User Guide

RH-10
System Module CCS Technical Documentation
Page 32 Nokia Corporation Confidential Issue 1 09/2002
1st TX VHF LO Synthesizer (Robin)
The TX VHF Synthesizer is integrated within the Robin RFIC and generates the LO signals
for the IQ-modulator in Robin. The synthesizer has an internal VCO with an external res-
onator. The VCO operates at two times the CELL IF frequencies. A band-switch signal,
VCO_Band, is used to shift the center frequency of the external resonator.
The synthesizer is a dual-modulus prescaler type, and utilizes a phase detector with a
charge pump that sinks or sources currents, depending on the phase difference between
the detector input signals. The width of the pulses depends on the phase difference
between the signals at input of the phase detector. The main divider, auxiliary divider,
and reference divider are programmable through the serial interface to Robin.
The TX VHF Synthesizer generates 346.2 MHz for Cell Band.
The TX VHF Synthesizer comparison frequency for Cell Band is 30 kHz.
2nd RX VHF LO Synthesizer (Batman)
The RX VHF Synthesizer is integrated within the Batman RFIC and generates the LO sig-
nals for the IQ demodulator in Batman. The synthesizer has an internal VCO with an
external resonator. The VCO operates at two times the common 128.1MHz RX IF fre-
quency. A band-switch signal, Band_Sel, is used to select the band of operation for the
UHF VCO.
The synthesizer is a dual-modulus prescaler type, and utilizes a phase detector with a
charge pump that signals or sources currents, depending upon the phase difference
between the detector input signals. The width of the pulses depends on the phase differ-
ence between the signals at input of the phase detector. The main divider, auxiliary
divider, and reference divider are programmable through the serial interface to Batman.
The RX VHF Synthesizer generates 256.2 MHz for the Cell Band.
The RX VHF Synthesizer comparison frequency for the Cell Band is 160 kHz.
VCTCXO - System Reference Oscillator
The VCTCXO provides the frequency reference for all the synthesizers. It is a voltage-con-
trolled, temperature-compensated, 19.2MHz crystal oscillator that can be pulled over a
small range of its output frequency. This allows for an AFC function to be implemented
for any frequency accuracy requirements. This is done by DSP processing of received I/Q
signals.
Closed loop AFC operation allows very close frequency tracking of the base station to be
done in CDMA mode. This will enable the unit to track out aging effects and give the
required center frequency accuracy in cellular bands.
The most practical way of clock distribution is driving all three chips (UHF PLL, Batman,
and Robin) directly from the VCTCXO. A buffer is used to drive the UPP in order to isolate
the UPP’s digital noise from the VCTCXO, which prevents contamination of the 19.2 MHz
reference onto the PLL chips of the system. Since the VCTCXO output is a sinewave, such