Novel RF-MEMS widely-reconfigurable directional coupler

This paper presents an innovative widely reconfigurable directional coupler based on concentric selectable squares. The device can be reconfigured by simply addressing the RF signal to the selected square through independent sets of MEMS switches. A very wide tuning range of the operating frequency can be attained, still maintaining good performance in terms of both return loss and isolation in the all states. A 2-state MEMS prototype has been designed on a 525 mum high resistivity silicon substrate, employing a well-established eight-mask surface micro-machining process developed at Fondazione Bruno Kessler, Trento, Italy. A 41% tuning range has been achieved ranging from C to X band with a return loss and isolation better than 25 dB in both states. Two test circuits have been realized in microstrip technology confirming the feasibility of the proposed architecture.