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Chapter 5 133
CDMA Measurements - Screens and Control Fields
CDMA Measurements
ADC FS
ADC FS is displayed when channel power is measured. ADC FS
indicates how close the measured power level is to the maximum
allowed input level at the RF IN/OUT port for a particular Gain setting
(on the CDMA ANALYZER screen). Changes to ADC FS can be made by
altering the Gain field setting and by altering the signal level into the
RF IN/OUT port. ADC FS should be between −1.0 and −0.5 dB.
Measurement accuracy may be degraded if ADC FS goes below −10 dB
when the Gain field is set to Auto, and can be manually set up to −0.5
dB when set to Hold. The measurement will be aborted if ADC FS goes
above.
Screens on which this measurement is displayed
• CDMA ANALYZER
• CDMA GENERATOR
Rho Measurements
Rho
Rho is a measure of CDMA waveform quality which indicates how well
the measured signal (the pilot signal transmitted by the base station
under test) correlates with the ideal reference waveform (the ideal pilot
generated by the Test Set which is mathematically perfect). This
measurement is done through a complex DSP algorithm. Perfect
correlation is when rho is equal to 1. The CDMA standard specifies
0.912 as the minimum accepted performance for CDMA base stations.
To make rho measurements, the base station needs to be configured to
transmit only a pilot signal. The test equipment is then triggered by
any of the selectable CDMA clocks.
Many different factors can contribute to rho failure, including:
• compression in the linear power amplifier
• phase non-linearities (group delay)
• carrier feedthrough (see “Carrier Feedthrough” on page 136)
• I/Q magnitude and phase errors (see “Magnitude Error” on page 138
and “Phase Error” on page 138)