Tunable defected ground slits for mutual coupling reduction applications

Novel tunable slit structures in a ground plane are presented for reducing the electromagnetic coupling between closely spaced monopole antennas. Ultra wideband CPW-fed monopoles are employed in order to demonstrate the tuning range of the slits. The proposed slits are etched in the common ground between the monopoles and the tuning is provided by a varactor diode placed within the slit. A tunable transmission zero is obtained in the S21 leading to a significant reduction of the mutual coupling within the antennas' operating frequency band. The proposed slits have a small size and are positioned close to the edge of the ground plane thereby occupying very little space. Simulation results were obtained in 3D electromagnetic simulation software (CST Microwave studio) and are presented.