Atec Agilent-8703A - Manual (Page 15)

Group delay measurements
Group delay is computed by measuring the phase change
within a specified frequency aperture (determined by the
frequency span and the number of points per sweep).
The phase change, in degrees, is then divided by the
frequency aperture, in Hz (times –360).
Aperture
Determined by the frequency span, the number of
steps per sweep, and the amount of smoothing applied.
(Minimum aperture limited by source frequency resolution
of 1 Hz.)
Minimum aperture = (frequency span) / (number of
points–1)
Maximum aperture = 20 % of the frequency span
Range
The maximum delay is limited to measuring no more
than ±180 degrees of phase change within the minimum
aperture. For example, with a minimum aperture of
1 Hz, the maximum delay that can be measured is
500 milliseconds.
Accuracy
Accuracy is a function of the uncertainty in determining
the phase change. The following is a general formula for
calculating typical accuracy, in seconds, for a specific
group delay measurement.
±0.003 x Phase Uncertainty (deg)
Aperture (Hz)
Data accuracy enhancement
Lightwave measurement calibration types
Response: Simultaneously accounts for magnitude and
phase errors due to a system’s modulation frequency
response. This applies for either transmission or reflection
tests.
Response and match: Accounts for magnitude and
phase responses as well as microwave source and receiver
return loss errors. The isolation part of this calibration
can be included to compensate for directivity (reflection)
and crosstalk (transmission).
Response and isolation: Compensates for modulation
frequency responses plus directivity (reflection) or
crosstalk (transmission).
Microwave measurement calibration types
Frequency response: Simultaneously corrects for
magnitude and phase frequency response errors for either
reflection or transmission measurements.
Response/isolation cal: Compensates for frequency
response plus directivity (reflection) or crosstalk
(transmission).
1-port cal: Correction of test set port 1 or port 2
directivity, frequency response and source match errors.
2-port cal: Compensates for directivity, source match,
reflection frequency response, load match, transmission
frequency response, and crosstalk.
Reference plane extension
Applies to lightwave and microwave. Redefines the plane
of the measurement reference (zero phase) to other
than the source or receiver ports of the lightwave and
microwave test sets. Is defined in seconds of delay from
the test set port and ranges between ±10 seconds.
Calibration kits
Select from standard lightwave and microwave calibration
kits. Lightwave calibration kits are internally defined for
an optical “thru” and “Fresnel”. Microwave calibration
kits for 3.5mm, 7mm, or type-N 50 ohm connectors are
also defined for electrical “open”, “shorts” and loads
(sliding or fixed broadband loads). Customized calibration
kits, called “User Kits”, can be be defined or modified,
and saved and recalled internally or from disc, for use
with other calibration kits.
Data averaging
IF bandwidth: Selectable from 10 Hz, 30 Hz, 100 Hz,
300 Hz, 1 kHz, and 3 kHz bandwidths.
Sweep-to-sweep averaging: Averages vector data on
each successive sweep. Averaging factors range from
1 to 999.
Segmented cal
Perform a single calibration in frequency list sweep mode
for all segments. Afterwards, calibration remains valid for
any one segment selected from the list.
Frequency subset cal
Perform a calibration in linear sweep mode, up to 1601
points over entire frequency range. Afterwards, calibration
remains valid for any frequency subset (smaller frequency
range within endpoints used during calibration). Analyzer
measures over nearest arbitrary number of cardinal
calibration points.
15
General
information