Direct- and Quarter-Wave-Coupled Microwave Band-Pass Filters with Adjustable Transmission Characteristics and Fixed Center Frequencies

A theoretical study of the properties of "constant-phase" two-ports is presented which leads to a simple experimental synthesis technique for a broad class of microwave band-pass filters. "Constant-phase" two-ports consisting of modified step-twist-junctions are employed in experimental multiple cavity direct-coupled filter configurations which have the unique property of continually adjustable bandpass characteristics and fixed center frequency. These experimentally obtained characteristics are predicted from the theory.