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Frequency-domain
narrow frequency span
Time-domain
wide impulse width
frequency
narrow impulse width
time
wide frequency span
frequency
time
Figure 6-4 Frequency, Amplitude/Scale, Bandwidth/Average Menu Structure
The time domain measurement response under a narrow frequency span shows that the impulse
response pulses that should be separated independently overlap each other.
The microwave analyzer can distinguish between different response pulses when performing time
domain measurements over a wide frequency span.
The frequency span is inversely proportional to the pulse width. The wider the frequency span, the
narrower the impulse response pulse, and the shorter the step response rise time, the higher the
resolution of the response measurement.
b)
Window function
If the cable and antenna mode is used for frequency time domain transformation, the length of data
processed is limited. To reduce the effects of ringing caused by data truncation, the microwave analyzer
usually provides the option of windowing. Windowing can reduce the ringing effect and reduce the side
lobes, but it will increase the width of the main lobe and reduce the resolution.
Frequency-domain
Time-domain
without window
S
-1
start
end
frequency
time
with window
start
end
frequency
time
Figure 6-5 Using Window Filtering to Suppress Side Lobes
S5105D/E/F provides three kinds of window functions, which are maximum value, normal value,
minimum value. The main lobe width and side lobe height of three kinds of window functions can select
different window according to specific test needs.
