Window Filtering; Advantages Of Window Filtering - Saluki S3601 Series User Manual

spot number - 1 and in inverse scale to frequency span, to increase Measure range, setting of two items below can be modified:
Increase Sweep spot number.

Reduce frequency span.

Measure range in meter can be obtained by multiplying vacuum light velocity with Measure, in order to calculate physical length of
actual Measure range, relative speed rate of transmission medium shall be multiplied also and relative speed rate of some medium
are below:
Vpolythene = 0.66

Vpolytef = 0.70

Physical length of actual Measure range =

8.3.Window Filtering

Due to effect of sidelobe and pulse width, time domain transformation is limited in term of resolution. Window filtering function can be
used to mitigate the effect when performing Measure. Window function provided by the Analyzer in time domain can distinguish
various responses effectively and it can change width of response pulse, rise time of step response and sidelobe level.

8.3.1. Advantages of Window Filtering

In frequency domain Measure, sudden change exists at initial and terminal frequencies, which will result in overshoot and ringing in
step response of time domain. Using window filtering function can reduce effect caused by sudden change in frequency domain;
besides, Analyzer also has following deficiencies when performing time domain Measure:
Pulse width of impulse response or rise time of step response: this is caused by limitation property of the system itself, limiting

the capability of Analyzer to distinguish two adjacent response signals. Pulse width is in inverse scale to frequency span
measured, and to reduce pulse width, frequency span shall be increased.
Impulse response sidelobe: this is caused by sudden change at terminal frequency. Sidelobe of adjacent high electrical level

response will cover low level response signal, which limits dynamic range of time domain Measure, however, using window
filtering can inhibit sidelobe, as shown in the figure below:
Using narrow window can reduce width of impulse response pulse and improve response resolution to distinguish two adjacent

responses in a better way.
Using broad window can reduce sidelobe level of impulse response and improve dynamic range to measure low level response

in a better way.
V
8
 3 10
medium m/s
F
△
Fig.8-7 Inhibiting Sidelobe by Use of Window Wave Filter
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