S-Matrix and Bandpass Negative Group Delay Innovative Theory of Ti-Geometrical Shape Microstrip Structure

A theoretical investigation of distributed microwave circuit built with Ti-shape topology is developed. The topology under study consists of neighbored T- and i-shape interconnect lines. The Ti-topology equivalent S-matrix is calculated as a function of crosstalk coupling coefficient and coupled line (CL) delay. To highlight the NGD modelling feasibility, parametric analyses with respect to the T- and i-element coupling and delay are introduced. More practical validation is carried out with designed, simulated and measured microstrip prototype. It is found that because of T- and i-crosstalk, the Ti topology can behave as a bandpass NGD function. A good NGD performance with NGD level of approximately -1 ns around the center frequencies 2.2 GHz with transmission coefficient of approximately -2.1 dB and reflection coefficient better than -14 dB. The measured results are in good agreement with calculated models and simulations. Two-cell Ti-NGD circuits were also investigated to illustrate the designability of the topology for multi-band and widened single band NGD responses.