Experimental investigations on electronically tunable microstrip antennas

The frequency tunability of a microstrip antenna on barium strontium titana te (BST) substrate is presented in this paper. This investigation has been made as a first step toward the realization of an electronically tunable mi crostrip antenna, taking advantage of the voltage-tunable dielectric substr ate. It is already established that the change in dielectric constant of th ese substrate material is more than 50%, depending on the stoichiometric co mposition of BST and the bias voltage. It is also possible to control the d ielectric constant during processing of the substrate in the range of 15-15 00 with some tradeoff in tunability. A microstrip patch antenna is printed on the tunable substrate, and the radiation performance was studied for dif ferent bias conditions; frequency tuning is demonstrated experimentally. Th e antenna frequency can abe changed by varying the applied dc voltage. To t ake further advantage of the tuning range of the substrates, it is necessar y to design and develop high-performance dc-blocking circuits. (C) 1999 Joh n Wiley & Sons, Inc.