Microwave seminar | 27 November 2025

About 20 years ago, growing interest to metamaterials and their unusual properties in the course of last several years, stimulated invention and design of numerous microwave devices, based on transmission-line representation of metamaterials. I will report on an advanced phase compensation principle, which employs combined backward-forward transmission lines having similar frequency dispersion. Various applications of this principle to the design of microwave devices allow for an exceptionally low dispersion in a wide frequency range while keeping the structure very compact and simple compared to conventional solutions. To illustrate the idea, we present the performance of (i) phase shifters, (ii) power dividers and (iii) baluns (complete antenna feeders) built on the reported principle. Corresponding phase shifters are characterized with negligible frequency dependence in a wide frequency range. We show that for an ideal performance, phase deviation can be less than 1% within a 20% bandwidth while excellent impedance matching is retained. The power dividers offer a performance, comparable with conventional Wilkinson dividers, occupying, however, two times smaller area or even less. For antenna feeders, the reported principle opens an excellent opportunity to combine a power divider and an adjacent balun into one simple structure, also leading to essential size reduction while keeping characteristics, comparable with conventional assemblies.