V1.00 Page 21 of 49 ICM MP CCQ GRM
S55/S57 Company Confidential © Copyright Siemens AG 12/02
4.5.2 Transmitter: Power Amplifier
The output signals (PCN_PA_IN , and GSM_PA_IN) from the TX-VCO are led to the
power amplifier (Z900) passing a matching circuit. The PA is a “two in one” PA (one
for EGSM 900 and one for GSM1800 and GSM 1900) and is connected directly to
BATT+. The band selection switching is done via GSM_ON from the Bright IC. After
amplification, a part of the output signals (TX_PCN_OUT and TX_GSM_OUT) is
decoupled via a directional coupler. The other part runs through the antenna switch
(Z880) inside the FEM and the antenna connector (X870) to the antenna. The
decoupled part is equalised by the detector diode (V920) and used from the RF-Power
Regulator IC (D920) to get a PA control voltage, by comparing this voltage with the
PA_RAMP signal provided from the EGOLD+ (
analogue interface J2). The (N920) is
activated through the signal TXON1. TXONPA enables with a “high” signal the output
“a” (pin 4).
The required voltage BATT+ is provided by the battery.
The required voltage VCC2_8 is provided by the ASIC D361.
Blockdiagram of LML240 (PA control IC)
Vd
Vd
Vs
Vd
Vd
Vs
Vd
Vs
Comp
Comp
Out
Out
VsVdBSPA
ON
Gn
TC
Ra
V
Vf
Vho
1 2 3 4 5
10 9 8 7 6
Top
view
to Ant.
connector
from TX-
VCO
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