Vector Network Analyzer Measurement Guide : VNA View Menus : Domain Setup Menus : FGT Menu
 
FGT Menu
Preliminary Key Sequence: Measure > Domain Selection > FGT
or
Preliminary Key Sequence: Freq/Time/Dist > Domain Setup > Setup FGT
Key Sequence: Freq/Time/Dist
FGT Menu
Start Freq
Press this soft key to set the start frequency in units of Hz, kHz, MHz, or GHz. If you enter a start frequency that is higher than the currently‑set stop frequency, and if CAL = On, then the start frequency is set to the same value as the stop frequency. If you enter a start frequency that is higher than the currently‑set stop frequency, and if CAL = Off, then both start and stop frequency are set to the new frequency.
Stop Dist
Press this soft key to set the stop frequency in units of Hz, kHz, MHz, or GHz. If you enter a stop frequency that is lower than the currently‑set start frequency, and if CAL = On, then the stop frequency is set to the same value as the start frequency. If you enter a stop frequency that is lower than the currently‑set start frequency, and if CAL = Off, then both stop and start frequency are set to the new frequency.
Center Freq
Press this soft key to set the center frequency in units of Hz, kHz, MHz, or GHz. The center frequency can be set with the arrow keys, the rotary knob, or the number keypad. When using the number keypad, the menu displays soft keys with Hz, kHz, MHz, and GHz units. Pressing the Enter key has the same effect as pressing the MHz soft key.
Span
Press this soft key to set the span in units of Hz, kHz, MHz, or GHz. The span setting determines the frequency range over which the instrument sweeps. The span may be set from 0 (zero) to the maximum frequency of the instrument.
Gate
Press this soft key to display the Gate Menu.
Domain Setup
Press this soft key to return to the Setup Domain Menu. The message on the key face reflects the setup feature (Distance) that is in use.
 
Gate Menu
Key Sequence: Measure > Domain Selection > Gate
Gate Menu
Gate Function
Off Display On
Press this soft key to toggle the Gate Function status to Off, Display, or On.
When set to Off, the gate is not displayed on the screen nor applied to the data.
When set to Display, the gate shape is displayed on the screen but the gate filtering is not applied to the data.
When set to On, the gate shape is displayed on the screen, and the gate filtering is applied to the data.
Start Gate
Press this soft key to set the start Gate value. The values will be in units of time if the active trace is in the Time Domain, or in units of distance if the active trace is in the Distance Domain. Use the arrow keys, the rotary knob, or the number keypad to set a Gate value. When using the number keypad, the menu displays soft keys with seconds (s), milliseconds (ms), microseconds (µs), nanoseconds (ns), or picoseconds (ps), if in the Time Domain. Otherwise, it displays meters (m), centimeters (cm), or millimeters (mm) as units, if in Distance Domain. Pressing the Enter key has the same effect as pressing the seconds (s) soft key or the meter (m) soft key. If the Application Options Menu (VNA Mode) menu is used to set units in feet rather than meters, then the distance settings are in feet (ft) only, and pressing the Enter key sets the units to feet.
Stop Gate
Press this soft key to set the stop Gate in either time or distance units, depending on whether the active trace is in the Time Domain or the Distance Domain. In time domain, the units are in seconds (s), milliseconds (ms), microseconds (µs), nanoseconds (ns), or picoseconds (ps). In distance domain, the units are in meters (m), centimeters (cm), or millimeters (mm). If the Application Options Menu (VNA Mode) menu is used to set units in feet rather than meters, then the distance settings are in feet (ft) only.
This menu description is continued on the next page.
 
Gate Setup Menu (continued)
Gate Setup Menu (continued)
 
Center Gate
Press this soft key to set the center Gate in either time or distance units, depending on whether the active trace is in the Time Domain or the Distance Domain. In time domain, the units are in seconds (s), milliseconds (ms), microseconds (µs), nanoseconds (ns), or picoseconds (ps). In distance domain, the units are in meters (m), centimeters (cm), or millimeters (mm). If the Application Options Menu (VNA Mode) menu is used to set units in feet rather than meters, then the distance settings are in feet (ft) only.
Span Gate
Press this soft key to set the span Gate in either time or distance units, depending on whether the active trace is in the Time Domain or the Distance Domain. In time domain, the units are in seconds (s), milliseconds (ms), microseconds (µs), nanoseconds (ns), or picoseconds (ps). In distance domain, the units are in meters (m), centimeters (cm), or millimeters (mm). If the Application Options Menu (VNA Mode) menu is used to set units in feet rather than meters, then the distance settings are in feet (ft) only.
Gate Notch
On Off
Press this soft key to turn On or Off the Gate Notch feature. When Gate Notch is set to OFF, the polarity of the Gate is set to keep everything between start and stop. When the Gate Notch is set to ON, the polarity of the Gate is set to reject everything between start and stop.
Gate Shape
Press this soft key to open the Gate Shape Menu. The Gate Shape value is displayed on the key face, and may be Minimum, Nominal, Wide, or Maximum.
Back
Press this soft key to return to the previous menu.
 
Gate Shape Menu
Key Sequence: Measure > Domain Selection > Gate > Gate Shape
Gate Shape Menu
 
 
Minimum
Press this soft key to set the gate shape value to Minimum.
 
Nominal
Press this soft key to set the gate shape value to Nominal. The Nominal gate shape is the default value and most commonly used one.
 
Wide
Press this soft key to set the gate shape value to Wide.
 
Maximum
Press this soft key to set the gate shape value to Maximum.
 
 
 
 
Back
Press this soft key to return to the previous menu.
Note that the gate shape is analogous to the window selection. If the data are truncated with a sharp gate (minimum, related to rectangular window), then maximum resolution is used in determining the gate, but ripple is introduced in the frequency domain. For more gradual gates, the resolution decreases in separating defects, but the size of the artifacts that are added to the frequency domain data also decreases.
The window and gate shapes cannot be selected entirely independently because they interact through the transform. In particular, the use of a very sharp gate with a low side lobe window can lead to large errors. The following table shows the recommended combinations.
Window Type and Gate Shape — Recommended Combinations
Window / Gate
Minimum
Nominal
Wide
Maximum
Rectangular
OK
OK
OK
OK
Nominal
OK
OK
OK
OK
Low side lobe
 
OK
OK
OK
Minimum side lobe
 
 
OK
OK