User Guide

RH-17
Troubleshooting — RF CCS Technical Documentation
Page 42 Nokia Corporation Confidential Issue 1 04/2003
Probing/Troubleshooting Tables
When measuring CDMA transmit signals, if the spectrum analyzer does not have a CDMA
personality card, then the CDMA signal power can be approximated by setting the Reso-
lution Bandwidth to 1 MHz and using the marker. This is because CDMA signal power is
measured by integrating power over a 1.23 MHz bandwidth, and the marker measures
power at only one frequency.
In most cases, probing is done in local mode (i.e., not in a call). Situations may arise
whereby the troubleshooter may need to probe while in a call, however in some cases
probing may disturb the circuit so that the call drops.
Although the tables list power levels for many combinations of AGC values, it is generally
only necessary to check one combination. The extra information is provided in case it
may be useful in an unexpected situation. Likewise, although probing points and signal
level information are given for each point in the receiver and transmitter chains, the
troubleshooter is not expected to probe each point on every phone, only the suspected
trouble spots.
Absolute power measurements were made with an Anritsu MT8802A using common RF
probe. Other probes can be used (but should be high impedance so that the measurement
does not load the circuit) but may very well have a different gain, therefore adjust the
absolute measurements accordingly. Also, adjust measurements if using a probe attenu-
ator.
Where a range is given for loss, typically the higher loss occurs at the band edges.
Power depends on the impedance of the circuit. For example, if a filter has a nominal loss
of 5 dB, then straightforward probing on the input and output, then subtracting, might
not result in 5 dB because the input impedance might be different from the output
impedance. However, after mathematically adjusting the power on either the input or
output to compensate for the difference in impedance, 5 dB is then calculated. Most
components in the RF section have the same input and output impedance (50 ohms), but
where this is not the case, absolute power is noted in the tables in dBm, rather than loss
or gain in dB.
When testing the CDMA receiver, it is easier to inject a CW tone into the receiver. The
gains and losses will be the same for a CW signal as for CDMA.
Transmitter Probing
Table 1: Transmit Output Powers and Associated AGC PDM values and voltages
Channel 384 (Cell)
fc= 836.52 MHz
AMPS
Probed RF RF power
TX RF AGC TX IF AGC power on PA AGC on RF