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A novel type of waveguide phase shifter utilizing tunable electromagnetic crystal (EMXT) surfaces is incorporated in a 16-element two-dimensional (2-D) millimeter wave (38 GHz) phase-scanned lens. EMXT surfaces integrating semiconductor varactors are used as the sidewalls of a waveguide to provide a tunable impedance boundary for the waveguide. The EMXT waveguides are used as 360° analog phase shifters as well as radiating elements to realize electronic beam scanning with microseconds of response time. The four-by-four array achieved +/-30° of beam scanning in both the E and H planes. The electrical and mechanical design, top-level array calibration, and scan performance of the 16-element proof-of-concept 2-D space fed phased array lens are described. The waveguide phase shifter insertion loss performance and plans for further improving insertion loss are discussed. The average insertion loss is expected to be less than 2.0 dB at an operating frequency of 38 GHz for GaAs substrate-based EMXT surfaces with planar Schottky diode tuning elements. This new type of EMXT waveguide array may provide a low-cost and high performance alternative to a conventional phased array.
Date of Publication: Jan. 2005