Fault Finding Chart For Receiver - Nokia RH-6 Series Rf Description & Troubleshooting

RH-6
7 - RF Description & Troubleshooting
The SAW filters have maximum insertion losses of:
• 3.5dB@EGSM900
• 4.0dB@GSM1800
• 4.0dB@GSM1900
RX paths of Mjoelner RF ASIC
The balanced RX signal is amplified by the integrated LNA and the subsequent Pre-Gain
stage. After amplification the RX signal is down-converted with a LO signal coming from
the local oscillator.
The RX paths of Mjoelner RF ASIC consist of following building blocks:
• Separate LNAs for each of the three bands: EGSM900, GSM1800 and GSM1900.
• Two PREGAIN amplifiers, one for EGSM900 and one common for GSM1800 and
GSM1900.
• Two passive I/Q mixers (MIX), one for EGSM900 and one common for GSM1800
and GSM1900.
The resulting BB signal is further amplified in the BB chain. For that no external circuitry
is required:
• Baseband amplifiers (BBAMP1). These amplifiers implement the initial channel
filtering.
• Low pass filters (LPF1).
• DC compensation / AGC amplifiers (DCN1). These implement gain steps from 0dB
to 24dB in 6dB steps.
• Attenuators (AGC). These implement gain steps from -48dB to 0dB in 6dB steps,
yielding a total gain range of 72dB together with DCN1.
• Bi-quad filters (LPF2).
• DC compensation amplifiers (DCN2).
The differential baseband outputs are internally DC coupled and can be connected
directly to the ADC inputs of the RF converter chip. The common mode level is set equal
to the VBEXT reference voltage.

Fault finding chart for receiver

The phone layout offers dedicated test points for the analogue differential RX I and Q
signals (RXIINP, RXIINN, RXQINP, RXQINN) from Mjoelner RF ASIC to UEM. The BB part is
used to measure those signals by means of RSSI reading. It is assumed that correct cali-
bration of RSSI reading has been carried out in production.
RSSIreading [dBm] = 20log(U
Page 12
Company Confidential
) + AGC
BB calibrated
Copyright © 2003 Nokia Corporation.
Company Confidential
CCS Technical Documentation
Issue 1 10/2003