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PAMS Technical Documentation
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For easy error tracing it is important to know the signal path of the EGSM receiver. The components
can be grouped into blocks and drawn as shown below.
SAW
LNA
SAW
RX
PCN
TX
LNA
RX
GSM
TX
Last edit 07:49 15.03.00
HDa12 RF Troubleshooting.doc
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From the antenna-pad the RF signal is lead to the RX/TX switch (Z502).
The RX/TX switch is normally open to the two RX outlets GSM_Rx and DCS_Rx. If no control voltage
is present at VC1 or VC2 the RX/TX switch will work as a diplexer and the EGSM signal is pass to
GSM_Rx and the GSM1800 signal to DCS_Rx.
From GSM_Rx the EGSM signal is feed to the 1
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The EGSM front-end consists mainly of two SAW filters (Z501 and Z500) and one LNA (V501) in-
between and finally one balun (T501). The SAW filters provides out-of-band blocking immunity, the
LNA provides front-end gain and the balun provides a balanced signal for Hagar (N500)
The signal-path is through Z501 (In-band insertion-loss 3,5dB), through the matching circuit (C545,
L507 and C541) and to the EGSM LNA (V501, RFin).
The LNA has about 18dB gain when it is "on" (LNA_G = 2.8V and LNAB_D = 2.8V). If the signal
applied to the antenna-connector is more than –45dBm the AGC will gain-step the LNA (LNA_G = 2.8V
and LNAB_D = 0V) which means the LNA Gain will now have negative gain (loss) of –12 dB.
From the LNA (V501 RF out) the signal is lead through the LNA-output-matching-circuit (C537, L520
and C534), through the 2
T501. From the balun the signal is balanced and is lead to Hagar (N500 IMP_G_RX and INM_G_RX).
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Hagar
INP_P_RX
INM_P_RX
INP_G_RX
INM_G_RX
2
2
2
LNA_P /
LNAB_G
2
2
RF
LNA_G /
Controls
LNAB_D
st
nd
Dual RX SAW Z500 (In-band insertion-loss 3,5dB) to the EGSM balun
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BIQUAD
DtoS
8 / 18 dB
BIQUAD
DtoS
8 / 18 dB
2
Dual RX SAW filter via C556.
NHM-2/5nx,ny/6/9
Troubleshooting
BB_Gain
RXI
DNC2
0-40dB
VREF_RX
BB_Gain
RXQ
DNC2
0-40dB
3DJH
VRF_RX
VREF
RXI
VREF_RX
RXQ
VCP
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