Learning Forum

[Thiago Mello]

I would like to measure the input impedance of a dipole nanoantenna excited by a plane wave or dipole source. However, the results do not match those obtained in the articles. I would like to know if there is any practical way (for example, V = ∫E dl and I = ∫H dl) and how to implement it.

[Guilin Sun]

You are right that  V = ∫E dl and I = ∫H dl are implemented. However due to discretization and numerical error, it may have some differences with theoretical analysis.

When comparing results with other papers or experiments, there are many things to be considered carefully. Please refer to this post: 

Ansys Insight: Why my simulation result is different from published paper or experiment?

[Thiago Mello]

I forgot to reply your answer, sorry Guilin

[Thiago Mello]

Indeed, I understand that errors due to differences in implemented numerical methods may arise. My issue has been understanding how to create the voltage across the gap, as Finite Element Method (FEM), for example, has lumped ports that facilitate this process. I will attach an image of my simulated system for reference.

[Guilin Sun]

I guess you have strong background in antennas and microwaves. In FDTD simulation it is prurely optic simulation, no voltage or current is involved other than electrix and magnetic fields. FDTD is simulating the "antenna" radiation with optical signal, eg, the excitation of FDTD. 

Please refer to this example https://optics.ansys.com/hc/en-us/articles/360042041094-Quarter-wave-impedance-transformer 

Maybe a better alternative is: what result do you want to simulate? 

[Thiago Mello]

Consider that a reference article provides an impedance of 2kΩ for f=800THz. When I perform my simulation with a dipole as the source and calculate the integrals of E and H, I find something close to 40 (2kΩ/50Ω). My question is whether I should use the integrals directly or if there is some normalization, such as the output being a dimensionless value that should be multiplied by a constant.