Receive; Band Selection - Motorola W208 Manual

W208 Level 3 Circuit Description

1 Receive

1.1 Band selection

The radio frequency signal is received from internal PIFA-type antenna. Received
GSM RF signal enters to PCB through the RF switch JP201. At this moment the T/R switch
SW201 is switched to RX mode to let the signal input to next stage. Then the signal goes
into SAW filter, BF201 and BF202
from single-end to balanced. And the matching circuits between T/R switch and SAW
filter reduce the unwanted RF signal reflection and provide a flat frequency response in the
operation band. Finally the received signal will fed into Locosto Plus
through a balanced MLCC matching network. The following table describes the control
voltages of T/R switch and PA:
W375 EU
Standby
RX EGSM900
RX DCS1800
TX GSM900
TX DCS1800
The RF signal is received by internal antenna or by RF plug, and the signal is passing
through the RF switch JP201 and then fed into T/R switch. The low band (GSM900) RX
received signal is transmitted from
BF201, while the high band (DCS1800) RX received signal from
input to high-band SAW filter BF202. The last stage of RX on PCB is Locosto
(Loocsto-Plus), and the DRP process will make the signal into binary data.
, which reject out-band signal and transfer the signal
SW_LO_TX SW_HI_TX
PIN 5
of T201 of T201
Low
Low
Low
High
High
SW201
Figure 1: Locosto TX/RX Paths Description
Service Engineering & Optimization
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PA_EN
PIN 2
TP201
x Low
Low Low
Low Low
High High
High High
(Pin 11) and input to low-band SAW filter
U101 DRP core
VAPC
BS1
PIN 20
TP202
of U201
Low x
Low Low
Low High
High Low
High High
SW201 (Pin 1) and then
U101