User Guide

PAMS Technical Documentation 3. System Module
NSD-5
Issue 1 05/02 Nokia Corporation Page 47
CDMA AGC
The RIF IC contains a wide dynamic range AGC circuit for CDMA. The AGC provides +42.5
to -42.5dB of gain controlled by the PDM line RX_IF_AGC.
IQ Demodulator
The IQ demodulator mixes the 128.1MHz IF signal down to DC with two mixers, one at
quadrature to the other. The LO is at 256.2MHz and is divided by two in the demodulator.
Synthesizer
The synthesizer module supplies local oscillator signals for up/down conversion, channel
selection, AFC control, and system clock requirements. Devices are manufactured by
Fujitsu and National Semiconductor. The dual synthesizer is LMX2330L; the single syn-
thesizer is MB15C130. The four submodules include:
1st Rx/2nd Tx UHF LO Synthesizer
This submodule contains a UHF VCO, a loop filter, and the RF half a dual synthesizer IC.
The function of this section is Tx/Rx channel selection. The step size is dependent on the
channel spacing of the band to be tuned. In the Rx path, the LO drives the down-con-
verter. In the Tx path, the LO drives the up-converter. Dual-buffered output VCOs are
being used.
1st Tx VHF LO Synthesizer
This submodule contains a VHF VCO, a loop filter, and the IF half of a dual synthesizer.
This synthesizer is only tuned to a single frequency. The LO converts baseband data at
the input of the I/Q modulator to the 1st IF. The lock detect signal is filtered and sent to