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Start and stop: to define -6dB cut-off time of the gate.
Center: to define center time of the gate.
Span: it equals to terminal time minus start time.
Gate Type:
Band-pass:
to filter response outside the gate.
Band
-
stop:
to filter response inside the gate.
8.4.3.
Gate Form
Similar to window wave filter, the gate also has corresponding wave filter form and Measure can be optimized by selecting
reasonable wave filter form:
Minimum gate:
the wave filter has highest sidelobe level, with sharpest edge falling and maximum band-pass ripples.
Maximum gate:
the wave filter has lowest sidelobe level, with slowest edge falling and minimum pass band ripples.
8.4.3.1.
Passband ripples of the gate
The gate is a pass band (or band-stop) wave filter on time domain and each form of wave filter has different filter property. Figure
below indicates band-pass ripples of four filters in different forms and the scale in the figure is 0.5dB/grid. It can be seen from the
figure that the minimum gate has the largest band-pass ripples.
Fig.8-11 Band-Pass Ripples of Different Gate Wave Filters
8.4.3.2.
Sidelobe level of the gate
Four wave filters of different forms have different sidelobe levels, in actual Measure, there must be a balance between lower sidelobe
level and faster cut-off ratio.
The minimum gate is with highest sidelobe level and fasted cut-off speed, which is very applicable to filtering undesired
interference near the response.
The maximum gate is with lowest sidelobe level, slowest cut-off speed, widest gate band-pass and maximum attenuation
outside the gate band.