Dielectric loss

About: Dielectric loss is a research topic. Over the lifetime, 20296 publications have been published within this topic receiving 349254 citations.

A Parallel-Plate Waveguide Approach to Microminiaturized, Planar Transmission Lines for Integrated Circuits

Abstract: The parallel-plate waveguide with a two-layer loading medium, a conducting semiconductor substrate, and a relatively thin dielectric layer approximates the interconnections in many integrated systems if the fringing fields are ignored. The fundamental mode of this structure is an E mode which is a surface wave. Its propagation behavior is analyzed in this paper and the equations are evaluated by highly accurate numerical methods. The semiconducting substrate is characterized by its dielectric constant and conductivity. A critical conductivity /spl sigma//sub min/ exists and is related to the cross sectional and material parameters. If the substrate conductivity is given by /spl sigma//sub min/ then the attenuation constant of the line is a minimum. The same value of conductivity yields minimum phase distortion at maximum bandwidth. If the conductivity is larger than /spl sigma//sub min/ the substrate acts as a poor conductor with associated skin effect; if it is smaller, lossy dielectric behavior results. Analysis shows that it is appropriate to subdivide the frequency range into three intervals. The lowest-frequency interval is characterized by propagation which resembles diffusion. This is caused by the loss in the dielectric layer. The next frequency range extends to some upper frequency which is determined by substrate conductivity and the cross-sectional dimensions. In this interval, the phase velocity of the fundamental mode is controlled by the ratio of dielectric to semiconductor thickness, which, if typical interconnections are considered, implies a very low velocity. This property indicates that the structure can serve as a delay line. Further increases in frequency result in higher phase velocities. Skin effect and dielectric loss behavior describe the propagation in this third interval.

Electric field dependent dielectric properties and high tunability of BaZrxTi1−xO3 relaxor ferroelectrics

Abstract: This letter reports the E-field tunable behavior of the environmental friendly lead-free perovskite BaZrxTi1−xO3 (x=050 and 060) relaxor ceramics in the temperature range from 300to30K dc electric field dependence of dielectric behavior of the ceramics has been studied The results have been analyzed in relation to tunability (%) and K factor of the tunable dielectric materials It is shown that manipulating the Zr:Ti concentration in BaZrxTi1−xO3 ceramics and optimizing the applied dc bias field the properties for specific applications in tunable filters, phase shifters, antennas, etc, can be tailored in the temperature range from 100to300K

Well-Defined Core–Shell Fe3O4@Polypyrrole Composite Microspheres with Tunable Shell Thickness: Synthesis and Their Superior Microwave Absorption Performance in the Ku Band

Abstract: Highly regulated core–shell Fe3O4@polypyrrole composite microspheres have been successfully prepared via chemical oxidative polymerization in the presence of poly(vinyl alcohol) and p-toluenesulfonic acid. The polypyrrole shell thickness can be adjusted from 20 to 80 nm with the variation of the pyrrole/Fe3O4 ratio. Investigations of the microwave absorbing properties indicate that the polypyrrole shell plays an important role, and the maximum reflection loss of composite microspheres can reach as much as −31.5 dB (>99.9% absorption) at 15.5 GHz with a matching layer thickness of 2.5 mm. Compared to the physically blended Fe3O4–PPy composites, Fe3O4@polypyrrole composite microspheres not only possess better reflection loss performance but also have a wider absorbing bandwidth of 5.2 GHz (12.8–18 GHz) in the Ku band, which may be attributed to the intensive synergistic effect of dielectric loss from polypyrrole shells and magnetic loss from Fe3O4 cores. Therefore, regulated core–shell Fe3O4@polypyrrole com...