Receiver Part - LG GD510 Service Manual

GD510 Operational Description
LBAND_PAM_IN
HBAND_PAM_IN

3.17. Receiver part

The constant gain direct conversion receiver contains all active circuits for a complete receiver chain for
GSM/GPRS/EDGE (see Figure 39). The GSM850/900/DCS1800/ PCS1900 LNAs with balanced inputs
are fully integrated. No inter-stage filtering is needed. The orthogonal LO signals are generated by a
divider-by-four for GSM850/900 band and a divider-by-two for the DCS1800/PCS1900 band. Down
conversion to baseband domain is performed by low/high band quadrature direct down conversion
mixers. The baseband chain contains a LNB (low noise buffer), channel filter, output buffer and
DC-offset compensation. The 3rd order low pass filter is fully integrated and provides sufficient
suppression of blocking signals as well as adjacent channel interferers and avoids anti-aliasing through
the baseband ADC. The receive path is fully differential to suppress on-chip interferences. Several gain
steps are implemented to cope with the dynamic range of the input signals. Depending on the baseband
ADC dynamic range, single- or multiple gain step switching schemes are applicable. Furthermore an
automatic DC-offset compensation can be used (depending on the gain setting) to reduce the DC-offset
at baseband-output. A programmable gain correction can be applied to correct for front end- and
receiver gain tolerances.
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LG Electronics
Only for training and service purposes
C618 C634
3p 3p
C624 C605
100n 4.7n
L603
18n
FE2
33
VBIAS
34
VDDTX1V5
35
TX1
36
TX2
37
VDDTX2V8
R605 10
38
VDDMIX2V8
39
C622 C604
GND3
40
100n 100n
GND4
41
VRF_1V5 VRF_2V85
R601 10
C607 C648
220n 100n
Figure 25 RF transceiver PMB6272 SMARTi-PM schematic
Figure 26 Receiver part block diagram
C612 C611
C617 C616
C629 C609
3.9p 3.9p 2.2p 2.2p 2.4p 2.4p
L606 L601
L602
15n 5.1n
4.7n
VRF_1V5
C628
100n
VDDRX2V8
C627 47n
20
VDDRX1V5
U602
R603 820
19
VCO_RC
PMB6272
18
VDDVCO2V8
17
EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
X601 TSX-3225
4
3
GND2 HOT2
1 2
HOT1 GND1
26MHz
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3. Technical brief
Revision A
VRF_2V85 VRF_2V85
C650 C649 C623
100n 100n 100n
RF_EN
C619 1n
26MHZ_MCLK
BT_CLK
RF_CLK
RF_DA
QX
Q
IX
I
LGE Internal Use Only
LGE Property