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Open Install Example
Design Notes
Load Pull Script Example
This example shows how to use the Load Pull script. The example device u=
sed is a Curtice FET model.
Overview
At the center of simulated load pull is the load pull template. Once cre=
ated, a bias sweep can be activated by toggling on the SWPVAR block. When t=
he load pull script is run (see below) a Generalized MDIF (GMDIFD) swept lo=
ad pull file will be generated. DUTs can be easily changed in the load pull=
template by swapping out a particular FET model for the current default de=
vice (the CURTICE FET).
Simulated Load Pull is performed using two HBTUNER3 elements, allowing c=
ontrol of terminating impedances. Both use bias tees which provide DC block=
ing and bias voltage to the FET.
This project contains a power swept load pull file, LP_Data, which can b=
e used to view the functionality of the load pull measurements without a si=
mulation. In order to run bias or harmonic impedance sweeps a load pull tem=
plate will need to be created, discussed below.
Note that the output from the Load Pull is saved under "Data Files" and =
can be exported from the project to be used elsewhere.
Load Pull Script Usage
The first step in simulated load pull is to run the load pull template s=
cript available from Scripts > Load Pull > Create_Load_Pull_Templa=
te . When this is run, if no load pull template exists then a new one wi=
ll be added to the project and a dialog will pop up telling you that the lo=
ad pull template has been created. This schematic template, named Load_Pull=
_Template, is located under the Circuit Schematic node in the Project Brows=
er. The template is organized with notes to aid you in the configuration of=
desired sweeps and replacement of the default DUT.
After the configuration is complete and the DUT swapped out, the load pu=
ll simulation should be run which is accessed by choosing scripts Script=
s > Load Pull > Load_Pull . This script is interactive with the us=
er, and is used to set up the parameters of the load pull simulation.
The first dialog is used to select Load or Source Pull, and select which=
harmonics are to be pulled. The next dialog is used to set up the gamma po=
ints for the load pull simulation. Custom gamma points can be created, spec=
ifying the density and distribution across the smith chart, viewable from t=
he smith chart titled _LP_Gamma Points_.
The third dialog allows the selection of Source and Load tuners and the =
voltage and current meters used in the simulation. Set these according to y=
our load pull template configuration. Note that if no changes were made to =
the names of the tuners and meters in Load_Pull_Template then all the field=
s in this dialog will default to the correct value. From this dialog the lo=
ad pull data file produced from the load pull simulation can be named, and =
the number of harmonics stored in the data file can be chosen. After the se=
tup is complete, push the 'Simulate' button.
When the simulation is complete the new swept load pull file will be pro=
duced and appear under the Data Files node in the Project Browser.
Load_Pull_Template Schematic
This schematic shows the device load / source pull setup using HBTUNER3 =
elements along with current and voltage meters for the Gate/Base and Drain/=
Collector. A SWPVAR block is available for toggling on and off bias sweeps.=
Note that additional templates can be added to the project at any time b=
y choosing Scripts > Load Pull > Create_Load_Pull_Template .
PAE vs Output Power
This graph shows the Power Added Efficiency (PAE) plotted against the po=
wer delivered to the load (Pload). The quantities are computed directly fro=
m the LP_Data GMDIF swept Load Pull file and plotted using the PlotMD_R. Pl=
otMD_R allows for the direct visualization of real-valued quantities comput=
ed directly from an ABwave formatted GMDIF file and is available as a measu=
rement in the Data section.
The grey traces are all possible swept values of PAE vs PLOAD, whereas t=
he blue trace is tied to marker m1, located on the Contours graph (denoted =
m1@Contours in the PAE vs Output Power legend). These measurements are inhe=
rently tied together with the use of the marker, and dragging the marker to=
a different gamma point on the graph Contours will cause an update to the =
blue trace in PAE vs Output Power, which will correctly reflect the appropr=
iate value based on the gamma selection.
Input Power Level
This graph shows the power level of the input signal against its sweep i=
ndex. The point of this graph is to validate the load pull simulation power=
sweep and to allow for the creation of a marker, which is then used to upd=
ate the contours for PAE and PLOAD specified in the Contours graph.
Contours
This graph plots contours for PAE and PLoad and their respective max val=
ues, with respect to the input power level. This is achieved by tying the m=
easurements to the Input Power level graph through its marker (m1@Input Pow=
er Level). Adjusting the marker on the Input Power Level graph will cause a=
n immediate update to the contours displayed in the graph Contours.
Reference Material - Graphically Viewing Load Pull Data
Load pull data can be viewed via measurements. These measurements are fo=
und under the "Load Pull" or "Data" heading.
G_LPCM : This commonly used measurement plots the contours of the =
selected calculated value and is intended to be used with the Smith Chart. =
The data file, calculated value to plot, contour step size, max number of c=
ontours plotted, characteristic impedance and sweep reference must be speci=
fied.
G_LPCMMAX : This measurement plots the maximum value of the select=
ed calculated value and is intended to be used with the Smith Chart. The da=
ta file, calculated value to be plotted, and characteristic impedance must =
be specified along with a specified sweep reference.
G_LPGPM : This measurement allows you to view the reflection coeff=
icient (impedance/gamma) points the swept load pull data was taken at. This=
measurement is used with the Smith Chart. The characteristic impedance wit=
h which the reflection coefficients are normalized must be specified (defau=
lts to 50 ohms).
PlotMD_R : This measurement allows you to visualize a real-valued =
data from a swept load pull file. This includes calculated values, such as =
PAE, which can be selected from the measurement dialog.
Optimizer goals can be set up for this measurement to optimize on circui=
t parameters in the schematic for a desired measured data level (for exampl=
e, optimizing the parameters of a matching circuit to obtain maximum power =
added efficiency).