Marcel
If you Google "Software Radio" you will find a heap of information on
similar projects. (Mostly using DSPs etc rather than FPGA, but the
idea's the same).

RP

On 26/11/2008, Marcel Birthelmer <marcel@carrietech.com> wrote:
> On Tue, Nov 25, 2008 at 12:06 PM, PAUL James <James.Paul@colibrys.com>wrote:
>
>  >
>  > Martin,
>
>
>  Martin is just an innocent bystander, I'm the newbie here.
>
>  >
>  >
>  > I'm not sure what you have in mind exactly, but I believe you may be
>  > either misinformed, or uninformed.
>
>
>  Probably both.
>
>  >
>  >
>  > Take this quote "The reason I chose AM is that its frequency band is
>  > still digitizable - I don't have to mix it down like I would with FM or
>  > whatever."
>  >
>  > I'm not sure what you mean here by "its frequency band is still
>  > digitizable".  Unless you mean that since you are dealing with AM, you
>  > only have amplitude to be concerned about.  And that indeed is
>  > digitizable.  However, FM is also just as digitizable.
>
>
>  My point was that it's much easier to sample and digitize a 1MHz (AM Radio)
>  signal than a 100MHz (FM Radio) signal.
>
>  >
>  > And where you say I don't have to mix it down like I would with FM or
>  > whatever.".  What does that mean? [snip]
>
>
>  Jim, thank you very much for the detailed explanation. I am somewhat
>  familiar with how radios work, but my plan was not to build a receiver, but
>  more specifically to implement as much of a receiver as possible in an FPGA.
>
>  By "mix it down" I meant the frequency shifting process (the LO part, I
>  think). My plan is/was to take a raw 1MHz signal (obviously processed for
>  the ADC stage), and do the frequency tuning, detecting, and low-pass
>  filtering by means of digital transformations. So basically instead of using
>  the LO, the idea would be to convolve the incoming signal with a band pass
>  filter. Likewise for all the other steps.
>
>  I understand that this is not the way radios are commonly built, but it's
>  mainly a learning exercise anyway.
>
>  Of course, it may very well not be feasible, and I'd appreciate any further
>  insight (or flames for my RF-level incompetence).
>
>  Thanks again for your time.
>  - Marcel
>
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