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PSS parametric Analysis in rectifier design

SanHad

I am working on the design of an energy harvesting (rectifier) block for a passive RFID system working at 5.8GHz,as my PhD thesis. Currently I am working on a Dynamic Threshold Voltage Cancellation technique based on the paper entitled:  "High-Efficiency Differential-Drive CMOS Rectifier for UHF RFIDs", K. Kotani, et al., in IEEE JOURNAL OF SOLID-STATE CIRCUITS.

After several months of try, finally I could get a relatively correct response for rectifier PCE, using PSS analysis. As the rectifier circuit is quite nonlinear, in order to get the optimum PCE results I need to sweep the size of the mosfets, and based on another reference ("Power efficient multi-stage CMOS rectifier design for UHF RFID tags, Shu-Yi Wong", Chunhong Chen), there is actually an optimum ratio of transistors' sizes which maximizes the PCE.

Considering g= (µn*Wn)/(µp*Wp), while " µn" and " µp" are the electron and hole mobility of the NMOS and PMOS devices.


1. Now I would like to know how I can sweep this ratio as a parameter in PSS analysis. Is there a way which I can define this parameter g as a variable to sweep?

2. When I try to sweep the values of Wp and Wn seperately, it keeps getting the convergence error after a long simulation time. (Itried to change the Options but still no convergence)


I would be grateful to have your suggestions in this case.


Regards,
Sanaz

  • Andrew Beckett

    Hi Sanaz,

    I would generally advise that you use the parameters capability (variables and parameters assistant) in ADE XL to do this, which would involve setting an expression for Wn and Wp as a function of g (note that I'm assuming that rather than having a variable Wn and Wp you directly set the values of the width of the transistors on the n and p devices). Or you could just have a set of dependent expressions between your variables.

    However, I'm not sure that this is doable in this case, because there are multiple values of Wn and Wp which give the same g, so how are you going to "sweep" them? You could sweep the values of Wn/Wp as a "paramset" - both ADE L parametric analysis and ADE XL variable sweeps allow you to do this. In ADE L parametric analysis tool you specify that you want to do a paramset sweep and then list the values of the two variables and they will be swept together (rather than orthogonally). In ADE XL you can either list the values of each variable (or use one of the sweep types such as start:step:stop)) and then select both variables in the Data View assistant and Right Mouse->Group as parametric set. In both L and XL you'll need to ensure you have the same number of sweep points for both variables.

    Not sure that helps, but maybe it will point you in the right direction.

    Regards,

    Andrew.

  • SanHad
    Dear Andrew,

    Thank you for your response. I guess you are right about the multiple values of Wn and Wp which gives the same g, and at the moment I just need to find the value of g which maximizes the PCE. So the only parameter to sweep is actually the g, and when I could find the optimum ratio, then the sizes of Wn and Wp would be define later based on the load value of the circuit. But I just don't know how do I have to define this Paramset (Wn/Wp) in ADE L and then sweep it! I would be thankful for a more detailed explanation or a reference!

    Regards,
    Sanaz
  • msharma
    Hi Sanaz,

    Could you define Wn=g*Wp in your schematics, enabling you to sweep Wn/Wp=g?

    Thanks,
    Mohit
  • Andrew Beckett

    Or you could have three design variables, where two of them are an expression of g.

    Or you could use the paramset feature I mentioned. This is in the run mode of ADE L's parametric analysis tool (Tools->Parametric Analysis in ADE):

    Regards,

    Andrew

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