C-shaped slot loaded reconfigurable microstrip antenna

Introduction: Compared to broadband antennas, reconfigurable microstrip antennas offer the advantages of compact size, frequency selectivity and similar radiation pattern and gain for all designed frequency bands [1]. Several interesting approaches to electronic tunability for different antenna structures have been carried out. However, the tuning mechanisms used are complex and need extra matching networks in order to operate over a wide frequency range [2]. Dual-frequency patch antennas may provide an alternative to large-bandwidth antennas. The key to providing a flexible solution is to have the radiators relatively independent [3, 4]. In this Letter, we present a novel, single-feed, dual frequency microstrip antenna design with independent frequency selection. Dual-frequency tuning has been realised using a varactor diode. The radiation pattern, gain and polarisation are essentially unaffected by the frequency tuning, which is highly desirable for frequency reconfigurable microstrip antennas.