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84 Chapter 4
CDMA Measurements - Screens and Control Fields
Rho Measurements Rho Measurements
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 things can contribute to rho failure; this is a short list of
them:
• compression in the linear power amplifier
• phase non-linearities (group delay)
• carrier feedthrough (see "Carrier Feedthrough" on page 87)
• I/Q magnitude and phase errors (see "Magnitude Error" on page 88
and "Phase Error" on page 88)
Figure 4-1 Rho
Screens on which this measurement is displayed.
• CDMA ANALYZER
• CDMA GENERATOR
ρ
ρ
ρ
Power that correlates with ideal
Total Power
Signal Power
Signal Power + Error Power
0.912
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