Simulation: NPR Test Simulation

So during my time at work today (yes I worked on Saturday), I made an attempt to try and simulate an NPR test for an amplifier in Agilent's EESof/ADS.  Now there is a way to accomplish this using the DSP portion along with the Analog Envelope technique but I haven't found a way to do it directly with the RF/Analog system.  This is quite the disappointment...

Figure 1: NPR Test Stimulus (courtesy Agilent)

So I have been researching into solutions.  Only one has presented itself up to this point: Spectral Balance Simulations.  Unfortunately, ADS doesn't support this directly (at least not to my knowledge).  This is different than the typical Harmonic Balance Simulation most people are used to.  In fact the main difference is that the Spectral Balance simulation stays in frequency domain.  The Harmonic Balance simulation instead does a transient analysis then an FFT to complete the simulation (Of course it's more complex than this).


So how do I get around it?  I really have no idea right now.  The fact is, this is a known issue.  Why hasn't someone developed this into the more popular SPICE simulations?  There are random Matlab tools that can do the trick but not directly in SPICE packages.


Anyways, that's my rant for the day.  I'll go into more detail, hopefully, at a later date.


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Justin Coulston
justin.coulston@gmail.com

Simulation: Netlist Template

I have spent the last 2 days trying to figure out how to generalize the process of subcircuits for the SPICE software.  I've gone through a few design possibilities and finally came to the conclusion that simple netlist style templates will work perfectly.

So instead of reinventing the wheel, I'll use the classic technique of netlisting.  I will end up using a different netlist for different simulation types.

Example:
The capacitor companion model for a ...

Transient Analysis: Consists of a resistor in parallel with a current source.
DC Analysis: Consists of either a perfect open or very high value resistor (> 1 Gigaohm)
Small Signal or AC Analysis: Consists of a resistor with equation R = 1/(2*pi*f*C)

So I'll have different models for different simulation types as you can see.  The biggest question will be how to define the equations for the individual parameters.  How should I implement these into classes inside the program?  Creating text file models is the easy task.  It's a little more difficult to implement into Classes.

That's the extent of where I am currently.

--------------------
Justin Coulston
justin.coulston@gmail.com