Article by: TMY Technology Inc.
In a 5G mobile terminal, beam scanning capability is a critical factor for millimeter wave antenna arrays. Here’s how TMYTEK enables an accurate yet streamlined antenna testing process.
To overcome the relatively high path loss and increase beam coverage, millimeter wave (mmWave) antenna array design is a critical circuit design in 5G NR mmWave FR2 applications.
Professor Lu-Yu Zhao’s team from Xidian University has developed a multi-band, dual-polarization 1×4 mmWave beam-scanning compact antenna array for 5G mobile terminals. The overall size of the network antenna is small enough to fit in a mobile phone, and it fully supports the 5G NR band from n258 to n261.
The antenna element in the array is a critical design which affects the overall characteristics of the antenna array. It is necessary to validate the performance of the array through the front-end system by adjusting the phase and gain. After the antenna array design was completed, Prof. Zhao needed to fully verify the beamforming radiation patterns by setting up a beamforming test environment, which Prof. Zhao aims to build, quickly and economically with existing instruments.
Beamforming is a necessary technique in mmWave applications. However, antenna array designers must overcome various test limitations before performing beamforming measurements. To acquire the beamforming radiation patterns, post-processing of the antenna array is needed to simulate the beamforming radiation patterns, or a beamforming front-end circuit to adjust the amplitude and phase.
Before conducting beamforming tests, Professor Zhao faces the following challenges.
- Professor Zhao wanted to focus on element/antenna array design and did not have the time and effort to develop beamforming post-processing algorithms or design beamforming front-end circuits .
- To effectively measure beamforming patterns, Professor Zhao needed to invest in an 8-port (or more) vector network analyzer to test his 1×4 dual-polarized antenna, but he lacked funding.
To meet the beamforming measurement requirements, and given that Prof. Zhao’s antenna design is a compact 1×4 dual-polarized antenna array, TMY Technology Inc. (TMYTEK) suggested three options :
Option 1. Use the existing 2-port VNA: it measures radiation patterns by manually switching each antenna element in a chamber and simulating beamforming patterns with the post-processing method.
Option 2. An 8-port (or more) VNA: It measures the radiation patterns of each antenna element directly in a chamber and simulates the beamforming pattern with the post-processing method.
Option 3. Use the existing 2-port VNA with TMYTEK’s BBox One: This setup directly measures radiation patterns in a room by adjusting phase and gain with the BBox One.
Of the three options, option 1 takes time; Option 2 is expensive to install, requires multiple cables that are not easy to install in a room, and intertwining the cables can affect measurement accuracy or damage the DUT. The two options mentioned above also share something in common, which is that they both use the post-processing method to simulate the beamforming radiation pattern.
Figure 1 Option 3 Trial system
Figure 2 Prototype and measurement setup. (a) Prototype of Professor Zhao’s 4-element antenna array. (b) S-parameter measurement configuration. (c) Table under test with a BBox One. (d) Radiation pattern measurement setup.
TMYTEK BBox One helps antenna designers save testing time and effort by eliminating the need to develop beamforming algorithms or design additional front-end beamforming circuits. With TMYTEK’s in-house designed GUI, antenna designers can directly control phase, gain and beam direction on a single panel, making beam steering and management easier than ever. The combined benefits allow antenna designers to focus on antenna development and efficiently verify antenna performance without worrying about beamforming algorithms.
The TMYTEK BBox One has 16 independent RF channels with individual phase and amplitude control, and therefore Professor Zhao only had to connect the BBox One to his existing 2-port VNA to test the diagram. antenna of its 1×4 dual polarized antenna at different angles. For Professor Zhao, who needed to measure beamforming patterns, the TMYTEK solution is the simplest, most convenient and cost-effective.
Table 1 Comparison of various beamforming radiation pattern test options
1 8 (no element) 15 min (CATR measurement time/lap) = 120 min
*2 15 min (CATR measurement time/lap)
*3 40 ms (BBox beam switch time/pattern
In a 5G mobile terminal, beam scanning capability is a critical factor for millimeter wave antenna arrays. For comparison, Professor Zhao measured the sweep angle of the beam in different directions with his proposed mmWave antenna and the TMYTEK BBox One 28GHz, and compared it with the measurement results of the simulated pattern. As shown in the figure below, Prof. Zhao measured the beam scanning capability of the antenna array at 26.6 GHz and scanning angles from 0 to 60 degrees. The difference between the final measurement and the simulation is less than 0.2 dB, which means that testing with TMYTEK BBox One is just as accurate.
2D beam scan patterns of the antenna array in the theta = 90° plane
picture 3 (Left) Simulated +45° polarization patterns at 26.6 GHz for the proposed antenna array.
Figure 4 (Right) Simulated -45° polarization patterns at 26.6 GHz for the proposed antenna array.
Figure 5 (Left) Measured patterns of +45° polarization at 26.6 GHz.
Figure 6 (Right) Measured polarization patterns -45° at 26.6 GHz.
Figure 7: BBox One GUI developed by TMYTEK, which allows users to intuitively control the amplitude and phase of each channel.
Professor Zhao incorporated TMYTEK’s BBox One with his existing 2-port VNA and completed his 1×4 dual-polarization antenna verification experiment within his budget. With 16 independent RF channels, TMYTEK BBox One is applicable to teacher’s different antenna setups and used in OTA room to measure beam patterns to check antenna performance. By using TMYTEK’s BBox One, the antenna testing process remains accurate but simplified, and Professor Zhao does not have to worry about the beamforming algorithm or post-processing.
Y. He, et al., including Luyu Zhao, “A Compact Dual-Band and Dual-Polarized Millimeter-Wave Beam Scanning Antenna Array for 5G Mobile Terminals”, in IEEE Access, flight. 9, pages 109042-109052, 2021.