2.2 RX Circuit
At first, the GSM signals received by the antenna will go through the front model
SAW filter to the MT6166. They are amplified, mixed and modulated into the I/Q carried
by the 100KHz wave, done by the band pass filter, amplifier (controlled gain), filter,
amplifier(controlled gain) and mixer. Then the 4 tracks of I/Q signals are putout the
transiver and sent to the MT6166
The FEM is the ASM, a select switch of RX and TX, GSM and DCS. By this way, the
isolation will be well strengthened and signals will be well protected.
2.3 RF Part examine and Repair -TX
2.3.1 Necessary condition
a. Test condition1：voltage=3.8V-4.2V
b. Test condition 2：GSM Band
TX mode CH62 Freq=902.4MHz Power Level：5
c. Test condition3：DCS Band
TX mode CH700 Freq=1747.4MHz Power Level：0
c. Test Instrument：CMU200,Oscillograph, spectrum analyzer
d. Examination of the TX
Make the mainboard into the transmit states by using the special software. In the GSM
band, select the 62
nd
channel, 5
th
power level. In the DCS band, select the 699
th
channel, 0
power level. Then observe whether the current will raise and check the wave by using the
spectrum analyzer or the oscillograph.
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