Creating Scenarios of Predefined Loads

HoSim allows users to create scenarios that realize sequences of predefined reflection coefficients. This is particularly useful for automating the generation of reflection coefficient sequences that evenly cover portions of the Smith chart. Such scenarios are useful, for example, for measuring Rieke diagrams of magnetrons.

The predefined reflection coefficients can be:

  • Tuner input reflection coefficients GI.

  • Reflection coefficients GR at the input of a two-port network with known S-parameters, connected at the tuner input (see topic Transforming Input Reflection Coefficient for details).

The procedure is as follows:

  • A prerequisite (one time only): Have the Tun.mem file available for the Homer with which you wish to realize the reflection coefficients. To load the Tun.mem from the Homer device, start HomSoft, connect to the Homer and download the file using the Tools|Load from Homer menu item. In the Save Dialog:

  • Select the target directory on your PC to save the Tun.mem.

  • Save as type: Any File

  • File name: Tun.mem.

  • Start HoSim.

  • In the Homer Model window, set the frequency that you expect to be generated by your magnetron under test. As a first guess, it can be the nominal frequency of this magnetron (e.g., 2460 MHz for 2M244).

  • In the System Info window:

  • Click the  Load Mem  button to load the Tun.mem of the Homer for which you wish to realize the reflection coefficients.

  • In the Homer or Tuner tab, verify that the model matches your Homer.

  • If you want to predefine reflection coefficients GR at the input of a two-port network with known S-parameters, load a file of such S-parameters and keep it activated using the items of the Homer|Transform menu.

  • In the Tuner View window, click the button to open the Scenario window.

  • In the Scenario window, click the  Cre  button or right-click the table area and select Create in the context menu to open the Create Scenario window. Please note that this button and this menu item are visible only in the HoSim simulation program. Following the click, the Create Scenario window will open (an example is shown in Fig. 52). The bottom text windows (memos) will initially be empty.

Fig. 52.  Create Scenario window.

  • Select the Trajectory. This setting controls whether the generated reflection coefficients will “move” along the rectangular axes (Rect) or along circles with increasing or decreasing radii (Circ).

  • Set the inputs determining the generation of the list of the desired reflection coefficients:

Start, Stop, Step (magnitudes),

Start Angle, Stop Angle, Rot, Clockwise, Segment, Shuttle,

Add Match.

Notes:

  • All numeric values must be integers.

  • Settings that do not apply to the selected Trajectory will be disabled.

  • Depending on these inputs, the list will represent a rectangular or circular (polar) grid in the shape of a circle, a ring, a circle segment, or a ring segment.

  • Stop magnitude can be higher than Start, lower than Start, or equal to Start.

  • Step must be a positive integer.

  • If |Stop – Start| < Step, then only Start will be considered.

  • Only for Circ trajectory: When Shuttle is checked, the trajectory will change direction at the end of each generated circle or arc.

  • The whole pattern can be rotated by Rot degrees (e.g., counter-clockwise by 30° if Rot = 30).

  • If Add Match is checked, a zero reflection coefficient will be appended at the end of the list.

  • A warning will be issued if some of the inputs are illegal; such inputs will be automatically set to their default values.

  • Click the  Create List  button. The left-hand text box (Input memo) will be filled with a list of desired reflection coefficients that will be interpreted as GI or GR (the latter if the Transform file has been loaded). The format is as in the following example:

# No  MHz       Rfl_Re   Rfl_Im

1     2455.000  -0.5000   0.0000

2     2455.000  -0.4000  -0.3000

3     2455.000  -0.4000  -0.2000

4     2455.000  -0.4000  -0.1000

5     2455.000  -0.4000   0.0000

...

81    2455.000   0.5000   0.0000

82    2455.000   0.0000   0.0000

End

  • Each numerical data row begins with a serial number (although the numbers will be, in the end, ignored).

  • The items are separated by one or more tabs or spaces.

The list will be automatically copied to the clipboard.

  • You can edit the list, and then save it to a text file by clicking the  Save List  button, or copy it to the clipboard by clicking the  List to Clipb  button.

  • Alternatively, you can create a list of arbitrary reflection coefficients with the above format by any text editor or Excel, and paste it to the left-hand Input Memo, or you can load such a list from a properly formatted file by clicking the  Load List  button. You can use the above example list as a model for your editing.

  • Generally, the frequencies for each individual reflection coefficient can differ.

  • Dwell defines the time the stubs will remain in a set position before any other action is started (e.g., a measurement or stepping to a next position).

  • Check Skip Matches if all zero reflection coefficients except the one at the very end of the list should be ignored when creating the scenario from the list.

  • Click the  Make Sce  button. A Scenario file will be created in the right-hand text box (Scenario Memo). The Scenario Memo includes the tuning stub positions needed for realizing the reflection coefficients in the Input Memo.

  • If you want to combine scenarios with different settings (e.g., to cover a certain area more densely than the others):

  • Change the inputs as required.

  • Click  Create List .

  • Click  Add Sce  button.

The new scenario will be appended to the existing one in the Scenario Memo.

You can combine more of such sub-scenarios.

  • If you wish, you can edit the info lines at the beginning of the Scenario . In Fig. 52, for instance, the original lines are:

[Scenario Info]

SceInfo = STHT V1.4/310. Transf=NO. 0 to 400 step 200 mU. Rot=0 dg.

[Page1]

After editing, they may become, for example:

[Scenario Info]

SceInfo = STHT V1.4/310. Transf=NO. 0 to 400 step 200 mU. For testing only.

[Testing]

In the above example, the edited text is shown in green. The first line (red) must remain unchanged. The third line text will be shown as the sheet title after loading the scenario in the Scenario window.

  • Click the  Save Sce  button to write the Scenario contents to a text file. The default extension is sce but you can change it to, say, txt.

  • Alternatively, click  Sce to Clipb  to copy the Scenario to Clipboard. Then you can paste it directly to an Excel file.

Creating Scenario Examples

Example 1: Combined Rectangular-Trajectory Scenario

The scenario reflection coefficients shown in Fig. 53 were created by adding three sub-scenarios. The settings used are shown in the following table:

No. 1 2 3
Trajectory Rect Rect Rect
Start 0 250 250
Stop 250 700 700
Step 50 50 25
Segment n y y
Start Angle n.a. -45 -45
Stop Angle n.a. 45 45
Clockwise n.a. y n
Shuttle n.a. n.a. n.a.
Rot 0 0 0
Add Match y y y
Skip Matches y y y

As a side effect of this combination, 12 of the total 1024 reflection coefficients are duplicate. This may not matter if the scenario is used, for instance, for Rieke diagram measurement. If necessary, the duplicate reflection coefficients can be deleted manually, thus decreasing the scenario size to 1012.

Fig. 53.  A rectangular-trajectory scenario composed of three sub-scenarios: a circle (green), a segment (red), and a complementary, denser segment (blue). The trajectory is shown only for the circle part.

Example 2: Simple Circular-Trajectory Scenario

A disadvantage of rectangular-trajectory scenarios is the regular occurence of large jumps of the reflection coefficient. To reduce the number and size of these jumps, a circular-trajectory scenario is a better choice. This is perhaps the most useful scenario.

The reflection coefficients shown in Fig. 54 were created according to the settings in the following table:

Trajectory Circ
Start 200
Stop 700
Step 100
Segment n
Start Angle n.a.
Stop Angle n.a.
Clockwise n
Shuttle n
Rot 0
Add Match n
Skip Matches y

As seen in Fig. 54, only small jumps in the reflection coefficient occur.

Fig. 54.  A simple circular-trajectory scenario.

Example 3: Combined Circular-Trajectory Scenario

The reflection coefficients shown in Fig. 55 were created by adding three sub-scenarios. The settings used are shown in the following table:

No. 1 2 3
Trajectory Circ Circ Circ
Start 0 400 700
Stop 300 700 350
Step 100 100 50
Segment n y y
Start Angle n.a. 45 45
Stop Angle n.a. -45 -45
Clockwise n n y
Shuttle n y y
Rot 0 0 0
Add Match n n y
Skip Matches y y y

As seen in Fig. 55, there are only two moderately large jumps in the reflection coefficient.

Similarly to the rectangular scenarios, some reflection coefficients are duplicate.

Fig. 55.  A circular-trajectory scenario composed of three sub-scenarios: a circle (green), a segment (red), and a complementary, denser, segment (blue).