Filter Solutions
- Software solutions for passive, active, Tx line, IIR, and FIR filter design, synthesis, and analysis.
- http://www.filter-solutions.com

OMICRON
- Specializes in filter design software tools and consulting foractive, passive, and digital electronic filters. Description of company and presentation of the software. Download possible.
- http://www.omicronsw.com

Tyder Ltd
- Provides digital filter design software which can produce specialised filters e.g. Windowed FFT, Optimal FIR filters, and IIR filters.
- http://www.tyder.com/

Schematica Software
- Filter design software for electronics engineers and technicians. Filter Wiz for active filter design; OpFil for both passive and active filter design.
- http://www.schematica.com

FILPRO
- Microwave and RF filter and multiplexer design software. Provides detailed information about the product.
- http://www.eee.metu.edu.tr/~nyil/filpro.html

ALK Engineering
- Filter Design: Passive radio frequency filters, LC, comb-line, and interdigital. Offers two industry-standard filter design programs, and a freeware program for coil design.
- http://www.alkeng.com/