Radial-Shaped Single Varactor-Tuned Phasing Line for Active Reflectarrays

A novel phasing line is proposed in this work for a broadband dynamic tuning of an active aperture-coupled reflectarray cell. A couple of wide-band radial stubs, loaded by a single varactor diode, is adopted to realize the dynamic phase shift mechanism, thus combining unit cell beam-scanning and/or reshaping pattern capabilities with frequency reconfigurability feature, as demanded by several radar or satellite communication applications. When compared to existing solutions on the same task, the proposed configuration integrates a single tunable lumped element (i.e. varactor diode), requiring a very simple biasing network. The proposed approach is adopted to design an X-band reflectarray cell giving a 320° phase agility within a measured frequency range of about 8.5%, significantly greater than that achievable through the use of a standard linear phasing line. As a further feature, the designed cell shows a useful improvement of the instantaneous bandwidth at the middle of the tuning band.