Dirty distorted transmit signal

  • 18
  • Problem
  • Updated 4 years ago
  • In Progress
After upgrading to v1.5 my carrier (tune) signal is very distorted and when transmitting audio i'm seeing audio on both side-bands on the pan adapter. 
Reverting back to v1.4 solves the issue and no distortion at all.
Flex 6300 
v1.4.16.63  Clean signal
v1.5.0  corrupted signal

FYI I totally uninstalled v1.4 before updating to v1.5
tried several times installing then uninstalling each version with the same results.
I can e-mail screen shots if needed (not seeing an upload function here) 
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George Moranian

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Posted 5 years ago

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Photo of Steve - N5AC

Steve - N5AC, VP Engineering / CTO

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Official Response
We have now located the root cause of the issue that a handful of FLEX-6300 customers are experiencing with the distortion in transmit signals.  After finding a presumed cause, we tested sample software with five customers in the field and all reported that the issue was cured for them.  The change that we made in this test software detected and corrected the issue as it happened, which is not the ultimate correction, but was a conclusive test that we had found the problem.  We expect to have the ultimate correction within the next week which will not test and fix the issue, but will instead correct the source of the issue before it ever materializes.

The root cause is rather technical in nature, but I will provide it for those that are curious.  There are a lot of high-speed serial and parallel connections inside the FLEX-6000 radios.  All of these interfaces require precise timing and clocking to work correctly.  Due to changes made over time (new features such as the WNB), the timing of one of these interfaces, the Ethernet connection between the FPGA and the main processor, had changed inside the FPGA resulting in very infrequent mis-alignment of data.  Once the data was mis-aligned, data alignment would not recover.  For those familiar with FPGAs, the resulting fix is a different kind of constraint, a kind of technical directive to the FPGA tools, placed on the interface that will force the proper timings in the interface. The interface did have constraints on it before, but not sufficient ones to prevent this issue.

Our expectation is that this change will fix this issue on the FLEX-6300 as well as prevent this issue from occurring on any of the FLEX-6000 radios in the future.  We're now working hard to prepare an updated software release to all customers containing this important fix and will let everyone know when it has been completed and tested.  I appreciate the five customers who worked with us to help locate and fix the issue since we were unable to duplicate this in the lab.