Antenna performance Achieving Precise and Fast ESA Antenna Characterisation 

Related Vendors

Rohde & Schwarz GmbH & Co. KG

Fastems Systems GmbH

Rohde & Schwarz and Greenerwave achieve precise and fast ESA antenna characterisation using near-field technology.

A joint measurement trial, Rohde & Schwarz and Greenerwave have demonstrated that a near-field system can record a full radiation pattern of a 50 cm (approx. 20 inches) Ku band electronically steerable array for a SATCOM antenna in just half an hour. The achieved results match simulation models within a decibel, making this approach a fast and reliable way to verify antenna performance. For manufacturers of SATCOM systems facing large chamber constraints, it offers a clear path to quicker, more cost-effective testing. 

Electronically steerable array (ESA) antennas are becoming key components in modern SATCOM systems. Accurate knowledge of their radiation pattern is required for reliable operation in LEO, MEO and GEO orbits. However, conventional far‑field testing demands chambers that are often larger than practical for Ku or Ka band antennas, especially when the aperture of the Antenna Under Test (AUT) reaches half a meter or more. Compact Antenna Test Ranges (CATR), on the other hand, are still relatively large for these AUTs and require time-consuming dual-axis positioning of AUT to map the radiation pattern.

Rohde & Schwarz and Greenerwave have reached a breakthrough in ESA antenna testing in a recent joint measurement trial, achieving highly accurate radiation pattern characterisation in the near-field, significantly reducing measurement time. Greenerwave’s innovative SATCOM user terminals are based on reconfigurable intelligent surfaces (RIS), allowing the company to design electronically steerable antennas that deliver high-performance connectivity while reducing energy consumption and reliance on semiconductors compared with conventional solutions.

For the joint measurement campaign, T&M expert Rohde & Schwarz provided its R&S TS8991 over‑the‑air and antenna measurement system, equipped with a conical cut positioner, and its R&S ZNA vector network analyser. Together, they evaluated Greenerwave’s passive single‑aperture ESA that uses RIS technology for beamforming. The antenna under test (AUT) features a 50 x 50 cm (approx. 20 x 20 inches) aperture and is designed for low power consumption and easy integration. 

Part 2: Achieving phase repeatability

Phase Sync in Digital Phased Arrays Through Direct RF Sampling

The measurement covered an extended upper hemisphere down to a polar angle of 120 degrees, using a one-degree step size. Ten Ku band frequencies were recorded in a total of 32 minutes, thanks to the system’s hardware trigger function. Data was processed using the R&S AMS32 antenna measurement software, which applied a FIAFTA near-field-to-far-field transformation algorithm. 

Comparison with the original simulation based on a numerical twin model and with results from Greenerwave’s CATR setup showed peak gain or directivity variations of max. 1 dB and typically 0.3 dB, validating the accuracy of the near-field solution. Export options allow users to continue analysis in tools such as CST Microwave Studio or MATLAB.

The trial shows that even large SATCOM antennas can be characterised quickly and accurately with the R&S TS8991 antenna test system from Rohde & Schwarz in a near-field setup, providing a practical alternative to large-sized far-field chambers or CATRs. This system setup can be used by other SATCOM makers testing broadband, IoT or back haul antennas for applications requiring flexible beam control and high data rates. The setup can be integrated more easily into research lab environments, and it shortens test cycles, reducing overall development cost.