User Guide

CCS Technical Documentation System Module
RH-10
Issue 1 09/2002 Nokia Corporation Confidential Page 31
Synthesizer
The following block diagram illustrates all three synthesizers and how they interconnect
in the system.
Figure 3: Synthesizer System Block Diagram
UHF LO Synthesizer
The UHF LO synthesizer generates the first RX LO frequency for the receiver (down-con-
version) and the second TX LO frequency for the transmitter (up-conversion). The synthe-
sizer is a dual-modulus prescaler type and utilizes a phase-frequency detector with a
charge pump that sinks or sources currents, depending upon the phase difference
between the phase detector input signals.
Channel spacing is 30 kHz for the cellular AMPS/CDMA band. An external buffer is pro-
vided for high isolation between Robin and the VCO to reduce VCO pulling due to chang-
ing load.