Normal modes in an overmoded circular waveguide coated with lossy material
Abstract
The normal modes in an overmoded waveguide coated with a lossy material are analyzed, particularly for their attenuation properties as a function of coating material, layer thickness, and frequency. When the coating material is not too lossy, the low-order modes are highly attenuated even with a thin layer of coating. This coated guide serves as a mode suppressor of the low-order modes, which can be particularly useful for reducing the radar cross section (RCS) of a cavity structure such as a jet inlet. When the coating material is very lossy, low-order modes fall into two distinct groups: highly and lowly attenuated modes. However, as a/lambda (a = radius of the cylinder; lambda = the free-space wavelength) increases, the separation between these two groups becomes less distinctive. The attenuation constants of most of the low-order modes become small, and decrease as a function of lambda sup 2/a sup 3.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- September 1985
- Bibcode:
- 1985STIN...8535320L
- Keywords:
-
- Attenuation;
- Lossy Media;
- Radar Cross Sections;
- Waveguides;
- Dielectrics;
- Electric Fields;
- Magnetic Fields;
- Transmission Lines;
- Wave Propagation;
- Communications and Radar