Reconfigurable ultra-wideband array with tunable band rejection across a 7∶1 Bandwidth

A reconfigurable tightly-coupled array (TCA) for tunable band rejection is presented. This is achieved, for the first time, by a capacitively-reconfigured balun feed, integrated with an ultra-wideband phased array. The carefully-introduced capacitance creates a resonance that can be tuned within the total array´s bandwidth covering 0.6 to 4 GHz (7:1). The achieved gain rejection is of at least 15dB at the resonance without any efficiency reduction at other frequencies. The design is carried out using equivalent-circuit simulations of the array´s unit cell and verified via respective full-wave simulations. Preliminary measurements of the balun are performed by introducing fixed capacitors on the integrated Marchand balun. Three different capacitance values are tested corresponding to different rejection frequencies across the entire band. Future work entails a fully reconfigurable, 8×8 array prototype with variable capacitors to be presented at the symposium. It should be noted that the proposed system is the first reported reconfigurable array that enables interference rejection critical for ultra-wideband antennas.