Fabrication and testing of a microstrip phase shifter using micromachined reconfigurable ground plane

A micromachined phase shifter is implemented along a microstrip transmission line using thin film membranes in the ground plane. Actuation of the membranes controls the spacing of the transmission line to the ground plane, varying line impedance and enabling signal phase shift. Thin film copper membranes on silicon substrates were constructed using micromachining techniques. An array of five 4.3 mm diameter membranes phase shifted a signal by 30.0/spl deg/ at 12.08 GHz. A single 10.4 mm membrane demonstrated a phase shift of 37.1/spl deg/ at 11.01 GHz and 55.5/spl deg/ at 14.25 GHz. Continuous positioning of the ground plane membranes is possible, enabling continuous phase shift control.