Rx Am Suppression - Nokia RM-57 Service Manual

RM-57/58
RF Troubleshooting and Manual Tuning Guide

Rx AM suppression

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 added with an 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 the module jig's GSM connector to the signal generator.
2. From the dropdown menus, set "Operating mode" to "Local" and Band to "GSM900".
3. From the Tuning menu, choose "Rx AM Suppression".
4. Check the "Automatic" check box.
5. Connect the signal generator to the phone according to the frequency and modulation parameters displayed
in the tuning window:
Frequency
Power level
Modulation
AM modulation depth
Modulation signal
6. Click Start.
Issue 1 Company Confidential
Copyright ©2005 Nokia. All Rights Reserved.
891.667710MHzMHz / 952.46771MHz /
1852.86771MHz / 1970.06771MHz (depending on
the band used)
-31 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)
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