Design and development of tunable multi-layer smart antennas using ferroelectric materials

It is well known that microstrip antennas on high permittivity substrates (e.g., ferroelectric materials) suffer from narrow bandwidth and poor efficiency that is due to the energy loss associated with the excitation of surface waves modes. This problem could be solved with several multi-layered antenna configurations presented in this paper. It is known that the optimization of these multi-layer antennas requires simultaneous variation of the dielectric constant, air gap, and the thickness of substrate layer. The simulation studies presented in this paper, using Ansoft Ensemble shows that for electromagnetically-coupled air gap multi-layered structure, a positive gain of 2 dB is achieved, resulting in a gain improvement of at least 5 dB compared to the poor gain performance of a single layered structure. It is shown that stacking a ferroelectric layer directly on top of a conventional microstrip antenna could eliminate the air gap spacing. This design has additional advantages like improvement in gain and creates a tunable dual band antenna performance. A larger gain improvement is also realized with this direct-stacking arrangement compared to the air-gap coupled structure. These antennas may find wide applications in intelligent systems and structures.