The golden anniversary of electric wave filters

In filter technology, the synthesis techniques of Cauer and Darlington, among others, have come into wide-spread use. With the swing to higher and higher frequencies, these techniques have enabled circuit designers to obtain high performance with coils of moderate Q in L-C circuits, with quartz resonators of high Q, and with mechanical and ceramic resonators with desirable qualities somewhere between those of L-C components and of quartz.