Nokia 2270, 2272, 2275, 2285 Service Manual
CCS Technical Documentation
System Module
RH-3
Issue 1 06/2003
Nokia Corporation Confidential
Page 27
1st TX VHF LO Synthesizer (Jedi)
The TX VHF Synthesizer is integrated within the Jedi RFIC and generates the LO signals
for the IQ-modulator in Jedi. The synthesizer has an internal VCO with an external reso-
nator. The VCO operates at two times the CELL and PCS IF frequencies. A band-switch
signal, VCO_Band, is used to shift the center frequency of the external resonator.
for the IQ-modulator in Jedi. The synthesizer has an internal VCO with an external reso-
nator. The VCO operates at two times the CELL and PCS 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 Jedi.
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 Jedi.
The TX VHF Synthesizer generates 357.2 MHz for Cell Band and 457.2 MHz for PCS band.
The TX VHF Synthesizer comparison frequency for Cell Band is 30 kHz and PCS band is
50 kHz.
50 kHz.
2nd RX VHF LO Synthesizer (Yoda)
The RX VHF Synthesizer is integrated within the Yoda RFIC and generates the LO signals
for the IQ demodulator in Yoda. The synthesizer has an internal VCO with an external
resonator. The VCO operates at two times the common 183.6 MHz RX IF frequency. A
band-switch signal, Band_Sel, is used to select the band of operation for the UHF VCO.
for the IQ demodulator in Yoda. The synthesizer has an internal VCO with an external
resonator. The VCO operates at two times the common 183.6 MHz RX IF frequency. 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 Yoda.
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 Yoda.
The RX VHF Synthesizer generates 367.2 MHz for both Cell Band and the PCS Band.
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.
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 and PCS bands.
done in CDMA mode. This will enable the unit to track out aging effects and give the
required center frequency accuracy in cellular and PCS bands.
The most practical way of clock distribution is driving all three chips (UHF PLL, Yoda, and
Jedi) directly from the VCTCXO. An internal buffer is used to drive the UPP in order to iso-
late 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 clock distribution will not cause any clock signal integrity problems, even for rela-
tively long traces (what might occur in case of a digital square waveform with fast tran-
Jedi) directly from the VCTCXO. An internal buffer is used to drive the UPP in order to iso-
late 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 clock distribution will not cause any clock signal integrity problems, even for rela-
tively long traces (what might occur in case of a digital square waveform with fast tran-