In this post we will take a reasonable 10 GHz bandpass filter (at least for a new grad student) and see how a new substrate will change how this filter works.

This is the original bandpass filter with the standard substrate:

If you can read the numbers on the above pic, you could also build this filter. Let’s get a better picture of what the substrate is for the original circuit:

Let’s try a silicon dielectric, shall we?

One thing is for sure – it’s not a bandpass filter anymore.

Let’s add a 20 mil Indium conductive layer below the dielectric:

Voilà! It’s centered at 8 GHz! Brilliant!

Here’s a thought – how well does your bandpass filter work underwater?

It looks like your bandpass filter might give you a little gain there at some frequencies in water!