A Novel Wide, Dual-and Triple-Band Frequency Reconfigurable Butler Matrix Based on Transmission Line Resonators

In this paper, a novel reconfigurable Butler matrix based on transmission line resonators is presented and implemented. This matrix is built from embedding a reconfigurable multilayer directional coupler with an open stub resonator and p-i-n diodes to operate over three different states, such as dual band, triple band, and wideband. The coupler reconfigurability allows creating bandstop filters in the UWB band by controlling the p-i-n diode states in the quarter wave (
$\lambda $
/4) of the open stub resonator length. To demonstrate the design approach, two prototypes of coupler and Butler matrix are fabricated and tested. Good agreement between the measured and simulated results is obtained. The proposed designs show good results in terms of compactness, low insertion loss, and high isolation with a minimal number of RF p-i-n diodes used for all states.