Figure 54 RF transmitter module
Simple external component matching at the radio output pins produces adequate drive power and a stable
input match for the FEM input.
The FEM is a combined PA and switch supporting both quad band (GSM850/900/1800/1900) and dual mode
operation (GMSK/EDGE).
In GMSK mode, the FEM is operated in saturated mode using fixed input (0..6 dBm) and variable gain. VRAMP
signal is generated in the BB section and feed to the FEM module for power ramping control.
In EDGE mode the FEM is operated in linear mode with variable input and fixed gain. In this mode the VRAMP
act as bias for the FEM. Depending on Power levels the bias will have different values. This feature is needed
in order to improve the efficiency of the PA section and thereby lowering the current especially at the lower
levels.
The antenna output of the FEM is connected to the RF test switch or Antenna feeding point depending on
conducted or radiated state.
Introduction to Transmitter Functionality
The digital baseband signal (i.e., from the microphone) is converted to an analogue signal, which is then
amplified and transmitted from the antenna. The frequency of this signal can be tuned to match the
bandwidth of the system in use (i.e., GSM900).
The transmit chain consist of the transmitter section of the D2800 Juno’s integrated RF and a quad-band-
dual-mode FEM Module. The transmitter functions are implemented in the D2800 Juno BB ASIC. The
transmitter provides the following capability:(GSM1800/GSM1900).
•
GMSK mode: Power Class 4 for GSM850 and GSM900 bands (up to 33 dBm), Power Class 1 for DCS1800 and
PCS 1900 bands (up to 30 dBm)
•
EDGE/8PSK mode: Power Class E2 (27 dBm LB, 26 dBm HB).
RM-497
System Module
Issue 1 COMPANY CONFIDENTIAL Page 5 – 43
Copyright © 2010 Nokia. All rights reserved.
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