Atec Agilent-8510C - Manual (Page 14)

14
Accuracy considerations when using
ramp sweep
The uncertainty values for the preceding systems assume
that the microwave source operates in the synthesized
step sweep mode. Selecting ramp sweep saves time; the
8510C allows switching between step and ramp sweep
without the need to recalibrate
1 .
The frequency accuracy of the 8510 in ramp sweep mode
is determined by the swept frequency accuracy of the
source.
For 8360 series synthesizers, the swept frequency accu-
racy is summarized in the following table:
Sweep width
Accuracy
f ≤26.5 GHz f >26.5 GHz (% of span, or MHz)
≤n x 10 MHz ≤n x 10 MHz 0.1% ± time base accuracy
>n x 10 MHz and >n x 10 MHz and
≤400 MHz ≤800 MHz 1%
>400 MHz and >800 MHz and
≤4 GHz ≤8 GHz 4 MHz/8 MHz
>4 GHz >8 GHz 0.1%
Frequency range n (Multiplier)
10 MHz to <2 GHz 1
2 to <7 GHz 1
7 to <13.5 GHz 2
13.5 to <20 GHz 3
20 to <26.5 GHz 4
26.5 to <38 GHz 2 6
38 to 50 GHz 8
The plots below indicate the typical swept mode
accuracy.
Phase errors due to device electrical length
Ramp sweep adds phase uncertainty to the measurement of
electrically long devices. The phase uncertainty
∆ø is
given by the following equation:
∆ø = (–360/c) x ∆F x L
where c is the propagation velocity in a vacuum
(3 x 10
10 cm/sec),
∆F is the frequency accuracy specifica-
tion of the synthesizer in ramp mode, and L is the electri-
cal length of the device under test. The following graph
shows this uncertainty for the 8360 series synthesizers in
ramp sweep.
Agilent Technologies recommends the 8360 series synthe-
sized sweepers in step sweep mode whenever measuring
phase or group delay of electrically long devices, or when-
ever the highest system accuracy is required. Ramp sweep
is recommended for measurements of electrically short
devices, or for applications where maximum trace update
rate is desired (for example, tuning).
1. Ramp sweep mode is not available in the 8510XF systems.
2. This band is 26.5 to 40 GHz on the 83640A.