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20 Chapter 1
Agilent EXA Signal Analyzer
Frequency and Time
Description Specifications Supplemental
Information
Frequency Readout Accuracy ±(marker freq. × freq. ref. accy. + 0.25%
× span + 5% × RBW
a
+ 2 Hz + 0.5 ×
horizontal resolution
b
)
a. The warranted performance is only the sum of all errors under autocoupled conditions. Under
non-autocoupled conditions, the frequency readout accuracy will nominally meet the specifica-
tion equation, except for conditions in which the RBW term dominates, as explained in exam-
ples below. The nominal RBW contribution to frequency readout accuracy is 2% of RBW for
RBWs from 1 Hz to 390 kHz, 4% of RBW from 430 kHz through 3 MHz (the widest autocou-
pled RBW), and 30% of RBW for the (manually selected) 4, 5, 6 and 8 MHz RBWs.
First example: a 120 MHz span, with autocoupled RBW. The autocoupled ratio of span to
RBW is 106:1, so the RBW selected is 1.1 MHz. The 5% × RBW term contributes only 55 kHz
to the total frequency readout accuracy, compared to 300 kHz for the 0.25% × span term, for a
total of 355 kHz. In this example, if an instrument had an unusually high RBW centering error
of 7% of RBW (77 kHz) and a span error of 0.20% of span (240 kHz), the total actual error
(317 kHz) would still meet the computed specification (355 kHz).
Second example: a 20 MHz span, with a 4 MHz RBW. The specification equation does not
apply because the Span: RBW ratio is not autocoupled. If the equation did apply, it would
allow 50 kHz of error (0.25%) due to the span and 200 kHz error (5%) due to the RBW. For
this non-autocoupled RBW, the RBW error is nominally 30%, or 1200 kHz.
b. Horizontal resolution is due to the marker reading out one of the trace points. The points are
spaced by span/(Npts - 1), where Npts is the number of sweep points. For example, with the
factory preset value of 1001 sweep points, the horizontal resolution is span/1000. However,
there is an exception: When both the detector mode is “normal” and the span > 0.25 × (Npts -
1) × RBW, peaks can occur only in even-numbered points, so the effective horizontal resolu-
tion becomes doubled, or span/500 for the factory preset case. When the RBW is autocoupled
and there are 1001 sweep points, that exception occurs only for spans > 750 MHz
Single detector only
c
c. Specifications apply to traces in two cases: when all active traces use the same detector, and to
any trace that uses the peak detector. When multiple simultaneous detectors are in use, addi-
tional errors of 0.5, 1.0 or 1.5 display points will occur in some detectors, depending on the
combination of detectors in use. In one example, with positive peak, negative peak and average
detection, there is an additional error only in the average detection trace, which shifts the
apparent signal position left by 0.5 display points.
Example for EMC
d
±0.0032% (nominal)