Simultaneous GPS & GLONASS signal generation?

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jrh_engineer
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Joined: Mon Dec 14, 2015 7:08 pm

Simultaneous GPS & GLONASS signal generation?

Post by jrh_engineer » Wed Dec 16, 2015 4:21 pm

Hi,
I'm a total newbie when it comes to SDR's.
I need to generate a C/A signal for one satellite vehicle in the GPS L1 band and the equivalent for a satellite vehicle (SV) in the GLONASS L1 band. This is for over-the air testing of a GNSS receiver front-end in production. All I want to do is get CNo data for each SV and compare this to a reference receiver's data. I have a whole bunch of (possibly ignorant) questions:
  • Is it possible to generate these signals simultaneously on a single BladeRF?
  • Alternatively, should I expect to need 2x BladeRF boards?
  • How do I generate whatever input is required to the hardware? I found GNSS-SDRLIB and gps-sdr-sim but I'm not sure how I'd drive the former and I think the latter only offers GPS (no GLONASS).
  • Can the hardware be pre-loaded and run autonomously, or will it need tehering to a PC?
  • Is this exercise straightforward or would I have to budget for a lot of "mucking around" time?
My alternative appears to be speding upwards of $10k on a commercial satellite simulator. I can get a whole lot of BladeRF boards for the same dosh.
Thanks in advance for any help and advice,
John

bpadalino
Posts: 303
Joined: Mon Mar 04, 2013 4:53 pm

Re: Simultaneous GPS & GLONASS signal generation?

Post by bpadalino » Wed Dec 16, 2015 7:43 pm

Understandable on the noobishness. Please forgive my noobishness when it comes to GPS, so feel free to reply to this thread to get more clarification.

Googling shows me that the center frequency for GPS is 1575.42MHz. GLONASS L1 seems to be centered around 1602MHz. Both of these frequencies are within the transmission range of a bladeRF, so you're good there. The distance between those signals is around 28MHz, so you'd be stretching the bandwidth of a single transmitter. I'd recommend going with a 2 transmitter approach in this case. For a bladeRF, you can synchronize their baseband clocks to each other, so the two devices can be synchronized.

Now, generation of the GPS and GLONASS signals which need to be transmitted get very tricky. I have seen some code out there for GPS signal simulation, but not necessarily GLONASS. One of our customers currently has a demo which transmits GPS to a bladeRF through MATLAB. I will inquire if they can also support GLONASS.

Cutting to the chase, and the meat of your question "is this exercise straightforward" then I think you can conclude that no - it is not straightforward at all. Can it be done with the bladeRF? Absolutely. Unfortunately, it's just a little too much "mucking around" right now.

I'll ask our customer about GPS and GLONASS signal generation and post to this thread again. Maybe things are easier than I imagine.

bpadalino
Posts: 303
Joined: Mon Mar 04, 2013 4:53 pm

Re: Simultaneous GPS & GLONASS signal generation?

Post by bpadalino » Thu Dec 17, 2015 4:57 pm

I was just shown a blog post from Skydel Solutions which may make things a little more tolerable for you!

I would recommend you contact them and see if they can help you out?

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