AFE7769DEVM: Set up of LMK

Hi Mr. Park,

A few things to point out...

1. From the Log window, it looks like only Device Bringup was executed as it ends with "AFE configuration Complete".
   1. Try navigating to the TX-Test tab in Latte, and in the bottom-right corner, clicking "Relink JESD" to repair the FPGA Rx Sync, or AFE.adcDacSync(1).
   2. Also, try navigating to RXFB-Test, and clicking "Select RX/FB Channel" to fix the error.
2. It doesn't look like "Load Custom Data to FPGA" was executed in the above screenshot; however, can you please share the waveform you are trying to use for the use case?
3. Can you please share what the 7 warnings were? I wonder if this has to do with the configuration (.xlsx) file itself...

Please review the above. Thank you!

Best regards,

Simran

Hi Mr. Park,

A few comments:

• I tested the Excel file on my end and received no errors. Can you please try a few things:
  • Close Latte.
  • Power off the AFE7769DEVM, then the TSW14J58EVM.
  • Disconnect the two EVMs from each other and reconnect, making sure they softly snap together at the FMC connection.
  • Re-power on the EVMs, ensuring both are at 5.5V.
  • Re-open Latte.
  • Try re-doing a Device Bringup with the same Excel file you are using.
• One other thing I noticed: you are trying to load a 20MHz signal, however in your Excel file it says you are working with a 100MHz bandwidth signal. Does your test case call for 20MHz or 100MHz? If it is 20MHz, change the four green cells from 12 (indicator of 100MHz) to 3 (indicator of 20MHz) for item 43 in the DPD-CFR tab of your Excel file.

Thank you!

Best regards,

Simran

Hi Mr. Park,

Thank you for sharing your results. There is definitely room for improvement, and I have a few recommendations:

• Regarding the configuration (.xlsx) file:
  • Your use case involves a bandwidth of only 20MHz, but your interface rate is currently set to 245.76MSPS, which is very high. This is one critical reason that you are not seeing the performance you would like to. If you use the Config-Gen tool in Latte and enter 20MHz for the bandwidth, you will receive a recommended interface rate of 61.44MSPS, and a DPD rate of 122.88MSPS or 184.32MSPS is sufficient.
  • Also, the bandwidth in your configuration file was set to 100MHz, which can be changed in row 62 of the DPD-CFR section, for future reference.
    • 
  • Overall, I recommend you start with a fresh configuration (.xlsx) file; please see attached for an example, which you may need to modify when it comes to CFR gain and peak limit, depending on your input RMS and target PAR.
    • Excel file: Nextivity_Sample.xlsx
    • Corresponding signal file (new one generated for the new interface rate of 61.44MSPS): Nextivity_Signal_TM3p1a_61p44Msps.txt
    • Please try out this new configuration file & signal file (both shared above), but I still recommend to re-generate the .xlsx using the Config-Gen tool and modifying the below two parameters, input RMS and PAR, based on your preference / setup.
    • 
• Can you please share a block diagram of your setup, including the specific power amplifier (PA) in use and gain lineup of the driver(s) / pre-driver(s) / PA / attenuation? This would help immensely.
• Also, which post-bringup script are you currently using for tuning and triggering DPD?
• For your reference: input RMS = PAR + CFR gain + CFR threshold value
  • Example: 17.5dBFS (input RMS, which will be a negative number when you input into Config-Gen) = 8dB (PAR) + 9.3dB (CFR gain) + 0.2dB (CFR threshold value)

Please provide feedback on the above, and try out the new files as well. 

Thank you!

BR,

Simran

Hi Mr. Park,

Great questions, absolutely!

Jeong Park said:

Could you explain about "CFR gain" & "CFR threshold value" little more detail?

To give a bit more context, CFR, or Crest Factor Reduction, is a process that helps to reduce the peak-to-average ratio (PAR) of a transmitted signal in a given RF lineup/system. At a larger scale, CFR helps improve a power amplifier's power efficiency and minimizes the (negative) impact seen on ACLR results!

The CFR gain is the amount of gain needed to help reduce the PAR (which it does by clipping the signal at higher-than-normal peaks of amplitude) without clipping the overall signal you see on the spectrum analyzer. 

The CFR threshold value of 0.2dBFS is simply recommended when configuring the AFE to present great ACLR purely at the AFE TX output.

I recommend reviewing the AFE77xxD Configuration Guide (section 7) on CFR, for more information. I hope the above helped! Please let me know if you have additional questions.

BR,

Simran

Hi Jeong Park

Redirecting our conversation here:

Hi Mr. Park,

 1. Regarding the long runtime, that may be related to the system requirements before downloading Latte. I am checking the specifics on this with my team and will get back to you on it.

 2. When it comes to the expected carrier power level, this will depend on the power level of the chosen PA in your system. -15dBFS input RMS is fine, but it is important to settle on a desired PAR, which will then allow you to modify your CFR gain accordingly.

Some calculations, for reference:

-15dBFS = 0dB -> 0dBFS = +15dB

+15dB = xdB PAR + ydB CFR gain + 0.2dB CFR threshold (this last number is fixed)

If you choose a target PAR of 8dB, then the desired CFR gain will be 6.8dB.

8dB PAR + 6.8dB CFR gain + 0.2dB CFR threshold = 15dB = 0dBFS RMS

It is recommended to keep the input RMS the same, but depending on the rated power output of the PA, the PAR can be changed based on what the PA can handle.

3. Regarding the TX controls, the TX TDD is mean for both TDD and FDD. It is meant to simply act as a channel enabler, which can either be done on that page or the RXFB-Test page in Latte.

Please let me know if you have additional questions as you work through your setup. Thank you!

Hi Mr. Park,

Please see below for the newly-generated waveform. Please verify that your configuration file is aligned from a carrier profile perspective (CFR gain/peak limit, carrier profile) in the DPD-CFR tab of the .xlsx file. Thank you!

NR_1C_100MHz_30khz_FDD_256QAM_122.88.txt

BR,

Simran

Hi Mr. Park,

Please see below for system requirements/recommendations, per our validation team:

"8GB+ RAM is needed though we test it typically with 16GB RAM. We know that it works for Windows 7+"

Thank you!

BR,

Simran

Hi Mr. Park,

That message is normal, but it is recommended to upgrade your RAM to get to the optimal Device Bringup time.

Before I provide the configuration Excel, can you please specify the target PAR you require for testing? Also, if you are going to test DPD performance for the actual setup instead of just the TX output, can you please provide details around your RF lineup (i.e., power amplifier, attenuators etc.) if you are choosing to do so? Thank you!

BR,

Simran

Hi Mr. Park,

Thank you for your questions.

Jeong Park said:

Could you explain about the meaning of target PAR?

Target PAR is simply the PAR you would like to have for your setup (i.e., 8dB is a typical value). If your input RMS is -15dBFS (or +15dB/m), the chosen PAR will help determine the CFR value to help clip the waveform signal at an appropriate place. It also helps ensure that the ACLR at the end of tuning DPD is most optimal. 

Jeong Park said:

LTE TM11 signal PAR is about 9.5dB and 5GNR could be similar.

Have you created a new signal to ensure the above is accounted for? Also, if you choose a PAR of 9.5dB, the CFR gain will be 5.3dB. This can be updated with the following C APIs:

1. CAFE.updateCfrOpGain()
2. CAFE.cfrConfig()

I also recommend you review my previous responses around CFR configuration and working with Latte - they should help as well.

Jeong Park said:

my DPD test set up.

Are you also using an FPGA in your system, or is this a loopback/repeater case? Just for clarity.

Thank you!

BR,

Simran

Hi Mr. Park,

Thank you for clarifying. Please see below for the configuration file as requested. In addition, should you have more questions or need of assistance to help with DPD tuning and triggering, please don't hesitate to let the team know. We would be happy to walk you through the recommended steps. Thank you!

Nextivity_3p5G_100M_8dB_PAR.xlsx

BR,

Simran