LG U8210, Service Manual, Page: 181 / 231

3. Store the NV item such that: NV_CDMA_TX_LIM_VS_FREQ[i] = 12*(PowerRef - Power[i])
Note that the first index will correspond to the lowest frequency.
E. RX Linearity Calibration
- Purpose
This item contains the DVGA gain value that makes the RSSI of the DVGA equal to the corresponding
power levels at the antenna port, at ambient temperature, and reference frequency. This value is
represented by a 10-bit signed two’s complement number in 1/12 dB units. Once calibrated, our DVGA
gain value will have an ideal mapping of min RSSI to -512 and max RSSI to 511 (see Figure 7-3).
- Procedure Proposal
1. Set phone in WCDMA mode.
2. Set phone to a reference channel (a reference channel usually is in the middle of the band).
3. Set signal generator frequency to a reference channel plus an offset of 685 kHz.
4. Set to highest LNA gain state.
5. Set LNA offset 1,2 and 3 to zero.
6. Set input power to recommended value of -80 dBm, let’s call this value ‘rxInput’
7. Set VGA gain offset to 0.
8. Read RSSI.
9. vgaGainOffset = { RSSI - [-512 - (RxLinMinPwr - rxInput) * (1024/dynamicRange) ] }
10. Set VGA gain offset to vgaGainOffset
11. Read RSSI again and we should see a value of approximately -200.
NV_WCDMA_VGA_GAIN_OFFSET = vgaGainOffset
NOTE Assuming a dynamic range of 85.3 dB, RxLinMinPwr = -106 dBm, we have -200 = -512 - -(-106 -
(-80) ) * (1024/85.3).
7. CALIBRATION
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Figure 7-3. DVGA gain value