HP 85106D, Manual

Page: 75 / 244

2-30 HP 85106D mm-Wave System
Operation
Example Measurements
To make this measurement, first enter the waveguide cutoff frequency (f
co
)
by pressing the following keys:
RESPONSE [
MENU
] {
MORE
}
{
WAVEGUIDE DELAY
}
The active function is now WAVEGUIDE CUTOFF at the waveguide cutoff
frequency f
co
. This value is a part of the instrument state that was loaded
with the Machine-Dump file for the frequency band. If the value is incorrect
for the band in use, enter the appropriate f
co
for the waveguide band in use.
The electrical delay then applied varies as a function of frequency to account
for dispersion. Now press the keys:
PRIOR [
MENU
]
{
ELECTRICAL DELAY
}
Move the measurement marker to the center of the frequency range, then
press {
AUTO DELAY
} to automatically choose a value for waveguide delay.
Now use the knob to enter the appropriate electrical delay value to flatten the
trace and view the deviation from characteristic waveguide phase response.
This measurement shows the phase response of the 10 cm line with electrical
delay applied. Note that coaxial delay (linear) cannot flatten the phase
response. With waveguide delay the phase response can be flattened so the
actual device length may be measured.
Time Domain
Measurements
With the HP 8510C Option 010 Time Domain feature, use {
TIME BAND PASS
}
to locate impedance changes within the device under test. Figure 2-10 on
page 2-31 illustrates the S
11
time band pass response of a shorted 10 cm
waveguide section with and without waveguide delay applied.