Hello,

I'm trying to simulate a microstrip ring resonator using an FDTD simulation. In order to achieve the desired result (I have the real measures of the circuit) I've build a dense grid to include all the details of the circuit to approach as much as possible to the real measure. The problem is that the S-parameter graph obtained with the simulation has very few points. The resonator frequencies are correct (2 GHz and 4 GHz) but the graph looks horrible with such few points.

I tried to change all FTDT simulation options but there is no way to set the number of points that will appear on the graph, however, I realised that the number of points has a relationship with the timestep parameter. When the timestep decreases, the frequency range between points increases. The timestep parameter depends on the size of the smallest cell of the grid, so the only way I've found to increase the number of points of the graph is decreasing the cell size and loosing a little bit of precision.

The frequency range I'm evaluating is from 1GHz to 5GHz and the smallest cell size is 0.1x 0.1 x0.017 mm.

Is it possible to decrease the frequency range between points without changing the cell size?

Thanks all!

Sergi

I'm trying to simulate a microstrip ring resonator using an FDTD simulation. In order to achieve the desired result (I have the real measures of the circuit) I've build a dense grid to include all the details of the circuit to approach as much as possible to the real measure. The problem is that the S-parameter graph obtained with the simulation has very few points. The resonator frequencies are correct (2 GHz and 4 GHz) but the graph looks horrible with such few points.

I tried to change all FTDT simulation options but there is no way to set the number of points that will appear on the graph, however, I realised that the number of points has a relationship with the timestep parameter. When the timestep decreases, the frequency range between points increases. The timestep parameter depends on the size of the smallest cell of the grid, so the only way I've found to increase the number of points of the graph is decreasing the cell size and loosing a little bit of precision.

The frequency range I'm evaluating is from 1GHz to 5GHz and the smallest cell size is 0.1x 0.1 x0.017 mm.

Is it possible to decrease the frequency range between points without changing the cell size?

Thanks all!

Sergi

When you are creating a graph from the Results page, one of the options you'll see in the setup dialog box is "FFT size". This controls the sampling of the time domain data that is being converted to frequency domain data. Try increasing this until you get the frequency resolution you want. Note that you don't want to set it too high because it will take longer to create the plot, and you may get oversampling. I believe the default is 15 (meaning 2^15 samples). Try increasing this to 18 and see if that improves your plot.

Hope this helps,

Marc