Corrugated copper membranes for use in reconfigurable ground plane antenna

Thin-film copper membranes on silicon substrates were constructed using micromachining techniques. Membranes possessed surface corrugations 10 µm deep and ranged in size from 1.04 mm to 10.0 mm in diameter. Membranes were released using a combination of both KOH and xenon difluoride (XeF ) backside etching. Surface corrugations were made using KOH etching on the frontside of the wafer. The membranes were electrostatically actuated using a high-voltage dc supply, and flexibility was studied as a function of diameter. Measured data were compared to simulations of flat and corrugated membranes. Copper membranes were used as a reconfigurable ground plane under a microstrip transmission line. Actuation of the membranes induced phase shift in the transmitted signal. An array of five 4.3 mm diameter membranes was tested, as was a single 10.0 mm membrane, over frequencies ranging from 9.95 GHz to 35 GHz. A phase shift of 55.63° at 34.42 GHz was achieved for the array of five 4.3 mm membranes, and a phase shift of 57.93° at 35.0 GHz was achieved for the 10.0 mm membrane.