Design and development of electronically tunable microstrip antennas

The narrow bandwidth of conventional microstrip antennas has many restrictions in real-time applications. The tunable dielectric and magnetic materials offer solutions to this problem. This paper presents the design and experimental investigations on a dietectric tunable microstrip antenna on barium strontium titanate substrate. The resonant frequency of the antenna is found to change more than 3% by changing the applied bias voltage. It would be possible to achieve more tunability by using proper de blocking circuits and higher bias voltages. It is already established that the changes in dielectric constant of these substrate materials are more than 50% depending on the BST composition on changing the bias voltage. It is also possible to control the dielectric constant during the processing of substrates in the range of 15 to 1500 with some trade-off in tunability. The tunability of the EST substrate is found to have advantages in development of wideband microstrip antenna arrays and phase shifters.