Time Domain Gating

Time domain gating is a function, which mathematically removes the unwanted responses in time domain. The function performs time domain transformation and applies reverse transformation back to frequency domain to the user-defined span in time domain. The function allows the user to remove spurious effects of the fixture devices from the frequency response, if the useful signal and spurious signal are separable in time domain.

The function involves two types of time domain gating:

• • • bandpass – removes the response outside the gate span,
    • notch – removes the response inside the gate span.

The rectangular window shape in frequency domain leads to spurious sidelobes due to sharp signal changes at the limits of the window. The following gate shapes are offered to reduce the sidelobes:

• • • maximum;
    • wide;
    • normal;
    • minimum.

The minimum window has the shape close to rectangular. The maximum window has more smoothed shape. From minimum to maximum window shape, the sidelobe level increases and the gate resolution reduces. The choice of the window shape is always a trade-off between the gate resolution and the level of spurious sidelobes. The parameters of different window shapes are represented in Table 29.

Table 29Time domain gating window shapes

Time Domain Gate Activating

Time Domain Gate Span

To define the span of time domain gate, you can set its start and stop, or center and span values.

Time Domain Gate Type

Time Domain Gate Shape Setting

| | | To set the time domain gate shape, use the following softkeys: | | --- | --- | --- |