> On Apr 9, 2017, at 4:29 PM, Attila Kinali <att...@kinali.ch> wrote: > > On Wed, 5 Apr 2017 08:27:58 -0400 > Bob kb8tq <kb...@n1k.org> wrote: > >> Galileo E5 is a bit of a strange case. It’s really E5a and E5b. >> You can either grab it all as one giant signal or as two separate signals. >> You may (or may not) care about the data on E5a or b depending on what you >> are trying to do. Getting the entire very wide signal likely has some >> interesting benefits when it comes to working out very small differences >> in location or … errr… time. > > I wouldn't call it strange, but rather neat :-) > The E5 signal is created as a single, 8-PSK signal(see [1]), which is > modulated such, that the positive and negative frequency parts get > a specific signal structure. This is done in order to allow an extremely > wide band signal to be demodulated in parts. I guess they feared that a > receiver for a 50MHz wide signal would be too expensive for the > commercial market and made it possible to process the signal as two > 20MHz wide pieces. There is a slight loss in correlation energy in this > case, but for most applications it should not matter. The bigger issue > is that the path delays for the two receiver channels would need to be > calibrated and tracked during operation in order to make full use of > the E5 signal. > > BTW: I have been told, that using the full E5 signal makes the use > of any other signal kind of unnecessary as its extremely wide bandwidth > allows a very fine tracking of the signal. Thus the use of any other signal > (e.g. E1 OS) would actually degrade the receivers timing performance than > improve it.
Without a “second frequency” you can’t do local ionosphere corrections. That’s true regardless of the bandwidth of the signals ….. Bob > >> >> One way to do the E5 signal would be a dual (duplicate) IF ISB >> downconverter. >> How practical that turns out to be is an open question. The more conventional >> approach is to take a monstrous chunk of L band down to a high speed >> sampler. > > As I have written above, to be able to do this is the reason for the E5's > signal structure. And apparently the designers thought that this would be > the way how most users would decode it. I am currently not aware of any > commercial E5 receiver that is already on the market, so it is kind of moot > to ask what the common way to decode E5 is. > > BTW: Rodriguez' PhD thesis[2] (which is the basis of navipedia) gives a very > nice overview of the trade-off's that went into the Galileo signals and > gives a few hints where future GNSS signals could further improve things. > > Attila Kinali > > [1] Galileo OS SIS ICD Issue 1 Revision 2, > Section 2.3.1.3 "Equivalent Modulation Type" > > [2] "On Generalized Signal Waveforms for Satellite Navigation", > by José Ángel Ávila Rodríguez, 2008 > https://athene-forschung.unibw.de/node?id=86167 > -- > 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 > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.