Microstrip phase shifter using ground-plane reconfiguration

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Shafai, C
Sharma, SK
Shafai, L
Chrusch, DD
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In this paper, a new reconfigurable microstrip structure is presented where line impedance can be actively controlled to induce phase shift on a transmission-line signal. Micromachining is used to fabricate thin-film copper membranes in the ground plane below the transmission line. Actuation of these membranes enables control of transmission-line to ground-plane spacing and, thus, the line capacitance. The performance of this reconfigurable microstrip transmission line as a phase shifter is investigated between 5-32 GHz for a variety of membrane geometries. A phase shift of up to -32.1degrees at 15.00 GHz is achieved by actuating an array of five 4.3-mm-diameter membranes beneath a 30-Omega microstrip line. A single 10.0-mm-diameter membrane achieved a phase shift of -25.57degrees at 15.05 GHz on a 5642 line, while a 10.4-mm membrane achieved a phase shift of -55.5degrees at 14.25 GHz on a 30-Omega line. Both single and multiple series ground-plane membranes are possible, and they can be activated with discrete or continuous control signals, individually or together. Discrete and continuous phased array beam steering are, therefore, feasible.
microelectromechanical system (MEMS), membrane, micromachining, microstrip, phase shifter, reconfigurable antenna, BAND
0018-9480; IEEE TRANS MICROWAVE THEORY, JAN 2004, vol. 52, no. 1, p.144 to 153.