Tektronix RFA300A, User Manual

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Reference
3- 4
RFA300A Measurement Set 8VSB
of the actual digitally modulated television signal and an ideal signal of the same
data. This measurement is the major all-in-one indicator of the transmitter’s
signal quality. The test is an early indication of system problems before they
become bit errors and is more sensitive to modulation errors than Bit Error Ratio
(BER) tests.
The EVM (Error Vector Magnitude) measurement also provides a broad analysis
of the transmitted signal. EVM analysis can reveal incorrect filter shaping (see
VSB Modulation on page 3--18) and other modulation quality problems.
Complex MER is a complex form of S/N. The measurement is made by
including Q (quadrature) channel information into the calculation. Refer to
Complex MER calculation in the online help.
This measurement shows any error of the pilot signal amplitude.
Phase Noise
This section provides a brief overview of the Phase Noise measurement window.
For more in-depth information, refer to the online help.
This measurement window measures the random low frequency phase deviations
of the entire 8VSB signal. Phase noise is typically added by the transmitter’s
frequency synthesizer system. Phase noise can reduce the S/N ratio.
The measurement set performs this measurement by calculating the residual
phase jitter. This jitter is what is left after removing the effects of other transmis-
sion errors.
The Phase Noise measurement window is shown in Figure 3--4. The measure-
ment window contains the following areas:
H
Listing of measurement results
H
A mask test pass or fail indicator
H
Cursor direction controls
H
Listing of each cursor’s position and the difference between the two
H
Graphic showing the pilot’s phase noise spectral density measured in dBc/Hz
versus frequency. The selected mask is overlaid on the display, if you
enabled any in the setup (see
Phase Noise Setup next).
EVM
Complex MER
Pilot Amplitude Error