Antenna Calibrations Extended to 60-110 GHz

NIST engineer Katherine MacReynolds prepares a new NIST "tabletop" range for characterizing high-performance antennas, such as horn antennas (small gold pyramids) operating at 94 Gigahertz. The surrounding blue foam cones absorb electromagnetic fields to reduce scattering from nearby objects, thereby improving measurement accuracy.
Credit: © 2006 Geoffrey Wheeler

The National Institute of Standards and Technology (NIST) has developed a new "tabletop" sized facility to improve characterization of antennas operating in the 60 to 110 gigahertz (GHz) frequency range. This extended frequency capability serves needs for advanced civilian and military communication and radar systems.

A number of electronic systems are moving to higher frequencies to attain higher channel capacity, better spatial resolution and other advantages. The new measurement facility will help accelerate development of technologies such as automobile collision-prevention radars, which operate at 94 GHz and require antennas small enough to be integrated into car bumpers. Improved NIST antenna calibration capability also helps to assure the accuracy of a number of systems. "NIST is the start of the measurement traceability chain," says Perry Wilson, leader of the Radio Frequency Fields Group. "For instance, we calibrate the probes used by aerospace companies to calibrate instruments launched on satellites and other critical systems. Weather satellites are an example; improvements in antenna accuracy mean better data for weather models, resulting in better weather predictions".

The new facility continues NIST's history of innovation in antenna measurements, building on the "extrapolated gain" technique developed several decades ago. The original extrapolation range and techniques made it practical for scientists to accurately compute an antenna's far-field characteristics based on near-field measurements. By making the range compact, costs are significantly reduced. In addition, the extrapolation technique uses over-sampling and averaging techniques to minimize the effects of scattering and range imperfections.........