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RM-512; RM-513; RM-514; RM-515; RM-543
System Module
System
GSM900
GSM1800
GPRS
E-GPRS
Transmitter - general description
The transmitter has separate, parallel paths covering the different bands. The transmitter operates in GMSK
mode only. The power level control circuitry is integrated in the front-end module.
Each path of the transmitter is composed of a baseband lowpass filter for the I/Q signals and a quadrature
direct modulator integrated in PMB3258. At the modulator's output there is a bandpass filter for each band
(so-called H3 filter) and a balun transformer to convert the differential output signal from the modulator into
a single-ended 50 ohm signal. This signal is fed into the input of the PA. The two power amplifiers and the
antenna switch are integrated in a single module with built-in power control loop.
The two control methods used are open-loop Vcc control (RFMD) and feedback control with current sensing.
The reference waveform (TXC) for the control loop comes from the baseband. The output of the PA goes into
a low pass filter located inside the FEM (Front End Module). Finally the transmit signal goes through the band
selection and TX/RX switches to the antenna port.
The FEM is controlled with four digital control signals (TXP, Vc1, Vc2 and Vc3) to meet the TDMA frame timing
requirements.
Transmitter - signal processing
The I/Q signals coming from the baseband section are fed into the modulator and converted up to the carrier
frequency. The I/Q are post filtered by a 1st order passive RC filter (discrete components on PWB) and a 3rd
order active filter (Legendre type) inside PMB3258.
The nominal output level of the modulator is +3.5 dBm in both bands. The modulator's output is an open-
collector type and need an external load and a DC supply feed. The load and the DC supply feed are
implemented as the part of the H3 filter.
The filtered signal is fed into the input of the FEM, which amplifies it to the desired power level and provides
the signal at the antenna port.
There is also a temperature sensor close to the FEM to enable SW temperature compensation for e.g. the
power levels. The sensor is connected to one of the slow ADC channels in the baseband.
Receiver - general description
The receiver is a direct conversion linear receiver. It is a dual-band receiver with receiver paths for either
GSM850/1900 or GSM900/1800 configuration.
Issue 2
Table 14 Frequency bands and TX power class
Frequency band
Tx: 880 – 915 MHz
Rx: 925 – 960 MHz
Tx: 1710 – 1785 MHz
Rx: 1805 – 1880 MHz
Table 15 Multi-slot class
Multislot Class
MSC 10 (4Dn/2Up), sum=5
MSC 6 in DL, max. 3Dn
COMPANY CONFIDENTIAL
Copyright © 2009 Nokia. All rights reserved.
TX power class
4 (33dBm)
1 (30dBm)
Page 6 –19
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