[TangerineSDR] PSWS System Specification preliminary Ver 0.1

[Tom McDermott]

Hi Lyle,  thanks for the comments!

There is no other document about the Space Weather Station System.  What in
particular would
that document cover?  Use Cases ?  Narrative description?   The central
server?
We could ask the NJIT folks to draft something if we can tell them what we
need.

On the RF module...  the plug-on filter could be called plug-in filter. It
could even be an in-line filter.
What would be more clear?

I think the ENOB refers to the SNR of the converter, not the dynamic
range.  Perhaps this view
is not shared by everyone.

If one were to integrate 2 sets of time-domain measurements, the noise
floor would drop by 3 dB compared
to the peak signal.  As more frames are integrated the noise floor
continues to drop until at some
point the spurious signals begin to emerge.  In the analog domain these are
3rd order products. In the
digital domain they are spurious signals (due to nonlinearities, clocks,
etc.)   The ADC driver we
are familiar with has 3rd order products DR of about 91.5 dB.  The ADC
dynamic range is specified as SFDR
using a large FFT (essentially integrating away a lot of noise), and it's
close to 100 dB.

So what is the right vocabulary or method to specify this that everyone
will understand?
I did not find ENOB specs, but my understanding is the 14-bit ADC has about
the same ENOB as the 16-bit ADC.
If you found or have ENOB data on the 14-bit converter, that would be
helpful.

On the magnetometer, we did not agree on the specifications of the
magnetometer with the research team yet.
The desired one has a bare sensor cost exceeding the entire project. So
we've been looking for cheaper
alternatives (which don't have as much resolution by a factor of 6).
Scotty and I talked with Univ of Michigan (?)
students on the $20 unit that they found (it's a commercial product, uses
SPI). It has about 1-dgreee orthogonality
error.

The host could easily handle SPI, I2C, or other since it's such a slow rate
and time precision is unimportant.
I tried to capture that possibility in section 6, first paragraph.  Is
there better wording to use?

-- Tom, N5EG







On Thu, May 2, 2019 at 9:29 AM Lyle Johnson via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> Hello Tom!
>
> Is there a document that describes the Space Weather Station System so I
> can more easily see where the weather station fits into the overall scheme
> of things?
>
> 5. RF Module
>
> I worry about pluggable filter modules because that implies custom stuff
> and thus a need for someone to design it/them.  Still, an external filter
> module (small Hammond or other shielded box with 50-ohm in and out) could
> always be used so this is probably a Good Thing to include.
>
> Not sure what 88 dB dynamic range for directly sampled signals means.  A
> perfect 14 bit ADC would have about 84 dB raw dynamic range.  The LTC2208,
> still one of the best 16-bit ADCs I think, has an effective number of bits
> of just under 13 (12.6 is the number I've seen) though the spec sheet
> claims a Spurious  Free DR of 100 dB.
>
>
> 7. Host Computer
>
> Since the magnetometer specification is so vague, and since it only needs
> to be processed once per second (and I assume a few microseconds or even
> milliseconds of uncertainty in that sampling would have negligible impact)
> I suspect the host computer is much better suited to collect and format the
> data.  If the interface is some standard thing easily implemented by a
> standard FPGA library (like a SPI or SPI port) then the FPGA could gather
> the raw samples.
>
> Hopefully a magnetometer thingy can be located that meets whatever the
> needs are for it, that is already equipped with an interface that can be
> read by a PC over a standard interface.
>
> ---
>
> Just some initial thoughts,
>
> Lyle
> On 5/2/19 7:47 AM, Tom McDermott via TangerineSDR wrote:
>
> Attached in PDF format is a very preliminary system specification for the
> Personal Space Weather Station (PSWS).
>
> There are lots of open issues and questions at this point, the document
> tries to highlight a few of the key ones.
>
> It would be nice to have several sets of eyeballs look this over before we
> advance it any further.
>
> -- Tom, N5EG
>
>
>
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20190502/5df45f69/attachment-0001.html>