SBAA555 august   2023 AFE8092

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2RF Droop
    1. 2.1 Reasons Behind RF Droop
    2. 2.2 Digital Correction of RF Droop
    3. 2.3 Overview of RF Droop Correction Measurements
    4. 2.4 Enabling the RF Droop Correction
    5. 2.5 Example for Using the RF Droop Correction
    6. 2.6 Frequency Response Before and After Droop Correction and Limitations
  6. 3Summary
  7. 4References

2.4 Enabling the RF Droop Correction

To enable the RF droop correction following steps are used.

  1. Bring-up the device in the desired system configuration. Once the bring-up is done, check if the jesd link of the device is up and FPGA is able to send the data. (AFE80XX configuration guide gives details about this in JESD configuration section.).
  2. Transmit tones at FNCO, FNCO- ΔF and FNCO+ ΔF , measure the amplitudes at either Meas1 or Meas2 tap-off point as shown in Figure 2-1.
  3. ΔF must always be less than or equal to 0.4 × ( Transmit data interface rate). The function will try to flatten the frequency response in band FNCO ±∆F.
  4. The input of tone amplitude to the function is given in terms of LHS and RHS (both in logarithmic scale). LHS and RHS are amplitudes of tones with respect to the tone at Fc. Ie. LHS = Amplitude(dBm) of tone at Fc - Amplitude(dBm) of tone at Fc - ΔF.
  5. After M1 and M2 are determined, the correction can be applied using CAFÉ function configureTxRfDroop.

See Table 2-1 to understand how to input the measurements and enable the RF droop correction block through a micro. Once the micro is enabled the input values can be used across bring-ups.

Table 2-1 Functions and Variables to Enable RF Droop Correction
Functions and Variables Remark
configureTxRfDroop(afeInst,txChSel, bandNo, ncoNo, deltaFreq, amp1, amp2) CAFE function to enable the RF droop correction[NP1]
afeInst AFE Instance
txChSel

Select the TX Channel

0 for TXA

1 for TXB

2 for TXC

3 for TXD

4 for TXE

5 for TXF

6 for TXG

7 for TXH
bandNo Select the TX Band. 0-Band0, 1-Band1
ncoNo

Select the NCO

0 for nco1

1 for nco2

2 for nco3

3 for nco4
deltaFreq ∆F ×216/ Fdata , where ±∆F + FNCO is the frequency where amp1 and amp2 measured and Fdata is the transmit data interface rate
amp1 int(10**(RHS/20)*2**15)
amp2 int(10**(LHS/20)*2**15)