The Gain Compression button availability and access to the underlying GAIN COMPRESS menu depends on the Sweep Type set as described below. In addition, there are two GAIN COMPRESS menu variants described here as the GAIN COMPRESS Self Normalization menu and the GAIN COMPRESS Compress Param menu. The conditions for each is described immediately below.
Types of Gain Compression
The GAIN COMPRESS. (GAIN COMPRESSION) menu provides control of all gain compression parameters. Two menu variants are available depending on the power sweep type selected.
• CW Frequency Gain Compression – The CW Frequency gain compression is a trace function in power sweep CW mode and separate compression points can be set for each trace display. The trace labels are changed with an @CP notation after the measured S-Parameter. Typical trace labels are shown below:
• Without Gain Compression: Tr1 S21 Trans LogM
• With Gain Compression: Tr1 S21@CP Trans LogM
• Swept Frequency Gain Compression – The Swept Frequency gain compression is also a trace function in power sweep swept-frequency mode, and by default, the displays shows the output power verses frequency at the gain compression point. The compression parameter is set to S21 and the plotting parameter set to B2/1 (B2 divided by 1). The trace labels also change with the @CP notation as described above
Gain Compression Button Not Available
If the Gain Compression button on the DISPLAY menu is not available, Sweep Types is set to one of the following:
To make the Gain Compression button on the DISPLAY menu and GAIN COMPRESS menu available, Sweep Types on the SWEEP SETUP menu must be set to Power (CW Freq) or Power (Swept Freq). Each setting enables a different menu variant which are described in the sections below.
GAIN COMPRESS Self Normalization Menu
If Sweep Type is set to Power (CW Freq), the GAIN COMPRESS. menu is termed the GAIN COMPRESS. Self Normalization) menu, has six (6) buttons, and the top button is Self Normalization.
If Sweep Type is set to Power (Swept Freq), the GAIN COMPRESS. menu is termed the GAIN COMPRESS. Compress Param menu, has six (6) buttons, and the top button is Compression Param.
The appearance and button availability of the GAIN COMPRESS menu depends on settings on the SWEEPTYPES menu. Consult the Gain Compression Menus and Dialog Boxes section above for menu identification and prerequisites.
Prerequisites
• On the SWEEP TYPES menu, Sweep Type is set to Power (CW Freq).
Select toggles the self normalization function OFF and ON. If ON, self normalization normalizes the trace display reference to the first data point of each sweep.
Compression Indicator (Off/On)
Select toggles the screen trace display compression indicators between OFF and ON. If the Compression Indicator is toggled ON, and the instrument finds the compression points, the general display is R and C where:
• The reference point indicator is labeled R
• The gain compression indicator is labeled C with parametric data displayed at the top of the trace window
• The Trace Label is identified with the @CP label after the Measurement Type such as Tr3 S21@CP Trans LogM.
Reference (R) Indicator
If the instrument cannot find the reference points, the RandClabels will not be displayed and will instead display the following messages:
• C: Not Found in the graph display area
• Invalid Reference Value in the display status bar
Compression Reference Point
If the compression reference is set to maximum gain, the instrument will always find the reference point. The instrument may not be able to find the reference point if:
• The compression points are outside the range setting
• The Hold Power setting is outside of the X-axis range on the trace display graph
• The P-in setting is outside of the X-axis range on the trace display graph
Compression (C) Indicator
If the instrument cannot find the compression points, the C label will not be displayed and will instead display the message C: Not Found in the graph display area.
DUT or Compression Point Value
The instrument may not be able to find the compression point because of the characteristics of the DUT or because of compression point value.
Compression Reference Button Selection Group
The Max P Out, Hold Power, and P in buttons of the Compression Reference area form a three-button selection group where the selection of one button de-selects the other two (2) buttons.
Max P Out
Select sets the maximum power output available to the instrument.
Hold Power (-XX dBm)
Read-only display. Shows the hold power level on a per-system basis. It defaults to the lowest port source power of -20 dBm. The Hold Power Level is set on the HOLD CONDITIONS menu.
• The appearance and button availability of the GAIN COMPRESS menu depends on settings on the SWEEP TYPES menu. Consult the section above for menu identification and prerequisites.
• MAIN | Display | DISPLAY | Gain Compression | GAIN COMPRESS. Compression Param.
GAIN COMPRESS. Compression Param. Menu
Display Example
For a sample display, see Figure: Gain Compression Display with Power Sweep below. When Gain Compression is on, the Trace Label is identified with the @CP label after the Measurement Type such as Tr3 S21@CP Trans LogM.
Compression Param
Select displays the COMP PARAM (Compression Parameter) menu which allows the user to select which S-Parameter (S11, S12, S21, S22) is to be used.
The three (3) buttons of the Compression Reference area form a button selection group where the selection of any one button de-selects the other two (2) buttons.
Max Gain
Select sets the maximum gain output available to the instrument.
Hold Power (-XX dBm)
Read-only display. Shows the hold power level on a per-system basis. It defaults to the lowest port source power of -20 dBm. The hold power level is set on the Hold Conditions menu.
• MAIN | Display | DISPLAY | Gain Compression | GAIN COMPRESS. Compression Param | Compression Param | COMP. PARAM
Auto-Return Button Selection Group
The COMP. PARAM menu buttons form an auto-return button selection group where selection of one button de-selects all other buttons and then auto-returns to the GAIN COMPRESS menu.
COMP. PARAM (COMPRESSION PARAMETER) Menu
S11 (Comp Param)
Select sets the compression parameter to S11 - Forward Reflection and auto-returns to the GAIN COMPRESS. menu.
