Transmission Line Filters Approximating a Constant Delay in a Maximally Flat Sense

An exact method is presented to find transmission factors of transmission line filters which approximate a constant delay in a maximally flat sense. The class of filters considered is a doubly loaded arbitrary cascade of transmission lines and open- or short-circuited stubs in series or in shunt, all elements being of equal length and nondispersive. This includes a variety of transmission line filters: transformers, distributed lowpass filters, stub filters of various configurations, interdigital filters, etc. Explicit expressions, valid for any order of the filter, are derived for the normalized transmission factor, and for its squared magnitude, and its phase on the imaginary axis. In addition, a table and design curves are provided for the cases , and 5 and an example is given to demonstrate their use.