In some printed antenna designs, generally, the gain in the upper band is larger than the lower band. However, in some cases (in my design having printed circle on both side of the substrate like a dipole), the gain in the upper band decreases, Why?
If you are looking at the realised gain, then it depends on the matching performance of the antenna (check the reflection from the antenna port across the band). Other reasons for the gain variation could be the aperture size at each band being different. A large radiating aperture would result in a more directive radiation (more gain) compared to a smaller aperture.
Dielectric losses are higher at higher frequencies - this could be one reason for decreased gain.
another reason could be dielectric waves excited inside bulk structure and part of energy does not radiate.
third thing here - when we talk about antenna gain we have to see radiation pattern - some of energy is radiating to not maximum direction...
- Badges
- Science topic