ABSTRACT
There are numerous techniques for designing filters. Some are based upon formal methods using numerical analysis; many others are based upon individual process, rules of thumb, and trial and error. This chapter provides technical discussion and analysis, including techniques that may be employed in the design of electromagnetic interference (EMI) filters that reduce conducted interference. The design of any EMI filter must start with a formal requirements specification such as MIL-STD-461, DO-160, or some other requirement such as CISPR. There are several methods to use in designing an EMI filter, and they all have their own merits and weaknesses. The chapter covers intermediate testing and assumes prefilter design test and assessment of harmonic composition. EMI filters are often designed for low-output impedance compared to that of the load, or to meet the needs of incremental negative resistance, and for that reason, a 50-ohm filter is often not practical.
