Low Dk materials are a solution to high-frequency constraints.
With the rollout of early commercial services, the 5G revolution is happening now and will touch more lives in more ways and be more disruptive than perhaps any before it. This is probably because the revolution is not about 5G technology itself, but instead is about the many visions of the connected world that finally can be made real.
We’ve been dreaming big with concepts like the IoT and autonomous mobility, e-health, Industry 4.0, to name a few. The potential benefits are huge, but so is the scale of the connectivity they envisage. 5G is designed to handle this, but sheer volume is only one part of the equation. Exciting applications linked to mobility and industrial automation, for example, are obviously time-critical too. 5G’s provision for ultra-reliable low-latency communication (URLLC) will enable the timely responses needed to ensure safety and proper coordination between machines or large numbers of self-driving vehicles moving within the same geographical area.
5G will cut communication latency between cloud services and endpoints to about 1ms, which is a massive improvement over the 40-70ms typical over a 4G connection. Because ultra-reliability comes as part of the package, autonomous vehicles, for example, can interact with applications running in the cloud and relieve demand for on-board computing. This can help reduce vehicle costs, power consumption and software-maintenance overhead. Moreover, 5G’s extra speed makes time for cloud-based V2X applications that will enable sophisticated communication between vehicles and with intelligent infrastructure. Also, the combination of reliability and low latency will enable greater fuel efficiency and use of road capacity through capabilities such as organizing vehicles in convoys.
This has not been achievable safely before now, but with 5G it becomes a possibility and should deliver advantages not only for private motorists but fleet operators and logistics businesses too.
So 5G is an enabler, a vital fabric that can link the huge numbers of distributed sensors and connected machines, digital data streams, and the cloud-based AI we will harness to mine that data and drive decisions in real-time. It will help turn our dreams of what should be possible into reality.
But there are technical and societal challenges. Security is, of course, critical, to protect equipment and services from all manner of malicious attacks ranging from random exploits to organized data theft or sabotage. Safety will also be a critical concern, particularly for autonomous mobility. While URLCC will permit a greater proportion of the computing load to be shifted to the cloud, embedded or edge systems will likely handle emergency responses and failsafe mechanisms.
Other challenges stem from the fact that 5G New Radio (NR), the RF part of the network closest to connected devices in the field, is pushing hard against the laws of physics. Carrier frequencies are increasing, to 6GHz for Frequency Range 1 (FR1) into the mm-wave range at 24-52GHz in FR2, and ultimately through the V-band frequencies to 75GHz and beyond.
Signal attenuation in normal air is high at these frequencies, so cell density is much higher than in 4G or earlier networks. To achieve the desired coverage, network installers are seeking access to infrastructure such as lamp-posts that permit close antenna spacing and provide a clear line of sight to connect with subscriber equipment. For this reason, 5G is well-suited to urban deployment but more challenging to roll out to rural areas. This is an issue that is sure to command the attention of councils and planners.
As engineers, we only have to worry about the technical points. The combined effects of high-frequency signal absorption and the requirement to support many more connected devices means increased volume demand for infrastructure equipment. From a business perspective, this provides many opportunities for vendors of 5G NR cells, for instance. On the other hand, it’s worth ensuring there is enough supply-chain capacity to meet this increased demand. Only a small number of vendors have substrate materials suitable for high signal speeds and qualified for use by equipment makers, so it’s worth discussing supply assurances upfront to avoid possible lead-time issues later.
As for performance, we can expect more advanced classes of substrate materials and innovative chemistries to emerge to meet the demands placed on 5G equipment, particularly RF circuitry such as the MIMO phased-array beamforming antennas critical for high channel capacity and fast over-the-air data rates. At high speeds, a significant proportion of signal power is dissipated in conventional FR4-based substrates, which have dissipation factors (Df) of about 0.02. On the other hand, the feature sizes for such high frequencies are so small that controlling the dimensions to ensure maximum power transfer becomes challenging. A material with low dielectric constant (Dk) can help relieve some of the constraints here.
FR-4-type materials are at the limit of their capabilities, so the way forward lies in migrating to classes such as ceramic-filled hydrocarbon materials for high-speed signal integrity and minimal power loss.
5G infrastructure is being deployed in the field, in live commercial pilots, right now. Expecting the supply-chain vagaries mentioned earlier can be overcome, it will be fascinating to see 5G develop as an enabling technology for untold numbers of advanced services over the next few years. We should all get ready for profound changes in the way we live, work, travel, connect with each other, and relate to increasingly intelligent and interactive machines.