A new research report reveals that while most electronic components benefit from decreased size antennas – whether in a cell phone or on an aircraft, they suffer limitations in gain, efficiency, system range, and bandwidth when their size is reduced below a quarter-wavelength.
According to researchers, recent attention has been directed toward producing antennas by screen-printing, inkjet printing, and liquid metal-filled microfluidics in simple motifs, such as dipoles and loops. However, these fabrication techniques are limited in both spatial resolution and dimensionality, yielding planar antennas that occupy a large area relative to the achieved performance.
They explained that Omni directional printing of metallic nanoparticle inks offers an attractive alternative for meeting the demanding form factors of 3D electrically small antennas (ESAs).
To their knowledge, this is the first demonstration of 3D printed antennas on curvilinear surfaces. These antennas are electrically small relative to a wavelength (typically a twelfth of a wavelength or less) and exhibit performance metrics that are an order of magnitude better than those realized by monopole antenna designs.
There has been a long-standing problem of minimizing the ratio of energy stored to energy radiated – the Q – of an ESA. By printing directly on the hemispherical substrate, they have a highly versatile single-mode antenna with a Q that very closely approaches the fundamental limit dictated by physics (known as the Chu limit).
Conformal printing allows the antenna’s meander lines to be printed on the outside or inside of hemispherical substrates, adding to its flexibility.
Researchers noted that unlike planar substrates, the surface normal is constantly changing on curvilinear surfaces, which presents added fabrication challenges. To print features on hemispherical substrates, the silver ink must strongly wet the surface to facilitate patterning even when the deposition nozzle is perpendicular to the printing surface.
To fabricate an antenna that can withstand mechanical handling, for example, the silver nanoparticle ink is printed on the interior surface of glass hemispheres. Other non-spherical ESAs can be designed and printed using a similar approach to enable integration of low Q antennas on, for example, the inside of a cell phone case or the wing of an unmanned aerial vehicle. The antenna’s operating frequency is determined primarily by the printed conductor cross-section and the spacing (or pitch) between meander lines within each arm.
According to the researchers, their design can be rapidly adapted to new specifications, including other operating frequencies, device sizes, or encapsulated designs that offer enhanced mechanical robustness. This conformal printing technique can be extended other potential applications, including flexible, implantable, and wearable antennas, electronics, and sensors.
