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Re: [Xylo-SDR] Eurocard Cyclone II PCB


Hey! You think you could port your plans for your HPSDR objective number
three to a "2x4" to the cyclone II that Leon is designing? Sorry to publish
your PM, but hey, neat stuff, and now we gotta GROUP, which offloads
sections of the entire project!

Phil Covington said in a PM: 

3.  I have samples of the new Analog Devices AD9446 16 bit 100 MSPS A/D
convertor.  I was working with various QSD designs (trying to improve the
performance at 18+ MHz), but I have come to the conclusion that this is
becoming a waste of time with the new 16 bit high speed converters coming
out.  I think I am going to change the design of the HPSDR to use this 16
bit 100 MSPS A/D instead of a QSD based design. 
I will use the Xilinx FPGA to act as a DDC (direct digital down converter -
see AD6620).  So basically the RX chain will consist of a
AD9446 A/D and a Xilinx FPGA!  Can't get much simpler than that...  By using
a DDC I can increase the dynamic range of the high speed 16 bit A/D by as
much as 26 dB which will put it at a level of performance
that is superior to the QSD - 24 Bit Audio A/D designs.   The AD9446
costs about $80 in single unit quantities but it does not need a QSD, does
not need a DDS, and requires less board real estate, so the cost is about
the same in the end.  Running the AD9446 at 100 MHz sample rate will allow
you to digitize from 0 to 30 Mhz.  The DDC will down sample this 30 MHz
swath of spectrum to something the PC can handle over USB 2.0.


All the stuff you mention really fits what is going on here! Since you are
amoungst us other working stiffs now, perhaps you could give this a shot.
I'll have the motherboard - daughter card - enclosure concept nailed in a
few days.


-----Original Message-----
From: xylo-sdr-bounces@lists.ae5k.us [mailto:xylo-sdr-bounces@lists.ae5k.us]
On Behalf Of Philip Covington
Sent: Sunday, January 08, 2006 3:45 PM
To: Xylo-SDR Discussion
Subject: Re: [Xylo-SDR] Eurocard Cyclone II PCB

On 1/8/06, Leon Heller <leon.heller@bulldoghome.com> wrote:
> I'll do it!
> I'll order some of the 96-way connectors and a couple of FX2 chips
> so I can check the footprints. I've already got the Cyclone II chips, but
> need to get some of the configuration chips, as well.
> I've got the 96-way straight and right-angle connectors in the Pulsonix
> library.
> I'll use a four-layer board. There is no point in cutting corners and
> be much easier to design, as well as cutting down on emissions. As most of
> the connections will be to the DIN connector, I'll save a lot of time by
> using the autorouter on them. I might as well put a 24.576 Mhz oscillator
> the board, feeding one of the FPGA clock inputs and brought out to the
> connector, to save having one on the ADC board, as well as a 50 MHz
> oscillator. I've had my Flex board running at 125 MHz, so we could got a
> faster.

Maybe the clocks should stay on the individual boards instead of
putting them on the motherboard?  They can always be routed to other
boards if needed.  It would be nice to make the motherboard all
passive components.

Phil N8VB
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