1. Eagle PCB – a PCB designer – http://www.cadsoftusa.com/download-eagle
2. Filter Lab – Filter designer – http://www.microchip.com/pagehandler/en_us/devtools/filterlab-filter-design-software.html
3. Filter Pro – Filter designer – http://www.ti.com/lsds/ti/analog/webench/webench-filters.page?DCMP=sva-web-filter-en&HQS=sva-web-filter-powerhouse-20140204-lp-en
4. LtSpice – Design Simulation – http://www.linear.com/designtools/software/