GPS Simulation Toolkit not working

[JMU_ISAT]

I am familiarizing myself with the NI GPS Simulation Toolkit though am having issues.  I am simply trying to generate a GPS signal and have my off the shelf Garmin GPS receiver lock on and display its LLA.  The Garmin GPS receiver sees the signal and displays which satelites are visible, though it takes a long time to do this and never locks on and dispalys its LLA.  I am using the examples "niGPS Adjust Satelite Power.vi" and also generated a GPS binary file and tried the "niGPS Streaming from File.vi".  I am directly connecting the VSG to the Garmin GPS receiver antenna port and have tried various combinations of DC Block, attenuation, and signal power levels.  I have verified that the Garmin GPS receiver is functioning properly.

What am I doing wrong here??

[Timothy_S]

JMU_ISAT,

I have a few questions to clarify what we're working with here.

• What hardware are you using to generate the GPS Data from? You note that you're using a VSG, but which one and what is the configuration of it in the system?
• It sounds like we're just trying to read back the generated location information on the Garmin Receiver, but how is the GPS Receiver being configured? Is it just going through standard operations? How is it connected to the VSG? Are they directly wired or are we transmitting the GPS data via antenna?
• When you run the examples are you using your own location/data files or have you tried the default examples? The niGPS Streaming from File.vi should have a default Binary file to be used with that. Are we seeing the same behavior using that or the defaults from an example like niGPS Direct Streaming Generation?
• Have you tried or can you connect back the GPS signals being generated to a VSA or other signal analyzer to ensure we're generating proper signals in the first place?

It sounds like the issue could be one of configuration or data type in what is being generated, so let me know what you can about the system and it's configuration so we can narrow that down. I'd also try to default (I believe it is Mt) Binary data files from the niGPS Streaming from File example or the Direct Streaming Generation examples first and confirm the behavior you're seeing. Let me know what you can. Thanks.

[JMU_ISAT]

I am using the PXIe-5673E 6.6 VSG to generate the GPS signal.  The Garmin GPS receiver is directly connected to the RF Output port of the VSG via a conducted connection to its antenna port.  The Garmin receiver is running like it would off the shelf.  I am simply generating the GPS signal and then powering on the Garmin receiver and waiting for it to lock on to the GPS signal and display its latitude and longitude information.

I have used a PXI-5661 VSA to verify the VSG is generating the signal.

I am using the default niGPS examples to generate the GPS signal.  I have tried both the adjust satelite power vi and the stream from file vi.  The default ephemeris and almanac files are being used.

I have also tried using a DC block at the Garmin GPS receiver port and varrying levels of attenuation.

[Timothy_S]

Just to confirm, you're getting the receiver to lock on to the satellite information from the VSG, but you can't get the GPS to actually locate any site information or latitude/longitude values? Do you know which Garmin Receiver in particular it is that you're using? I'll try to see if there are any additional caveats for the setup that you're starting with and let you know what I can get together.