RH-18/36/38 Company confidential
Engine module CCS Technical Documentation
Page 28 Nokia Corporation. Issue 1 10/03
Transmitter signal path
The I/Q signal from the BB is routed to the modulators for both 850 and 1900 MHz. The
output of the modulators is either terminated in a SAW filter (Z603) for GSM 850 or a
balun for GSM1900. Both signals are amplified in buffers.
The amplitude limited signal is then amplified in the PA (N700) where the gain control
takes place. The TX signal from the couplers is fed to the RX/TX switch, used to select
which signal to route to the antenna.
Figure 15: Transmitter signal path
PLL
The PLL supplies Local Oscillator (LO) signals for the RX and TX-mixers. In order to be able
to generate LO-frequencies for the required EGSM and PCN channels a regular synthe-
sizer-circuit is used. All blocks for the PLL except for the VCO, reference X-tal and loop
filter is located in the Mjoelner IC.
The reference frequency is generated by a 26MHz Voltage Controlled X-tal Oscillator
(VCXO) which is located in the Mjoelner IC. Only the X-tal is external. 26MHz is supplied
to BB where a divide-by-2 circuit (located in the UPP IC) generates the BB-clock at
13MHz. The reference frequency is supplied to the reference divider (RDIV) where the
frequency is divided by 65. The output of RDIV (400kHz) is used as reference clock for the
Phase Detector (ϕ).
The PLL is a feedback control system controlling the phase and frequency of the LO-sig-
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