GPS TK Ubloks 6t Ni 5644R

[JÞB]

Yes just another of those insane VST questions.  I have a UUT that contains a GPS COTS receiver.  I have used the GPS TK to emulate a constelation of satelites and write the data to file with enough dynamic range to contain GPS information.  The UUTs GPS Module reports "NSAT" (Number of satelites seen} is approximatly the number of satelite signals generated.  Yet there is no location fix!  This is a precision timing GPS Module!  one of its functions is to deny a location fix if no GPS signals pass the quality of signal gate   and the timbases of the orbiting GPS satelites are pretty good. 

So Two questions.

1. If I provide a Rubidium standard to the 5644 will the satelites in orbit simulated by the GPS Similation toolkit stop jittering too much too be rejected by the LEA-T
2. We really only want to prove reciever sensitivity of the GPS module since fix/non fix is a function of received signals and quality of signals (where poor quality signals appear to the receiver as satalites engaged with multiple small black holes)  and receiver sensitivity.  so how would you advise justifying a change to the existing (poor) requirement in laymen's terms?

Again, the simulated satelites are seen and recognized by the receiver they are just not good enough to be used by that device for acuratly determining a position within the limits it needs to produce its timing output so, no position fix despite seeing simulated satelites.

[Sastry]

Are you using VST's streaming reference design VIs ?

I am assuming that you are since I get a hint that you are doing streaming using VST. Please correct me if I am wrong. 

With the uBlox DUT I have, I could see a lock. But then, the one I have is LEA-6H(I think).  

If you have access to a external precise clock, I would suggest to try it out. Another small thought is, if you have 5672 (by chance) you can use its OCXO to provide the reference clock. 

Also, try a cold start on the receiver and see. 

Please do let me know on the questions I asked above. 

Sastry 

[JÞB]

Yes I am using a driver created from the VST streaming sample project to implement a GPS stream from file using the RF out of the VST without an external timebase.

I did rough approximations on the math.

that LEA 6T doesn't seam like it will be able to accept the quality of signal to use any satellites emulated for a fix. It is a timing reference synced to the GPS constellation so it needs to know location within a gnat's ear to generate the impulse within the LEA 6T's specified accuracy. QOS on the simulated satelite signals is my suspected reason that the UUT will not use seen sats for a fix. Can you run the math again and confirm?

[JÞB]

Lets go aheand and bump this thread again. just to get people back in the groove.  (Yup we are revisiting that again) and getting on a Rb standard today.