SAN ANTONIO — July 29, 2025 — Southwest Research Institute (SwRI) is expanding its antenna measurement capabilities with a state-of-the-art spherical near-field antenna range. The 1,260-square-foot indoor range, lined with radio frequency and microwave foam absorbers, is equipped to accurately sample the near field of an antenna. Near-field measurements can be mathematically transformed into far-field data.
"Near field" refers to the complex electromagnetic fields close to the antenna, while the "far field" encompasses the predictable planar waves farther away from the antenna. Analyzing both fields allows a more complete performance evaluation of an antenna under test. Near-field measurements are typically collected in a planar, cylindrical or spherical formation.
"Spherical data collection is the most comprehensive and flexible method of measuring antenna patterns for all antenna types," said Dr. Jimmy Li, a lead engineer in SwRI's Defense and Intelligence Solutions Division. "We get the full 3D radiation pattern data for an antenna — not just limited perspectives obtained with other methods."
Antennas enable the transmission and reception of signals and are the interface between electromagnetic waves and electronic devices. Testing is necessary to evaluate performance and ensure compliance with industry standards and regulations. Antennas are crucial for a wide range of technologies, including cellular networks, Wi-Fi, radar, satellite communications and positioning and navigation systems.
SwRI's spherical near-field antenna range offers several new advantages, including:
- No restrictions associated with antenna far-field distances exceeding the size of the range because far-field data can be calculated from near-field measurements
- A built-in, overhead, half-ton hoist to install large antennas up to 10 feet in diameter and 1,000 pounds
- Operation at frequencies from 200 megahertz to 40 gigahertz
- Faster data collection enabled by continuous-rotation sampling
- Full characterization of antenna radiated patterns, including multi-polarization 3D patterns across all angles
- Faulty antenna element diagnostics, array performance evaluations, radome systems tuning and reflector surface area mapping
- No limitations due to weather fluctuations that impact outdoor ranges
- No limitations from Federal Communications Commission (FCC) regulations that impact outdoor ranges
"Because the range is indoors, we do not have to follow FCC requirements regarding antenna height and other transmission restrictions for outdoor antenna testing," said Nils Smith, vice president of SwRI's Defense and Intelligence Solutions Division. "We can now perform thorough testing of antennas on-site at SwRI, and we have more versatility. That translates into a stronger analysis of antenna performance for our clients."
In the next phase of development, the SwRI spherical near-field antenna range will support emerging millimeter wave technologies, a crucial component for ultra-fast 5G data transmission.
SwRI designs, develops and tests antennas and signal processing software for government and industry clients, including the Navy, Air Force, Marines and intelligence entities.
Watch a video for a look around the new antenna testing chamber: https://youtu.be/VFlrLE6qjUk .
