Ceyear 4051 Series, User Manual

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4. Operating Instruction
4.2 Advanced operation guide
137
 Gate length < τ-SUT.
In this example, providing that the SD is 0, the SUT will be equal to the gate delay time; otherwise, the gate
delay time is equal to the SUT plus SD. See Fig. 4.55 for the positioning parameters of the time gate.
Fig. 4.55 Positioning parameters of the time gate
Similar to the resolution bandwidth filter, the video filter also needs a certain time for charging and
discharging. As a post detector, it is used to smooth the track. No matter how long the actual pulse is, seen
from the video filter, the pulse length will not exceed the gate width, and it will take some time to charge. If
the video bandwidth value is reduced too fast, the amplitude on the screen will decline. For the value selection
of video filter, the value can be set to the max, and then decreased until the signal level drops slightly, where
the video bandwidth value is set for that before the signal level begins to have a slight decrease. The values of
resolution bandwidth and video bandwidth are set to the manual mode so that the values are constant even
though the bandwidth changes.
6) General principles for measurement of time gate
For most control setup, the signals are determined by two key parameters, pulse repetition interval (PRI) and
pulse width τ. If both parameters are known, the standard setup may be applied. The setting principle of the
Series Signal Analyzer is given in Table 4.4 during the observation of pulse RF signal.
Table 4.4 Setup of Series Signal Analyzer during the observation of pulse RF
Parameters of Series
Signal Analyzer
Setting principle
of Series Signal
Analyzer
Note
Scanning time Unlimited Although the scanning time does not affect the measurement
results of gating LO, the scanning time is required to be
increased if it is set too short.
Gate delay Gate delay = SD
+4/resolution
bandwidth The setup of gate delay should assure the pulse can be captured
upon the Gate On. If the gate delay is too short or long, the
pulse will be lost or the response of resolution bandwidth filter
in transition zone will be included.
Gate width Gate length = τ-
SUT If the gate is too wide, the response of resolution bandwidth
filter in transition zone will be contained.
The gate is recommended to set at the position of 25% of the
pulse
Resolution bandwidth Resolution
Bandwidth
>
(4/SUT)
The resolution bandwidth value must be large enough to
ensure the charging time of the filter is less than the signal
pulse width.