LG U8138 Service Manual page 217

8. CALIBRATION
2. Measure the relative power between the 1950 MHz carrier and 1949.04 MHz at the antenna output.
Jump to step 6 if the requirement is met.
3. Step RECDCI from 0 to 3. Set TXON = 0 and wait 1 ms before changing RECDCI from 3 to 5. Set
TXON = 1, wait 1 ms and continue with stepping from 5 to 7.
4. Set RECDCI to the value that minimizes the 1950 MHz carrier. If this involves a change of sign the
TXON switching and delay sequence in point 3 must beexecuted. Jump to 6 if the requirement is
met.
5. Find and set RECDCQ to the value that minimizes the 1950 MHz carrier. This can be made by
stepping RECDCQ from 0 to 7 with the TXON switching and delay sequence in step 3.
6. If the requirements are not met, repeat steps 3, 4 and, if necessary, 5 once with the new RECDCI
and RECDCQ (found in 4 and 5) as initial values. Otherwise proceed with step 6.
7. Save the finaldBcvalue (for statistics), RECDCI and RECDCQ. Store the calibrated parameters in
GD_RF_TX_CONFIG_ID.
C. TX LPF Bandwidth Calibration
- Purpose
The low pass filters within the Ericsson DB 2100 (hereafter referred to as DB 2100) are designed to
prevent spurious emissions output from the TX IQ-D/A (Digital-Analog) converters Πwithout adversely
affecting the signal or causing a deterioration of the modulation accuracy.
The objective of this calibration is to determine the values forLPQ and LPBW that offer the best trade
off against the system-related requirements. These settings determine the cut-off frequency and
should always have the same value.
- Procedure Proposal
1. Use typical TX settings. Generate a 960 kHz square-wave at baseband without phase shift between
I and Q. The amplitude should be about 50% of fullscale.
2. Measure the relative power between 1952.88 MHz (fc+ 3*960 kHz) and 1949.04 MHz (fc Π960
kHz) in dB at the antenna output. Find the setting of LPQ =LPBW between 3 and 15 that obtains the
dBcvalue closest to the typical value. Start with the best value from earlier calibrated units.
Spectrum analyzer settings (example):
RBW = 300 kHz, Span = 8 MHz.
3. Set LPQ=LPBW to the found value in 2. Also save thedBcand the decided LPQ = LPBW value for
statistics. Store the calibrated parameters in GD_RF_TX_CONFIG_ID.
D. TX Maximum Output Power Calibration
- Purpose
These procedures verify that the ME can meet the requirements onmaximum output power. The
calibration aims to establishWPABias, VGA and QVGA settings that fulfill ACLR requirements for
maximum output power, both in high, medium, and low gain mode.
These calibrations are designed to conform to the ME maximum output power and ACLR requirements
specified in 3GPP Spec TS34.121.
- Procedure Proposal
1. Use typical TX settings, mid channel.
2. Set gain to the best value based upon previous calibrated units.
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