New low loss soft thermoplastic blends for microwave applications

Abstract

All organic soft dielectrics are growing more and more interest in the electronic industry owing to their light weight, low cost and the flexibility they yield compared to the rigid devices. In the specific field of microwave communicating devices planar printed (patch) antennas on a soft dielectric substrate are sought for their conformability and advantageous compactness. In this article, two soft thermoplastic elastomer blends based on polypropylene (PP) or lowdensity polyethylene (LDPE) were tested. The fabrication process and the established characterization steps have been fully presented. More specifically, in order to characterize the dielectric film up to 40 GHz, the microstrip ring resonator with coplanar waveguide access has been adapted to a new configuration specimen sample. The results of the characterizations obtained showed very encouraging performances for microwave applications. Indeed, the measured dielectric constant and loss tangent up to 40 GHz were found to be ε r ≈ 2.45 and tan δ ≈ 0.01 for both blends. The fabrication and the radiation characteristics of a patch antenna on a new performing PP or LDPEbased elastomer blends as the soft dielectric substrate was demonstrated and analysed. The proof of the concept of the investigated device consists of a microstrip patch antenna with an operation frequency of about 10 GHz. These dielectric features render the polyolefin based blends very promising as a soft material for microwave engineering, which is confirmed by the measured antenna properties: the gain, the directivity as well as the efficiency have been calculated from the measured radiation pattern and were recorded as 4.6 dB, 7.7 dB and 46% respectively for the rPP based blend and 4.8 dB, 8.1 dB and 51% for the LDPE based blend.