Abstract
The author of this paper explored Vivaldi [1] [2] line theory and technology and used it as a basis to propose a Vivaldi antenna array to replace a single Vivaldi antenna. This was to achieve a dual-polarized antenna with high directivity and high isolation in the MIMO anechoic chamber, and one that is minimally affected by the environment. The operating frequency of this antenna array covers a frequency range of 0.7–6.0 GHz and is composed of four Vivaldi units with relatively high isolation between them to reduce measurement errors caused by coupling. In each unit, two identical Vivaldi antennas are connected in parallel to form the same polarization unit, and a microstrip power divider was used and the impedance matching of circular holes was performed to design this connected antenna with an ultra-wide operating frequency and the same polarization. The authors then interconnected two polarization units orthogonally at 90 degree cross to form the antenna described in this study, which has high directivity, high isolation, an ultra-wide frequency and dual polarization. During the design process, an FR4 printed circuit board (PCB) was used to effectively reduce the cross-sectional area of the antenna and reduce reflection and interference on the basis of ensuring an ultra-wide operating frequency. Additionally, the two orthogonal units of each polarized antenna unit had to work separately, and the electric field data collected from different polarization directions were sequentially transmitted to the receiver for postprocessing to satisfy the measurement requirements of the MIMO OTA anechoic chamber. In this study, SEMCAD electromagnetic simulation software was used to adjust and complete the analysis of antenna characteristics and obtain a favorable operating frequency and voltage standing wave ratio, as well as excellent isolation and radiation characteristics.
Highlights
The requirements of modern mobile communication technology for Multiple Input Multiple Output (MIMO) over the air (OTA) measurement methods and test precision are becoming more stringent
Because the multichannel transmission pathways of reflection, diffraction, and refraction in the actual environment must be simulated to overcome the limitations of site space and distance in far-field measurements, multiple antennas must be set up in an anechoic chamber to transmit multiple sets of signals
Frequency bands used by LTE-A mobile communication were referenced to select four frequency points representing low, medium, and high frequencies to perform simulation calculations
Summary
The requirements of modern mobile communication technology for Multiple Input Multiple Output (MIMO) over the air (OTA) measurement methods and test precision are becoming more stringent. In 2000, the French firm Satimo announced an anechoic chamber featuring antenna arrays at 0.7–6.0 GHz (Fig. 1), leading to another revolution in antenna measurement technology. In 1979, Gibson [3] proposed a broadband, exponentially tapered microstrip Vivaldi slot antenna. The microstrip line and signal distributor for signal feeding are printed on the front side of the PCB, whereas its exponential V-shaped open antenna body is printed on the other side of the PCB. Such a configuration design serves as an impedance transformation network for the signal feeding distributor and radiance propagation in free space, as well as the coupling feed of signals. Based on the aforementioned publications, scholars have achieved several results in research work regarding Vivaldi antennas
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