Survey [special filter issue]

The special filter issue (consisting of 25 tutorial, state of the art, and summary papers) aims systematically at converting filtering for EMC from an art into a science. In contrast to conventional filtering, operating under well defined simple premises, filtering for EMC often requires a broad perspective for lack of normally occurring constraints. The first part, pertaining to filtering conditions where the power spectra of signal and noise are clearly separable, is divided into two major groups: 1) impedance matched filtering (microwave, active analog, and digital filters); and 2) power-line filters operating under strong bias and having severe interfacial mismatch (juxtaposing the various solutions of handling and measuring such common situations). The second part deals with filter conditions for which the power spectra of signal and 'noise' overlap. It treats three groups: 1) directional filters (specifically using helicon waves); 2) principles of frequency-selective limiters; and 3) correlation technique and signal design (four papers deviating from the conventional premise of white Gaussian noise).