Practical Filter Design (2)

56 EE February 1989 PRACTICAL FILTER DESIGN (2) by H. Baggott Each filter has its own typical properties and these can be laid down in a few parameters. The second part of this series explains what these parameters are and what they mean There are a number of parameters that characterize the properties of a filter. One of these is the frequency response characteristic or curve. The designer, having drawn up a target specification for the ripple in the pass-band and the slope of the filter skirt, will have to make a choice from several possibilities. The type of filter, whether it is a high-pass or band-pass, and so on, is not of import- ance at this stage. Any type of filter can be converted into a standard low-pass with a cut-off fre- quency of 1 Hz. The target requirements must be translated into a normalized low-pass filter specification. After that, they may be compared with available standard curves with a 1 Hz cut-off point. After a choice has been made, the re- quired filte...