HP ESA-L1500A, User'S And Calibration Manual

Page: 92 / 326

Chapter 4 91
Front-Panel Key Reference
Measure
N dB Points On Off
automatically places two markers at points N dB from the highest point
on the highest displayed signal, and determines the frequency
difference between the two markers. N dB is the active function and the
value of N is set by the user. The measurement defaults to -3 dB when it
is first turned on. The measurement runs continuously, re-executing at
the end of each sweep.
No other signal can appear on the display within N dB of the highest
signal. The measured signal cannot have more than one peak that is
greater than or equal to N dB. A signal must be greater than the peak
excursion above the threshold to be identified. The setting for peak
excursion may be increased from the 6 dB default value so that noise
will not be identified as signals. Increasing the value too much may
cause a smaller signal to be missed or misinterpreted as part of a larger
signal. The amplitude scale may be either linear or logarithmic.
Key Access:
Measure
% AM On Off
determines the percent of amplitude modulation of the largest
displayed signal and its two sidebands. The sidebands are assumed to
be entirely from amplitude modulation. If there are differences in the
sideband amplitude, the larger value is used. The measurement runs
continuously, re-executing at the end of each sweep.
The three signals that make up the AM signal, must all be displayed.
The frequency spacing of the sideband signals must be the same within
the span accuracy of the measurement. All of the signals must be
greater than the peak excursion above the threshold. The amplitude
scale may be either linear or logarithmic. Key Access:
Measure
TOI On Off
finds the third-order intercept of the two highest amplitude signals and
the two associated distortion products. The measurement compensates
for unequal test signal amplitude. The measurement runs continuously,
re-executing at the end of each sweep. The units for the displayed value
can be selected by pressing the
Amptd Units
softkey. The two test signals
and the two associated distortion products must all be displayed for the
measurement to function. The relative amplitudes and frequencies of
the displayed signals must fit the TOI pattern. All of the signals must
be greater than the peak excursion above the threshold.
Key Access:
Measure