Frequency Gated By Time - Anritsu MS2024B Manual

Time Domain, Option 2 8-3 VNA Master Implementation

Frequency Gated by Time

Often times, you would like to measure the characteristics of a DUT by connecting to it with a
cable. Unfortunately, the cable is not ideal and degrades the measurement of the DUT.
Frequency Gated by Time (FGT) is a feature that allows the unwanted characteristics of the
devices surrounding the DUT to be "gated" out of the measurement. FGT first transforms the
frequency data into the time domain, "gates" out the unwanted time domain data, and then
transforms the gated time domain data back into the frequency domain.
The screen capture in Figure 8-7 shows the measurement of a DUT at the far end of a 30 cm
cable. The top-left graph shows that the cable and DUT together have a worst-case return loss
of approximately 13 dB. The top-right graph shows the time domain step response of the
cable and DUT along with a gate that is placed around the DUT from 29 cm to 33 cm. The
bottom-right graph shows how the gated time domain step response appears. The mismatches
and reflections of the cable leading up to the DUT are now gone. The bottom-left graph shows
the Frequency Gated by Time response of the DUT with the degradations of the cable
removed. The worst-case return loss is improved by approximately 21 dB.
Figure 8-7. DUT at Far End of Cable Measurement – Frequency Gated by Time (FGT)
Vector Network Analyzer MG PN: 10580-00289 Rev. K 8-9