What I find even more mind-blowing is that GHz range frequency filters in cellphones are mechanical. They have excellent selectivity and need very little energy

What I find even more mind-blowing is that GHz range frequency filters in cellphones are mechanical. They have excellent selectivity and need very little energy. Check it out: http://www.telecomabc.com/s/saw-filter.html http://www.telecomabc.com/s/saw-filter.html