(A) study on development of electromagnetic wave measurement facilities for assessment of OTA performance of wireless devices

Abstract

In the present communication network, anechoic chambers are continuously used for evaluating OTA (Over-The-Air) performance of wireless devices such as smart phones, and they are considered as a powerful method in the 5G wireless communications in the future. In recent years, interest in reverberation chambers has been increasing to overcome drawbacks of anechoic chamber. Reverberation chamber technology provides a variety of methodologies in testing the key performance indicators for wireless devices. In this case, the design of reverberation chamber that has a more stringent field uniformity performance than the standard, which is for electromagnetic compatibility (EMC), is required. To this end, new reasonable design approach is required. In the case of anechoic chamber, it is necessary to solve the disadvantages for specific purposes in the development stage, such as improving the internal electromagnetic environment and reducing costs while supporting approximate measurement of performance of wireless devices. Therefore, a thin planar absorber structure capable of replacing the pyramidal absorber of anechoic chamber is required.

A study on development of new electromagnetic wave measurement facilities for performance assessment of wireless devices is presented in this thesis. First, in the case of reverberation chamber, a reverberation chamber structure consisting of new mode stirrer and reflector for EMC and wireless device performance evaluation is proposed. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume. The fabricated reverberation chamber satisfies the requirements exceeding the specifications of commercial product, shows the same level of results as the anechoic chamber in the evaluation of OTA performance of commercial long-term evolution (LTE) mobile phone, and has excellent reproducibility characteristics. In the case of anechoic chamber, a planar resonance type electromagnetic wave absorber based on a periodic structure is proposed as a substitute for a pyramidal absorber to support performance measurements of small antennas for a specific mobile communication frequency band and to make an eco-friendly testing space that can reduce manufacturing and maintenance costs. Analytical methods based on impedance matching are proposed for effective design and a novel technique for widening the absorption bandwidth is introduced. In order to verify the feasibility of the proposed objective, an anechoic chamber composed of a simple structure absorber is fabricated and the measurement results of internal electromagnetic wave environment and antenna performance are presented.

The developed electromagnetic wave measurement facilities can be competitive with the products of overseas monopoly company, and it can be said that it is significant in that they were transferred to domestic companies and localized.