  The elements of the metamaterial made in the form of wave-guiding coplanar
strip line type strip structures, the current-carrying strip of which is
located on the upper surface of the substrate, have been experimentally
investigated. On the same surface, side screens, connected to the lower
grounded base, through metallized holes are made. A volumetric lithium niobate
crystal is placed on the upper surface of the strip lines. Frequency
dependences of the modulus and phase of the transmission coefficient and
reflection coefficient of models with a lithium niobate bulk crystal are
measured when a linear-frequency modulated signal in the range from 10 MHz to
25 GHz with a fast change of the incident wave direction is applied to the
strip line input. The occurrence of quasi-chaotic oscillations in the tested
models was demonstrated. Modeling of the strip structure allowed to determine
the frequency dependence of the complex propagation coefficient, indicating the
cause of quasi-chaotic oscillations due to the occurrence of a large number of
normal waves and their interference. Frequency regions with negative group
delay were detected.
