Complex E-field magnitude for time domain visualisation

How to use openEMS. Discussion on examples, tutorials etc

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_neil_
Posts: 18
Joined: Sun 06 Feb 2022, 23:07

Complex E-field magnitude for time domain visualisation

Post by _neil_ » Thu 21 Apr 2022, 13:06

open EMS is a fantastic tool for e/m simulation that i'm just getting to grips with. I've had great success visualising propagating E-fields in the time domain. The oscillatory nature of the wave in space is clear from the results.

However, for an easier interpretation of the propagation of waves, could the complex E-field of a wave be generated. This then enables the magnitude of the complex E-field to be displayed in space. This is effectively the envelope of the E-field oscillation and viewing this would make interpretation of results easier.

In particular, if the simulation does not extend down to DC, ie the simulation is for a RF bandpass system, then is not the time domain complex? This is how it is with a VNA measurement, and that is what i'm comparing simulations to. In that case, does openEMS then not have the possibility to create the complex time domain response?

I realise the imaginary part of the E-field could be constructed from the Hilbert transform of the generated E-field, this then enabling the magnitude to be constructed. However, is there a direct way of extracting the complex field or the magnitude directly from the simulation?

many thanks, N

_neil_
Posts: 18
Joined: Sun 06 Feb 2022, 23:07

Re: Complex E-field magnitude for time domain visualisation

Post by _neil_ » Thu 19 May 2022, 10:13

If you use the Octave/Matlab 'hilbert' routine on the real time-domain electric field, this then adds the Hilbert Transform of the real signal into the imaginary part, so creating a complex version of the time-domain signal. This then represents the so-called 'Analytic Signal' of the time-domain response. From this you can use the routine 'abs' or 'angle' to create respectively the magnitude of the electric field (effectively the envelope of the time-domain signal) and the phase. These are also referred to as the 'instantaneous amplitude and the 'instantaneous' phase. This seems to work well and was what i was looking for.
BW, N

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