[time-nuts] GPS down converter question

[paul swed]

Appreciate everyones guidance here. Interesting on the other threads. They
might be fine on there own so they can be more easily searched in the
future. They will be important as new systems come online.

Other notes on the GPS down converter for an old receiver.
OK I cheated and order a more classic GPS filter with SMA connectors from
Ebay. Can easily add a LNA after it. Also ordered active low drive mixers
HP IMA81008. Lastly the mini-circuits synthesizer that turns out to
actually be a Analog Devices ADF4135 but with the VCO and such all in the
package. So you have to download the analog devices tools to get the
programming words.

What is interesting is that one of the AD tools will program the device by
either a classic parallel port or a USB parallel port it seems. So that
will allow the validation of the right bit sequence very quickly. Then I
will code them into a arduino or SXB. The code only has to run one time at
start or reset.

So sort of on the way and just waiting for the parts.
The Synthesizer and filter should get here pretty quickly. In the interim I
can leverage other mixers I have.
Regards
Paul


On Fri, Dec 4, 2015 at 4:56 AM, Attila Kinali <attila at kinali.ch> wrote:

> Moin Peter,
>
> On Wed, 2 Dec 2015 13:26:57 -0800
> Peter Monta <pmonta at gmail.com> wrote:
>
> > Yes, but I suspect some receivers will implement just the BOC(1,1) for
> cost
> > reasons.  (Spectral peak is at 6 MHz actually, or rather 6*1.023.)
>
> Right, 6MHz. I shouldn't write highly technical mails when it's late :-)
>
> Yes, I think a lot of the receivers that claim Galileo compatibility
> these days are still BOC(1,1) receivers. But i'm not sure whether the
> price impact is actually that high. Most ADCs for GNSS applications
> are still of the sign-magnitude style (aka 2bit) and thus pretty cheap
> to manufacture (4 comparator are enough), even at "high speed". The use
> of higher BW low pass filters might actually make things cheaper
> (smaller components). The bigger question is the availability of
> wide band SAW filters. Unless the consumer (aka phone) market orders
> SAW filters wide enough for full MBOC(6,1) use, there will not be
> any cheap filters available for anyone else (SAW filters might be
> cheap to manufacture, but initial costs are relatively high).
>
> > > ... Although it's possible to track both
> > > of these signals with just a BOC(1,1) decoder (and thus a narrower
> > > bandwidth),
> > > this will induce a slight bias into the tracking loop and thus an error
> > > in the PVT solution.
> > >
> >
> > But BOC(6,1) is orthogonal to BOC(1,1), so I'm not seeing the bias.  I
> > could be wrong, though; some of these things are subtle.  If you have a
> > reference I'd be curious to read about it.
>
> Apparently the cross correlation function of an MBOC with its BOC is not
> exactly symmetric. I haven't understood the details yet (still reading)
> but this popped up a couple of times in different papers.
>
> BTW: how is the work on the GNSS Firehose going?
>
>                         Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>                  -- Miss Matheson, The Diamond Age, Neil Stephenson
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