NIST employs robot for antenna measurements and calibrations

The National Institute of Standards and Technology (NIST) has introduced a robot to extend its antenna measurements to higher frequencies while characterising antennas faster and more easily than previous NIST facilities.

The robot's formal name is the Configurable Robotic Millimeter-Wave Antenna (CROMMA) facility. It will be used to rapidly and accurately measure the properties of antennas used in advanced communications, remote sensing for weather prediction and climate monitoring, imaging systems and radar.

"We designed this system to address a need in the antenna community for high-precision and configurable scanning at short, millimeter wavelengths," lead researcher Joshua Gordon said. "Past systems haven't been as complete as they need to be. The robot allows us to explore many ways of doing measurements. There's a lot of configurability and an extremely high level of repeatability."

Robotics is the latest advance in the near-field scanning technique. The method uses complex mathematical models to determine antenna properties and calculate performance at long distances using data collected indoors close to the antenna, where it's easier to get accurate readings. Near-field scanning allows researchers to assess an antenna's gain, polarisation and pattern.

The six-axis robot can twist into unusual positions to measure the properties of a test antenna up to 2m in diameter positioned on a hexapod stage. A laser tracker monitors and records positions used for fine correction of robot postures to ensure the necessary precision.

Antennas can be dynamically positioned with a precision of tens of micrometers in all six degrees of freedom. The arm can hold up to 35kg and can measure antenna properties in almost any user-definable pattern, including spherical, planar and cylindrical, eliminating the need for a separate antenna measurement setup for each path type.

At first, the robot will measure frequencies from 100 to 300GHz with the goal of eventually reaching 500GHz and higher. High frequencies are used in many current and emerging applications due to improved spatial resolution, smaller antenna components and higher data rates. There is a particular need for accurate antenna pattern measurements above 100GHz, a range that holds promise for future generations of advanced communications antennas and improved weather and climate prediction.