Using cacti to spread Wi-Fi

In wireless communication, the interaction between electromagnetic waves and vegetation is usually a limiting factor, creating additional attenuation channels that must be considered. However, the high water content within cactus may allow it to act like an antenna, transforming the vegetation into a communication asset.

Jain et al. designed a broadband omnidirectional antenna element based on the Opuntia ficus-indica, also known as the nopal cactus.

The antenna uses Mie resonances, which result from the scattering that occurs when a spherical object is irradiated with electromagnetic radiation at a wavelength larger than or comparable to the object. The high fraction of water inside the cactus (75 to 85 percent) gives rise to multiple of these resonances.

“Cacti may be a good candidate for future antenna technology,” said author Abhinav Jain. “One detrimental factor is the loss due to the high concentration of water in cacti, but the water also makes it a high dielectric material, so it’s a tradeoff between the two.”

The design is similar to the plant configuration, with the cladode, or flattened leaf-like structure of the cactus, excited by a monopole connected with a coaxial cable. It operates in several WLAN applications and covers all Wi-MAX frequency bands.

“The design principle is easily extendable to other vegetation depending on the dielectric properties of the plants,” said Jain.

As an inexpensive and effective device, the antenna provides a potential biofriendly communication technology. The team plans to continue work on the design, particularly in reducing signal losses and enhancing gain.

Source: “Green ultra-wideband antenna utilizing Mie resonances in cactus,” by Abhinav Jain, Dmytro Vovchuk, Roman E. Noskov, Eran Socher, and Pavel Ginzburg, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0077338 .