How to extract Bilateral High Frequency memory Thermal (B-HFTH) model for High Power
Amplifier (HPA). The HPA-B-HFTH model provides an excellent representation of the
effects of self-heating and HF frequency dispersion. However, it ignores memory effects due
to polarization. On the other hand, it makes it possible to take into account the changes in
load and source impedance.
An input file build from B-HFTH measurement data or B-HFTH simulation data.
See "B-HFTH measurement" or "Simulation template for B-HFTH data".
A thermal impedance file.
The basic steps for extract a B-HFTh model are:
Create a new HPA device
In an opened project, you can create a device from Applications window
or Workspace window.
From Applications window, right-click on Device modeler
and click on Create device. You can also right-click on
HPA and click on Create HPA device.
From Workspace window, click on Device modeler button,
select HPA and click on Open button then New
button.
The Create a new device dialog box is displayed. Figure: Create a new HPA device
In Type field, select HPA.
In Model field, select HPA-B-HFTH.
In Name field, edit the name of your device. Here, we will name
it "HPA_example_BHFTH".
Click on Create button to display the new device in the tree of
Applications window and the settings of the extraction in
Workspace window.Figure: Extraction Settings
Choose your data file
In the Extraction Settings
section, fill in the Data file field with the absolute or relative path
of your measurement or simulation file with the extension .dat. Click on Browser button to open the file browser and select your file in the local
file system. The file browser opens directly to the data directory specified
when creating the project.
Tune power and frequency approximation order parameters and thermal
characterization configuration
In Bilateral model
order drop-down list, choose the order corresponding to the measurement
data.
In Power approximation order and Frequency approximation order
fields, start to put low orders and checks results graphically after
extraction.
Nota Bene:
The HPA-B-HFTH model is identified from the pulsed
load-pull measurement. This corresponds roughly to a model HPA-B-HF
parametrized in temperature. The HPA-B-HFTH model is declined in several
bilateral order, ranging from 0 to 3. The greater the order, the
more the model is able to take into account strong load mismatches in the
nonlinear operating zone. It takes a minimum of 3 load impedances to be able
to identify the simplest bilateral model (Bilateral order 1), 6 impedances
for bilateral order 2 and 10 impedances for bilateral order 3.
The
power approximation order can not be greater than the number of
power points included in the data file.
The frequency approximation
can be carried out either by polynomial function or by poles-residues
decomposition. The polynomial approximation is more adapted to weakly
varying characteristics according to the frequency. Otherwise, it is
recommended to use poles-residues approximation.
The frequency
approximation order can not be greater than the number of frequency
points included in the data file. If exceeded, VISION will send a message in
the Output Console window and automatically truncate the order of
approximation to the maximum number allowed.
It is recommended to
consider a frequency approximation in poles-residues if you are interested
in the transient response of the amplifier. In this particular case, you
must also take care to consider the order of poles-residues approximation as
low as possible (do not seek a perfect fit of the frequency characteristics
by pushing the order of approximation to the maximum).
Temperature:
The Technological dispersions
option allows to specify a distribution law of the gain (module) and phase
shift characteristics of the amplifier. Two laws of dispersion are possible
(Uniform or Gaussian law). The dispersion is characterized by two
parameters: the standard deviation Module, given in % of the nominal
value for the gain, and the standard deviation Phase in degrees for
the phase shift.
The HPA-B-HFTH model accepts different types of
thermal characterization:
Dipole (single RC cell to ground): the thermal impedance is
here represented by an equivalent RC network whose value of thermal
resistance and thermal capacitance must be indicated.
Dipole (thermal impedance to ground): the extraction process
of the thermal model is based on a 3D thermal simulation followed by
order reduction techniques allowing to obtain a reduced thermal
model in the form of a dipole impedance. Thermal impedance
can be non-linear, i.e. a function of the temperature or the
dissipated power. Fill in the Thermal impedance file field
with the absolute or relative path of your file. Click on Browser button to open the file browser and select your file
in the local file system. In Thermal impedance approximation
field, set the number of poles of the approximation function.
Two-port (thermal S2P to sink): the extraction process of the
thermal model is based on a 3D thermal simulation followed by order
reduction techniques allowing to obtain a reduced thermal model in
the form of an impedance quadrupole matrix. Thermal impedance
can be non-linear, i.e. a function of the temperature or the
dissipated power. Fill in the Thermal impedance file field
with the absolute or relative path of your file. Click on Browser button to open the file browser and select your file
in the local file system. In Thermal impedance approximation
field, set the number of poles of the approximation function.
External thermal network only: it is possible to connect an
external thermal network to represent the flow of heat in the
environment.
Extract behavioral model and check with output graphs
Click on Extract button to start the extraction
process of the model. The output console is displayed:
The message Model Fit Error is showing the normalized mean square error
(NMSE) between data and model. Close the window to see in the
Applications window the number of the newly created extraction, here,
001. The results are saved and can visualized at any time by designating in the
tree the associated extraction. Click on the Output graphs tab to see
comparisons between data and model. Figure: Output graphs after B-HFTH model extraction 001
Various graphs are available to check the quality of the model according
to three dimensions: power, frequency and temperature. To examine the quality of
the approximation of the nonlinear pseudo parameter S21, select
Volterra Model HPA-B-HF [Output reflected power wave: B2] in
Figures section and choose graphs you want to display in
Graphs section:
Tick dB[S21 = B2/A1] [par=Pin, Load, Temp] to display, for
different input power, load impedances and temperatures, the modulus of
the nonlinear pseudo parameter S21 in dB as a function of
dFreq, the offset between the central frequency of the device
characterization band and the frequency of the CW signal.
Tick phase[S21 = B2/A1] [par=Pin, Load, Temp] to display, input
power, load impedances and temperatures, the phase of the nonlinear
pseudo parameter S21 in dB as a function of dFreq, the
offset between the center frequency of the device characterization band
and the frequency of the CW signal.
Tick dB[S21 = B2/A1] [par=Freq, Load, Temp] to display, for
different carrier frequencies, load impedances and temperatures, the
modulus of the nonlinear pseudo parameter S21 in dB as a function
of Pin, the power of the CW input signal.
Tick phase[S21 = B2/A1] [par=Freq, Load, Temp] to display, for
different carrier frequencies, load impedances and temperatures, the
phase of the nonlinear pseudo parameter S21 in dB as a function
of Pin, the power of the CW input signal.
Tick dB[S21 = B2/A1] [par=Freq, Load, Pin] to display, for
different carrier frequencies, load impedances and input powers, the
modulus of the nonlinear pseudo parameter S21 in dB as a function
of the Temperature in degree.
Tick phase[S21 = B2/A1] [par=Freq, Load, Pin] to display, for
different carrier frequencies, load impedances and input powers, the
phase of the nonlinear pseudo parameter S21 in dB as a function
of the Temperature in degree.
The graphs show the curves of data (from measurement or simulation) in red
lines and the extracted model in blue lines. The legend recalls the error NMSE
between model and data. If the number of curves makes the graphs unreadable,
click on Configure button to reduce the density of curves and/or limit the input
power range and frequency band. Select Volterra Model HPA-B-HF [Input
reflected power wave: B1] in Figures section to display the
nonlinear pseudo parameter S11 depending on input power, frequency
and load impedances. Select Volterra Model HPA-B-HFTH [DC power
consumption] in Figures section to display power consumption of
the device depending on input power, frequency, load impedances and temperature.
Select Volterra Model HPA-B-HFTH [Temperature] in Figure section
to display the temperature rise of the substrate for a 1 Watt power dissipation.
Figure: Output graphs after B-HFTH model extraction 001 - Filtering curves
with Graph configuration window
Check measurement aberration and noise measurement
The first extraction is an opportunity to verify the data, especially if there
is measurement noise or measurement error. This type of phenomena can make it
difficult to extract a model and can lead to aberrant results when the model is
subjected to more complex signals. VISION provides some tools to limit or
eliminate these phenomena in order to avoid doing measurements again. In
Applications window, click on your device, here
HPA_example_BHFTH, to show up Settings tab in the
Workspace window. Click on Extraction Options section to
reveal some options:
Measurement aberration and noise polish filters: for the U-HF
model, the option CW power gain aberrations is available to
filter the noise that can be encountered on the measurement data. The
user must choose the filter order appropriately.
Extraction power and frequency range tune: depending on the needs
or observations on the data, one can modify the range of input power
and/or the frequency band of the data with which the extraction of the
model can be performed.
Tune power and frequency range
If the first extraction is not satisfactory, it is necessary to increase the
order of approximation power and/or frequency.
Start by increasing the order of approximation power as long as the
error NMSE decreases significantly. Check graphically the comparison
between the data and the model.
Then, increase the order of approximation frequency as long as the error
NMSE decreases significantly. Check graphically the comparison between
the data and the model.
If the error is not small enough,
restart
in step a from the current settings
The user can find in the following table an example of the extraction process.
Here, the parameters of extraction 007 allow to have the smallest error between
the data and the model.
Table 1. Extraction settings HPA_example1
Extraction
Power approximation order
Frequency approximation order
NMSE-S11 (dB)
NMSE-S21 (dB)
001
1
1
-7.39
-6.72
002
2
1
-7.52
-6.75
003
1
2
-7.39
-6.72
004
1
3
-7.39
-6.72
005
1
4
-7.39
-6.72
006
1
5
-7.39
-6.72
007
2
5
-7.52
-6.75
008
2
6
-7.52
-6.75
009
2
7
-7.52
-6.75
010
2
8
-7.52
-6.75
011
2
9
-7.52
-6.75
012
2
10
-7.52
-6.75
Figure: Output graphs after B-HFTH model extraction 011
You can label an extraction as a reference to differentiate it from others
for use in System Architect. To do so, select the appropriate extraction of your
device in the Applications , right-click on it, and subsequently select
the add to favourites option.Figure: Add favorite button in Workspace window
Browser button to open the file browser and select your file in the local
file system. The file browser opens directly to the data directory specified
when creating the project. 
Extract button to start the extraction
process of the model. The output console is displayed:
The message Model Fit Error is showing the normalized mean square error (NMSE) between data and model. Close the window to see in the Applications window the number of the newly created extraction, here, 001. The results are saved and can visualized at any time by designating in the tree the associated extraction. Click on the Output graphs tab to see comparisons between data and model.
Configure button to reduce the density of curves and/or limit the input
power range and frequency band. Select Volterra Model HPA-B-HF [Input
reflected power wave: B1] in Figures section to display the
nonlinear pseudo parameter S11 depending on input power, frequency
and load impedances. Select Volterra Model HPA-B-HFTH [DC power
consumption] in Figures section to display power consumption of
the device depending on input power, frequency, load impedances and temperature.
Select Volterra Model HPA-B-HFTH [Temperature] in Figure section
to display the temperature rise of the substrate for a 1 Watt power dissipation.
