Agilent Technologies ENA Series User Manual page 192

Analysis in Time Domain (Option 010)
Transformation to time domain
Effect of the window function on the response resolution
Lowering the sidelobe level with the window function elongates the width of the impulse
signal and the rise time of the step signal. As described in "Effect of frequency sweep
range on response resolution" on page 183, because the response resolution is equal to the
width of the impulse signal and the rise time of the step signal, lowering the sidelobe level
enlarges the response resolution. Table 8-1 shows the relation between the response
resolution and the window setting.
Table 8-3 The shape of window and response resolution
Window
Maximum
Normal
Minimum
Figure 8-6 shows how the response changes when changing the window shape. You can
see that, if the magnitudes of adjacent peaks are comparable, you need to make the
resolution higher and, if they differ significantly, you need to set the window so that
smaller peaks with lower sidelobes appear.
Figure 8-6 Effect of window on response resolution
Effect of the transformation type on the response resolution
Although both transformation types, band pass and low pass impulse, simulate the
response of the impulse signal, the impulse width in the low pass impulse mode is half the
width in the band pass mode as shown in Table 8-1. Therefore, the resolution is better in
the low pass mode. If the DUT can be measured in the low pass mode, response data with
better resolution is obtained in the low pass mode.
184
Low pass step Low pass impulse
0.45/frequency span 0.60/frequency span
0.99/frequency span 0.98/frequency span
1.48/frequency span 1.39/frequency span
Band pass
1.20/frequency span
1.95/frequency span
2.77/frequency span
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