I made a SAW filter at university. Mostly in make-shift labs and with old gear our professor collected from industry donations of scraped stuff. We did everyth

I made a SAW filter at university. Mostly in make-shift labs and with old gear our professor collected from industry donations of scraped stuff. We did everything from design to preparing the silicon, lithography, etching and even bonding the chip so we ended up with a nice working filter in a package that is indistinguishable from a professionally made one. I still have it somewhere. The nice thing about a SAW filter is that you have to basically do all the steps you do for an integrated circuit but many steps are a little simpler. The design is pretty well doable with undergrad math (fourier transform). The lithography can be relatively low-res and you can test it pretty easily with standard electronics lab equipment.