1 / 6

Complex dielectric permittivity

Complex dielectric permittivity The relative complex dielectric permittivity of a medium, e r ( f ), describes the energy propagation characteristics of the electrical component of electromagnetic radiation within that medium.

konane
Download Presentation

Complex dielectric permittivity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Complex dielectric permittivity • The relative complex dielectric permittivity of a medium, er(f), describes the energy propagation characteristics of the electrical component of electromagnetic radiation within that medium. • Dielectric losses are energy losses due to rotational polarization (relaxation), e"rel(f), and electrical conductivity (EC), sdc (von Hippel, 1954):

  2. Cole-Cole (1941) model for modeling of complex dielectric constant The relative dielectric permittivities of most materials may be described via the Cole-Cole (1941) model: where e∞ is the dielectric constant at infinite frequency, es the static dielectric constant (where f = 0 Hz) and b a factor accounting for possible spread in relaxation frequencies.

  3. Relaxation losses are greatest at the relaxation frequency, frel. • EC losses are greatest at lower frequencies, with the greatest loss occurring at f = 0 Hz (DC). • Where f << frel, e’(f) is directly proportional to the viscosity of the medium. • frel is inversely proportional to viscosity. • Viscosity is inversely proportional to temperature. • As f increases toward frel, e’(f) will begin to decrease, with the greatest decreases occurring in the vicinity of frel.

  4. Relax. freq. 5°C Relax. freq. 25°C Relax. freq. 25°C Figure 1: Dielectric permittivity of water as predicted via the Cole-Cole (1941) model and measured using a network analyzer at 5, 25 and 55°C.

  5. Figure 2. er of distilled water at P, L, C and X bands as a function of temperature. Solid black and red symbols represent measured real and imaginary e values, respectively. Please note that measured values for e’ at 420 MHz and 1.26 GHz are overlapping.

  6. A e” dominated by EC losses e” dominated by relaxation B C Figure 3A-C: Dielectric permittivities of DDW and 3 CaCl2 solutions at A. 5°C, B. 25°C and C. 55°C.

More Related