On numerical technique in analog filter synthesis
Philip R. Geffe · IEEE Transactions on Circuits and Systems II Analog and Digital Signal Processing · 1997
After a brief review of the accuracy problem found in filter synthesis, we describe a computer program designed to measure the precision of the product method in the s-plane (i.e. without using transformed variables). This is found to give 15 digit precision for all degrees, with possibly several units off in the least significant digit. The tests were done in double precision up to degree 60.