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Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
4. RF Circuit Technical Brief
GD910 service manual
4.2 GSM Part
4.2.1 GSM Receiver
[Figure 4.2.1-1] GSM 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 4.2.1-1] ). The GSM900/DCS1800/ PCS1900 LNAs with balanced inputs are fully
integrated. No interstage filtering is needed. The orthogonal LO signals are generated by a divider-by-four for
GSM900 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 lowpass 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.
Содержание GD910
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