Triple-slot phase-shifting cell loaded with one variable capacitance for reflectarray applications

Introduction: Active reflectarrays are promising solutions for reconfigurable radiating apertures at reasonable cost [1]. One of the main challenges is to design phase-shifting cells whose phase can be controlled dynamically over a 360° phase range with smooth frequency variations, low losses and reduced number of active elements. MEMS [2] or diodes [3] are usually used to dynamically control the electric length of a single resonator. On the other hand, multiple resonators have been advantageously used to increase the overall phase range of passive cells up to twice or three times the required 360° value [4, 5]. Singlelayer structures are preferable as they result in a simpler technological process. In [6] and [7], simulations showed the capabilities of reconfigurable single-layer structures, using either 2or 3-slot resonators controlled by a convenient capacitive loading. This tuning mechanism is appropriate to modulate the slot’s length without fundamentally changing its resonant mode (as may be observed for switched multiple-resonators [8]). In this letter, experimental validation for the new triple-slot phase-shifting cell is presented; we demonstrate that very satisfying performances can be achieved with just one variable capacitance loading the central slot while benefiting from the bandwidth enlargement brought by both external slots.