Fault Finding Chart Of The Receiver - Nokia RM-94 Rf Troubleshooting Instructions

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RM-94

6(b) - RF Troubleshooting

Signal amplitude

DC offset

Frequency

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, following steps

shall be carried out:

• Check if AGC calibration is within limits.

• Check if SNR reading is o.k.

Use an oscilloscope to check levels of "RXI" and "RXQ".

The RF ASIC generates only single ended I and Q signals (RXI, RXQ). As the A/D converter

in UEM requires two differential signals, an artificial mid voltage is generated from VrefRF02.

The phone layout has dedicated test points for the analogue RX I and Q signals (J512, J513).

The BB part is used to measure those signals by means of RSSI reading. This works only if

correct calibration has been carried out in production.

Issue 1 04/2005

1.40Vpp

ª 1.28V as the offset is floating, switch to the operating mode

<Burst> in Phoenix and read the DC offset

67kHz

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