HP 54750A, User Manual, Page: 141 / 478

The Digital Communications
Analysis Menus
Mask T est Menu
N O T E
F or proper operation, the channel external scale must be set to the total attenuation in the path. F or
example , when using the HP 11852B in conjunction with a 10 dB attenuator , set the channel external
scale to 15.7 dB . T o set external scale , select Channel, External Scale , and enter the appropriate
attenuation value .
Data Rate Z ero Level V oltage One Level V oltage Recommended Pad
V alue
1
2.048 Mb/s 0 V 2.37 V 10 dB
8.448 Mb/s 0 V 2.37 V 10 dB
34.368 Mb/s 0 V 1.00 V 6 dB
139.000 Mb/s 0 0.5 V +0.5 V 6 dB
1 In addition to 5.7 dB loss due to 75-50 ohm minimum loss pad
User-dened masks The Mask T est menu also contains a mask editing feature that allows you
to create your own masks . These masks may be created using one of two
methods: by using the Edit Mask menu to create a new or modify an existing
mask, or by using the A uto Mask menu to create a mask from a waveform.
The rst method involves constructing polygons , while the second method
involves the use of a reference waveform.
Using the rst method, polygons are created to mask o failure regions of
the graticule . Up to eight polygons can be positioned in the graticule area.
Each polygon can have from 3 to 512 sides . V ery complex masks can be
constructed by placing polygons within polygons . Similar to margin testing
discussed above , this method allows testing of waveform failure rates to
varying tolerances , because failures are listed individually for each polygon.
Using the reference waveform method, masks are constructed by adding a 1X
and 1Y tolerance around a reference waveform. This method is simple to use ,
though not as exible as the polygon method.
6-5