In the early 1970s, NIST researchers pioneered the near-field scanning technique, now the standard method for testing high-performance antennas designed to communicate across tens of meters or millions of kilometers. The Antenna Metrology Project continues to advance the technique both theoretically and experimentally.
In hundreds of test ranges worldwide, engineers test antennas using NIST-developed algorithms and NIST-calibrated probes. Near-field scanning involves measuring an antenna’s performance at relatively short distances of a few wavelengths, then applying mathematical algorithms to accurately determine the far-field performance. This allows antenna measurements to be made in smaller, well controlled environments, such as anechoic chambers, with improved accuracy and test efficiency.
Near-field scanning allows for accurate assessment of the gain (the amount of power transmitted or received in the antenna’s primary direction), polarization (the orientation of the electromagnetic field) and pattern (the angular distribution of transmitted or received energy) of antennas. NIST’s Antenna Metrology Project is now extending near-field scanning techniques to very-high-frequency millimeter-wave antennas expected to play central roles in next-generation 5G wireless systems, as well as current and planned satellite antennas and radiometer instrumentation.
To this end, NIST’s Antenna Metrology Project is at the vanguard in the development of dynamic antenna testing systems using industrial robots. This work is vital for two reasons: first, because shorter wavelengths demand greater precision in near-field scanning; second, because to test the performance of high-frequency mobile wireless systems destined for vehicles, aircraft, ships, pockets and purses, the antenna tests themselves must incorporate physical motion.