This is a graphics-intensive bandpass filter design and analysis program based on the helical resonator.

Here are the highlights of this program:
The program designs bandpass filters with a selection of the order from 2 to 12, odd or even.

Center frequency, bandwidth, and passband ripple are all adjustable. The ripple value may be set to zero for a Butterworth response.

The dimensions of the individual resonators are set by specifying an impedance value. Then the actual terminating impedances are separately chosen.

Analysis is based on an equivalent circuit using capacitive input, interstage and output coupling.

Analysis is delivered in both tabular and graphical form and includes transmission, return loss, phase, envelope delay and input impedance with its angle.

The dimensions of the resonator(s) delivered by the program are shown in graphical form.

Updated to 2.05 – added note “Dimensions are in inches”
Updated to 2.04 – corrected failure to use correct value of Q for inductors in analysis via equivalent circuit
Updated to 2.03 – show unloaded resonator Q values, both round and square chambers

References:

The ARRL Handbook For Radio Communications
Published by ARRL
ISBN numbers for 2011 edition:
ISBN 978-0-87259-095-3 (softcover)
ISBN 978-0-87259-096-0 (hardcover)

Coaxial Resonators with Helical Inner Conductor
W. W. Macalpine
Proceedings of the I.R.E., December 1959

Need A Helical Filter?
Lee R. Watkins
RF Design, May/June 1981

Realization of a Filter With Helical Components
A. I. Zverev and H. J. Blinchikoff
I.R.E. Transactions on Component Parts
Volume CP8, September 1961

Design Of A New, Low-Cost Helical-Resonator Filter
Solomon I. Hecht
Microwaves, February 1966

Helical Filters (Chapter 9)
A. I. Zverev
Handbook of Filter Synthesis
John Wiley & Sons, 1967
Library of Congress Card Number 67-17352

Helical-Resonator Filter Design,
Vincent G. Heesen
RF Design, July 1985