First, a two-port MIMO antenna using the multifunction mesh coplanar monopole type was optimized, using air as its dielectric. The resulting antenna and its predicted performance is shown in Figure 3. This antenna has reasonably good VSWR and isolation for the dual-band Wi-Fi frequencies for both ports, with a maximum VSWR of about 1.8:1 and a maximum coupling of about ‐16.5 dB. At the lowest frequency, the antenna edges are separated by less than 0.093 λ, and the ports themselves are only 0.41 λ apart. As can be seen, the shapes of these two elements have some similarities, but they are not identical. This is expected and improves the isolation.
The antenna was imported into NI AWR Design Environment, specifically Microwave Office circuit simulator, and further simulated using AXIEM 3D planar EM solver from 2 to 6 GHz. The results match well with AntSyn’s predictions; the worst-case coupling is ‐16.8 dB. Although coupling and VSWR do rise between the Wi-Fi bands, in-band performance is very good.
AntSyn was also used to optimize a three-port antenna using a matching network to improve performance with the tighter spacing. The maximum VSWR was about 1.8:1, while the maximum coupling was ‐14.7 dB, which occurs between the two ports closest together (the right and center ports in Figure 4). The spacing is only 0.163 λ at 2.4 GHz between these ports, with a minimum spacing of 0.048 λ between the elements. The distance from the center to the left port is also 0.31 λ. Even more than in the two-port antenna example, the shapes of these antennas are very diverse. Essentially, AntSyn created a different antenna for each port, placing a parasitic fence between the center and left ports. This complexity was created automatically by AntSyn, demonstrating the inherent strength and robustness of the genetic algorithm, enabling the design space to be fully explored to produce MIMO antennas with optimal performance.
AntSyn provides an automated antenna design, synthesis and optimization tool well-suited for complex antennas, including compact MIMO arrays. It helps designers address the challenges of next-generation antenna design and integration within mobile devices and IoT components.
AWR Group, NI
El Segundo, Calif.