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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.

LG GD910 Service Manual

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