LG KU730 Service Manual page 29

3. TECHNICAL BRIEF
Figure 3.5.3-1 UMTS PA functional block diagram
The directional coupler provides RF input signal into the duplexer and coupled signal into the HDET at
the same time. this protects interference between the duplexer and the HDET and improves PA
stability, ACPR performance, and harmonic suppression, as well as duplexer isolation, insertion loss
and ripple. Transmitter performance is always improved when a coupler is included and is well worth
the added cost.
3.5.4 Thermistor (R140 : 68K_2012_10%)
This thermistor senses temperature variations around UMTS PA to adjust PA gain deviation for assure
compliance with the applicable transmit power control standards. Negative temperature compensation
thermistor is used in the KU730.
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