What’s driving the need for transparent antennas? Over the last several years, network operators have been densifying their networks to provide additional capacity and support new use cases. There has been significant new spectrum allocated by the FCC, which will result in more and sometimes larger antennas. The continuing trend in increasing data utilization, 80% of which is either originated or terminated indoors, makes in-building antennas particularly important as a present and future component of 5G communications infrastructure.
Additionally, aesthetics is becoming a significant consideration in the proliferation of in-building antennas. Many venues and office spaces have increasingly strict aesthetic requirements for antennas and other network infrastructure.
The Transparent Antenna Solution from 3M: Inconspicuous, robust, and efficient
3M™ Transparent Conductor Film for antenna applications allows antennas to be constructed with a transparent medium, reducing conspicuity of installed antennas. 3M™ Transparent Conductor Film enables the creation of visually transparent antennas that helps networks meet the same performance requirements as a conventional antenna.
There are several technologies available to create optically transparent, electrically conductive thin films. However, most are not suitable for 5G antenna applications. Analysis of the key characteristics of transparent conductor alternatives found that metal mesh worked better in antenna applications than other available alternatives. Low sheet resistance, high power handling capability and good PIM performance were key aspects of the selection criteria.
Moreover, the typical surface roughness of the conductive traces is on the order of 100 nanometers (nm). This is much less than the skin depth at 6 GHz (0.85 mm in Cu) so the surface roughness does not significantly increase effective RF resistivity in the sub-6 GHz range. It is even less than a skin depth at 28 or 39 GHz (0.4 and 0.33 mm, respectively) so although 3M has not yet produced mmWave antennas, similar conductor film optimized for mmWave applications is on the 3M roadmap. 3M uses a highly conductive metal mesh material that allows for high efficiency and high gain antennas. By using this transparent material, you can achieve greater efficiency and gain compared to other transparent conductive film technologies.
And so, despite the fact that we’re using a mesh material that is actually 80% open area, it performs pretty similarly to the same antenna that uses solid copper.
A surface treatment is applied to the mesh to reduce the reflected light and provide a neutral gray, as opposed to a copper color. This surface treatment also inhibits oxidation to provide improved environmental robustness.
3M engineers directly measured local PIM performance over the surface of 3M™ Transparent Conductor Film. The 3M™ Transparent Conductor Film was placed on a stage with a near field probe in close proximity, with an IR camera focused on the film to measure localized temperatures. Since the local temperature increases with current density, measurements of PIM and temperature over the antenna could be used to demonstrate that the highest current regions, i.e. those with highest local temperatures, were the source of the highest PIM.
Summary of benefits of 3M™ Transparent Conductor Film
• High transparency: >80% open area
• High efficiency: <0.1 ohms per square sheet resistance
• High flexibility: sheet enables a wide variety of deployment options
• High power capability: 50W continuous power has been demonstrated
The 3M business model is to provide 3M™ Transparent Conductor Film to antenna vendors, enabling transparent antennas meeting performance objectives previously obtained with solid Cu designs.
Highly conductive grid construction enables efficient antenna design and high visible light transmission.
The conductive, transparent material from 3M enables inconspicuous antenna designs capable of supporting high input power. This is intended to allow the proliferation of antennas in locations previously inaccessible for aesthetic reasons, thereby allowing wireless service providers to accelerate network deployments and improve in-building and outdoor coverage.
For indoor applications, the antenna has aesthetics value. For outdoor applications, the antenna may be built into spotlight or streetlight lens covers.
How could a customer access this 3M technology?
End users will purchase their custom antenna patterns formed on the 3M™ Transparent Conductor Film, available as sheet or roll (future) formats. Visit our product page to learn more.
5G infrastructure build-out and cell densification will drive greater numbers of antenna installations. There is a demand for faster data transmission speed, up to multi-Gbps speeds and greater capacity, fueling a massive amount of IoT and other devices per square kilometer.
Certain venues such as office spaces, retail, hi-rise buildings, health care facilities, and architectural spaces will value inconspicuous antennas for outdoor and in-building wireless. The 3M™ Transparent Conductor Film will allow antenna OEMs and system integrators to meet the need to provide high gain, low PIM inconspicuous antenna systems in those venues.