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Yeah, I would like to show you here, I’m standing in front the MMIC design flow booth
at MTT 2009, and I would like to show you one of the demos here on extracting X-parameters
from simulation. Now, this product is coming in August, in two months, and the benefits
of it is once you extract X-parameters from simulation you can send the extracted model
to the system integrator and the system integrator takes this file and simulates it, speeds up
the design cycle, and will be able to do trade-off analysis at the whole system level with those
models that are very fast to simulate. The IC design house who makes these models have
IP protected files, so they don’t have to disclose or show their actual design, but
the X-parameter file is the mean to send it to the system integrator.
And, on top of that, is that the extracted model of the nonlinear amp has high accuracy,
it replicates the actual amplifier or the circuit being given to the system integrator.
So the system integrator basically is having, like when they have the model it’s like
having the actual circuit with them. Let me show you a demo of this extractor, which is
coming up in a month, in ADS 2009 Update 1.
So, what is shown here is a PA amp, power amplifier design, that it’s a two stage
PA design that I want to create an X-parameter model to send to the system integrator. So,
if you look at the PA and look inside it’s a circuit level design. So, you can see this
is the output, FET, that’s the device, it has feedback, it has all the elements that’s
coming from a design kit, foundry design kit. And you can see the other elements, the first
FET, the input, matching network, the interstage matching network. So, it’s an actual design
that I would like to make an X-parameter model of.
All I have to do, I put the X-parameter controller that I can put the frequency and the order
of harmonics, I put the XP source, X-parameter source, in that source, if you double click,
you can do the power sweep. In this experiment, I’m doing it from -40 dBm to plus 10 dBm,
you know, sweeping the power. So, all these parameters are inputted in this page and the
load, in this demo, I am extracting the load at 50 ohm, it’s a 50 ohm load. But in this
product you can actually specify the gamma and the phase, and you can specify load-pull
contours for power delivery and also the power added efficiency by specifying the value of
the gamma from zero to one to cover the whole Smith chart and also cover the angle from
0 to 360 degrees. So, you can get a model that works all over the Smith chart with any
load.
Let me show you how this works. So, here’s my circuit, all I have to do right now is
just click on simulate and it will extract the model. So, I hit the simulate button and
it will take about 10 to 12 seconds to generate the model. Okay, so it took 15 seconds to
generate the model, now I want to show you how it works.
I built a schematic here as you see, and I inserted the model inside that schematic.
So, when I simulate that model it will show me the nonlinear characteristics of the model.
So, notice here, this is the results of the model. Notice here this is the fundamental
and this is the phase, the second harmonic and this is the phase, this is the third harmonic
and this is the phase. But now you might ask me how accurate is this? How does it compare
with the actual circuit?
So, what I did is I simulated the actual circuit, and I overlaid the two together to see how
accurate it is. Notice here
if you zoom the camera on the screen, you will see the two traces, the red and the blue.
The blue one is the power amplifier, the circuit design, and the red one is the model. If you
zoom on it you can see how close and how accurate the model to the circuit design. This is the
beauty, this is the benefits of X-parameter modeling. It gives you the magnitude, the
phase at all the harmonics, it allows you to cascade components with mismatches, and
it will characterize all this.
You can sweep the voltage, you can sweep the power, if you want to also sweep the temperature.
The nature of the MDF file, the multidimensional file of the model allows you to sweep any
parameter you want, and it will give you that model.
Here, one more thing I would like to show you. This is another extraction that we did with
gamma equal to 0.5 and the phase angle, we swept it from 0 to 360 degrees. So, you can
see now within that region, this is the load-pull measurements of the power amplifier and of
the model. So, you can see how close it is. This means that you can use this amplifier
to design, to cascade, to do any kind of simulation and analysis within that region with full
accuracy.
So, basically what I’m saying here, before we generated the model at 50 ohms, now we’re
generating the model with a bigger region in the Smith chart. So, you can go all over
the Smith chart too.