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Immediately, the plot traces and attributes dialog appears, and it always does this for
any plot or list. Notice the contents of Circuit Envelope. We have both frequency and time,
and we saw that in the list. It also has this mix table, which is a list of indexes for
the frequency points. There’s our source, V-in and V-out. These are the two wire labels
or nodes. So, I’m going to select V-out once again, and we add it. Immediately, you’re
prompted for how you want to handle the data. Spectrum, baseband, let’s select the magnitude
of the carrier and the time-domain and click “Okay.” And what we get is the magnitude
of our pulsed RF signal, and that’s what you’d expect, over the 80 nanoseconds of
time.
I’ll make this a little bit bigger. And now, we’re going to double-click once again,
select our V-out data, and use this “Advanced” button, and run this function on it, “TS”
for our transform time series. And I’ll put V-out in parenthesis; so we have our function
and our argument. Click “Okay,” again, and now you can see that the envelope contains
what we would expect, which is our pulsed RF source signal injected in and then amplified.
And to prove this, I’m going to add the V-in data.
Once again, V-in, and I want the magnitude, and I’ll click “Okay.” And here we have
our V-in and our V-out magnitude. So, we have the gain from the amplifier, and you could
imagine that if we had to do a time-domain analysis at every point to replicate this
pulsed RF signal, it would take a lot of time.
Now that we’ve covered the basics of Circuit Envelope, I want to show you an example where
other modulated sources are used. Here in the examples directory you can see that this
project here, which is the mod-sources project in the tutorial folder, has a lot of different
sources. We’re going to use this one down here. It’s the Pi/4-DQPSK, and it has both
the design and the data display. So, let’s open it up right now.
As you can see, there’s a lot of information here and a lot of settings that we couldn’t
possibly cover in this short video. But, basically, we have a carrier, we have a pseudo-random
bit stream, and that’s fed into a modulator. All of these are ADS components, including
this raised-cosine filter. And again, this is the Pi/4-DQPSK modulation format that we’re
looking at here. We have our wire label V-load, that’s our output node, and then we have
our envelope set-up. Now, if we look closely at the set-up, it corresponds to the modulation
format.
The source carrier is set to a variable RF freq, and you can see that right here, 850-megahertz.
We only need to look at the carrier so the order is one, and that takes care of our frequency
for envelope. For our time settings, the stop and the step, that’s also done with variables,
and that’s because of our modulation format. And you can see that we have the symbol rate
here, and then this samples per symbol, and that’s how we get our time-step.
This measurement equation here, V-load fund, is what we’ll use to plot the output data.
Let me show you what that looks like in the Data Display. And here’s our data. We have
the spectrum – it’s done using the V-load fund equation from schematc – a trajectory
diagram, even an Eye-diagram done with equations, and ACPR upper and lower channel measurements
done with equations. And you can copy and paste these equations into your own data display
in your own projects, so you don’t have to recreate them.
In addition, there’s another page of power calculations that you can see here; envelope
power over time, and even a distribution here. And thinking back to the set-up and schematic,
labeling this V-load and simply creating an equation here, a measurement equation, we’re
able to create all the data using ADS functions in the Data Display for this Pi/4-DQPSK modulation
and circuit envelope.
So, in review, we covered the basic set-up for Circuit Envelope, which includes the frequency
and the time settings, which correspond to our time-domain or modulated source. That’s
always very important. And we saw the data plotted, typically, in the time domain, or
you can look at the spectrum. And that concludes our short video on Circuit Envelop simulation
in ADS.