Radiating Shape-Shifting Surface Based on a Planar Hoberman Mechanism

In this communication a new approach for realizing a reconfigurable microstrip patch antenna is proposed on the basis of radially-foldable linkage kinematic theory. Using a Hoberman's planar foldable linkage, in which rotation in the $\phi$ -direction provides translation in the radial direction, a radiating shape-shifting surface (RSSS) can be developed. To demonstrate the interesting characteristics of the approach, two resonant frequency-tunable antennas were prototyped. The antennas incorporate parasitic patches, which are repositioned over a fixed circular microstrip patch antenna. The mechanical movement results in tunability of the antenna resonant frequency without degrading the return loss bandwidth or radiation pattern. Experimental results for a design with electromagnetically-coupled parasitic patches demonstrate tuning of the resonant frequency by ${>}{10}\%$ over the 2.7-3 GHz frequency range with essentially constant gain and return loss bandwidth. Greater than 26% tuning bandwidth is achieved with the second design in which the parasitic patches make electrical contact with the primary antenna element.