Investigating the effect of foam properties on the attenuation of coaxial cables with foamed polyethylene dielectric

Polymeric foams are one of the new candidates for the insulation of signal cables due to their effect on decreasing the signal loss. Accordingly, the effect of using foamed polyethylene in the dielectric section of coaxial cables on their transmission properties is investigated in this study. The samples were coaxial cables with identical properties in all sections except the dielectric part which had different foam structures. The expansion ratio and structural properties including cell size and cell density of the foams were measured. In the next step, the attenuation along the cable was determined both experimentally and theoretically. Due to the results, attenuation showed up to 38.46% reduction by foaming the dielectric compared to the solid dielectric sample. The experimental results showed good accordance with theoretical data. However, in higher frequencies, difference between these two approaches rose. A comparison of experimental and theoretical data also revealed that the expansion ratio of the foam is not the only effective parameter on the attenuation of cable. There are two other major factors: cell density and open‐cell content. High cell density foams show a lower attenuation, while in foams with high open‐cell content, a major increase was observed in the attenuation.