Nokia 5140 Manuales De Servicio
NPL-4/5
Company confidential
Troubleshooting Instructions
Nokia Customer Care
Page 48
Copyright © 2004 Nokia Corporation. All rights reserved.
Issue 1 05/04
The VCO frequency is twice the Rx frequency in the GSM1800 band:
f
VCO
= 2 * f
RX
= 2 * 1842.8 MHz =
3685.6 MHz. The VCO frequency shall be measured at
VCO output.
The tuning voltage can be easily measured at the Vc input of the VCO. The voltage shall
be measured at C503.
be measured at C503.
The tuning voltage should be
2.1V
DC
.. 2.6V
DC
at f
VCO
= 3685.6MHz.
The tuning sensitivity of the VCO is typically 250MHz/V. The typical relation of VCO fre-
quency and tuning voltage is shown in the following diagram:
quency and tuning voltage is shown in the following diagram:
Figure 28: Typical Feature Tuning Curve for the Matshushita VCO
If the frequency or the tuning voltage have other values than given above, then go to
chapter
chapter
Reference oscillator 26 MHz (VCTCXO)
The reference oscillator is implemented as Voltage Controlled Temperature Compensated
Crystal Oscillator (VCTCXO) module. The component (G501) is located in the Small Signal
chamber.
Crystal Oscillator (VCTCXO) module. The component (G501) is located in the Small Signal
chamber.
The reference oscillator has two functions:
Temperature: +25°C
3000
3500
4000
4500
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
VCTRL [V]
Frequency [MHz]
2.55V @ 24.4 .. 25.4°C
2.7V @ 24.4 .. 25.4°C
2.85V @ 24.4 .. 25.4°C
High limit
Low limit