Design and development of smart microstrip patch antennas

The major weakness of a microstrip patch antenna is its narrow bandwidth characteristic. One method that has been investigated to increase bandwidth is the addition of a parasitic element to the microstrip patch antenna. In an active microstrip patch antenna, variable bandwidth can be achieved by varying the spacing between the antenna and the parasitic element, which is fixed to a dielectric plate. In this study an actuator is developed, tested and employed on an actual microstrip patch antenna and its parasite. Since a relatively large displacement (1 cm) is needed, the actuator is comprised of a stack of RAINBOW actuators. This study takes advantage of the fact that, for antennas operating at higher frequencies, smaller absolute displacements will result in significant percentage changes in antenna bandwidth. The use of the parasite and the active system accounted for up to a factor of five increase in antenna bandwidth. Various control techniques were employed to counteract the effects of hysteresis and creep on the actuator. Because the use of metal components can degrade antenna performance, emphasis was placed on synergy in the design process.