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 effici ency that is due to the energy loss associated with the excitation of surfa ce waves modes. This problem could be solved with several multi-layered ant enna configurations presented in this paper. It is known that the optimizat ion of these multi-layer antennas requires simultaneous variation of the di electric constant, air gap, and the thickness of substrate layer. The simul ation studies presented in this paper, using Ansoft Ensemble shows that for electromagnetically-coupled air gap multi-layered structure, a positive ga in of 2 dB is achieved, resulting in a gain improvement of at least 5 dB co mpared to the poor gain performance of a single layered structure. It is sh own that stacking a ferroelectric layer directly on top of a conventional m icrostrip antenna could eliminate the air gap spacing. This design has addi tional advantages like improvement in gain and creates a tunable dual band antenna performance. A larger gain improvement is also realized with this d irect-stacking arrangement compared to the air-gap coupled structure. These antennas may find wide applications in intelligent systems and structures.