**5. Conclusion**

Key technologies on the design, construction and validation of a highperformance OATS have been provided, based on the author's many years of experience. Some famous OATS in the world regarding their structure, the dimensions of the ground plane (GP), the location of the control room, and performance have been summarized. A detailed case study is provided on NIM's high-performance OATS. A measurement uncertainty example has been provided in measuring the free-space antenna factor of biconical antennas.

## **Acknowledgements**

Dr. Alexander KRIZ and Dr. Katsumi Fujii provide many details on their OATS. There are many persons involved in the design, construction, and validation of NIM's OATS. Special acknowledgments are due to TDK, Mr. Gao X. X, Dr. Cui X. H., Dr. Song Z. F., Mr. Hong L., and Ban H.

### **Conflict of interest**

The author declares no conflict of interest.
