Electronically steerable array antennas (ESA) are becoming a central component of modern SATCOM systems. Precise knowledge of their radiation pattern is essential for reliable operation in LEO, MEO and GEO orbits. However, conventional far-field tests require large measurement chambers, which can become impractical for Ku- or Ka-band antennas – especially if the aperture of the antenna under test is half a meter or more. Compact antenna test rigs (CATR), on the other hand, are still relatively large for these DUTs and also require time-consuming two-axis positioning to capture the radiation pattern.
Rohde & Schwarz and Greenerwave have achieved a breakthrough in ESA antenna testing in a recent joint measurement study. The companies achieved a highly accurate characterization of the radiation pattern in the near field and were able to significantly reduce the measurement time.
Greenerwave’s innovative SATCOM user terminals are based on reconfigurable intelligent surfaces (RIS). This allows the company to develop electronically steerable antennas that provide high-performance connectivity while reducing energy consumption and reliance on semiconductors compared to traditional solutions.
For the joint measurement campaign, measurement technology expert Rohde & Schwarz provided the R&S®TS8991 over-the-air and antenna measurement system, equipped with a truncated cone turntable, as well as the R&S®ZNA vector network analyzer. Together they evaluated Greenerwave’s passive single aperture ESA, which uses RIS technology for beamforming. The antenna test specimen has a 50 x 50 cm aperture and is designed for low power consumption and easy integration.
The measurement covered the entire upper hemisphere up to a polar angle of 120 degrees with a step size of one degree. Thanks to the system’s hardware trigger function, ten Ku-band frequencies were recorded in a total of 32 minutes. The data was processed using R&S®AMS32 antenna measurement software, which applied a FIAFTA near-field far-field transformation algorithm.
Comparison with the original simulation based on a numerical twin model and with results from Greenerwave’s CATR setup showed deviations in peak gain and directivity of a maximum of 1 dB and typically 0.3 dB, respectively, confirming the accuracy of the near-field solution. The export options allow the user to continue the analysis in tools such as CST Microwave Studio or MATLAB.
The test shows that even large SATCOM antennas can be characterized quickly and accurately in a near-field setup using the R&S TS8991 antenna test system from Rohde & Schwarz. The solution thus offers a practical alternative to large-format far-field chambers or CATRs. The system setup can also be used by other SATCOM manufacturers testing broadband, IoT or backhaul antennas for applications that require flexible beam steering and high data rates. In addition, the setup is easier to integrate into research lab environments and shortens test cycles, reducing overall development costs.
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Further links
👉 www.rohde-schwarz.com
Photo: Rohde & Schwarz
