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Re: [Xylo-SDR] Eurocard Cyclone II PCB

----- Original Message ----- From: "Eric Ellison" <ecellison@comcast.net>
To: "'Xylo-SDR Discussion'" <xylo-sdr@lists.ae5k.us>
Sent: Sunday, January 08, 2006 9:18 PM
Subject: 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.

I was already thinking along those lines, I think I've mentioned that I've got an evaluation board for that ADC coming that I was intending to the interface to the S3 board. I've got a couple of samples of the similar 14-bit ADCs, I should have ordered the 16-bit ones, instead. The former is really intended for IF processing.

73, Leon