Specifications

9
2. Place a marker in the center of the band and
activate the electrical delay feature,
[MARKER] {MARKER 1} {12 GHz}
RESPONSE [MENU]
{COAXIAL} OR {WAVEGUIDE}
depending upon whether the media exhibits intrin-
sic linear or dispersive phase shift.
{AUTO DELAY}
3. {ELECTRICAL DELAY} is now the active function.
Use the knob, STEP keys, or numeric and units
to fine tune the electrical delay for a flat phase
response near the center of the passband. The
linear phase shift through the AUT is effectively
removed and all that remains is the deviation
from this linear phase shift.
4. Use the markers to measure the maximum peak-
to-peak deviation from linear phase.
[MARKER]
{MARKER 1}
{MORE} {MARKER TO MINIMUM}
[PRIOR MENU]
{MARKER 2}
{MODE MENU} {REF=1}
{MORE} {MARKER TO MAXIMUM}
Group delay
Group delay is calculated from the phase and fre-
quency information and is displayed in real time
by the 8510C network analyzer.
1. Set up the 8510C for an S
21
group delay meas-
urement.
[S21] [DELAY]
2. Activate a marker to measure the group delay at
a particular frequency.
Group delay measurements may require a specific
aperture (∆f) or frequency spacing between meas-
urement points. The phase shift between two adja-
cent frequency points must be less than 180°, oth-
erwise incorrect group delay information may
result.
Approximate delay of AUT <
number of points – 1
2 * (frequency span)
The effective group delay aperture can be
increased from the minimum by varying the
smoothing percentage. Increasing the aperture
reduces the resolution demands on the phase
detector and permits better group delay resolution
by increasing the number of measurement points
over which the group delay aperture is calculated.
Since increasing the aperture removes fine grain
variations from the response, it is critical that
group delay aperture be specified when comparing
group delay measurements. To adjust the aperture
press RESPONSE [MENU] [SMOOTHING ON] and
adjust aperture as necessary.
Figure 6. Group delay measurement with minimum and
increased aperture