Probing/Troubleshooting; Overview - Nokia RH-10 Series Troubleshooting Manual

CCS Technical Documentation

Probing/Troubleshooting

Overview

When measuring CDMA transmit signals, if the spectrum analyzer does not have a CDMA
personality card, the CDMA signal power can be approximated by setting the resolution
bandwidth to 1 MHz and using the marker. CDMA signal power is measured by integrat-
ing power over a 1.23 MHz bandwidth while the marker measures power at only one fre-
quency.
Probing is generally done in local mode, although situations may arise whereby the trou-
bleshooter may need to probe while in a call. If this is done, be aware that in some cases,
probing may disturb the circuit so that the call drops.
The following tables list power levels for many combinations of AGC values; however, it
generally is only necessary to check one combination. 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
suspect trouble spots should be probed.
Absolute power measurements were made with an Agilent (HP) 85024A active high
impedance probe. While other probes may be used, it is strongly recommended that the
probe be high impedance so that the measurement does not load the circuit. Adjust
absolute measurements if the probe has a different gain or if a probe attenuator is used.
If a range is provided for loss, typically the higher loss occurs at the band edges.
Power depends on the impedance of the circuit. For example, if a circuit 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.
Issue 1 09/2002
Nokia Corporation
Confidential
RH-10
Troubleshooting
Page 21