load pull with nonlinear transistor model

[neutrino]

loadpullfiles

Dear sirs,
how can i make a load pull measurement with microwave office? I have a non-linear model of HEMT and i need an automated method for extract the load pull contours. I appreciate a schematic example and equation.

regards

 

[vfone]

simulation load pull harmonic

M*W*O has a Load Pull wizard example located in Examples. Here is the text of this wizard:


Load Pull Wizard Example

This example shows how to use the Load Pull Wizard. The example device used is a Curtice FET model.

Overview

Two different load pull tuners are used, the LTUNER2 and HBTUNER2. The difference between the two is that the HBTUNER2 allows the user to control the termination impedances for the harmonics, while the LTUNER2 only allows control of the fundamental termination impedance.

Both tuners have bias tees, and the FET bias is provided through these.

There is a saved load pull state in the project that can be seen by expanding the “Wizards” section under the Proj tab and then expanding the Load Pull Wizard. The state is called “LPTuner” and can be brought up double clicking. A detailed explanation of the Load Pull Wizard usage can be found below in the “Load Pull Wizard Usage” section.

Note that the output from the Load Pull Wizard is “Data Files” that are saved in the project and can be exported.

HBTuner Load Pull Schematic

This schematic shows the device load / source pull setup using the HBTUNER2 element. The contours shown are for Total Power delivered at Port 2 and Power Added Efficiency (PAE). The “+” and “x” shown on the plot indicate the maximum values for each of the measurements.

Note that the parameters on the load tuner are setup for tuning - the effect on total power delivered and PAE can be seen by tuning these while looking at the “Total Power and Efficiency” Graph.

LTuner Load Pull Schematic

This schematic shows the device load / source pull setup using the LTUNER2 element. The contours shown are for Total Power delivered at Port 2 and Power Added Efficiency (PAE). The “+” and “x” shown on the plot indicate the maximum values for each of the measurements.

Note that the parameters on the load tuner are setup for tuning - the effect on total power delivered and PAE can be seen by tuning these while looking at the “Total Power and Efficiency” Graph.

Input Match Schematic

This schematic is used to compute large signal S11 of the device so that the source tuner can be set for maximum power transfer at 10 dBm input power during the load pull.

Total Power and Efficiency Graph

This graph shows the total power delivered to Port 2 and the PAE for both the “LTuner Load Pull” and “HBTuner Load Pull” schematics. The numbers shown are for 50 ohm source and load. The effect or tuning (or changing) the load conditions for either schematic can be seen on this plot.

Note that the results for Total Power and Power Added Efficiency are not idential for the LTuner simulation and the HBTuner schematic. This is due to the LTUNER terminating the harmonics with the specified impedance, while the HBTUNER is terminating the harmonics with a user specifed impedance (50 Ohms in this case).

Input Match Setting Graph

This graph shows the large signal S11 of the device for the drive level used in load pull (+10 dBm). Also shown is the conjugate of S11, which is used to set the source tuners on both load pull schematics. The conjugate is computed in the "Output Equations" area.

Load Pull Data Contour Graph

This graph is automatically generated when the Load Pull Wizard is used.

Load Pull Wizard Usage

Elements required for the use of Load Pull Wizard
The Load Pull Wizard uses tuner elements to tune the impedance points presented to the device at either the load and/or source side. These elements are:

· LTUNER: This is a frequency-independent, lossless, 2-port network that transforms the impedance (Z0) seen at port 2 to a user-defined impedance seen at port 1. Specifying the magnitude and angle of the reflection coefficient as well as the system reference impedance sets the user-defined impedance. It is assumed that port two of this element is loaded in the same Z0 specified for the element.

· LTUNER2: This model is identical to the LTUNER model except that a bias-tee is incorporated. A bias voltage can be applied to port 3 of this model to bias the device, therefore eliminating the need of a BIASTEE element to bias the device.

· HBTUNER: This model is identical to the LTUNER model except that it is frequency-dependent. The magnitude and angle of the reflection coefficient for the fundamental, second-harmonic, and third-harmonic frequencies can be adjusted independently.

· HBTUNER2: This model is identical to the HBTUNER model except that a bias-tee is incorporated. A bias voltage can be applied to port 3 of this model to bias the device, therefore eliminating the need of a BIASTEE element to bias the device.

These elements can be found in the Element Browser under General/Passive/Other. Please refer to the specific element help for more details about a particular element.

Project set-up
To use the Load Pull Wizard, at least one of the four mentioned tuner elements must reside in a schematic. In addition, a graph with at least one non-complex (real) measurement must be included in the project. If neither of these are in the project, a message box will appear when pressing the Wizard 'Simulate' button notifying the user of what needs to be included.

Setting up the load pull wizard simulation
Once the project has been set up as described above, the Load Pull Wizard can be started; this is done by double-left clicking the “Load Pull Wizard” icon that appears under the Wizards node in the Project View. A Smith Chart entitled “Load Pull Points” will be added to the project that shows the impedance points for Harmonic Balance simulation.

Dialog Box Settings

· Select Schematic with Tuner: This box lists all of the schematics in the project that contains a load pull tuner.

· Select Tuner: This box lists all of the load pull tuners in the selected schematic. For this version, only one tuner can be tuned during a simulation.

· Measurements Specified for Contour Plotting: This box lists all of the measurements that have been selected for contour plotting. When the Add… button is pushed, a dialog box with a list of all the real (non-complex) measurements in the project. A measurement is selected here. When the simulation runs, a tabular data file will be created and added to the project. This tabular data file contains the values of the selected measurement(s) at all of the impedance simulation points. It is recommended that this data file be given a descriptive name, since the contour plots that are created after the simulation is run will refer to this data file as the source. Multiple measurements can be added for simulation, but must be added one at a time. The Remove and Remove All buttons are used to remove measurements from the list.

· Tune Harmonic: For the LTUNER and LTUNER2 elements, only the fundamental impedances will be tuned. For the HBTUNER and HBTUNER2 elements, the fundamental, second harmonic, or third harmonic frequency impedances can be tuned. For this version, only one harmonic is allowed to be tuned during a simulation. The others will remain constant.

· Reflection Coefficient (Gamma) Points to Simulate At: There are three choices for specifying the simulation points: Pre-defined points, points from a measured Focus or Maury data file, or points from a two-column tabular data file. A minimum of three points is required for contour plotting.

· Specify Center and Radius for Points (Pre-defined points): This is the default option. For this option, a set of pre-defined points is used. The center and radius of the points is specified. In order to change the center and radius, type the appropriate values into the boxes and click “Set Center and Radius”. The center magnitude must be greater than or equal to zero, and the radius must be greater than or equal to 0.05. The density is selected by choosing Coarse, Medium, Fine, or Extra Fine.

· Use Points from Measured Data Measurement: To use this option, the project must contain a measured Focus or Maury data file, as well as a LPGPM measurement for the file. The Wizard will then simulate at the same points specified in the data file.

· Use Points from Tab Data File Measurement: To use this option, the project must contain a two-column tabular data file that specifies the real and imaginary reflection coefficient points, as well as a LPGPT measurement for the file. The Wizard will then simulate at the same points specified in the data file.

· Simulate: Pressing this button starts the simulation. During the simulation a circle appears on the Smith Chart showing which gamma point is the current simulation point.

· Close: This button closes the Wizard.

Running a Load Pull Wizard Simulation
Simulation starts when the Simulate button is pressed. The “Load Pull Points” graph will show the simulation points as well as the current simulation point. A Harmonic Balance simulation is performed at each point. The results of the simulation are stored in a data file (or data files if more than one measurement was selected for contour plotting) with the name specified by the user. After simulation is complete, the data file(s) is added to the project and a graph entitled “Load Pull Data Contour Graph” is created with the appropriate contour plots using the LPCS measurement. The user can change the default start/stop/step values of the contours by modifying the measurement after the simulation is performed.

Also, after a simulation is run, the Wizard dialog box settings will be saved. The saved state will appear as a new node below the "Load Pull Wizard" node in the "Wizards" tree.

Summary of Wizard Limitations
Only one tuner may be tuned during a simulation.
The impedance of the selected tuner (mag/angle) is the only parameter that changes during the simulation. The Wizard will only record the value at the first sweep point of the selected measurement(s) for contour plotting. Therefore, swept frequency measurements will use only the first frequency point in the list. The same is true for swept power measurements.
Only one harmonic may be tuned during a simulation. All others remain constant.
Due to the contour algorithm, a minimum of three impedance points are necessary during simulation. Also, points should not be co-linear (i.e. the impedance points used for the simulation should not be in a straight line on the Smith chart).

Load Pull Data File Detail

Reference Material - Graphically Viewing Load Pull Data
Load pull data can be viewed via measurements. These measurements are found under the “Load Pull” heading.

 LPGPM: This measurement allows you to view the reflection coefficient (impedance) points the data was taken at. This measurement is used with the Smith Chart. The characteristic impedance with which the reflection coefficients are normalized must be specified (defaults to 50 ohms).

 LPCM: This measurement plots the contours of the selected column of measured data and is intended to be used with the Smith Chart. The data file, max contour level, min contour level, step size, column of data to be plotted, and characteristic impedance must be specified.

 LPCMMAX: This measurement plots the gamma value that corresponds to the maximum value in the selected column of measured data and is intended to be used with the Smith Chart. The data file, max contour level, min contour level, step size, column of data to be plotted, and characteristic impedance must be specified.

 LPINT: This measurement allows the measured data to be used with the linear simulator. The linear simulator provides an impedance looking into a port on the specified schematic/data file/EM structure to the load pull simulator. Using the “thin plate spline” two-dimensional interpolation algorithm, the load pull simulator calculates the interpolated value of the selected measured parameter at that impedance. This measurement allows the user to have more than one port that are “input” ports (ports connected to a measured device). An example of such a circuit would be for cases where multiple devices are connected via power combiners/dividers as part of the matching network. This measurement is intended to be used with a rectangular graph. A warning is given if the data point is being extrapolated (lies outside of the measured data) and not interpolated. Note: The number of the column in the data file must be specified for this measurement. For Focus files, the first three columns are ignored - the measurement considers column four as the first measurement column. For Maury files, the first two columns are ignored.

Optimizer goals can be set up for this measurement to optimize on circuit parameters in the schematic for a desired measured data level (for example, optimizing the parameters of a matching circuit to obtain maximum power added efficiency).

Other Load Pull Measurements
There are two other load pull measurements that have not yet been mentioned: LPGPT and LPCS. These measurements are generally used with the Microwave Office Load Pull Wizard. Here is a description of the measurements:

 LPGPT: This measurement allows the user to display a custom set of reflection coefficient (impedance) points. The points must be specified in a two-column, tab delimited, text data file (.txt extension). The first column specifies the real part, while the imaginary part is specified in the second column. Comment lines can be included and must be preceded by a ‘!’ character. A Load Pull Wizard can then be simulated at these specified, custom points. The measurement is used with the Smith Chart. The characteristic impedance with which the reflection coefficients are normalized (the Z0 of the data file) must be specified (defaults to 50 ohms). An option to display the points at a different Z0 is also provided (defaults to 50 ohms).

 LPCS: This measurement plots the contours of a row-column, tabular data file. This data file is created when running a simulation using the Load Pull Wizard. The data file, max contour level, min contour level, and step size must be specified.

 LPCSMAX: This measurement plots the gamma value that corresponds to the maximum value in the selected column of measured data and is intended to be used with the Smith Chart. The data file, max contour level, min contour level, step size, column of data to be plotted, and characteristic impedance must be specified.

A graph containing a LPCS measurement is automatically generated after running a simulation using the Load Pull Wizard.

Reference Projects

For an example using multiple data files, see "Examples/Circuit Features/Load Pull/Focus_Load_Pull2.emp.”

For an example using Focus load pull files, see “Examples/Circuit Features/Load Pull/Focus_Load_Pull1.emp”

For an example using Maury load pull files, see “Examples/Circuit Features/Load Pull/Maury_Load_Pull.emp”

 

[neutrino]

hbtuner

Dear vfone,
at least one measurement must be included in the project. I haven't a measurement. I have only non linear model and the wizard required a measure.

regards.