Antenna Systems & Technology - Winter 2016 - (Page 8)

FEATURE ARTICLE Configurable Robotic Millimeter-Wave Antenna Facility By Jeff R. Guerrieri, Josh Gordon, David Novotny, Alexandra Curtin & Mike Francis National Institute of Standards and Technology The demand for millimeter Wave (mmWave) antenna measurements (> 100 GHz) has increased due to the practical realizations of many mmWave systems and applications. Point-to-point communication links from 92 to 95 GHz and at 120 GHz are now commercially available, and 220 to 650 GHz systems are being researched for medical and security applications. New developments in climate monitoring require traceability in radiometric and remote sensing equipment from 100 to 850 GHz, including emissivity and antenna gain. To address the antenna measurement needs of the future, the National Institute of Standards and Technology (NIST) recently developed a new robotic arm scanning system for performing near-field antenna measurements at mmWave frequencies above 100 GHz, the Configurable RObotic MilliMeter-wave Antenna (CROMMA) facility, [1-2], shown in Figure 1. This system is designed for high-frequency applications, is capable of scanning in multiple configurations, and is able to track measurement geometry at every point in a data scan acquisition. The RF measurements are made using a vector network analyzer and at every measurement point the relative position and orientation of the probe relative to the test antenna are recorded with a laser tracker system. CROMMA is capable of pla- Figure 1. CROMMA facility positioners. Serial 6DoF robotic arm, parnar, spherical, cylindrical or mixed-geome- allel 6DoF hexapod, precision rotary stage, probe and test antenna. try scanning. The position and orientation information provided by the laser tracker system is used to assess the quality of the alignment and will eventually allow for the implementation of position and orientation correction algorithms. Facility Components The CROMMA facility uses two robotic positioners and one rotary positioner. The two robotic positioners are based on different kinematic model types. First, a six axis robotic arm, shown in Figure 1, is based on a serial kinematic model that consists of six rotation joints connected in series by ridged linkages. This allows for six degrees of freedom (6DoF), x, y, z, roll, pitch and yaw, positioning of the probe. The robotic arm has a 2 m reach, which spans a spherical volume of ~ 1 m radius with an end effector probe-antenna payload of up to 35 kg. After initial setup, alignment using the laser tracker, and applying position correction tables, the robotic arm provides probe positioning within ~25 µm [3]. The second robotic positioner is a Hexapod, shown in Figure 1, which uses a parallel network of six prismatic actuators, which allows for 6DoF positioning and alignment of the test antenna to the measurement azimuthal rotation axis. Individually the actuators have an accuracy of 500 nm giving a combined accuracy of 1 µm for the hexapod system [3]. The Azimuth Rotator shown in Figure 1, is a precision rotary stage is used to rotate the hexapod and test antenna ±180°. This rotary stage is used for the measurement azimuthal rotation axis for the test antenna when performing spherical near-field antenna measurements. The angular resolution of the rotator is 0.36 arc-sec and has an accuracy of 20 arc-sec. 8 Antenna Systems & Technology Winter 2016 www.AntennasOnline.com http://www.AntennasOnline.com

Table of Contents for the Digital Edition of Antenna Systems & Technology - Winter 2016

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Editor’s Choice
Configurable Robotic Millimeter-Wave Antenna Facility
Antennas
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Components/Subsystems
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Antenna Systems & Technology - Winter 2016