UWB antenna with pulse Excitation in HFSS

I would like to measure power absorbed into a lossy dielectric illuminated by a UWB pulse-excited antenna vs a lumped port excited antenna.

Is it possible to simulate a UWB antenna in HFSS with a pulse (or Gaussian Beam) excitation? Say I have a UWB microstrip antenna that was designed using a waveport. Now I would like to excite it with a pulse, is this possible in HFSS, or I would have to do this in a FDTD solver or HFSS transient?


Thanks.

hi
may be i didn't get your mean .if u want to lossy dielectric in front of antenna when antenna radiation a Gaussian pulse ?
if u want do like this u can simulated antenna separately and then define a new source for lossy material with Gaussian pulse and loading of the first antenna and then indicated it into the lossy material

ferdows,
Yes. I want to simulate a UWB antenna with a Gaussian pulse in front of a lossy dielectric. Please elaborate on how I can define a new source and load it with the first antenna that was simulated separately.

Thanks.

The question is fundamentally a time domain question, however you can indeed use the frequency domain solver to determine to total power loss of a temporal pulse. To do this you will need to take Fourier transform of the time domain pulse so that you know the power spectral density function (nice thing is that the FT of gaussian is a Gaussian ;)). This PSD function can then be entered as a piecewise linear data set into HFSS as the excitation value (HFSS -> Fields -> Edit Sources) so that the magnitude of excitation is a function of frequency. Then you run a discrete sweep of all the frequencies of interest and add the power loss for each frequency as determined from a volume loss density integration of the dielectric in the field calculator with the correctly weighted spectral amplitudes. Make sure you solve with Driven Modal so that the units work out well for the input of the PSD.

Have Fun

Thank you, tallface. This is really good info. I think I am getting close to something here. Now, I understand the part about the discrete sweep and the part about the volume loss density, but the part about the PSD is what I don't have experience with. First, I don't know how to find the FFT of the time domain pulse. Is their an equation for the time domain pulse that I would plug in matlab and find its fft there? Then take that psd function from matlab and plug it in the Edit Sources magnitude section in HFSS? If that's the case what is the equation of the time domain pulse? Is it a Gaussian beam? Also, isn't there a Gaussian beam excitation source under HFSS? Why can't I use this as source for my antenna? Or is this more like an incident plane wave that cannot excite an antenna structure?

Thanks a lot and sorry for all these questions at once.

Be careful not to mix up your Gaussians ;) A Gaussian temporal pulse, as in your antenna, involves an antenna whose excitation voltage is a gaussian function in time. If you fourier transform this gaussian function of time and multiply the resulting function by its complex conjugate, you will have the power spectral density (W/Hz) which will also be Gaussian as the Fourier Transform of a Gaussian function results in a gaussian function. The gaussian beam in HFSS is an excitation that has a Gaussian spatial distribution of amplitude. The Gaussian beam in HFSS will diffract from the beam waist the same as a laser that is running in the fundamental Gaussian mode.

As for how to take a Fourier Transform... you will need to look that up. Many resources available for that and basically a very good transform to know and understand ;)

Have Fun

Would it not be simpler to just use the time-domain solver in HFSS, which I believe does not require an additional license fee?

I get the feeling the time domain solver in HFSS might be a bit of an afterthought, as I've been on 3 HFSS courses by Ansys and not one of them has covered the time-domain solver. It seems it gets little coverage, which makes me wonder if it just added so companies like Agilent, CST, FEKO etc can't say their tools have capabilities that HFSS does not.

I'm interested in the views of someone who clearly knows a lot about HFSS. Why don't you suggest the use of the time-domain solver?

Deborah

The HFSS Time Domain solver would work very well for this ;) For commercial industry it seems that it is indeed an extra license to purchase. However, if I remember right from university, it comes with the academic license at no extra cost. The OP made mention of HFSS Transient, but I interpreted the question as whether they could use HFSS frequency domain, but if he/she has it, then I would have preference to use it.

Have Fun

I am tempted to use HFSS transient, but there is very little documentation, tutorials, etc....about it...plus it uses Discontinuous Galerkin Time Domain (DGTD) as opposed to the popular FDTD.

If anyone has project examples, please attach. Also, tallface, if you have an example of how to simulate a Gaussian temporal pulse in HFSS, please attach file.
So, I take it the Gaussian beam in HFSS is different from the Gaussian pulse. I think I can figure the Gaussian FT, but how do I enter the psd function as a piecewise linear data set into the magnitude of excitation under Edit sources? Is there a specific standard used for frequency variable, like the letter 'f'? An example would be appreciated.

Thanks.