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 × 2 m. For spherical, radii from 2 cm to 2 m are possible, while the coverage in θ is ±120° and in φ is ±180°. Robot positioning repeatability has been evaluated and determined to be about 30 μm, and absolute positioning determination via the laser tracker is ~15 μm. Specifics regarding the range evaluation are presented.