LG U8120, Service Manual

Page: 223 / 271

G. RX AGC Gain Max and RX RSSI Calibration
- Purpose
To prevent wind up in AGC algorithm, this procedure calibrates the absolute power levels at the
antenna connector against RSSI values and the maximum gain setting for AGC. Reference [6]
specifies that the reporting range of the RSSI should be between -100 dBm to -25 dBm. The specified
accuracy requirement is applied to the received power from -94 through -50 dBm. This is the last RX
calibration.
LPBW, LPQ, AGC_CR, AGC_LL and AGC_UL must be calibrated according to above calibrations
respectively and applied to this calibration. Initially, the AGC anti-wind up is turned on using
AGC_GMAX=127. Use the calibrated value after step 2, otherwise the AGC wind up may occur at the
beginning of the RSSI calibration.
- Procedure Proposal
1. Set the ME in RX-mode on channel 10695.
2. Feed a CW carrier at 2140 MHz with a power level of -105 dBm. Get average_Ak (output2), add 6 to
the value and store it in GDFS as AGC_GMAX (GD_RF_RX_CONFIG_ID), rounded off to an
integer. Set the AGC parameter AGC_GMAX to the calibrated value.
3. Clear Ak ‚table 0.
4. Change the CW carrier power level to -95 dBm.
5. Read Ak value (output2) and calculate Average_Ak (Equation 1). Store Pin_Corrected (Equation 2)
at Ak=round(Average_Ak). N in Equation 1 should be as large as possible.
Pin_Corrected = Pin-round(AverAverage_Ak Equation 2
6. Then increase the output level of the signal generator to -80, -60, -40 and -25 dBm and store the
corrected RF input level and Ak to the memory respectively.
7. Use the average Ak values and Pin_Corrected from the two lowest power levels (-95 and -80 dBm)
to extrapolate Ak and Pin_Corrected for -110 dBm according to:
Average_Ak_110 = 2*Average_Ak_95 – Average_Ak_80
Pin_Corrected_110 = Pin_Corrected_95 – Pin_Corrected_80
8. Store Average_Ak_110 and Pin_Corrected_110 according to step 4.
9. Perform the interpolation. AK_BANK_SEL in DB 2100 shall be set to 0.
10. Measure the ME temperature (T) and save for offline calculations.
11. Store the result to GDFS. (GD_RF_RX_AK_TB0_ID). When stored in GDFS, the first position in
the table (Ak=0) should be replaced with the table number (0-23) in bcd format and the second
position (Ak=1) set to 0xffff to flag that the table is calibrated. Position 2 to 5 should be set to zero.
12. Perform the offline calculations and check the requirements.
8. CALIBRATION
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