Appendix A: RF Troubleshooting
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A-35
3.1.1.3.3 Replace PA (N7502)
3.1.1.4 Are control voltages VC1, VC2 and VC3 coming correctly to the antenna switch (Z7503)?
•
Use “RF Controls” window in Phoenix test software to activate the GSM transmitter and to select
the wanted GSM band. Procedure is explained in section “Transmitter troubleshooting”. GSM RX
activation is described in section “GSM RX chain activation for manual measurements”.
•
Use an oscilloscope and probe to find out if antenna switch control lines are working according to
table shown below. “Hi” means that there is 2.4 – 2.8 V control voltage level in the corresponding
control line. “Lo” means levels 0 – 0.2 V. Remember to trigger the oscilloscope because control
voltages VC1, VC2 and VC3 are pulsed
•
Connect the probe to correct test points to measure VC1, VC2 and VC3 voltages (check test point
locations from section “Test point locations”). Notice: these test points are PWB pads for three
non-assembled capacitors.
3.1.1.4.1 Replace Hinku (N7500)
3.1.1.5 Replace antenna Switch Z7503
3.1.2 Does GSM TX transmit enough RF-power and power levels otherwise ok?
3.1.2.1 Is Vinku ASIC (N7501) transmitting correct RF-power?
•
GSM transmitter has to be active before Vinku’s output level can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
•
Measurements can be done with a spectrum analyser and an RF probe. RBW and VBW = 1 MHz,
Span = 0, sweep time 1 ms. Spectrum analyser centre frequency should be set according the used
TX channel (see section “Frequency mappings”). Notice that GSM transmission has pulsed nature
and power should be measured during TX burst (triggering needed). Another possibility is to use
following settings: RBW = VBW = 1 MHz, Span 200 kHz and sweep time at least 2.5 seconds.
•
EGSM900:
-
Connect the RF probe to Z7504 input. The level should be about the same on both input pins.
Check output level with at least the maximum (5) and the minimum (19) power levels.
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Maximum power level – Output level should be about -15…-25 dBm
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Minimum power level – Output level should be about -45…-55 dBm
