Viavi CX100 ComXpert Operation Manual page 132

5.2.7.6 Digital Demod Measurements
The CX100 contains a Vector Signal Analyzer (VSA) that processes and demodulates
digital data, which is then sent to the device's Digital Demod meters. The Digital Demod
meters are used to identify any impairments in the digital signal that may have been
introduced by the analog parts of the digital transmitter. More common impairments that
negatively impact the performance of a digital modulator are timing drift, frequency offset
and amplitude imbalance.
The CX100's VSA estimates certain values in relation to the impairments in the received
signal. In order to estimate the impairments, the VSA uses a perfect received signal, called
a reference signal, and compares the reference signal to the actual received signal, called
the measured signal.
VSA's main components.
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Figure 5-5 on page 5-24
CX100 ComXpert Operation Manual
Chapter 5 RF Instrument Function Descriptions
shows a high level block diagram of the
RF Test
Rev 002
5 - 23