China Electronics Technology Instruments AV3672 Series, User Manual

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Appendix
Appendix 2 Time Domain Measurement
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2.4.3.1 Gate Shape
The gate, similar to the window filter, is shaped like a filter. You can select the reasonable filter shape (smallest,
standard, wide and largest) to optimize measurement.
1) Smallest gate : the side lobe level of the filter is the highest, the edge drop is the steepest, and the passband
ripple is the largest.
2) Largest gate : the side lobe level of the filter is the lowest, the edge drop is the most gentle, and the passband
ripple is the smallest.
2.4.3.2 Passband Ripple
The gate is a band-pass (band-resistance) filter. Filters of various shapes have different characteristics. The
following figure shows passband ripples of four kinds of filters, in which the scale is 0.5dB/grid. It can be seen in
Fig. 2.11 that the smallest gate has the largest ripple.
Fig. 2.11 Passband Ripple of Various Gate Filters
2.4.3.3 Side Lobe Level
As shown in Fig. 2.12, four kinds of filters have different side lobe levels. The side lobe level and cutoff rate must
be balanced in actual measurement.
1) The smallest gate has the highest side lobe level and cutoff rate. It is applicable for removal of the unexpected
response near the measured response.
2) The largest gate has the lowest side lobe level and cutoff rate, the widest passband and the largest attenuation
outside the gate band.
Fig. 2.12 Side Lobe Levels of Various Gates
2.4.3.5 Gate Characteristics
Various gates have different characteristics. Schedule 2.3 lists the characteristic indicators of various gates. The
gate characteristics are defined with the following indicators:
1) Passband ripple and side lobe level : describe the gate shape.