Sonnet User's Guide - Sonnet Software

Chapter 22 Package Resonances
Below is the resulting S-parameter (S21) curve with the top cover set to free space.
Please note that while the resonance is still evident its level has been greatly attenuated.
Again, the data is from a simulation of the example project “package.son.”
The package resonances disappear when the top cover is removed.
Taking the top cover off works, provided the sidewalls of the box are large enough
to form a propagating waveguide up to the top cover, or you can place the top cover
close enough to the substrate surface to catch the fields in the box mode. High
order “box” modes tend to be confined primarily to the substrate and can be difficult
to remove in this manner. As you make the box bigger by increasing the substrate
surface area, the modes “loosen up” so that they can propagate to the top
cover and become absorbed.
The Capability to Ask: What if?
In the preceding section we mentioned some simple techniques for removing box
resonances from simulated data. But what if your package is well defined physically,
and you can’t simply take the cover off? In this situation, Sonnet can be an
invaluable tool. It allows the user to make changes to the structure and evaluate
the impact on box resonances. As noted earlier, the Box Resonance Estimator is a
great tool to judge, almost in real-time, the effect of the package size. From this
the user can gain an understanding of which dimension controls any one resonance
type (TE or TM) and may provide some insight as to the solution.
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