Rx Am Suppression (Gsm) - Nokia RM-42 Service Manual

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Rx AM suppression (GSM)

Context
Rx AM suppression is used to tune the AM suppression capabilities of the GSM receiver.
AM suppression is related to ability of the receiver to operate when there is disturbing AM modulated signal
near the received channel signal frequency.
RFIC has tunable compensation circuit which has an effect on the AM suppression ability.
In the tuning, a continuous useful signal + AM modulated signal 10MHz above current channel is fed to the
antenna. RFIC control word values are iterated until a minimum RSSI signal is found.
Steps
1. Connect module jig's GSM connector to signal generator.
2. From the dropdown menus, set "Operating mode" to Local.
3. From the Product menu, choose "System mode" and then choose WCDMA, GSM or Dual and click Write.
4. From the Tuning menu, choose GSM -> Rx AM Suppression.
5. From the droptown menus, set "Band" to GSM 900 and set "Tuning Mode" to Automatic.
6. Connect signal generator to phone according to the frequency and modulation parameters displayed in
the tuning window:
Frequency
Power level
Modulation
AM modulation depth
Modulation signal
7. Click Start.
8. Click Tune.
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RF Troubleshooting and Manual Tuning Guide
952.46771MHz / 1852.86771MHz / 1970.06771
MHz (depending on the band used)
-25 dBm / -26 dBm / -29 dBm (increase by cable
and jig attenuations)
AM
90%
50 kHz sinewave (or 15 kHz if 50 kHz is not
available)
RM-42
9241872 (Issue 1)