Note The Java 1.1 applet on this page should work on the HotJava 1.1 browser, Internet Explorer 4.0 or Netscape Navigator 4.0 with the Java 1.1 upgrade patch applied. This design method allows an FIR filter to be designed to a frequency response specification consisting of an arbitrary number of passbands and stopbands, in each of which a specified amount of ripple can be tolerated. The use of normalised frequencies has the advantage that the applet is not tied to a particular sampling frequency.
Outline instructions The various filter settings are reasonably self-explanatory.
Filter type Select the appropriate radio button to specify a LP, HP, BP or BS filter. Passband Enter the normalised passband frequencies in the text boxes. In the case of a BP or BS filter, the transition bandwidth applies equally to both transition bands. This specifies how much variation is allowed in the filter gain in the passband above and below the ideal value of 1. Once the filter settings have been chosen, click the Design button to design the filter.