LG KS660 - Receiver Part

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Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
3.19. Receiver part
3.19.1. Receiver part : RF block 1 (SG3)
< Fig 31. PMB6272 Receiver part block diagram >
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.
LNA
ANT
FEM
BBF1
GSM/EGSM
DCS/PCS
IQ MIX
VCO
PLL
DIV
by 2/4
BBF23
LNB
OutBu
12bit
ADC
OFC
SMARTiPM_Rx.vsd