Asus P552W, Manual

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3.4. General GSM debug
3.4.1 GSM path and test points
How RF signal is transmitted and received between components on
GM2 PCB is explained in this section. It is important to realize RF
transmission path (Tx) and receiving path (Rx) before starting out to
repair defective PCB, because engineers need to choose proper test
points which allow us to distinguish where the problem is.
The following paragraphs describe Tx/Rx path in GSM and
WCDMA bands. The related test points are listed in the following
figures.
●
GSM Tx path
GSM transceiver, B6PLD (U1802), receives modulation symbols
coming from baseband via Pin F9, and then B6PLD Pin J7 and Pin J8
emit the low band RF signal (GSM900) and high band RF signals
(DCS1800 or PCS1900) separately. The Tx path which RF signal is
transmitted depends on band selection of FEM (U1804).
In the low band, output signal from B6PLD Pin J7 passes through
C1844, and RPF09036B (U1803) Pin7, power amplifier, sequentially.
Pin25 of front-end module (U1804), also abbreviated to FEM, gets
the amplified signal from RPF09036B Pin13. FEM Pin19 transmits
RF signal to RF connector (CON1801) and the signal is radiated via
the antenna.
In the high band, output signal from B6PLD Pin J8 passes through
C1842, and PA RPF09036B (U1803) Pin1, sequentially. Pin22 of
FEM (U1804) gets the amplified signal from RPF09036B (U1803)
Pin19. FEM (U1804) Pin19 transmits RF signal to connector
(CON1801) and the signal is radiated via the antenna.
●
GSM Rx path
RF signals, receiving from base stations via GM2 antenna, pass
through RF connector (CON1801) and FEM Pin19 (U1804)
sequentially. There are three pairs of FEM output pins, including Pin3,
Pin4, Pin5, Pin6, Pin7, and Pin8. The output path which RF signal is
transmitted depends on band selection of FEM (U1804).