Nokia RM-761 Service Manual page 149

RM-761; RM-799; RM-800
System Module
receiver sensitivity performance. In the X-GOLD213 IC the RX input signals are amplified by a Low Noise
Amplifier (LNA) and down converted to Low IF and again amplified before demodulated and signal processed.
A detailed description of the RX path in the RF part of the Quantum engine can be found in Appendix A.
X-TAL/DCXO
The X-Tal and DCXO is the 26MHz Reference Clock used by the entire platform as an accurate clock. The clock
frequency can be controlled and adjusted by the embedded capacitor bank of the DCXO (Integrated in the X-
GOLD213). During synchronization to base-station or base-station emulator (Normal mode/signalling mode)
the accuracy of the clock should be max 0.1ppm, however in normal mode the accuracy can be ±60ppm
depending on the setting of the AFC DAC value.
Antenna detection
The antenna detection circuit is applied to determine if the RF test cable is mechanically mounted or not.
The antenna circuitry consist by a current sourced ADC from the X-Gold, that's are sourcing the resistors R7454
and R7460 to the X7450 RF connector then finally goes to FEM output pin (depend on RF test cable is assembled
or not). The FEM output pin has an 0 impedance @ DC to GND if mounted correctly. The ADC (embedded in
the X-GOLD213) measured the voltage and use this to evaluate if the antenna is mounted or not. The detailed
circuit is shown in the figure below.
Figure 71 Antenna detection circuit
FEM ID/PA ID
The FEM ID (PA ID) is used for FEM identification depending on the different release, see Table 2 . For more
info regarding the FEM ID see Appendix E.
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