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Operators not allowed in user-defined functions
Posted Feb 28, 2022, 5:05 a.m. EST RF & Microwave Engineering, Wave Optics, General Version 5.6 1 Reply
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Dear all,
I am trying to generate a pulse train using a step function in combination with an analytic function using a summation but it seems like the operator "sum" is not allowed and it generates the error "Operators not allowed in user-defined functions". Does anyone know how can I use the sum operator in comsol or how to define sigma notation for summation? I have used sum(expr,index,lower,upper).
STEP Location: tp from: 1 to: 0
ANALYTIC Expression: sum( S( t-(Np*(1/fr)) ) - S( t-(Np+tp) ), Np, 0, Np-1 ) arguments: t
sum(expr,index,lower,upper); operator sum as defined in comsol
Np: number of pulses fr: repetition rate tp: pulse duration
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Gabriel,
operators like sum() are only available in post processing. I am not completely sure but your question sound like you want to build a sum in a time dependent model along time while it solves. This can be done with an additional equation and the previous solution. This blog contribution may be useful: https://www.comsol.de/blogs/using-the-previous-solution-operator-in-transient-modeling/
Cheers Edgar
-------------------Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com