Fault Finding Chart Of The Receiver; Fig 11 Rx Iq Signals - Nokia NPL-4 Series Troubleshooting Instructions

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Correct signal amplitudes approximately
GSM850/900: ~140-150mVpp
GSM1800/1900: ~130-150mVpp
Signal frequency 67.7kHz
RX I/Q, phase difference 90 degrees between signals.
RX I/Q-signals measured from R423 (Q-signal), R421 (I-signal) simultaneously.
Used channel 37, input signal 942.467 MHz, level –60 dBm at antenna port, AGC setting
12.
Phase difference should be 90 degrees between RX I/Q-signals at all bands.

Fault finding chart of the receiver

During fault finding, the calibration procedure is used to find out, whether all bands are
affected (error in common part of the Rx chain) or only one band (error in a Rx part of
the failed band). Take care not to save calibration values to the phone memory,
which are out of limits. Find the error first and repair it.
When a defective phone has been calibrated, a possible error in RX front-end might be
masked. In that case one can get a reasonable RSSI reading, although the front-end
shows excessive losses. If it is not sure that incorrect re-calibration has been made, fol-
lowing steps shall be done:
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Issue 2 05/05
Company confidential
Figure 11: RX IQ Signals
NPL-4/5/
Troubleshooting Instructions
Page 21