LG U8110 Service Manual page 211

8. CALIBRATION
Acquire the following VCXO (13 MHz)frequencies:
fmin =13 MHz VCXO-frequency @DAC3=1
fmid =13 MHz VCXO-frequency @DAC3=1024
fmax =13 MHz VCXO-frequency @DAC3=2047
Note that it is necessary to translate the measured RF-frequency (EGSM,DCS,or W- CDMA)to the 13
MHz VCXO-frequency.
3. Acquire the ME temperature,TCal,from the temperature sensor in ME.
4. Store fmin,fmid,fmax and TCal for calculation.
5. Calculate the DAC-value,VCXOCONTCal,that gives zero frequency error at the mid channel, using
piecewise linear interpolation,and store the value in the memory
(GD_RF_SYNT_CONFIG_ID and GD_VCXO)
6. Calculate
K_LO =(fmid –fmin)/1023
K_HI =(fmax –fmid)/1023
Each value is then multiplied by 100 and rounded to nearest integer, with the results stored in the
memory (GD_RF_SYNT_CONFIG_ID).
AFC_DAC_STEP_LO =ROUND(100*K_LO)
AFC_DAC_STEP_HI =ROUND(100*K_HI)
where ROUND(x)=x rounded to the nearest integer.
F. TX Power Calibration
- Pur pose
These procedures describe how to tune the different power levels of the power amplifier to output
powers corresponding to values in GSM 05.05,and explain how to calculate intermediate power levels
that will ensure a good power versus time performance.
- Procedure Proposal
1. Reset the DIRMOD-block, and select a‚ mid channel using the trimmed value on the capacity array
for VCO tuning and a default IPHD value as phase detector current. Turn on dummy burst
modulation.
2. Use the Multi-burst method to characterize the relation between output power and the DAC-
value.Then store the DAC values that give the closest approximations to the power targets defined
in Table 8-3.
3. To avoid yield problems with the power template and switching transients spectrum a margin to the
compression point of the PA should be observed.However,the output power must be kept within the
tolerances specified in Table 8-3.
4. Store DAC values in memory (GD_FullPower_Band).
5. Initiate the intermediate value calculation,which calculatesand st or e t he val ues in memory
(GD_IntermediatePower_Up/Down_1.7_Band).
6. The difference between the transmitter power at two adjacent power control levels, measured at the
same frequency,shall not be less than 0.5 dB and not more than 3.5 dB.
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