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4 test methods for 5G base station antenna OTA
Source:Originally | Author:Calio Huang of C&T RF Antennas Inc | Publish time: 2019-05-03 | 1210 Views | Share:

The OTA test specification for all RF performance indicators of 5G base stations has been written in the 3GPP 5G new air interface protocol frozen in December 2017, which means that the integrated OTA test of 5G base station antennas will become the main solution for 5G base station hardware performance testing. However, the current OTA test of RF indicators still faces many difficulties. In this paper, the OTA test method of the large-scale active antenna system is deeply studied, and the test is carried out in different fields such as far field, compact field, multi-probe spherical near field and single probe near field. The advantages and disadvantages of each test scheme are compared. The analysis presented the problems faced and the corresponding solutions.

2. 5G base station antenna OTA test solution

The radiated performance of an antenna is typically tested in an OTA manner in its near-field or far-field region. The boundary between the near field and the far field of the antenna radiation is: the spherical wavefront emitted by the source antenna reaches the center of the antenna to be measured and the wave path difference is λ/16. The judgment based on the distance is d=2D 2 /λ, where d is the distance between the probe point and the antenna under test, D is the aperture of the antenna under test, and λ is the wavelength of the electromagnetic wave emitted by the antenna under test.

According to this, the antenna test is divided into two categories: far-field test and near field test, and different test plans will lead to differences in test results. Here are a few classic active antenna OTA test solutions.

(1) Far-field test plan

The far field test is the most direct test method. When the test distance is far enough, the incident wave approximates the plane wave on the receiving surface. Figure 1 shows the far-field test system. The device under test can be rotated 360° in the vertical and horizontal planes. The test probe is fixed in position and can be rotated and rotated. The test system can test the beamforming pattern of the 5G base station antenna and EIRP (Effective Isotropic Radiated Power), EVM (Error Vector Magnitude), occupied bandwidth, and EIS (Effective Isotropic Sensitive). Omnidirectional sensitivity and other RF radiation indicators.