Microstrip array antennas for bandwidth enhancement by using polymeric magneto dielectric substrates

Abstract

Microstrip antennas are fabricated using commercially available dielectric substrates such as Rogers, Taconic and FR4. However, microstrip antennas built using these materials have limited bandwidth besides would incur high losses. This thesis presents the development of a class of polymeric magneto used as antenna substrates. These new composite substrates are capable of boosting antenna bandwidth, miniaturizing antenna size and improving gain. In the study, Polydimethylsiloxane-magnetite iron oxide (PDMS-Fe3O4) dielectric composite consisting of Fe3O4 nanoparticles (sized at 10 nm) and polymeric PDMS was introduced. PDMS-Fe3O4 and PDMS exhibit favorable characteristics such as transparency, lightweight, low losses and ease of dielectric permittivity tuning by loading using different material compositions. In this case, Fe3O4 nanoparticles are suited for specific microwave/radio frequency applications. Furthermore, the study implemented a bandwidth enhanced microstrip grid and comb array antennas on molded PDMS and PDMS-Fe3O4 for high frequency applications as the first of their kind. The grid and comb array antennas were embedded inside the PDMS and PDMS-Fe3O4 dielectric substrates, which offer water resistance and improve mechanical robustness for the antenna. Four antennas structures were designed to validate the merit of the PDMS-Fe3O4, namely microstrip grid array antenna (MGA), microstrip polymeric grid array antenna (PGA), microstrip polymeric comb array antenna (PCA) and microstrip polymeric magneto comb array antenna (PMCA). Simulation and measurement results indicated increments in relative bandwidths, starting from 1.43% for MGA antenna, followed by PGA antenna with 6.43%, 18.21% for PCA antenna and nearly 56.25% for PMCA antenna. Measurements showed good agreement with simulations in terms of reflection coefficient and radiation patterns. Besides significant bandwidth improvements, the gain for all antennas have also improved, with 12.26 dBi obtained for MGA antenna, 14.79 dBi for PGA antenna, 11.38 dBi for PCA antenna and 11.34 dBi for PMCA antenna. Thus, it can be concluded that the use of PDMS-Fe3O4 composites and polymeric dielectric as substrates is suitable for use in high frequency applications to improve bandwidth and antenna compactness.