And matching materials to the equipment that will advance our world.
Whatever we may learn about the origins of Covid-19, and however inconclusive the information may be, we can be almost certain it had nothing to do with radio waves. I’m sure I’m not alone in feeling disappointed about the attacks made on mobile phone masts during this crisis, carried out in the misguided belief that this kind of vandalism can halt the virus.
Fortunately, instances of such extreme technophobia have been few. It seems every new technology wins vocal detractors, however beneficial its effect on peoples’ lives. In recent years, our industry has had to deal with claims about grisly health risks associated with mobile phones, the effects of “wind turbine syndrome,” and the evil propagated by 5G.
Advanced technologies will hold the key to our defense against Covid-19. We will need the knowhow of pharmaceutical labs to create an effective and practicable vaccine, and engineering skills to develop new respirator designs better adapted to the needs of coronavirus patients than are conventional ventilators or CPAP devices. Moreover, effective virucides will be needed to enhance cleaning in places such as hospitals, waiting rooms, factories, warehouses, public transport vehicles, and aircraft. Irradiating at-risk areas using germicidal UV-C lamps could be an option and could easily be automated using mobile robots.
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UV-C irradiation has been used successfully in applications such as water treatment for many years. The mercury-vapor germicidal lamp was commercialized in the 1930s, although the mercury’s natural radiation wavelength of 253.7nm is not quite perfect for maximum germicidal effect, and, in addition, conventional UV-C light sources are a human health hazard, being both carcinogenic and cataractogenic. However, it is possible to fine-tune LEDs to emit far UV-C at the exact wavelength required to disrupt virus DNA, while not causing biological damage to exposed mammalian cells and tissues. On the other hand, the LED die temperature must be kept stable to ensure the emitted wavelength remains within a narrow range as close as possible to the ideal far UV-C wavelength.
In LED lighting, thermal management is usually designed from a reliability standpoint. Wavelength shift is a secondary concern. Automotive lighting customers, for example, may choose insulated metal substrates (IMS) to stabilize the die temperature at a level calculated to ensure the lamp lasts for the intended lifetime of the vehicle. When designing a germicidal source, in contrast, thermal management is primarily tasked with stabilizing the emitted wavelength. A temperature-related drift of just a few nanometers could be critical.
Far UV-C radiation kills living cells by disrupting the DNA to prevent the cells from reproducing. Clearly, we need to use this technology sensitively to minimize damage to the wider ecosystem. However, although highly effective against microbes, the threat to human health is less than skin deep. The energy contained, at a frequency of about 1360THz, is unable to penetrate the outer, nonliving epidermis.
Humans have nothing to fear from far UV-C or, indeed, our mobile phones and the various wireless networking infrastructures that operate at radio frequencies several orders of magnitude lower. We know radiation up to about 300GHz, which is far above the highest frequencies planned for 5G, is nonionizing and poses no health risks.
5G will employ a greater variety of frequencies than any previous system to support more services, provide greater connection capacity, carry more data, and at the same time handle the growing volume of machine-to-machine communications. Conceived to provide all-enveloping and pervasive wireless connectivity, its positioning means there is no such “thing” as 5G. Instead, it will be many “things,” embodying an incredible diversity of technologies. In the future, it is likely to encompass Wi-Fi, as we know it today, to ensure optimized quality of service everywhere.
The first 5G networks will be non-standalone (NSA) hybrid implementations that combine 4G and 5G technologies. These will operate in the sub-6GHz range, aka 5G frequency band 1 (FB1). Given the rollout of 5G handsets is expected to take five to eight years to complete, the transition to full standalone (SA) 5G New Radio (NR) operating in FB2 (24GHz to 50GHz, eventually reaching into the V-band up to 77GHz) could take time.
Optimizing communication range, RF transmit power, and link margin becomes increasingly challenging at higher frequencies. In urban areas, closer cell spacing, combined with beamforming and antenna diversity, can overcome some of these limitations on communication distance. On the other hand, longer RF range is a must to serve locations such as rural areas. The reality is 5G will likely make full use of both FB1 and FB2 for the long term.
Designing equipment to operate at FB2 frequencies places stringent demands on materials. Signal loss in antennas becomes a huge issue, and conventional substrate materials, which tend to have a large dipole moment that results in excessive dissipation of high-frequency signal energy, are unsuited to the task. Ceramic materials have an extremely low dipole moment that helps maximize the signal-to-noise ratio (SNR) at the receiver. Ceramic-filled organic polymers are thus valuable in the search for greater SNR. Ultimately, I expect substrates incorporating PTFE, which is inherently non-polar, to become widely adopted as we search for ultimate signal performance at high frequencies.
Advanced materials represent just one technology among the many being brought together to unleash the full desired performance of 5G across FB1 and FB2. The end-user experience should be unified, uniform, and homogeneous. Under the surface, it will be fascinatingly complex and intricate.