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Envelop simulation and time waveforms

Question asked by john82 on Mar 3, 2015
Latest reply on Mar 4, 2015 by soni123

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Hello,

I am completely new to ADS, and I am trying to use it in order to evaluate the response of an RF circuit designed by a third person.
Basically I have the design, and I have added my time domain sources which I have already configured to retrieve signals from a dataset that I have previously generated in MATLAB.
What I am trying to do, is to measure the output voltage of a power amplifier.
The data read by my time domain sources are complex baseband signals, which I have sampled with 600 MHz, and that I am feeding into an IQ modulator (tuned) to mix them at a carrier frequency of 900 MHz.

I would have found easier to run the simulation in time domain, but unfortunately a part of the circuit can deliver data just if I simulate it by the envelope.

Now my problem is that, when I simply take the part of the circuit generating the RF signal for my PA, if I try to read the baseband waverform, or also output RF signal I don´t see exactly what I would expect.

How can I get from this representation to my normal waveforms? (real signals since I and Q are feeded separately).

The second question is about the sources, I have read on the help page that the envelope simulation can use both time and frequency sources, so in this case is it alright if I am using the voltage timed source?

Any good tip will be very appreciated.

BR,
Giovanni

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john82 Mar 3, 2015 7:00 AM

Hello again,

I have found out that my problem might just be that the mixer component doesn´t work for the circuit envelope simulator.
To be preciser I am talking about the IQ_ModTuned, which is working correctly just when I do a transient simulation.

Is there any other component that I could use instead of this one inside a circuit envelope simulaiton to obtain my result?

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aehoward

@ john82 on Mar 3, 2015 8:37 AM

The IQ_ModTuned component does work with the Envelope simulator. It is intended to be used with the Envelope simulator. The input I and Q signals should be baseband, time-domain data. The should be real numbers, not complex. There is an example showing this component used to generate a 16-QAM signal: examples/Tutorial/ModSources_wrk. You can use VtDataset sources to read in I and Q data, also.

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john82 @ aehoward on Mar 3, 2015 9:31 AM

Hello aehoward,

in first place I would like to thank you for your quick answer.
Well I was just saying this because appearantly, when I simulated the output waveform I didn´t get exactly what I expected. I have tried right now to include the mixer again inside my simulation, and now I see that the signal corresponds (a part of some amplitude constant factor in the middlle....) to my signal.
The only issue is that I am using 3.3 useconds of signal, and I run the simulation exactly for this time, but I get as a result just a smaller part of what I would expect.
For instance, according to ADS the simulation end at about 260 nseconds.

When I look at the waveform and I compare it to the one I would expect, I see that the part of the signal I see is actually 500 nseconds of my original signal, but still ADS quotes the X axis in a wrong way (there is almost a factor 2 in between). In addition to that my simulation data are still not complete.

Is there something particular I should be aware of when using the circuit envelope simulation? I must say that when I was just trying the transient simulation, everything worked fine and I saw my complete waveform at the output of th IQ modulator.

On what does the end of the simulation actually depends?

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aehoward

@ john82 on Mar 3, 2015 11:25 AM

Do you or your company have a support contract? If so, it would be faster and easier if you contact our technical support team to resolve this and advise you better. Since you are using such a small simulation time step, the Envelope simulator may not offer any advantage over the Transient simulator. The Envelope simulator is useful when the simulation bandwidth (=1/simulation time step) is much smaller than the carrier frequency.

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john82 @ aehoward on Mar 4, 2015 1:05 AM

Hello,

I dont´t know anything about this, but I am going to ask around. The issue here I think is that we are a University, so I don´t really know if together with the licenses we have something like that included.
I will check during today, and I will let you know.

BR,
Giovanni

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soni123 @ john82 on May 8, 2015 9:53 PM

test

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6 Replies

john82 Mar 3, 2015 7:00 AM
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Correct Answer
Hello again,

I have found out that my problem might just be that the mixer component doesn´t work for the circuit envelope simulator.
To be preciser I am talking about the IQ_ModTuned, which is working correctly just when I do a transient simulation.

Is there any other component that I could use instead of this one inside a circuit envelope simulaiton to obtain my result?
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- aehoward @ john82 on Mar 3, 2015 8:37 AM
  Mark Correct
  Correct Answer
  The IQ_ModTuned component does work with the Envelope simulator. It is intended to be used with the Envelope simulator. The input I and Q signals should be baseband, time-domain data. The should be real numbers, not complex. There is an example showing this component used to generate a 16-QAM signal: examples/Tutorial/ModSources_wrk. You can use VtDataset sources to read in I and Q data, also.
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  - john82 @ aehoward on Mar 3, 2015 9:31 AM
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    Correct Answer
    Hello aehoward,
    
    in first place I would like to thank you for your quick answer.
    Well I was just saying this because appearantly, when I simulated the output waveform I didn´t get exactly what I expected. I have tried right now to include the mixer again inside my simulation, and now I see that the signal corresponds (a part of some amplitude constant factor in the middlle....) to my signal.
    The only issue is that I am using 3.3 useconds of signal, and I run the simulation exactly for this time, but I get as a result just a smaller part of what I would expect.
    For instance, according to ADS the simulation end at about 260 nseconds.
    
    When I look at the waveform and I compare it to the one I would expect, I see that the part of the signal I see is actually 500 nseconds of my original signal, but still ADS quotes the X axis in a wrong way (there is almost a factor 2 in between). In addition to that my simulation data are still not complete.
    
    Is there something particular I should be aware of when using the circuit envelope simulation? I must say that when I was just trying the transient simulation, everything worked fine and I saw my complete waveform at the output of th IQ modulator.
    
    On what does the end of the simulation actually depends?
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    - aehoward @ john82 on Mar 3, 2015 11:25 AM
      Mark Correct
      Correct Answer
      Do you or your company have a support contract? If so, it would be faster and easier if you contact our technical support team to resolve this and advise you better. Since you are using such a small simulation time step, the Envelope simulator may not offer any advantage over the Transient simulator. The Envelope simulator is useful when the simulation bandwidth (=1/simulation time step) is much smaller than the carrier frequency.
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      - john82 @ aehoward on Mar 4, 2015 1:05 AM
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        Hello,
        
        I dont´t know anything about this, but I am going to ask around. The issue here I think is that we are a University, so I don´t really know if together with the licenses we have something like that included.
        I will check during today, and I will let you know.
        
        BR,
        Giovanni
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- soni123 @ john82 on May 8, 2015 9:53 PM
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  test
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Envelop simulation and time waveforms

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