This work contributes to development of relatively inexpensive electronically steerable antennas.

An experimental phased-array microwave antenna assembly includes an array of eight patch antenna elements connected to Microelectromechanical System (MEMS) phase shifters, by means of which the directional radiation pattern of the antenna can be controlled electronically. The antenna and the MEMS-based phase shifters were designed for a nominal operating frequency of 17 GHz. In addition, some 35-GHz MEMS phase shifters were designed, built, and tested. This work is part of a continuing effort to develop relatively inexpensive electronically steerable antennas.

Figure 1. This Reflection-Type Phase Shifter for 17 GHz includes six electrostatically actuated MEMS shunt switches and an integrated CPW Lange directional coupler. The overall dimensions are 2.75 by 4 mm.

The phase shifters were fabricated on high-resistivity silicon substrates. Both two- and three-bit phase shifters were designed and built. Figure 1 shows one of the 17- GHz two-bit phase shifters as it looks before it is packaged. Each phase shifter includes a coplanar-waveguide (CPW) Lange directional coupler and two delay lines with shunt switches at the locations appropriate for switching the desired increments of phase. The switches are actuated in left-right pairs to obtain in ascending sequence phase increments of 0°, 90°, 180°, and 270°, respectively. Assuming that the delays along the two delay lines are equal, the microwave signals reflected from the closed switches add in phase with each other at the output terminal of the directional coupler with a phase shift equal to twice the delay associated with length of one delay line. The transmission line shown as a vertical line at the top, which is terminated in a CPW short circuit, is used in the 270° switch state.