Microstrip Stub Filters -- Part 1

[@BalticLab]

Great video, thanks for sharing it publicly!

[@chasepe5762]

Can these microstrip filters be applied to +/-5v 0khz to 20khz range audio signals with minimum phase change?

[@thomasschneider6012]

I don't think so, because those types of filters only work if the wavelength (lamda) of the signals approach the dimensions of the elements/conductors ( for example lambda/4 stubs etc.)
A 20kHz signal would have a wavelength of c/f = 15 kilometers ! (in vacuum).
On a conductor the wavelength is a bit different, but still way too big to realize such a Microstrip filter for audio, unless you're willing to build such a big PCB... ;)

[@chasepe5762]

@@thomasschneider6012 thanks for the response! Maybe some day in the future it can be engineered

[@davidbrooks8621]

For audio, just use op. amp. with capacitors and resistors like everyone is doing. It is even smaller than 50GHz microstrip filter. Google for Sallen-Key filters

[@chasepe5762]

@@davidbrooks8621 the problem with capacitors in audio filters is the introduction of signal phase shifting, delay, and distortion at the filter cut off point.

[@davidbrooks8621]

@@chasepe5762 Every analog filter design with capacitors or inductors has the problem you mentioned. Use it first with wider bandwidth and then use a DSP and symmetric FIR filter and the job is done. Any way all the stuff with microstrips is for microwave frequency and not audio freq.