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RF operating modes
The MAX2821 has four primary modes of operation: shutdown, standby, receive active and
transmit active. The modes are controlled with RF_ENA, TX_ENA and RX_ENA signals.
Transmitter
The RF block diagram is shown in the figure below:
RF-conn.
The transmitter section of MAX2821 contains integrated baseband filter, IQ-modulator and a
driver amplifier with a variable output power. Balanced output of MAX2821 is converted to sin-
gle-ended with ceramic balun. The PA RF5117 amplifies the signal to the desired output level.
Decreasing or increasing of the transmit power is by applying the output signal from DAC
(TX_GC) to the driver amplifier VGA. This way the Tx output power level is constant regardless
of process or temperature variations. The accuracy of the detector is ±1 dB. TX_GC setting is
updated to DAC output only at the start of the transmission. The signal goes after the PA to the
Bluetooth selection switch and from there to Tx/Rx switch and the RF band pass filter. The RF
filter attenuates the transmitter wideband noise to a level where it does not interfere GSM re-
54
Table 13: RF operating modes
Mode
/SHDN
Shutdown
0
Stand-by
1
Receive
1
Transmit
1
Figure 23: WLAN RF block diagram.
BT
RF5117
COMPANY CONFIDENTIAL
Copyright © 2004 Nokia. All Rights Reserved.
7 - RF Description and Troubleshooting
Tx
Rx
Note
X
X
0
0
PLL on
0
1
1
0
MAX2821
PLL
RA-2/3
RX_ENA
rx level det.
RX_DET
RX I
RX Q
RX_GC
ATT_SW
22MHz
SERIAL BUS
TX I
TX Q
TX_GC
PA_ENA
TX_DET
RF_ENA
Issue 1 09/04
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Troubleshooting
