National Institute of Standards and Technology (NIST) engineers have developed a flexible handheld measurement system to support the design and repeatable laboratory testing of fifth-generation (5G) wireless devices with unprecedented accuracy over a wide range of signal frequencies and scenarios. This system is called SAMURAI, which is short for Synthetic Aperture Measurements of Uncertainty in Angle of Incident.
The new system is the first of its kind to offer 5G wireless measurements with an accuracy that can be traced back to fundamental physical standards, which is a key feature as even minor errors can lead to incorrect results. SAMURAI is also small enough to be transported to field trials.
Mobile devices such as cell phones, consumer Wi-Fi devices, and public safety radios currently operate primarily at electromagnetic frequencies below 3 gigahertz (GHz) with antennas that emit radiation equally in all directions. Experts predict that 5G technologies can boost data rates a thousandfold by using higher millimeter-wave frequencies above 24 GHz and highly directional, actively changing antenna patterns. Such active antenna arrays help overcome the loss of these high-frequency signals during transmission. 5G systems also send signals simultaneously over multiple paths – called spatial channels – to increase speed and overcome interference.
Many instruments can measure some aspect of the performance of directional 5G devices and channels. But most of them are focused on collecting quick snapshots in a limited frequency range to provide an overall view of the channel. In turn, SAMURAI provides a detailed “portrait”. In addition, many instruments are so large that they can distort the transmission and reception of millimeter-wave signals.
SAMURAI, which the developers talked about at the conference on August 7, is expected to help resolve many unanswered questions related to the use of 5G active antennas. For example, what happens when high data rates are transmitted over multiple channels simultaneously? The new system will help improve theory, equipment, and analysis techniques to provide accurate channel models and efficient networks.
SAMURAI measures signals in a wide frequency range, currently up to 50 GHz and next year up to 75 GHz. The system gets its name because it measures the received signals at many points in a grid or virtual “synthetic aperture”.
SAMURAI can be used for a variety of applications, from testing the performance of wireless devices with active antennas to measuring reflective channels in environments where metal objects scatter signals.
The main components are two antennas for transmitting and receiving signals, instruments with precise time synchronization for generating radio transmissions and analyzing reception, and a six-axis robotic arm that positions the receiving antenna at grid points that form a synthetic aperture. The robot maintains an accurate and repeatable antenna position and monitors various reception patterns in three dimensions, such as cylindrical and hemispherical shapes.
The system is usually attached to an optical table measuring 1.5 meters by 4.3 meters. But the equipment is portable enough to be used in mobile field tests and moved to other laboratories.