IN3LBQ on the Hühnerspiel (Amthorspitze) - photo by IN3OTD

Bandpass filters design

Here you can find the source code of the bpfilt program, for designing narrow-band bandpass filters. You can choose between the equiripple (Tchebyscheff), maximally flat (Butterworth) and minimum loss (Cohn) types.
The output is a netlist in APLAC (once available in a free Student Version, later acquired by AWR, which in turn was acquired by National Instruments) or Spice (OPUS Spice) format.

Download the bpfilt source code.

Here is a design example of a filter for the LF band, centered at 137.7 kHz, with several types of coupling and matching.

Here is another design example, comparing the Cohn, Tchebyscheff and Butterworth filter types.