{"id":829,"date":"2016-03-05T22:29:45","date_gmt":"2016-03-05T21:29:45","guid":{"rendered":"http:\/\/axotron.se\/blog\/?p=829"},"modified":"2016-05-04T19:36:01","modified_gmt":"2016-05-04T18:36:01","slug":"tool-for-designing-butterworth-and-chebyshev-filters","status":"publish","type":"post","link":"https:\/\/axotron.se\/blog\/tool-for-designing-butterworth-and-chebyshev-filters\/","title":{"rendered":"Tool for designing Butterworth and Chebyshev filters"},"content":{"rendered":"

Designing passive LC-filters typically involves looking up prototype filter component values in a table in reference books like “Handbook of Filter Synthesis<\/em>” by Zverev<\/a> or “Design of Microwave Filters, Impedance-Matching Networks, and Coupling Structures<\/em>” by Matthaei et. al.<\/a>, then transforming the values to produce a filter with the desired impedance and cut-off frequency. This can be a bit tedious and error prone, so when I found out about the classic Matthaei book, which is downloadable via the link above, and that it contains the math required to calculate the prototype filter component value tables, I set out to create a spreadsheet to help with the filter design.<\/p>\n

In addition to calculating the (previously) magical prototype tables for Butterworth and Chebyshev (with user-specified pass-band ripple) filters, the spreadsheet also performs the frequency and impedance transformation for filters of orders from 1 to 10.<\/p>\n

To make the design process even quicker and better, I added a feature to create LTSpice<\/a> schematics of the selected filter so that the filter properties can be simulated (and perhaps manually adapted to standard component values and to include parasitics) using LTSpice. I used the SI prefix formatting function I wrote about in the previous blog post<\/a> to write out the component values in a pretty manner.<\/p>\n

The usage of the spreadsheet should be fairly self-explanatory, but there are also usage instructions on the first tab. Basically, the user should fill out the values in yellow cells and leave the rest alone. I did not lock any cells, since I often get annoyed by spreadsheets with locked cells and I encourage others to modify and improve it.<\/p>\n

Here is a link to the Excel 2002 file:<\/p>\n

\"[Excel]\" FilterSynthesis_v1.0.xls<\/a><\/p>\n

Make sure that macros are enabled if you want to use the LTSpice export features.<\/p>\n

Here are some screenshots<\/h3>\n
\"Butterworth<\/a>
Butterworth tab<\/figcaption><\/figure>\n
\"LTSpice<\/a>
LTSpice simulation of a Butterworth schematic generated by the spreadsheet.<\/figcaption><\/figure>\n
\"Chebyshev<\/a>
Chebyshev tab<\/figcaption><\/figure>\n
\"LTSpice<\/a>
LTSpice simulation of a Chebyshev schematic generated by the spreadsheet.<\/figcaption><\/figure>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Designing passive LC-filters typically involves looking up prototype filter component values in a table in reference books like “Handbook of Filter Synthesis” by Zverev or “Design of Microwave Filters, Impedance-Matching Networks, and Coupling Structures” by Matthaei et. al., then transforming the values to produce a filter with the desired impedance and cut-off frequency. This can … Continue reading Tool for designing Butterworth and Chebyshev filters<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,12],"tags":[],"class_list":["post-829","post","type-post","status-publish","format-standard","hentry","category-electronics","category-pc"],"_links":{"self":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/829","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/comments?post=829"}],"version-history":[{"count":4,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/829\/revisions"}],"predecessor-version":[{"id":867,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/829\/revisions\/867"}],"wp:attachment":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/media?parent=829"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/categories?post=829"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/tags?post=829"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}