[hpsdr] Mercury

[Philip Covington]

On 9/23/06, Lyle Johnson <kk7p at wavecable.com> wrote:
> Philip Covington wrote:
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Hi Phil,
> >
> > Mercury:
> > If we go with the AD6636, by using a couple of 74LVC16374
> > <http://www.nxp.com/pip/74LVC16374ADL.html>
> > 16 bit D FFs, we can either route the ADC input to the AD6636 or
> > straight to the FPGA on the Mercury board.  That way we can support
> > radio mode with the AD6636 and spec/oscope mode in the FPGA.  To use
> > the board just as a scope or spectrum analyzer the AD6636 would not
> > have to be populated on the board.  It would also allow
> > experimentation with DDC in the FPGA with a fallback to the AD6636
> > otherwise.
>
> Since these are flip-flops and not MUXes, I don't understand their use.
>   Can't we just run the ADC output directly to the FPGA and to the DDC?

They are used as buffers.  They are fast enough to support the AD6636.
 They are D FFs to allow delaying the ADC clock if need be.

> Do we need a larger/different family FPGA for more resources or speed to
> implement a DDC?  I'm concerned that the ADI part may not have a long
> life.  And of course, it is BGA...  If we are prepared to use BGA, we
> can get a very fast, very dense FPGA.
>
> Lyle

To do what we want we would need a larger FPGA, yes.  The larger FPGA
and configuration device exceeds the cost of using the AD6636.

Unless we are going to build everything out of 2N2222s then we are
always going to have the problem of chips becoming obsolete.  I doubt
the AD6636 is going to become obsolete too soon.  What about the ADC?

I am not afraid of BGAs.

73 de Phil N8VB

 1159118742.0