Search

Superluminal wave propagation phenomenon achieved from a periodic structure in which a transmission line (TL) is loaded with non‐Foster negative capacitors is presented. The loading decreases the effective capacitance and the effective permittivity of the dielectric substrate of the TL. An experimental investigation of the superluminal phase and group velocity in the non‐Foster loaded TL is reported. The phase and group velocities are extracted from measured S‐parameters. To do so, three non‐Foster negative capacitors operating over [50–350 MHz] frequency band are integrated in a TL. Superluminal broadband effects are obtained from 50 to 220 MHz. The negative capacitors loaded TL paves the way to innovative broadband leaky wave antennas, active metamaterial surfaces and cloaking devices. [ABSTRACT FROM AUTHOR]

A passive microfluidically tunable power divider (PD) with a wide‐frequency‐agile range based on substrate integrated waveguide (SIW) has been presented. The proposed structure consists of two SIW resonators loaded on the same complementary split‐ring resonator and five identical filling‐water tubes placed on the top plane. By injecting water into five tubes, the effective permittivity of the substrate can be controlled, and thus the operating frequency of the PD can be precisely tuned. For demonstration, the proposed PD is designed and fabricated. The measured and simulated results are given, showing good agreement. [ABSTRACT FROM AUTHOR]

The concept of using additive manufacturing as a method to construct heterogeneous substrates from a single building material via stereolithography is introduced. The dynamic variation of air cavities within the bulk material is used to control the effective permittivity of the host medium. The digitally driven layer process enables full three‐dimensional variation of the local permittivity. The high resolution of stereolithography enables sub‐millimetre control of air inclusion features. Measurements of the effective permittivity with different air fractions have been compared to analytical results. [ABSTRACT FROM AUTHOR]