Performance Evaluation of a Robotically Controlled Millimeter-Wave Near-Field Pattern Range At the NIST

The Antenna Metrology Laboratory at the National Institute of Standards and Technology (NIST) is developing a robotically controlled near-field pattern range for measuring antennas and components from 50 GHz to 500 GHz. This new range is intended to address the need for accurate antenna pattern measurements for a variety of applications including remote sensing and imaging. This system incorporates a precision industrial six-axes robot, six-axes parallel kinematic hexapod, and high precision rotation stage. A laser tracker is used to determine position and to calibrate the robot. The robotic positioning arm is programmable and allows scanning in a variety of geometries including spherical, planar, cylindrical, and perform in-situ extrapolation measurements, as well as, other user defined geometries. For the planar geometry, the coverage is a rectangle 1.25 m x 2 m. For spherical, radii from 2 cm to 2 m are possible, while the coverage in is +/- 120 and in phi is +/- 180. Robot positioning repeatability has been evaluated and determined to be about 30 mu m, and absolute positioning determination via the laser tracker is similar to 15 mu m. Specifics regarding the range evaluation are presented.