Agilent Technologies N9010A, Manual

Page: 82 / 107

82 Chapter 10
Code Domain Measurements
Troubleshooting Hints
Troubleshooting Hints
Uncorrelated interference may cause CW interference like local
oscillator feed through or spurs. Another cause of uncorrelated noise
can be I/Q modulation impairments. Correlated impairments can be
due to the phase noise on the local oscillator in the upconverter or I/Q
modulator of the unit under test (UUT). These will be analyzed by the
code domain measurements along with the QPSK EVM measurements
and others.
Poor phase error indicates a problem at the I/Q baseband generator,
filter, or modulator in the transmitter circuitry of the UUT, or both. The
output amplifier in the transmitter can also create distortion that
causes unacceptably high phase error. In a real system, poor phase
error will reduce the ability of a receiver to correctly demodulate the
received signal, especially in marginal signal conditions.