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Chapter 2, Making Measurements
Modulation Quality (Rho)
Modulation Quality (Rho)
Overview In this measurement, the modulated signal is compared to an ideal, reference
waveform to determine the performance of the transmitter’s modulation circuitry.
Rho values are in the range of 0 to 1. A value of 1 indicates perfect correlation to
the reference (high modulation quality). CDMA base station standards require
that transmitters have rho performance of 0.912 or higher.
Figure 8
CAUTION: Before performing any transmitter measurements, make sure that the power level applied
to the RF IN/OUT port of the PCS Interface does not exceed the published limit. For
CDMA base station signals this is 1 Watt (+30 dBm). You may have to use an external
attenuator or directional coupler, depending on the power output for your transmitter.
Signal levels greater than the specified maximum can cause damage to the test equipment.
NOTE: The test procedures outlined in this section require that you have already configured the
Test System as outlined in chapter 1, "Getting Started".
Requirements • Synchronization is required, so you must have an Even-Second Clock signal and a
reference timebase (typically 19.6608 MHz) from the base station.
• You must have the ability to transmit the pilot channel only (Walsh 0).
• You must know the following about the base station and setup:
❒ The base station channel number setting.
❒ The PN Offset for the base-station-under-test. If you do not know the PN Offset,
determine it by selecting Search for PN Offset in the main menu.
H
H
RF IN/OUT
SYNTH
REF IN
(Rear Panel)
Time Base
Transmitter Port
EVEN SECOND/
SYNC IN
Even-Second
Clock