEC, a DDS and a PLL/VCO to deal with using I2S/I2C/SPI interfaces to a
>>>>> DSP.
>>>>>
>>>>> 73, Howard G6LVB
>>>>>
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Hi Richard

If the offer still stands, I'd love to pull together an alpha Phoenix.

73's
Kevin - M0KHZ


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